Content uploaded by Mohammed F Shamji
Author content
All content in this area was uploaded by Mohammed F Shamji
Content may be subject to copyright.
Molecular strategies for the treatment of malignant glioma—
genes, viruses, and vaccines
Lee A. Selznick,
Division of Neurosurgery, Duke University Medical Center, Durham, NC, USA
Mohammed F. Shamji,
Division of Neurosurgery, The Ottawa Hospital, Ottawa, Canada
Department of Biomedical Engineering, Duke University, Durham, NC, USA
2616 Erwin Road, #1416, Durham, NC 27705, USA
Peter Fecci,
Duke University School of Medicine, Durham, NC, USA
Matthias Gromeier,
Division of Neurosurgery, Duke University Medical Center, Durham, NC, USA
Allan H. Friedman, and
Division of Neurosurgery, Duke University Medical Center, Durham, NC, USA
John Sampson
Division of Neurosurgery, Duke University Medical Center, Durham, NC, USA
Mohammed F. Shamji: mohammed.shamji@duke.edu; John Sampson: john.sampson@duke.edu
Abstract
The standard treatment paradigm of surgery, radiation, and chemotherapy for malignant gliomas
has only a modest effect on survival. It is well emphasized in the literature that despite aggressive
multimodal therapy, most patients survive approximately 1 year after diagnosis, and less than 10%
survive beyond 2 years. This dismal prognosis provides the impetus for ongoing investigations in
search of improved therapeutics. Standard multimodal therapy has largely reached a plateau in
terms of effectiveness, and there is now a growing body of literature on novel molecular
approaches for the treatment of malignant gliomas. Gene therapy, oncolytic virotherapy, and
immunotherapy are the major investigational approaches that have demonstrated promise in
preclinical and early clinical studies. These new molecular technologies each have distinct
advantages and limitations, and none has yet demonstrated a significant survival benefit in a phase
II or III clinical trial. Molecular approaches may not lead to the discovery of a “magic bullet” for
these aggressive tumors, but they may ultimately prove synergistic with more conventional
approaches and lead to a broadening of the multimodal approach that is the current standard of
care. This review will discuss the scientific background, therapeutic potential, and clinical
limitations of these novel strategies with a focus on those that have made it to clinical trials.
Keywords
Glioma; Gene therapy; Virotherapy; Oncolytic viruses; Immunotherapy
© Springer-Verlag 2008
Correspondence to: John Sampson, john.sampson@duke.edu.
NIH Public Access
Author Manuscript
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
Published in final edited form as:
Neurosurg Rev
. 2008 April ; 31(2): 141–155. doi:10.1007/s10143-008-0121-0.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
Introduction
Malignant gliomas are the most common primary adult brain tumor and one of the most
difficult tumors to treat. Even with aggressive multimodal therapy, average survival is a
little more than 1 year, and less than 10% survive more than 2 years. Class I and II evidence
suggests a modest effect on survival for gross total resection, various radiation paradigms,
and several chemotherapeutic agents [13, 36, 119]. However, there have been no major
breakthroughs over the past 30 years that lead to significant or predictable long-term
survival. In addition, the few patients that do survive long term are often subject to the
deleterious effects of their aggressive treatment over time.
In the presidential address to the 2005 American Association of Neurological Surgeons
(AANS), Robert A. Ratcheson, M.D. acknowledged that “there has been little to suggest that
surgical treatment of malignant brain tumors will ever play more than a limited therapeutic
role, and then only as an adjunct, whereas true advances may evolve from a growing
understanding of molecular biology and the novel delivery of tumoricidal agents” [108].
Molecular strategies have now become the focus of a growing body of literature dedicated to
solving the limitations we currently face for the treatment of malignant gliomas. There are
three distinct yet complementary investigational approaches on a molecular scale that
dominate the flurry of investigation in this field, namely, gene therapy, oncolytic
virotherapy, and immunotherapy. This paper will review the scientific background, clinical
application, and limiting factors of these novel therapeutic agents (Fig. 1). By definition, the
scope of “molecular” approaches is quite broad (i.e., manipulation and targeting of tumor
cells at the subcellular level) and will, therefore, be limited in this review to gene therapy,
oncolytic virotherapy, and immunotherapy with a focus on those approaches that have led to
a previous or ongoing clinical trial.
Gene therapy
Background
Malignant gliomas, like all cancers, are because of genetic alterations that result in
uncontrolled cellular proliferation. These genetic alterations can be directly targeted or
indirectly exploited for the treatment of gliomas. A direct and logical approach is to replace
or correct the genetic alteration responsible for the malignant phenotype. Multiple genetic
alterations occur in malignant gliomas, however, and a single target is unlikely to be
curative. Nevertheless, the genetic alterations that are associated with the malignant
phenotype can be exploited to differentiate malignant cells from surrounding normal ones
and serve as indirect molecular targets for various therapeutic strategies. A number of gene
therapy approaches that utilize the genetic alterations associated with malignant gliomas as
direct or indirect targets have been investigated.
Gene therapy—correction of altered genetics
Direct gene therapy strategies aim to either replace the “loss of function” in a tumor-
suppressor gene or interfere with the “gain of function” in an oncogene that is responsible
for the malignant phenotype. The most frequently encountered alteration in malignant
gliomas is in the tumor-suppressor gene
p53
found on chromosome 17p [10]. The p53
protein has a number of functions, including a regulatory role in progression through the cell
cycle, DNA repair after damage, and induction of apoptosis. p53 mutations are encountered
in a variety of human cancers and have been reported in 30–60% of malignant gliomas,
particularly those that arise secondarily from lower grade astrocytomas, and less commonly
in primary glioblastomas [53].
Selznick et al.
Page 2
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
Replacement of wild-type
p53
gene function may halt growth or induce apoptosis of
malignant gliomas. A number of preclinical trials have provided proof of principal for this
approach [10, 65, 75, 84]. Merritt et al. were the first to develop an adenovirus vector that
expressed p53 under the control of a CMV promoter—this has been manufactured under the
trademark ADVEXIN (Introgen Therapeutics, Inc.) [84]. Kock et al. demonstrated that
adenovirus-mediated delivery of p53 resulted in dose-dependent inhibition of in vitro
cellular proliferation in five out of six glioma cell lines and inhibited tumor growth of
subcutaneous glioma xenografts [65]. Furthermore, adenoviral transfer of p53 has been
shown to induce apoptosis in U251 [75] and U87 [17] glioma cell lines and enhances
survival in nude mice with cerebral xenografts after intracranial injection.
In 2003, Lang et al. performed a phase I clinical trial of adenovirus-mediated p53 (ad-p53,
INGN 201) gene therapy for recurrent glioma [74]. This was a two-stage trial in which ad-
p53 was stereotactically injected intratumorally via an implanted catheter followed by
en
bloc
resection of tumor and catheter with post-resection injection of ad-p53 into the cavity.
Fifteen patients were enrolled in this study, and 12 underwent both treatment stages.
Exogenous p53 protein was detected within astrocytic tumor cells in all patients studied. It
was also demonstrated that the exogenous p53 activated downstream effectors and induced
apoptosis. Clinical toxicity was minimal, and there was no evidence of systemic viral
dissemination. However, transfected cells were on average only 5 mm from the injection
site, and widespread distribution within the tumor was not seen. Although the strategy is
sound in principle, technical limitations in delivery limit its therapeutic potential.
The variant epidermal growth factor receptor (EGFRvIII) is found in approximately 50–60%
of malignant gliomas, particularly in those that arrive de novo, and it is the most frequently
encountered oncogene in this setting [89, 138]. EGFR is a receptor tyrosine kinase that
mediates autocrine growth regulation and is overexpressed in a variety of human cancers in
addition to malignant gliomas. Both the wild-type EGFR and the mutated receptor, which
exhibits a characteristic deletion in the extracellular domain and is constitutively active, are
often overexpressed on tumor cells [62, 136].
Interference with the expression or function of EGFRvIII is a logical target for gene therapy,
and several approaches are being explored. Antisense gene therapy against EGFR has
proven effective in several preclinical studies [127, 142]. Antisense EGFR
oligodeoxynucleotides enveloped in Lipofectin have been shown to inhibit the in vitro
proliferation of three malignant glioma cell lines and decrease the activity of the receptor
tyrosine kinase [127]. Intracranial U87 human glial tumors in mice were treated in vivo with
a plasmid encoding for antisense mRNA packaged within an immunoliposome (nonviral)
vector and targeted with receptor-specific monoclonal antibodies [142]. Weekly intravenous
administration increased survival 100% relative to control treatments. Overexpression of a
dominant negative EGFR (Ad-EGFR-CD533) via a replication-incompetent adenovirus has
also been shown to enhance radiosensitivity of human glioma cell lines in vitro and in vivo
[73]. Primary gene therapy against EGFR is currently in phase I human trial for head and
neck squamous cell cancer at the University of Pittsburgh, but no trials have yet been
described for patients with malignant gliomas.
Gene therapy (indirect)—introduction of suicide genes
The genetic alterations within a malignant glioma can also be exploited as targets for the
introduction or activation of genetic strategies to induce cell death, i.e., suicide gene therapy
via introduction of pro-apoptotic genes or virus-directed enzyme-prodrug therapy. Whereas
pro-apoptotic gene therapy has yet to move beyond preclinical studies, virus-directed
enzyme-prodrug therapy is the only gene therapy strategy for malignant glioma to undergo a
phase III clinical trial in humans.
Selznick et al.
Page 3
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
The apoptotic pathway is often disrupted in tumor cells, making it an attractive target for
gene therapy. Adenovirus-mediated delivery of the pro-apoptotic Fas ligand or TNF-related
apoptosis-inducing ligand resulted in apoptosis in multiple glioma cell lines in vitro [112].
Coexpression was synergistic in five of 13 cell lines tested. However, sensitivity to ligand-
induced apoptosis was cell-line dependent apparently because of variable expression of the
respective ligand-specific cell–surface receptor. Likewise, adenoviral delivery of pro-
apoptotic BAX in vitro and to subcutaneous D54 MG glioma xenografts in vivo resulted in
apoptosis and synergistically radiosensitized the malignant cells [4]. The combined
treatment resulted in significant reduction of tumor size in nude mice with a favorable
therapeutic index.
Recent studies from researchers at the Cleveland Clinic have targeted pro-apoptotic Fas-
associated protein with death domain (FADD), caspase-8, and caspase-6 to malignant
gliomas using a telomerase-specific expression system [66–68]. Telomerase activity is
associated with many malignancies and is regulated at the transcriptional level of telomerase
reverse transcriptase (hTERT). These authors demonstrated via reverse transcription-
polymerase chain reaction that hTERT mRNA was expressed in human malignant glioma
cells but not in other proliferating cells within the brain (astrocytes, fibroblasts). Gene
transfer of FADD, caspase-8, or caspase-6 under the control of the hTERT promoter
specifically induced apoptosis in glioma cells in vitro and significantly suppressed growth of
subcutaneous tumors in nude mice compared with controls. This gene therapy approach was
also demonstrated to have an additive effect with chemotherapeutic agents that also induce
apoptosis [128].
A second suicide gene therapy strategy involves activation of otherwise innocuous
compounds (prodrugs) in tumor cells after transfection with a gene to induce expression of
an activating enzyme. The prototypical model of this strategy is the herpes simplex virus
thymidine kinase/ganciclovir (HSV-tk/GCV) system, which has been well studied and
reviewed in detail elsewhere [29, 45]. This approach involves the transfection of HSV-tk
into tumor cells and then administration of ganciclovir systemically. HSV-tk, unlike human
tk, monophosphorylates the nucleoside analog ganciclovir. This is then converted in host
cells to triphosphate ganciclovir, which gets incorporated into DNA, blocking chain
elongation and halting cell division. This strategy was first proposed by Moolten in 1986
[87] and was targeted to malignant cells by using a retrovirus vector that only transfects
dividing cells.
Preclinical studies utilizing the HSV-tk/GCV system have led to impressive results in
multiple cancer models, including the complete disappearance of experimental brain tumors
in 11 of 14 animals after transduction by retrovirus-expressing HSV-tk and treatment with
ganciclovir [20]. Most clinical studies have likewise utilized a retrovirus vector but with
much less impressive results. A randomized phase III clinical trial was completed in 2000 in
which patients were randomized to surgical resection and radiotherapy versus surgical
resection, radiotherapy, and HSV-tk/GCV gene therapy [103]. There was no difference
between both treatment arms in regard to median survival. Retroviruses, however, have poor
transduction efficiency and only infect proliferating cells, which accounts for a minority of
tumor cells at any given time. Adenoviral vectors, which have better transduction efficiency
and can infect proliferating and non-proliferating cells, may prove to be more effective. A
recent dose-escalating phase I trial utilizing an adenoviral vector was safe, and ten of 11
patients survived beyond 52 weeks from diagnosis with an average survival of 112.3 weeks
[35]. This is more than double the expected survival with conventional treatments, and one
patient was alive 248 weeks from diagnosis at time of publication.
Selznick et al.
Page 4
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
Despite the exciting preclinical data on gene therapy, there are still several hurdles that
prevent successful translation in a glioma patient population. Known limitations to gene
therapy at this time include:
1.
Transduction rates with gene therapy, even under the best circumstances, are very
low and inherently limit the effectiveness against an invasive malignancy such as
glioblastoma multiforme (GBM). While “gene replacement” strategies may make
sense in monogenic inherited diseases where even scant amounts of protein
produced in a few cells (cystic fibrosis) can make a clinical difference, their
usefulness against cancer is dubious.
2.
The majority of gene therapy trials, thus far, are based on adenoviral vectors, cell
entry of which is dependent on the coxsackie adenovirus receptor that has scarce
expression in most cancers including GBMs [5]. There have been several attempts
in resolving this issue by engineering adenoviruses with tropism for alternative
receptors more abundant on cancer cells or retargeting vectors with alternate
ligands such as fibroblast growth factor-2 [44].
3.
Adenoviruses are not neuropathogens and, hence, demonstrate limited ability to
spread from the inoculation site in clinical trials [52].
4.
The immunogenicity of the vector may also limit the efficacy of this strategy [88,
130].
Oncolytic virotherapy
Background
Whereas gene therapy strategies typically employ replication of
incompetent
viruses as mere
vectors for gene transfer, oncolytic virotherapy utilizes replication
competent
viruses to
infect and lyse cells with or without gene transfer. Although the ability of viruses to
specifically infect and kill tumors was first observed in 1912 [22], the clinical utility of
oncolytic viruses has not been a realistic goal until recent advancements in the genetic
manipulation of otherwise pathogenic viruses. The ability to select and manipulate viruses
based on target tropism and cellular entry (mediated by cell–surface interactions) and tumor-
specific replication (mediated by internal cellular conditions) has generated significant
interest in this strategy. Numerous viruses have been proposed and studied for therapeutic
use as oncolytic agents. Three human pathogenic viruses, HSV, adenovirus, and poliovirus
have been extensively studied and demonstrate the clinical potential of this approach.
Herpes virus strategies
HSV is an enveloped dsDNA virus with natural neurotropism and the ability to replicate in
dividing and non-dividing cells. Martuza in 1991 was the first to demonstrate that this
otherwise neurovirulent virus could be genetically engineered for oncolytic therapy of
malignant gliomas [80]. Thymidine kinase, the enzyme that is exploited in the enzyme-
prodrug paradigm of gene therapy described previously, is encoded by HSV and required for
viral DNA replication in non-dividing cells. Deletion of the gene that encodes thymidine
kinase results in a conditionally replicating virus (
dls
ptk) selective for dividing cells, and
this was shown to replicate within and kill glial tumors. However, this was never brought to
clinical trial because of concern over potential toxicity to normal brain and lack of
susceptibility to acyclovir or ganciclovir (because of the loss of thymidine kinase) if
encephalitis were to occur.
This ultimately led to the development of G207 by the same group [86]. G207 is another
conditionally replicating HSV with mutations in both copies of the neurovirulence gene
γ
1
34.5
and disruption of the gene encoding ribunucleotide reductase rather than thymidine
Selznick et al.
Page 5
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
kinase. G207 retains susceptibility to anti-HSV therapies (ganciclovir, acyclovir) because
the
tk
gene is intact. Preclinical studies demonstrated that G207 decreased growth of
subcutaneous U87-MG tumors, prolonged survival in intracranial U87-MG tumors, and was
well tolerated in non-human primates [35, 56]. A dose-escalation phase I clinical trial was
published in 2000 and was the first report of a replication-competent HSV mutant used in a
human brain tumor trial [79]. Twenty-one patients with recurrent malignant glioma were
enrolled, and no dose-limiting toxicities were encountered. Also of interest, eight of 20
patients had reduced enhancement volumes of their tumors, and there were two long-term
survivors at time of publication (54 and 52 months after inoculation).
Another HSV mutant, 1716, only has deletions in the γ
1
34.5
genes and also has completed
phase I clinical testing for recurrent glioma. Again, no rate-limiting toxicity was
encountered in nine patients, and viral replication was demonstrated in tumor explants with
the amount of recovered virus exceeding the input dose in some patients, thus further
providing proof of principle [107]. A phase II clinical trial of this mutant HSV delivered
intratumorally showed response in two of 12 patients, with three patients alive at latest
follow-up of 15 to 22 months. Viral recovery from serum and by tumor cytology was
observed in four patients [93]. Both G207 and 1716 are undergoing further clinical testing.
Adenovirus strategies
Adenoviruses are non-enveloped DNA viruses capable of infecting dividing and non-
dividing cells. They have minimal pathogenic potential and integrate into chromosomal
DNA in a defined region without insertional mutagenic effect. Bischoff et al. developed a
conditionally replicative adenovirus, ONYX-015, that has been extensively studied and
reviewed [8, 105, 133]. ONYX-015 has a deletion in the viral protein E1B-55K that
normally binds to and inactivates host cell p53 protein. It is, therefore, thought that cells
with functional p53 are unable to support viral replication without the presence of this
protein, whereas tumor cells with non-functional p53 are able to support viral replication.
Preclinical studies in human malignant glioma xenografts demonstrated cell lysis and
impaired tumor growth in response to ONYX-015, but the response was independent of p53
status [34]. Although the exact mechanism is not completely understood and may be
unrelated to p53, ONYX-015 is only the third oncolytic virus to be tested in human clinical
trials for malignant glioma (in addition to G207 and 1716). An initial phase I clinical trial of
intratumoral delivery showed none of 24 glioma patients to exhibit a significant response
with 96% experiencing disease progression. This was a dose-escalation study in which none
of the patients demonstrated any serious adverse events, and the maximum tolerated dose
was not reached [16]. Three of 12 patients that received the highest doses of virus remained
alive at the end of the study with more than 19 months of follow-up.
A similar strategy was employed in the creation of Delta 24, an adenovirus mutant with a
deletion in the E1A gene important in the retinoblastoma (Rb) tumor-suppressor pathway
[32]. Normal cells with functional Rb are unable to support viral replication without the
presence of a functional E1A protein to neutralize it, whereas tumor cells with abnormal Rb
and deregulated check point function are able to support viral replication. A further mutation
that allows adenovirus infection independent of the coxsackie adenovirus receptor (CAR)
drastically improves its effect on tumor cells with low levels of CAR expression. Preclinical
studies have demonstrated replication and cytotoxicity of the virus in glioma cell lines and
improved survival and tumor regression in animals with glioma xenografts [31, 72].
Poliovirus strategies
Poliovirus is a non-enveloped ribonucleic acid (RNA) virus with natural neurotropism. The
cellular receptor responsible for viral entry, CD155, is ectopically upregulated in malignant
Selznick et al.
Page 6
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
glioma [43, 82, 122], and the virulence of poliovirus can be manipulated in a cell-type
specific manner at the level of translation control [41, 42]. Viral protein translation is
mediated by the internal ribosome entry site (IRES) element within the 5′ non-translated
region of the viral genome. IRES function is subject to cell-specific constraints that can be
exploited to drive poliovirus gene expression and cytotoxicity preferentially in malignant
cells [83, 124]. These findings led to the development of a recombinant poliovirus for the
treatment of malignant gliomas. By exchanging the IRES element of poliovirus with that of
human rhinovirus type 2 (HRV2), Gromeier et al. created a recombinant virus (PV-RIPO)
with greatly diminished viral propagation in normal neuronal cells while retaining excellent
lytic growth in malignant glioma cells [43].
Preclinical studies of PV-RIPO provide the proof of principle data for a planned phase I
clinical trial. PV-RIPO significantly attenuated growth in neuronal cells in vitro and failed to
cause poliomyelitis both in mice transgenic for the CD155 receptor [82] and in
Cynomolgus
monkeys [43] when delivered directly into the spinal cord. Conversely, eight different
glioma cell lines tested in vitro were highly susceptible to PV-RIPO infection, and
intratumoral injection into HTB-14 astrocytic intracerebral tumors resulted in complete
regression in 18 of 25 mice [43]. Plans are underway for a phase I clinical trial of PV-RIPO
for recurrent malignant glioma.
An alternative strategy utilizes poliovirus replicons in which the gene encoding the capsid
protein has been deleted. Because new infectious particles cannot be generated, growth is
limited to a single lytic cycle. Replicons are otherwise competent in all other functions of
the poliovirus derivative and have demonstrated oncolytic activity in malignant glioma cells
in vitro and in vivo [3]. Poliovirus replicons are non-pathogenic in mice transgenic for
CD155 and non-human primates, and intratumoral injection extended survival in mice
implanted with intracerebral D54 glioma xenografts [9, 41].
Immunotherapy
Background
Tumor cells are notorious for their ability to evade detection by the normal surveillance
function of the immune system. Brain tumors have the additional advantage of being located
within the immune privileged central nervous system, aiding in their ability to remain
undetected. Immunotherapy entails the manipulation or enhancement of the immune system
machinery to attack and kill tumor cells. One system of dividing these strategies could be as
follows: (1) establishment of a systemic cellular antitumor immune response via anti-tumor
immunization or adoptive T-cell transfer strategies (vaccination), (2) local cytokine-focused
approaches to bolster nascent immune responses, or (3) passive immune-based targeting of
radiation, chemotherapy, or toxins by conjugation to monoclonal antibodies directed against
tumor cells.
Systemic vaccine immunotherapy
The mammalian brain may be an immunologically privileged organ, but by no means is it
completely isolated from the systemic immune system. Medawar was the first to
demonstrate that skin homografts may survive when transplanted to the brain, but these
same grafts break down if the host animal has previously received a cutaneous
transplantation [81]. This and other evidence [14, 91, 125] suggest that T cells activated in
the periphery are able to cross the blood brain barrier and function within the central nervous
system. Therefore, vaccination with killed tumor cells, peptides, or antigen presenting cells
loaded with tumor peptides may induce a systemic T-cell response that will likewise cross
the blood brain barrier and destroy malignant gliomas. Alternatively, T cells from patients
Selznick et al.
Page 7
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
can be selected for anti-tumor reactivity, directly expanded ex vivo, and transferred
adoptively back to patients to effect a similar manner of anti-tumor immunity.
The most promising and well-studied anti-tumor vaccination strategies employ professional
antigen presenting cells known as dendritic cells (DCs) that can be primed with tumor
antigen ex vivo. DCs ingest the exogenous tumor antigens and present them on MHC I and
MHC II molecules, hence priming naïve CD8+ cytotoxic T lymphocytes (CTL), as well as
helper CD4+ T cells, to elicit targeted tumor cell destruction. Various strategies exist for
loading DCs with glioma cell antigens including fusion with MHC-matched glioma cells or
pulsing with apoptotic tumor cells, total tumor RNA, tumor lysate, or tumor-specific
peptides [94]. Numerous preclinical studies demonstrate that DCs pulsed with glioma
antigens can prime a CTL response that is tumor specific and that provides protective
immunity in treated animals [51, 76, 90].
Phase I and II clinical trials have been completed using DC cells pulsed with glioma cell
lysates. In a phase I trial, Yu et al. [140] demonstrated a robust systemic cytotoxic response
in six of ten patients and a significant CD8+ T cell infiltrate within the tumors of three out of
six patients that underwent re-operation. The median survival was 133 weeks, and there
were no significant adverse events or evidence of autoimmune disease. In a phase I/II study,
Yamanaka et al. [139] evaluated 24 patients with recurrent malignant glioma resistant to
standard maximum therapy. Vaccination with DCs pulsed with tumor lysate was again well
tolerated, and overall survival (median 480 days) was significantly better than the control
group; at the end of the study period, only ten of the 24 patients had progressive disease.
Of note, strategies that involve loading DCs with total tumor cell lysates generate risk for
producing immune responses against not only antigens present specifically in the tumor cells
but also those that are merely overexpressed in tumors or are normal brain antigens
altogether. An approach that targets tumor-specific antigens, i.e., present
only
in tumor cells,
may enhance specificity and minimize the risk of autoimmunity that can result from cross-
presentation of normal brain antigens. One of the only truly tumor-specific antigens known
to date for malignant gliomas is EGFRvIII. Heimberger et al. [50] have generated a vaccine
consisting of a peptide encompassing the mutated segment of EGFRvIII (Pep-3) and
demonstrated in vitro and in vivo a cytotoxic response against gliomas in preclinical studies.
This vaccine impaired intracerebral tumor growth, prolonged survival of mice with
intracerebral gliomas, and conferred passive immunity when serum was transferred to non-
immunized mice [90]. Preliminary results from a recent phase II clinical trial include
significant prolongation of median time to disease progression to 12 months in treated
patients from 7.1 months in a historically matched control cohort [50].
Another approach gaining support is adoptive immunotherapy, a strategy that often entails
the harvesting, ex vivo expansion, and IL-2-stimulation of tumor-infiltrating lymphocytes
(TILs) followed by reimplantation. TILs may be relatively tumor specific (having already
demonstrated a predilection to arrive at the tumor site), and it was thought that harvesting
lymphocytes from a peritumoral location might provide a higher degree of tumor specificity
[25, 121]. Recent studies by Rosenberg and colleagues have highlighted the benefit of
adoptive immunotherapy using TILs conducted in the setting of treatment-induced
lymphopenia as a potent modality for skewing the recovering immune system toward anti-
tumor recognition and mediating regression of metastatic disease [24]. It is interesting to
note that transfer of TILs proved effective in mediating regression of malignant disease in
these studies, while similar attempts using tumor-specific clones expanded simply from
peripheral blood lymphocytes (PBLs) failed to do so [24, 26]. It is unknown, at this point,
whether intrinsic differences between TILs and PBLs or differences in the methods used in
the generation/expansion of these cells account for the marked difference in the efficacy
Selznick et al.
Page 8
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
observed in these trials. Currently, few studies have examined whether TILs in fact possess
any intrinsic advantages over T cells expanded from PBLs, a much more readily available
source of lymphocytes [121].
The recent discovery that human cytomegalovirus (HCMV) propagates within a high
proportion of malignant gliomas without infecting surrounding normal brain [18] provides
an unparalleled opportunity to subvert the highly immunogenic viral antigens expressed by
HCMV as tumor-specific targets. HCMV is a β-herpes virus endemic in the human
population and does not usually cause clinical disease except in immunocompromised hosts
[85, 120]. Recently, HCMV antigen expression and detection of intact virus has been
reported to occur within a large proportion of malignant tumors, including colorectal
carcinoma, prostate cancer, skin cancer, and malignant astrocytomas [18, 47, 115, 141]. It is
not known at this time whether HCMV plays a role in the pathogenesis of malignant brain
tumors and other cancers or whether tumor growth simply provides an environment
supportive of local reactivation and propagation of the virus. Recently, the EGFR was
identified as a cellular binding and incorporation site for the entry of HCMV into cells
[135]. This finding may help explain preferential replication of the virus within malignant
gliomas, as these tumors almost uniformly demonstrate amplified EGFR expression, while
normal brain is largely negative [31, 55, 89]. The presence of HCMV within malignant
astrocytomas affords a unique immunologic target for either DC vaccines or adoptive
immunotherapy directed against brain tumors.
Local cytokine immunotherapy
Cytokines are small proteins that are secreted and act in a local fashion to modulate an
immune response. A great number of cytokines exist that either stimulate or inhibit anti-
tumor immunity, and, therefore, they have been studied extensively as local therapeutic
targets for malignant glioma. Attempts to potentiate a local immune response may involve
the delivery of cytokines that stimulate antitumor immunity or, conversely, the impairment
of cytokines that inhibit an immune-mediated response.
Many cytokines are considerably toxic when administered systemically, prompting the
development of novel local delivery methods. IL-2, which is normally secreted by T helper
1 cells, stimulates growth and proliferation of activated T and B cells and natural killer (NK)
cells. H2K fibroblast producer cells engineered to secrete IL-2 inhibit glioma growth in vivo
after intratumoral delivery [37, 77]. Likewise, local delivery of IL-2 via biopolymers
resulted in secretion of IL-2 up to 21 days after injection and conferred protection against
brain tumors with evidence of immunologic memory upon subsequent tumor challenge [46].
Another strategy entails the harvesting, ex vivo expansion, and IL-2 stimulation of TILs
followed by reimplantation. TILs may be relatively tumor specific, and it was thought that
harvesting lymphocytes from a peritumoral location might provide a higher degree of
specificity. However, initial enthusiasm for this technique has been tempered by the fact that
TILs have not been effective in animal models and recent studies that demonstrate TILs may
have impaired function and proliferative capacity [101, 102].
Tumor growth factor-β (TGF-β) is secreted by a number of tumors, including malignant
gliomas, and functions to suppress cell-mediated antitumor immunity. TGF-β has been
shown to inhibit TIL proliferation by 70–85% and cytotoxicity by 60–100% in vitro [71].
The desired goal of blocking the effects of TGF-β has been explored using antisense
oligonucleotide therapy. In vitro studies demonstrate that antisense oligonucleotide directed
against TGF-β can augment cytotoxicity and lymphocyte proliferation in a dose-dependent
manner [57, 58]. Enhanced anti-tumor immunity was confirmed in vivo with enhanced
survival in a rat 9L intracranial gliosarcoma model [28]. More recently, inhibition of TGF-β
Selznick et al.
Page 9
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
synthesis by small interfering RNA technology has been shown to enhance the antitumor
response of CD8+ T cells and NK cells, promoting immune cell lysis of glioma cells and
impairing glioma invasiveness and tumorigenicity in vivo [30].
Passive antibody targeted radiation, chemotherapy, and toxins
Antibody-mediated drug delivery is predicated on specific recognition of tumor-associated
antigens to target a therapeutic effect to a designated site. This has dual purposes—to
increase the local drug concentration while minimizing non-specific systemic exposure. In
addition, the targeting antibody, a large biomacromolecule, often alters pharmacokinetics
and solubility of the delivered agent by dramatically increasing size and molecular weight,
usually prolonging residence time in the body.
The targeting is often by specific tumor antigens that are overexpressed in tumors but not in
normal tissue. Examples of such antigens in glioma include a mutant EGFR, tenascin, and
IL4 receptor [27]. Indeed, monoclonal antibodies with specificity for mutant EGFR
(EGFRvIII) recognize tumors overexpressing this receptor but neither normal surrounding
tissue, nor tumors expressing normal levels of wild-type EGFR [60].
Examples of conjugated modalities range from chemotherapy, to radiation, to toxins. An
immunoconjugate of aurostatin E with a monoclonal antibody against mutant EGFRvIII
exhibits potent in vivo dose-dependent cytostatic or tumoricidal activity in xenograft models
of human glioma in nude mice [61]. This sets the stage for targeted delivery of cytotoxic
agents in human clinical trials. Anti-tenascin and anti-EGFR antibodies have been shown to
be effective carriers for iodine radiolabels to provide specific, local radiotherapy to a
targeted glioma. A phase II clinical trial with
131
I-labeled anti-tenascin has suggested a
survival benefit in patients treated with radioantibody delivered into the post-surgical cavity
when compared with Karnovsky-matched literature controls [21, 109]. Another successful
technique for pretargeting radioisotope delivery for high-grade glioma in phase II clinical
trials exploits the concept of “affinity enhancement” by starting with intravenous delivery of
biotinylated anti-tenascin antibody followed by secondary delivery avidin/streptavidin and
completed with tertiary delivery of
90
Y-DOTA-biotin to yield 52% disease stabilization
among 48 patients [92]. Indeed, as a post-surgical adjuvant, the reported median disease
survival was 28 months in glioblastoma patients and 56 months in grade III glioma patients,
significantly longer than patients not receiving such intervention [40].
Immunotoxins are antibody conjugates of potent protein toxins that can be prepared by
chemical conjugation or recombinant DNA technology with fusion protein expression. Most
current immunotoxins are derived from plant, fungal, and bacterial toxins; and while they
are structurally heterogeneous, they typically share function of protein synthesis inhibition
[113].
Pseudomonas
exotoxin A conjugated to an anti-EGFR antibody has been shown to be
a high affinity, cytotoxic immunotoxin in vitro, although clinical studies addressing glioma
are awaited [78]. Toxin targeting using fusion protein cytotoxins have been used to
recombinantly express cytokine ligand domains fused to protein toxins. IL-4 and IL-13
fusions with
Pseudomonas
exotoxin have demonstrated potent cytotoxicity against human
tumor cell lines in vitro and animal models of glioma in vivo while sparing normal
surrounding immune, endothelial, and brain tissue. The evidence supporting both IL-4-PE
and IL-13-PE have been reviewed by Shimamura et al. [118]. The early clinical trial data
have demonstrated safety of these drugs administered by convection-enhanced delivery [69,
70, 104, 137]. A multicenter phase III clinical trial (PRECISE trial) of IL-13-PE for
recurrent glioblastoma is ongoing, with preliminary results of 36.4 weeks median survival
comparable to 35.3 weeks for Gliadel wafers.
Selznick et al.
Page 10
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
The power of antibody-mediated drug delivery techniques lies in the bivalent functionality
of the conjugated molecule—recognition specificity by the antibody domain and anti-tumor
activity by the molecular therapeutic domain. A significant drawback of this technique by
systemic administration is the high solid tumor interstitial pressure that is thought to limit
biomacromolecule penetration depth [59]. As such, it is more likely that immunotherapy
techniques would be valuable as a post-surgical adjuvant where administration could be
done either directly into the tumor cavity or systemically after debulking the tumor
significantly lowers intratumoral pressure.
Multimodal molecular therapy
Introduction
Multimodal treatment for gliomas is a more realistic goal than searching for a magic bullet
to control or eradicate these highly malignant tumors. The toxicity of high dose anti-tumor
strategies such as radiation and chemotherapy mandates that potentially suboptimal doses be
applied to minimize damage to susceptible surrounding normal nervous tissue and unrelated
body systems. A multi-faceted approach on the tumor in the face of complete repair
mechanisms of normal tissue potentially combines the additive and/or synergistic effects of
different modalities with different mechanisms of action. On a molecular scale, gene
therapy, oncolytic viruses, and immunotherapy can be combined as a single agent or in
tandem to offset the limitations of any one approach. On a larger scale, multiple modalities
can be combined to broaden the therapeutic effectiveness on an aggressive and
heterogeneous tumor cell population.
Immunogene therapy
Immunogene therapy involves the genetic manipulation of human cells to stimulate a
tumoricidal immune response. Gene transfer can be accomplished by viral, nonviral, or
antisense oligonucleotide strategies. Therapeutic approaches can range from the transfer of
pro-inflammatory genes, inhibition of anti-inflammatory mediator expression, or the transfer
of tumor antigen genes to maximize antigen presentation. Human gliomas are reported to be
immunosuppressed with low levels of B7-2, GM-CSF, IL-10, and IL-12 expression [96]. In
vitro studies with human glioma cells show successful gene transfer of each of these
immunostimulatory proteins, with expression that is unaffected by 200-Gy irradiation [97,
98]. A recent pilot clinical trial to evaluate safety of the immunogene approach was
attempted in six glioma patients receiving combined B7-2/GM-CSF immunogene therapy to
potentiate T-lymphocyte costimulation [95]. Most patients showed evidence of an
inflammatory response with three patients reported to have prolonged disease-free intervals
after vaccination. The study was too limited to draw conclusions about the generation of
specific anti-tumor immunity.
Oncolytic gene therapy
Oncolytic viruses can also serve as effective agents in combination therapy with gene
transfection to sensitize tumors. An engineered HSV mutant, rRp450, selectively targets
neoplastic cells in which it replicates and ultimately leads to oncolysis. In infected cells, it
also expresses two transgenes (cyclophosphamide-sensitive cytochrome p450 and
ganciclovir-sensitive thymidine kinase) that chemosensitizes the neoplastic cells, resulting in
synergistic effect upon treatment of human U87ΔEGFR glioma cells with
cyclophosphamide and ganciclovir [2]. More recently, another mutant containing the same
cytochrome p450 transgene in addition to secreted human intestinal carboxylesterase
transgene also increases anti-tumor efficacy against human glioma cells in vitro and in in
vivo animal models [131].
Selznick et al.
Page 11
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
Synergistic combination strategies
A rational combination of therapeutic strategies with different modes of action has the
potential to deliver synergistic benefit by using one agent to sensitize treatment by the other.
This has already been demonstrated with most of the therapeutic agents that compromise
standard multimodal therapy today. The concomitant use of radiotherapy with the alkylating
agent temozolomide has modestly extended median survival in both postoperative [132] and
non-operative [6, 126] patients when compared with radiotherapy alone, with the greatest
effect being observed among patients who had undergone complete gross resection.
The HSV mutant G207 is currently being evaluated for benefit upon combination with
radiation therapy in the management of recurrent or progressive malignant glioma.
Oncolytic adenoviruses have also been examined in the context of combination cancer
therapy. ONYX-015 exhibits enhanced, non-synergistic effect upon combination with
radiation therapy in in vivo xenograft models of malignant glioma [33]. Intra-arterial
administration of ONYX-015 in combination with 5 Gy irradiation provided for tumor
growth delays in p53 mutants. Another adenoviral vector, Ad5-Delta24, upregulates
expression of topoisomerase I, thus potentiating a synergistic oncolytic effect upon
treatment with irinotecan in vitro and in in vivo models of intracranial mouse glioma [38].
These combination regimens are rationally designed either combining therapeutics with
discrete mechanisms of action or those that by their mechanism of action would potentiate
the activity of the therapeutic partner. The clinical safety and efficacy of these combinations
have yet to be explored.
Another interesting example is combining molecular therapy against EGFR overexpression
with radiotherapy. The former therapy is typically associated with resistance to radiotherapy
[15], and the combination of monoclonal anti-EGFR antibodies with radiotherapy has
enhanced tumor control and survival in other head and neck cancers [7]. A phase I/II clinical
trial of erlotinib and radiation therapy for newly diagnosed young glioma patients is
currently ongoing to examine whether this benefit is manifest for intrinsic brain tumors.
Other molecular therapy combinations that include anti-angiogenic molecules such as
endostatin, anti-receptor antibodies for EGFR, VEGFR, and PDGFR, and inhibitors of
downstream signaling such as mTOR inhibitors have provided encouraging results in mouse
[39] and xenograft [1] models of glioma. A study of 28 patients with recurrent malignant
glioma administered an EGFR inhibitor, and an mTOR inhibitor demonstrated tolerance of
the regimen; 19% of patients having partial response and 50% having stable disease [23].
Six-month progression-free survival was 25% in the glioblastoma subgroup of 22 patients in
this study. This particular regimen is reported to be more effective in isogenic models of
glioblastoma that are PTEN deficient [134].
Conclusion
There is no magic bullet for malignant gliomas in the foreseeable future, and clinical
improvements will likely be because of the synergistic effects of a multi-pronged attack.
Although preclinical data are intuitively promising, clinical trials have been hampered by
ethical concerns, and all of the molecular strategies have yet to demonstrate a significant
survival benefit in a phase II or III clinical trial (Table 1). The strategies described herein
each have their own distinct advantages and limitations inherent to the technology
employed. Despite relatively rapid advancement in our scientific understanding and
technological capability, all of the major molecular approaches currently being investigated
have significant deficiencies in one or more of the following categories:
1.
Delivery—the ability to reach the tumor efficiently and spread throughout the
entire population of malignant cells
Selznick et al.
Page 12
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
2.
Effectiveness—the ability to control or eradicate malignant cells; to halt growth or
induce regression of malignant gliomas
3.
Adverse events (safety)—the ability to target tumor cells without significant
toxicity to the surrounding normal brain
4.
Durability—the ability to maintain control or eradication over time
A single therapeutic strategy that is not limited by at least one of these factors is yet to be
designed. However, as our understanding of molecular biology improves and technological
advances are made, this may become a tenable goal.
References
1. Abdollahi A, Lipson KE, Sckell A, Zieher H, Klenke F, Poerschke D, Roth A, Han X, Krix M,
Bischof M, Hahnfeldt P, Grone HJ, Debus J, Hlatky L, Huber PE. Combined therapy with direct
and indirect angiogenesis inhibition results in enhanced antiangiogenic and antitumor effects.
Cancer Res. 2003; 63:8890–8898. [PubMed: 14695206]
2. Aghi M, Chou TC, Suling K, Breakefield XO, Chiocca EA. Multimodal cancer treatment mediated
by a replicating oncolytic virus that delivers the oxazaphosphorine/rat cytochrome P450 2B1 and
ganciclovir/herpes simplex virus thymidine kinase gene therapies. Cancer Res. 1999; 59:3861–
3865. [PubMed: 10463570]
3. Ansardi DC, Porter DC, Jackson CA, Gillespie GY, Morrow CD. RNA replicons derived from
poliovirus are directly oncolytic for human tumor cells of diverse origins. Cancer Res. 2001;
61:8470–8479. [PubMed: 11731430]
4. Arafat WO, Buchsbaum DJ, Gomez-Navarro J, Tawil SA, Olsen C, Xiang J, El-Akad H, Salama
AM, Badib AO, Stackhouse MA, Curiel DT. An adenovirus encoding proapoptotic Bax
synergistically radiosensitizes malignant glioma. Int J Radiat Oncol Biol Phys. 2003; 55:1037–
1050. [PubMed: 12605984]
5. Asaoka K, Tada M, Sawamura Y, Ikeda J, Abe H. Dependence of efficient adenoviral gene delivery
in malignant glioma cells on the expression levels of the coxsackievirus and adenovirus receptor. J
Neurosurg. 2000; 92:1002–1008. [PubMed: 10839262]
6. Athanassiou H, Synodinou M, Maragoudakis E, Paraskevaidis M, Verigos C, Misailidou D,
Antonadou D, Saris G, Beroukas K, Karageorgis P. Randomized phase II study of temozolomide
and radiotherapy compared with radiotherapy alone in newly diagnosed glioblastoma multiforme. J
Clin Oncol. 2005; 23:2372–2377. [PubMed: 15800329]
7. Baumann M, Krause M. Targeting the epidermal growth factor receptor in radiotherapy:
radiobiological mechanisms, preclinical and clinical results. Radiother Oncol. 2004; 72:257–266.
[PubMed: 15450723]
8. Bischoff JR, Kirn DH, Williams A, Heise C, Horn S, Muna M, Ng L, Nye JA, Sampson-Johannes
A, Fattaey A, McCormick F. An adenovirus mutant that replicates selectively in p53-deficient
human tumor cells. Science. 1996; 274:373–376. [PubMed: 8832876]
9. Bledsoe AW, Gillespie GY, Morrow CD. Targeted foreign gene expression in spinal cord neurons
using poliovirus replicons. J Neurovirol. 2000; 6:95–105. [PubMed: 10822323]
10. Bogler O, Huang HJ, Kleihues P, Cavenee WK. The p53 gene and its role in human brain tumors.
Glia. 1995; 15:308–327. [PubMed: 8586466]
11. Brady LW. A new treatment for high grade gliomas of the brain. Bulletin et memoires de
l’Academie royale de medecine de Belgique. 1998; 153:255–261. discussion 261-252. [PubMed:
9988932]
12. Brewer CJ, Suh JH, Stevens GHJ, Barnett GH, Toms S, Vogelbaum MA, Weil R, Peereboom DM.
Phase II trial of erlotinib with temozolomide and concurrent radiation therapy in patients with
newly-diagnosed glioblastoma multiforme. J Clin Oncol. 2005; 23:1567.
13. Brown PD, Maurer MJ, Rummans TA, Pollock BE, Ballman KV, Sloan JA, Boeve BF, Arusell
RM, Clark MM, Buckner JC. A prospective study of quality of life in adults with newly diagnosed
high-grade gliomas: the impact of the extent of resection on quality of life and survival.
Neurosurgery. 2005; 57:495–504. discussion 495–504. [PubMed: 16145528]
Selznick et al.
Page 13
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
14. Bullard DE, Gillespie GY, Mahaley MS, Bigner DD. Immunobiology of human gliomas. Semin
Oncol. 1986; 13:94–109. [PubMed: 2420011]
15. Chakravarti A, Dicker A, Mehta M. The contribution of epidermal growth factor receptor (EGFR)
signaling pathway to radioresistance in human gliomas: a review of preclinical and correlative
clinical data. Int J Radiat Oncol Biol Phys. 2004; 58:927–931. [PubMed: 14967452]
16. Chiocca EA, Abbed KM, Tatter S, Louis DN, Hochberg FH, Barker F, Kracher J, Grossman SA,
Fisher JD, Carson K, Rosenblum M, Mikkelsen T, Olson J, Markert J, Rosenfeld S, Nabors LB,
Brem S, Phuphanich S, Freeman S, Kaplan R, Zwiebel J. A phase I open-label, dose-escalation,
multi-institutional trial of injection with an E1B-Attenuated adenovirus, ONYX-015, into the
peritumoral region of recurrent malignant gliomas, in the adjuvant setting. Mol Ther. 2004;
10:958–966. [PubMed: 15509513]
17. Cirielli C, Inyaku K, Capogrossi MC, Yuan X, Williams JA. Adenovirus-mediated wild-type p53
expression induces apoptosis and suppresses tumorigenesis of experimental intracranial human
malignant glioma. J Neurooncol. 1999; 43:99–108. [PubMed: 10533721]
18. Cobbs CS, Harkins L, Samanta M, Gillespie GY, Bharara S, King PH, Nabors LB, Cobbs CG,
Britt WJ. Human cytomegalovirus infection and expression in human malignant glioma. Cancer
Res. 2002; 62:3347–3350. [PubMed: 12067971]
19. Colombo F, Barzon L, Franchin E, Pacenti M, Pinna V, Danieli D, Zanusso M, Palu G. Combined
HSV-TK/IL-2 gene therapy in patients with recurrent glioblastoma multiforme: biological and
clinical results. Cancer Gene Ther. 2005; 12:835–848. [PubMed: 15891772]
20. Culver KW, Ram Z, Wallbridge S, Ishii H, Oldfield EH, Blaese RM. In vivo gene transfer with
retroviral vector-producer cells for treatment of experimental brain tumors. Science. 1992;
256:1550–1552. [PubMed: 1317968]
21. Curran WJ Jr, Scott CB, Horton J, Nelson JS, Weinstein AS, Fischbach AJ, Chang CH, Rotman M,
Asbell SO, Krisch RE, et al. Recursive partitioning analysis of prognostic factors in three
Radiation Therapy Oncology Group malignant glioma trials. J Natl Cancer Inst. 1993; 85:704–
710. [PubMed: 8478956]
22. De Pace N. Sulla scomparsa di un enorme cancro vegetante del collo dell’utero senza cura
chirugica. Ginecologia. 1912; 9:82–88.
23. Doherty L, Cigas DSK, Drappatz J, Kim R, Zimmerman J, Ostrowsky L, Wen P. Pilot study of the
combination of EGFR and mTOR inhibitors in recurrent malignant gliomas. Neurology. 2006;
67:156–158. [PubMed: 16832099]
24. Dudley ME, Wunderlich JR, Robbins PF, Yang JC, Hwu P, Schwartzentruber DJ, Topalian SL,
Sherry R, Restifo NP, Hubicki AM, Robinson MR, Raffeld M, Duray P, Seipp CA, Rogers-
Freezer L, Morton KE, Mavroukakis SA, White DE, Rosenberg SA. Cancer regression and
autoimmunity in patients after clonal repopulation with antitumor lymphocytes. Science. 2002;
298:850–854. [PubMed: 12242449]
25. Dudley ME, Wunderlich JR, Shelton TE, Even J, Rosenberg SA. Generation of tumor-infiltrating
lymphocyte cultures for use in adoptive transfer therapy for melanoma patients. J Immunother.
2003; 26:332–342. [PubMed: 12843795]
26. Dudley ME, Wunderlich JR, Yang JC, Hwu P, Schwartzentruber DJ, Topalian SL, Sherry RM,
Marincola FM, Leitman SF, Seipp CA, Rogers-Freezer L, Morton KE, Nahvi A, Mavroukakis SA,
White DE, Rosenberg SA. A phase I study of non-myeloablative chemotherapy and adoptive
transfer of autologous tumor antigen-specific T lymphocytes in patients with metastatic melanoma.
J Immunother. 2002; 25:243–251. [PubMed: 12000866]
27. Dunn IF, Black PM. The neurosurgeon as local oncologist: cellular and molecular neurosurgery in
malignant glioma therapy. Neurosurgery. 2003; 52:1411–1422. discussion 1422-1414. [PubMed:
12762886]
28. Fakhrai H, Dorigo O, Shawler DL, Lin H, Mercola D, Black KL, Royston I, Sobol RE. Eradication
of established intracranial rat gliomas by transforming growth factor beta antisense gene therapy.
Proc Natl Acad Sci U S A. 1996; 93:2909–2914. [PubMed: 8610141]
29. Fecci PE, Gromeier M, Sampson JH. Viruses in the treatment of brain tumors. Neuroimaging Clin
N Am. 2002; 12:553–570. [PubMed: 12687911]
Selznick et al.
Page 14
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
30. Friese MA, Wischhusen J, Wick W, Weiler M, Eisele G, Steinle A, Weller M. RNA interference
targeting transforming growth factor-beta enhances NKG2D-mediated antiglioma immune
response, inhibits glioma cell migration and invasiveness, and abrogates tumorigenicity in vivo.
Cancer Res. 2004; 64:7596–7603. [PubMed: 15492287]
31. Fueyo J, Alemany R, Gomez-Manzano C, Fuller GN, Khan A, Conrad CA, Liu TJ, Jiang H,
Lemoine MG, Suzuki K, Sawaya R, Curiel DT, Yung WK, Lang FF. Preclinical characterization
of the antiglioma activity of a tropism-enhanced adenovirus targeted to the retinoblastoma
pathway. J Natl Cancer Inst. 2003; 95:652–660. [PubMed: 12734316]
32. Fueyo J, Gomez-Manzano C, Alemany R, Lee PS, McDonnell TJ, Mitlianga P, Shi YX, Levin VA,
Yung WK, Kyritsis AP. A mutant oncolytic adenovirus targeting the Rb pathway produces anti-
glioma effect in vivo. Oncogene. 2000; 19:2–12. [PubMed: 10644974]
33. Geoerger B, Grill J, Opolon P, Morizet J, Aubert G, Lecluse Y, van Beusechem VW, Gerritsen
WR, Kirn DH, Vassal G. Potentiation of radiation therapy by the oncolytic adenovirus dl1520
(ONYX-015) in human malignant glioma xenografts. Br J Cancer. 2003; 89:577–584. [PubMed:
12888833]
34. Geoerger B, Grill J, Opolon P, Morizet J, Aubert G, Terrier-Lacombe MJ, Bressac De-Paillerets B,
Barrois M, Feunteun J, Kirn DH, Vassal G. Oncolytic activity of the E1B-55 kDa-deleted
adenovirus ONYX-015 is independent of cellular p53 status in human malignant glioma
xenografts. Cancer Res. 2002; 62:764–772. [PubMed: 11830531]
35. Germano IM, Fable J, Gultekin SH, Silvers A. Adenovirus/ herpes simplex-thymidine kinase/
ganciclovir complex: preliminary results of a phase I trial in patients with recurrent malignant
gliomas. J Neurooncol. 2003; 65:279–289. [PubMed: 14682378]
36. Gilbert MR. New treatments for malignant gliomas: careful evaluation and cautious optimism
required. Ann Intern Med. 2006; 144:371–373. [PubMed: 16520480]
37. Glick RP, Lichtor T, de Zoeten E, Deshmukh P, Cohen EP. Prolongation of survival of mice with
glioma treated with semiallogeneic fibroblasts secreting interleukin-2. Neurosurgery. 1999;
45:867–874. [PubMed: 10515482]
38. Gomez-Manzano C, Alonso MM, Yung WK, McCormick F, Curiel DT, Lang FF, Jiang H, Bekele
BN, Zhou X, Alemany R, Fueyo J. Delta-24 increases the expression and activity of topoisomerase
I and enhances the antiglioma effect of irinotecan. Clin Cancer Res. 2006; 12:556–562. [PubMed:
16428500]
39. Goudar RK, Shi Q, Hjelmeland MD, Keir ST, McLendon RE, Wikstrand CJ, Reese ED, Conrad
CA, Traxler P, Lane HA, Reardon DA, Cavenee WK, Wang XF, Bigner DD, Friedman HS, Rich
JN. Combination therapy of inhibitors of epidermal growth factor receptor/vascular endothelial
growth factor receptor 2 (AEE788) and the mammalian target of rapamycin (RAD001) offers
improved glioblastoma tumor growth inhibition. Mol Cancer Ther. 2005; 4:101–112. [PubMed:
15657358]
40. Grana C, Chinol M, Robertson C, Mazzetta C, Bartolomei M, De Cicco C, Fiorenza M, Gatti M,
Caliceti P, Paganelli G. Pretargeted adjuvant radioimmunotherapy with yttrium-90-biotin in
malignant glioma patients: a pilot study. Br J Cancer. 2002; 86:207–212. [PubMed: 11870507]
41. Gromeier M, Alexander L, Wimmer E. Internal ribosomal entry site substitution eliminates
neurovirulence in intergeneric poliovirus recombinants. Proc Natl Acad Sci U S A. 1996;
93:2370–2375. [PubMed: 8637880]
42. Gromeier M, Bossert B, Arita M, Nomoto A, Wimmer E. Dual stem loops within the poliovirus
internal ribosomal entry site control neurovirulence. J Virol. 1999; 73:958–964. [PubMed:
9882296]
43. Gromeier M, Lachmann S, Rosenfeld MR, Gutin PH, Wimmer E. Intergeneric poliovirus
recombinants for the treatment of malignant glioma. Proc Natl Acad Sci U S A. 2000; 97:6803–
6808. [PubMed: 10841575]
44. Gupta V, Wang W, Sosnowski BA, Hofman FM, Chen TC. Fibroblast growth factor-2-retargeted
adenoviral vector for selective transduction of primary glioblastoma multiforme endothelial cells.
Neurosurg Focus. 2006; 20:E26. [PubMed: 16709032]
45. Hamel W, Westphal M. Gene therapy of gliomas. Acta Neurochir Suppl. 2003; 88:125–135.
[PubMed: 14531570]
Selznick et al.
Page 15
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
46. Hanes J, Sills A, Zhao Z, Suh KW, Tyler B, DiMeco F, Brat DJ, Choti MA, Leong KW, Pardoll
DM, Brem H. Controlled local delivery of interleukin-2 by biodegradable polymers protects
animals from experimental brain tumors and liver tumors. Pharm Res. 2001; 18:899–906.
[PubMed: 11496947]
47. Harkins L, Volk AL, Samanta M, Mikolaenko I, Britt WJ, Bland KI, Cobbs CS. Specific
localisation of human cytomegalovirus nucleic acids and proteins in human colorectal cancer.
Lancet. 2002; 360:1557–1563. [PubMed: 12443594]
48. Harrow S, Papanastassiou V, Harland J, Mabbs R, Petty R, Fraser M, Hadley D, Patterson J,
Brown SM, Rampling R. HSV1716 injection into the brain adjacent to tumour following surgical
resection of high-grade glioma: safety data and long-term survival. Gene Ther. 2004; 11:1648–
1658. [PubMed: 15334111]
49. Harsh GR, Deisboeck TS, Louis DN, Hilton J, Colvin M, Silver JS, Qureshi NH, Kracher J,
Finkelstein D, Chiocca EA, Hochberg FH. Thymidine kinase activation of ganciclovir in recurrent
malignant gliomas: a gene-marking and neuropathological study. J Neurosurg. 2000; 92:804–811.
[PubMed: 10794295]
50. Heimberger AB, Crotty LE, Archer GE, Hess KR, Wikstrand CJ, Friedman AH, Friedman HS,
Bigner DD, Sampson JH. Epidermal growth factor receptor VIII peptide vaccination is efficacious
against established intracerebral tumors. Clin Cancer Res. 2003; 9:4247–4254. [PubMed:
14519652]
51. Heimberger AB, Crotty LE, Archer GE, McLendon RE, Friedman A, Dranoff G, Bigner DD,
Sampson JH. Bone marrow-derived dendritic cells pulsed with tumor homogenate induce
immunity against syngeneic intracerebral glioma. J Neuroimmunol. 2000; 103:16–25. [PubMed:
10674985]
52. Heise CC, Williams A, Olesch J, Kirn DH. Efficacy of a replication-competent adenovirus
(ONYX-015) following intratumoral injection: intratumoral spread and distribution effects. Cancer
Gene Ther. 1999; 6:499–504. [PubMed: 10608346]
53. Hilton D, Melling C. Genetic markers in the assessment of intrinsic brain tumours. Curr Diagn
Pathol. 2004; 10:83–92.
54. Holladay FP, Heitz-Turner T, Bayer WL, Wood GW. Autologous tumor cell vaccination combined
with adoptive cellular immunotherapy in patients with grade III/IV astrocytoma. J Neurooncol.
1996; 27:179–189. [PubMed: 8699241]
55. Humphrey PA, Wong AJ, Vogelstein B, Friedman HS, Werner MH, Bigner DD, Bigner SH.
Amplification and expression of the epidermal growth factor receptor gene in human glioma
xenografts. Cancer Res. 1988; 48:2231–2238. [PubMed: 3258189]
56. Hunter WD, Martuza RL, Feigenbaum F, Todo T, Mineta T, Yazaki T, Toda M, Newsome JT,
Platenberg RC, Manz HJ, Rabkin SD. Attenuated, replication-competent herpes simplex virus type
1 mutant G207: safety evaluation of intracerebral injection in nonhuman primates. J Virol. 1999;
73:6319–6326. [PubMed: 10400723]
57. Jachimczak P, Bogdahn U, Schneider J, Behl C, Meixensberger J, Apfel R, Dorries R,
Schlingensiepen KH, Brysch W. The effect of transforming growth factor-beta 2-specific
phosphorothioate-anti-sense oligodeoxynucleotides in reversing cellular immunosuppression in
malignant glioma. J Neurosurg. 1993; 78:944–951. [PubMed: 8487077]
58. Jachimczak P, Hessdorfer B, Fabel-Schulte K, Wismeth C, Brysch W, Schlingensiepen KH, Bauer
A, Blesch A, Bogdahn U. Transforming growth factor-beta-mediated autocrine growth regulation
of gliomas as detected with phosphorothioate antisense oligonucleotides. Int J Cancer. 1996;
65:332–337. [PubMed: 8575854]
59. Jain RK, Baxter LT. Mechanisms of heterogeneous distribution of monoclonal antibodies and other
macromolecules in tumors: significance of elevated interstitial pressure. Cancer Res. 1988;
48:7022–7032. [PubMed: 3191477]
60. Johns TG, Stockert E, Ritter G, Jungbluth AA, Huang HJ, Cavenee WK, Smyth FE, Hall CM,
Watson N, Nice EC, Gullick WJ, Old LJ, Burgess AW, Scott AM. Novel monoclonal antibody
specific for the de2-7 epidermal growth factor receptor (EGFR) that also recognizes the EGFR
expressed in cells containing amplification of the EGFR gene. Int J Cancer. 2002; 98:398–408.
[PubMed: 11920591]
Selznick et al.
Page 16
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
61. Keyt B, Liu Y, Chen F, Gudas J, Handa M, Zhang R, Senter P, Yang X. Human antibody drug
conjugates specific to the mutant EGF receptor (EGFRvIII) inhibit tumor growth observed with in
vitro and in vivo models of glioma. Proc Am Assoc Cancer Res. 2004; 45:162.
62. Khazaie K, Schirrmacher V, Lichtner RB. EGF receptor in neoplasia and metastasis. Cancer
Metastasis Rev. 1993; 12:255–274. [PubMed: 8281612]
63. Kikuchi T, Akasaki Y, Abe T, Fukuda T, Saotome H, Ryan JL, Kufe DW, Ohno T. Vaccination of
glioma patients with fusions of dendritic and glioma cells and recombinant human interleukin 12. J
Immunother. 2004; 27:452–459. [PubMed: 15534489]
64. Klatzmann D, Valery CA, Bensimon G, Marro B, Boyer O, Mokhtari K, Diquet B, Salzmann JL,
Philippon J. A phase I/II study of herpes simplex virus type 1 thymidine kinase “suicide” gene
therapy for recurrent glioblastoma. Study Group on Gene Therapy for Glioblastoma. Hum Gene
Ther. 1998; 9:2595–2604. [PubMed: 9853526]
65. Kock H, Harris MP, Anderson SC, Machemer T, Hancock W, Sutjipto S, Wills KN, Gregory RJ,
Shepard HM, Westphal M, Maneval DC. Adenovirus-mediated p53 gene transfer suppresses
growth of human glioblastoma cells in vitro and in vivo. Int J Cancer. 1996; 67:808–815.
[PubMed: 8824552]
66. Komata T, Koga S, Hirohata S, Takakura M, Germano IM, Inoue M, Kyo S, Kondo S, Kondo Y. A
novel treatment of human malignant gliomas in vitro and in vivo: FADD gene transfer under the
control of the human telomerase reverse transcriptase gene promoter. Int J Oncol. 2001; 19:1015–
1020. [PubMed: 11605003]
67. Komata T, Kondo Y, Kanzawa T, Hirohata S, Koga S, Sumiyoshi H, Srinivasula SM, Barna BP,
Germano IM, Takakura M, Inoue M, Alnemri ES, Shay JW, Kyo S, Kondo S. Treatment of
malignant glioma cells with the transfer of constitutively active caspase-6 using the human
telomerase catalytic subunit (human telomerase reverse transcriptase) gene promoter. Cancer Res.
2001; 61:5796–5802. [PubMed: 11479218]
68. Komata T, Kondo Y, Kanzawa T, Ito H, Hirohata S, Koga S, Sumiyoshi H, Takakura M, Inoue M,
Barna BP, Germano IM, Kyo S, Kondo S. Caspase-8 gene therapy using the human telomerase
reverse transcriptase promoter for malignant glioma cells. Hum Gene Ther. 2002; 13:1015–1025.
[PubMed: 12067435]
69. Kunwar S, Chang SM, Prados MD, Berger MS, Sampson JH, Croteau D, Sherman JW, Grahn AY,
Shu VS, Dul JL, Husain SR, Joshi BH, Pedain C, Puri RK. Safety of intraparenchymal convection-
enhanced delivery of cintredekin besudotox in early-phase studies. Neurosurg Focus. 2006;
20:E15. [PubMed: 16709020]
70. Kunwar S, Prados MD, Chang SM, Berger MS, Lang FF, Piepmeier JM, Sampson JH, Ram Z,
Gutin PH, Gibbons RD, Aldape KD, Croteau DJ, Sherman JW, Puri RK. Direct intracerebral
delivery of cintredekin besudotox (IL13-PE38QQR) in recurrent malignant glioma: a report by the
Cintredekin Besudotox Intraparenchymal Study Group. J Clin Oncol. 2007; 25:837–844.
[PubMed: 17327604]
71. Kuppner MC, Hamou MF, Sawamura Y, Bodmer S, de Tribolet N. Inhibition of lymphocyte
function by glioblastoma-derived transforming growth factor beta 2. J Neurosurg. 1989; 71:211–
217. [PubMed: 2545842]
72. Lamfers ML, Grill J, Dirven CM, Van Beusechem VW, Geoerger B, Van Den Berg J, Alemany R,
Fueyo J, Curiel DT, Vassal G, Pinedo HM, Vandertop WP, Gerritsen WR. Potential of the
conditionally replicative adenovirus Ad5-Delta24RGD in the treatment of malignant gliomas and
its enhanced effect with radiotherapy. Cancer Res. 2002; 62:5736–5742. [PubMed: 12384532]
73. Lammering G, Valerie K, Lin PS, Mikkelsen RB, Contessa JN, Feden JP, Farnsworth J, Dent P,
Schmidt-Ullrich RK. Radiosensitization of malignant glioma cells through overexpression of
dominant-negative epidermal growth factor receptor. Clin Cancer Res. 2001; 7:682–690.
[PubMed: 11297265]
74. Lang FF, Bruner JM, Fuller GN, Aldape K, Prados MD, Chang S, Berger MS, McDermott MW,
Kunwar SM, Junck LR, Chandler W, Zwiebel JA, Kaplan RS, Yung WK. Phase I trial of
adenovirus-mediated p53 gene therapy for recurrent glioma: biological and clinical results. J Clin
Oncol. 2003; 21:2508–2518. [PubMed: 12839017]
Selznick et al.
Page 17
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
75. Li H, Alonso-Vanegas M, Colicos MA, Jung SS, Lochmuller H, Sadikot AF, Snipes GJ, Seth P,
Karpati G, Nalbantoglu J. Intracerebral adenovirus-mediated p53 tumor suppressor gene therapy
for experimental human glioma. Clin Cancer Res. 1999; 5:637–642. [PubMed: 10100717]
76. Liau LM, Black KL, Prins RM, Sykes SN, DiPatre PL, Cloughesy TF, Becker DP, Bronstein JM.
Treatment of intracranial gliomas with bone marrow-derived dendritic cells pulsed with tumor
antigens. J Neurosurg. 1999; 90:1115–1124. [PubMed: 10350260]
77. Lichtor T, Glick RP, Tarlock K, Moffett S, Mouw E, Cohen EP. Application of interleukin-2-
secreting syngeneic/allogeneic fibroblasts in the treatment of primary and metastatic brain tumors.
Cancer Gene Ther. 2002; 9:464–469. [PubMed: 11961669]
78. Lorimer IA, Keppler-Hafkemeyer A, Beers RA, Pegram CN, Bigner DD, Pastan I. Recombinant
immunotoxins specific for a mutant epidermal growth factor receptor: targeting with a single chain
antibody variable domain isolated by phage display. Proc Natl Acad Sci U S A. 1996; 93:14815–
14820. [PubMed: 8962138]
79. Markert JM, Medlock MD, Rabkin SD, Gillespie GY, Todo T, Hunter WD, Palmer CA,
Feigenbaum F, Tornatore C, Tufaro F, Martuza RL. Conditionally replicating herpes simplex virus
mutant, G207 for the treatment of malignant glioma: results of a phase I trial. Gene Ther. 2000;
7:867–874. [PubMed: 10845725]
80. Martuza RL, Malick A, Markert JM, Ruffner KL, Coen DM. Experimental therapy of human
glioma by means of a genetically engineered virus mutant. Science. 1991; 252:854–856. [PubMed:
1851332]
81. Medawar P. Immunity to homologous grafted skin, III: the fate of skin homografts transplanted to
the brain, to subcutaneous tissue, and to the anterior chamber of the eye. Br J Exp Pathol. 1948;
29:58–69. [PubMed: 18865105]
82. Merrill MK, Bernhardt G, Sampson JH, Wikstrand CJ, Bigner DD, Gromeier M. Poliovirus
receptor CD155-targeted oncolysis of glioma. Neuro-oncol. 2004; 6:208–217. [PubMed:
15279713]
83. Merrill MK, Gromeier M. The double-stranded RNA binding protein 76:NF45 heterodimer inhibits
translation initiation at the rhinovirus type 2 internal ribosome entry site. J Virol. 2006; 80:6936–
6942. [PubMed: 16809299]
84. Merritt JA, Roth JA, Logothetis CJ. Clinical evaluation of adenoviral-mediated p53 gene transfer:
review of INGN 201 studies. Semin Oncol. 2001; 28:105–114. [PubMed: 11706402]
85. Michelson-Fiske S. Human cytomegalovirus: a review of developments between 1970 and 1976.
Part II. Experimental developments. Biomedicine. 1977; 26:86–97. [PubMed: 194635]
86. Mineta T, Rabkin SD, Yazaki T, Hunter WD, Martuza RL. Attenuated multi-mutated herpes
simplex virus-1 for the treatment of malignant gliomas. Nat Med. 1995; 1:938–943. [PubMed:
7585221]
87. Moolten FL. Tumor chemosensitivity conferred by inserted herpes thymidine kinase genes:
paradigm for a prospective cancer control strategy. Cancer Res. 1986; 46:5276–5281. [PubMed:
3019523]
88. Morral N, O’Neal W, Zhou H, Langston C, Beaudet A. Immune responses to reporter proteins and
high viral dose limit duration of expression with adenoviral vectors: comparison of E2a wild type
and E2a deleted vectors. Hum Gene Ther. 1997; 8:1275–1286. [PubMed: 9215744]
89. Moscatello DK, Holgado-Madruga M, Godwin AK, Ramirez G, Gunn G, Zoltick PW, Biegel JA,
Hayes RL, Wong AJ. Frequent expression of a mutant epidermal growth factor receptor in
multiple human tumors. Cancer Res. 1995; 55:5536–5539. [PubMed: 7585629]
90. Ni HT, Spellman SR, Jean WC, Hall WA, Low WC. Immunization with dendritic cells pulsed with
tumor extract increases survival of mice bearing intracranial gliomas. J Neurooncol. 2001; 51:1–9.
[PubMed: 11349874]
91. Owens T, Renno T, Taupin V, Krakowski M. Inflammatory cytokines in the brain: does the CNS
shape immune responses? Immunol Today. 1994; 15:566–571. [PubMed: 7848517]
92. Paganelli G, Grana C, Chinol M, Cremonesi M, De Cicco C, De Braud F, Robertson C, Zurrida S,
Casadio C, Zoboli S, Siccardi AG, Veronesi U. Antibody-guided three-step therapy for high grade
glioma with yttrium-90 biotin. Eur J Nucl Med. 1999; 26:348–357. [PubMed: 10199940]
Selznick et al.
Page 18
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
93. Papanastassiou V, Rampling R, Fraser M, Petty R, Hadley D, Nicoll J, Harland J, Mabbs R, Brown
M. The potential for efficacy of the modified (ICP 34.5(−)) herpes simplex virus HSV1716
following intratumoural injection into human malignant glioma: a proof of principle study. Gene
Ther. 2002; 9:398–406. [PubMed: 11960316]
94. Parajuli P, Mathupala S, Sloan AE. Systematic comparison of dendritic cell-based
immunotherapeutic strategies for malignant gliomas: in vitro induction of cytolytic and natural
killer-like T cells. Neurosurgery. 2004; 55:1194–1204. [PubMed: 15509326]
95. Parney IF, Chang LJ, Farr-Jones MA, Hao C, Smylie M, Petruk KC. Technical hurdles in a pilot
clinical trial of combined B7-2 and GM-CSF immunogene therapy for glioblastomas and
melanomas. J Neurooncol. 2006; 78:71–80. [PubMed: 16718522]
96. Parney IF, Farr-Jones MA, Chang LJ, Petruk KC. Human glioma immunobiology in vitro:
implications for immunogene therapy. Neurosurgery. 2000; 46:1169–1177. discussion 1177-1168.
[PubMed: 10807250]
97. Parney IF, Farr-Jones MA, Kane K, Chang LJ, Petruk KC. Human autologous in vitro models of
glioma immunogene therapy using B7-2, GM-CSF, and IL12. Can J Neurol Sci. 2002; 29:267–
275. [PubMed: 12195617]
98. Parney IF, Farr-Jones MA, Koshal A, Chang LJ, Petruk KC. Human brain tumor cell culture
characterization after immunostimulatory gene transfer. Neurosurgery. 2002; 50:1094–1102.
[PubMed: 11950413]
99. Plautz GE, Miller DW, Barnett GH, Stevens GH, Maffett S, Kim J, Cohen PA, Shu S. T cell
adoptive immunotherapy of newly diagnosed gliomas. Clin Cancer Res. 2000; 6:2209–2218.
[PubMed: 10873070]
100. Prados MD, McDermott M, Chang SM, Wilson CB, Fick J, Culver KW, Van Gilder J, Keles GE,
Spence A, Berger M. Treatment of progressive or recurrent glioblastoma multiforme in adults
with herpes simplex virus thymidine kinase gene vector-producer cells followed by intravenous
ganciclovir administration: a phase I/II multi-institutional trial. J Neurooncol. 2003; 65:269–278.
[PubMed: 14682377]
101. Prins RM, Graf MR, Merchant RE. Cytotoxic T cells infiltrating a glioma express an aberrant
phenotype that is associated with decreased function and apoptosis. Cancer Immunol
Immunother. 2001; 50:285–292. [PubMed: 11570581]
102. Quattrocchi KB, Miller CH, Cush S, Bernard SA, Dull ST, Smith M, Gudeman S, Varia MA.
Pilot study of local autologous tumor infiltrating lymphocytes for the treatment of recurrent
malignant gliomas. J Neurooncol. 1999; 45:141–157. [PubMed: 10778730]
103. Rainov NG. A phase III clinical evaluation of herpes simplex virus type 1 thymidine kinase and
ganciclovir gene therapy as an adjuvant to surgical resection and radiation in adults with
previously untreated glioblastoma multiforme. Hum Gene Ther. 2000; 11:2389–2401. [PubMed:
11096443]
104. Rainov NG, Heidecke V. Long term survival in a patient with recurrent malignant glioma treated
with intratumoral infusion of an IL4-targeted toxin (NBI-3001). J Neurooncol. 2004; 66:197–
201. [PubMed: 15015787]
105. Rainov NG, Ren H. Oncolytic viruses for treatment of malignant brain tumours. Acta Neurochir
Suppl. 2003; 88:113–123. [PubMed: 14531569]
106. Ram Z, Culver KW, Oshiro EM, Viola JJ, DeVroom HL, Otto E, Long Z, Chiang Y, McGarrity
GJ, Muul LM, Katz D, Blaese RM, Oldfield EH. Therapy of malignant brain tumors by
intratumoral implantation of retroviral vector-producing cells. Nat Med. 1997; 3:1354–1361.
[PubMed: 9396605]
107. Rampling R, Cruickshank G, Papanastassiou V, Nicoll J, Hadley D, Brennan D, Petty R,
MacLean A, Harland J, McKie E, Mabbs R, Brown M. Toxicity evaluation of replication-
competent herpes simplex virus (ICP 34.5 null mutant 1716) in patients with recurrent malignant
glioma. Gene Ther. 2000; 7:859–866. [PubMed: 10845724]
108. Ratcheson RA. Fast forwarding: the evolution of neurosurgery. The 2005 presidential address. J
Neurosurg. 2005; 103:585–590. [PubMed: 16266037]
109. Reardon DA, Akabani G, Coleman RE, Friedman AH, Friedman HS, Herndon JE 2nd, Cokgor I,
McLendon RE, Pegram CN, Provenzale JM, Quinn JA, Rich JN, Regalado LV, Sampson JH,
Selznick et al.
Page 19
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
Shafman TD, Wikstrand CJ, Wong TZ, Zhao XG, Zalutsky MR, Bigner DD. Phase II trial
ofmurine (131)I-labeled antitenascin monoclonal antibody 81C6 administered into surgically
created resection cavities of patients with newly diagnosed malignant gliomas. J Clin Oncol.
2002; 20:1389–1397. [PubMed: 11870184]
110. Reardon DA, Egorin MJ, Quinn JA, Rich JN, Gururangan S, Vredenburgh JJ, Desjardins A,
Sathornsumetee S, Provenzale JM, Herndon JE 2nd, Dowell JM, Badruddoja MA, McLendon
RE, Lagattuta TF, Kicielinski KP, Dresemann G, Sampson JH, Friedman AH, Salvado AJ,
Friedman HS. Phase II study of imatinib mesylate plus hydroxyurea in adults with recurrent
glioblastoma multiforme. J Clin Oncol. 2005; 23:9359–9368. [PubMed: 16361636]
111. Rich J, Reardon DA, Quinn JA, Vredenburgh J, Desjardins A, Sathornsumetee S, Gururangan S,
Lyons P, Bigner DD, Friedman HS. A phase I trail of gefitinib (Ireassa; ZD1839) plus rapamycin
for patients with recurrent malignant glioma. J Clin Oncol. 2005; 23:1565.
112. Rubinchik S, Yu H, Woraratanadharm J, Voelkel-Johnson C, Norris JS, Dong JY. Enhanced
apoptosis of glioma cell lines is achieved by co-delivering FasL-GFP and TRAIL with a complex
Ad5 vector. Cancer Gene Ther. 2003; 10:814–822. [PubMed: 14605667]
113. Rustamzadeh E, Low WC, Vallera DA, Hall WA. Immunotoxin therapy for CNS tumor. J
Neurooncol. 2003; 64:101–116. [PubMed: 12952291]
114. Rutkowski S, De Vleeschouwer S, Kaempgen E, Wolff JE, Kuhl J, Demaerel P, Warmuth-Metz
M, Flamen P, Van Calenbergh F, Plets C, Sorensen N, Opitz A, Van Gool SW. Surgery and
adjuvant dendritic cell-based tumour vaccination for patients with relapsed malignant glioma, a
feasibility study. Br J Cancer. 2004; 91:1656–1662. [PubMed: 15477864]
115. Samanta M, Harkins L, Klemm K, Britt WJ, Cobbs CS. High prevalence of human
cytomegalovirus in prostatic intraepithelial neoplasia and prostatic carcinoma. J Urol. 2003;
170:998–1002. [PubMed: 12913758]
116. Sandmair AM, Loimas S, Puranen P, Immonen A, Kossila M, Puranen M, Hurskainen H, Tyynela
K, Turunen M, Vanninen R, Lehtolainen P, Paljarvi L, Johansson R, Vapalahti M, Yla-Herttuala
S. Thymidine kinase gene therapy for human malignant glioma, using replication-deficient
retroviruses or adenoviruses. Hum Gene Ther. 2000; 11:2197–2205. [PubMed: 11084677]
117. Shand N, Weber F, Mariani L, Bernstein M, Gianella-Borradori A, Long Z, Sorensen AG,
Barbier N. A phase 1–2 clinical trial of gene therapy for recurrent glioblastoma multiforme by
tumor transduction with the herpes simplex thymidine kinase gene followed by ganciclovir.
GLI328 European–Canadian Study Group. Hum Gene Ther. 1999; 10:2325–2335. [PubMed:
10515452]
118. Shimamura T, Husain SR, Puri RK. The IL-4 and IL-13 pseudomonas exotoxins: new hope for
brain tumor therapy. Neurosurg Focus. 2006; 20:E11. [PubMed: 16709016]
119. Simpson JR, Horton J, Scott C, Curran WJ, Rubin P, Fischbach J, Isaacson S, Rotman M, Asbell
SO, Nelson JS, et al. Influence of location and extent of surgical resection on survival of patients
with glioblastoma multiforme: results of three consecutive Radiation Therapy Oncology Group
(RTOG) clinical trials. Int J Radiat Oncol Biol Phys. 1993; 26:239–244. [PubMed: 8387988]
120. Sissons JG, Carmichael AJ. Clinical aspects and management of cytomegalovirus infection. J
Infect. 2002; 44:78–83. [PubMed: 12076065]
121. Skornick Y, Topalian S, Rosenberg SA. Comparative studies of the long-term growth of
lymphocytes from tumor infiltrates, tumor-draining lymph nodes, and peripheral blood by
repeated in vitro stimulation with autologous tumor. J Biol Response Mod. 1990; 9:431–438.
[PubMed: 2395007]
122. Sloan KE, Stewart JK, Treloar AF, Matthews RT, Jay DG. CD155/PVR enhances glioma cell
dispersal by regulating adhesion signaling and focal adhesion dynamics. Cancer Res. 2005;
65:10930–10937. [PubMed: 16322240]
123. Smitt PS, Driesse M, Wolbers J, Kros M, Avezaat C. Treatment of relapsed malignant glioma
with an adenoviral vector containing the herpes simplex thymidine kinase gene followed by
ganciclovir. Mol Ther. 2003; 7:851–858. [PubMed: 12788659]
124. Song Y, Friebe P, Tzima E, Junemann C, Bartenschlager R, Niepmann M. The hepatitis C virus
RNA 3′-untranslated region strongly enhances translation directed by the internal ribosome entry
site. J Virol. 2006; 80:11579–11588. [PubMed: 16971433]
Selznick et al.
Page 20
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
125. Stevens A, Kloter I, Roggendorf W. Inflammatory infiltrates and natural killer cell presence in
human brain tumors. Cancer. 1988; 61:738–743. [PubMed: 3338036]
126. Stupp R, Mason WP, van den Bent MJ, Weller M, Fisher B, Taphoorn MJ, Belanger K, Brandes
AA, Marosi C, Bogdahn U, Curschmann J, Janzer RC, Ludwin SK, Gorlia T, Allgeier A,
Lacombe D, Cairncross JG, Eisenhauer E, Mirimanoff RO. Radiotherapy plus concomitant and
adjuvant temozolomide for glioblastoma. N Engl J Med. 2005; 352:987–996. [PubMed:
15758009]
127. Sugawa N, Ueda S, Nakagawa Y, Nishino H, Nosaka K, Iwashima A, Kurimoto M. An antisense
EGFR oligodeoxynucleotide enveloped in Lipofectin induces growth inhibition in human
malignant gliomas in vitro. J Neurooncol. 1998; 39:237–244. [PubMed: 9821109]
128. Takeuchi H, Kanzawa T, Kondo Y, Komata T, Hirohata S, Kyo S, Kondo S. Combination of
caspase transfer using the human telomerase reverse transcriptase promoter and conventional
therapies for malignant glioma cells. Int J Oncol. 2004; 25:57–63. [PubMed: 15201989]
129. Trask TW, Trask RP, Aguilar-Cordova E, Shine HD, Wyde PR, Goodman JC, Hamilton WJ,
Rojas-Martinez A, Chen SH, Woo SL, Grossman RG. Phase I study of adenoviral delivery of the
HSV-tk gene and ganciclovir administration in patients with current malignant brain tumors. Mol
Ther. 2000; 1:195–203. [PubMed: 10933931]
130. Tripathy SK, Black HB, Goldwasser E, Leiden JM. Immune responses to transgene-encoded
proteins limit the stability of gene expression after injection of replication-defective adenovirus
vectors. Nat Med. 1996; 2:545–550. [PubMed: 8616713]
131. Tyminski E, Leroy S, Terada K, Finkelstein DM, Hyatt JL, Danks MK, Potter PM, Saeki Y,
Chiocca EA. Brain tumor oncolysis with replication-conditional herpes simplex virus type 1
expressing the prodrug-activating genes, CYP2B1 and secreted human intestinal
carboxylesterase, in combination with cyclophosphamide and irinotecan. Cancer Res. 2005;
65:6850–6857. [PubMed: 16061668]
132. Van den Bent MJ, Stupp R, Mason WP. Impact of extent of resection on overall survival in
newly-diagnosed glioblastoma after chemo-irradiation with temozolomide: further analysis of
EORTC study 26981. Eur J Cancer Suppl. 2005; 3:134.
133. Vecil GG, Lang FF. Clinical trials of adenoviruses in brain tumors: a review of Ad-p53 and
oncolytic adenoviruses. J Neurooncol. 2003; 65:237–246. [PubMed: 14682374]
134. Wang MY, Lu KV, Zhu S, Dia EQ, Vivanco I, Shackleford GM, Cavenee WK, Mellinghoff IK,
Cloughesy TF, Sawyers CL, Mischel PS. Mammalian target of rapamycin inhibition promotes
response to epidermal growth factor receptor kinase inhibitors in PTEN-deficient and PTEN-
intact glioblastoma cells. Cancer Res. 2006; 66:7864–7869. [PubMed: 16912159]
135. Wang X, Huong SM, Chiu ML, Raab-Traub N, Huang ES. Epidermal growth factor receptor is a
cellular receptor for human cytomegalovirus. Nature. 2003; 424:456–461. [PubMed: 12879076]
136. Watanabe K, Tachibana O, Sata K, Yonekawa Y, Kleihues P, Ohgaki H. Overexpression of the
EGF receptor and p53 mutations are mutually exclusive in the evolution of primary and
secondary glioblastomas. Brain Pathol. 1996; 6:217–223. discussion 223-214. [PubMed:
8864278]
137. Weber F, Asher A, Bucholz R, Berger M, Prados M, Chang S, Bruce J, Hall W, Rainov NG,
Westphal M, Warnick RE, Rand RW, Floeth F, Rommel F, Pan H, Hingorani VN, Puri RK.
Safety, tolerability, and tumor response of IL4-Pseudomonas exotoxin (NBI-3001) in patients
with recurrent malignant glioma. J Neurooncol. 2003; 64:125–137. [PubMed: 12952293]
138. Wikstrand CJ, McLendon RE, Friedman AH, Bigner DD. Cell surface localization and density of
the tumor-associated variant of the epidermal growth factor receptor, EGFRvIII. Cancer Res.
1997; 57:4130–4140. [PubMed: 9307304]
139. Yamanaka R, Homma J, Yajima N, Tsuchiya N, Sano M, Kobayashi T, Yoshida S, Abe T, Narita
M, Takahashi M, Tanaka R. Clinical evaluation of dendritic cell vaccination for patients with
recurrent glioma: results of a clinical phase I/II trial. Clin Cancer Res. 2005; 11:4160–4167.
[PubMed: 15930352]
140. Yu JS, Liu G, Ying H, Yong WH, Black KL, Wheeler CJ. Vaccination with tumor lysate-pulsed
dendritic cells elicits antigen-specific, cytotoxic T-cells in patients with malignant glioma.
Cancer Res. 2004; 64:4973–4979. [PubMed: 15256471]
Selznick et al.
Page 21
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
141. Zafiropoulos A, Tsentelierou E, Billiri K, Spandidos DA. Human herpes viruses in non-
melanoma skin cancers. Cancer Lett. 2003; 198:77–81. [PubMed: 12893433]
142. Zhang Y, Zhu C, Pardridge WM. Antisense gene therapy of brain cancer with an artificial virus
gene delivery system. Mol Ther. 2002; 6:67–72. [PubMed: 12095305]
Comments
Michael Weller, Zürich, Switzerland
“Molecular strategies for the treatment of malignant glioma” are in some way as old as the
first efforts to use radiation or drugs in addition to surgery to improve patient outcome
compared with surgery alone. These strategies were introduced into the clinic and were used
with success, although it remained unclear what the precise molecular target was. For
instance, molecular features almost certainly determine in part which tumors show
prolonged local control in response to radiotherapy and which tumors progress even during
this treatment. Moreover, although MGMT promoter methylation is now our first
convincing molecular predictor of response to a meaningful type of medical treatment,
chemotherapy with temozolomide, this marker was identified by retrospective analysis only,
and the pivotal EORTC NCIC did not pursue the goal to demonstrate the predictive value of
MGMT promoter methylation.
In contrast, as outlined in the present review article, the experimental clinical approach to
malignant glioma has undergone tremendous changes in the last decade. We now hope that
we are increasingly able to design molecular treatments a priori once we have the
opportunity to examine tissue as well tissue cultures derived from this material. The idea
behind this is to enrich study populations with patients most likely to benefit from a given
treatment. For instance, molecular characterization of kinase pathways activated in a given
tumor may be necessary to identify a subgroup of patients responsive to old and novel
kinase inhibitors. Although the number of novel approaches to malignant glioma is steadily
increasing, Selznick and colleagues still undertook the admirable effort to provide a broad
overview about what they feel are the most promising concepts beyond surgery,
radiotherapy and classic genotoxic chemotherapy. They focus on gene therapy including
apoptosis signaling and classical suicide gene therapy, oncolytic viruses, and vaccines, and
restrict themselves to approaches close to or already in the clinic. They aptly stress that none
of the current treatment approaches alone may lead to a breakthrough in the treatment of
malignant gliomas, but that intelligent combination approaches must be looked for. They
have provided us with a very helpful overview about the current concepts of treatment that
are close to stand or fall upon their first application in man.
Selznick et al. Page 22
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
Fig. 1.
Classification scheme of molecular approaches to the treatment of malignant gliomas
Selznick et al. Page 23
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
Selznick et al. Page 24
Table 1
Clinical trials of molecular therapy for malignant glioma
Type Agent Author Phase
Gene therapy Ad-P53 Lang et al. 2003 [74] I
HSV-tk/GCV Germano et al. 2003 [35] I
Harsh et al. 2000 [49] I
Sandmair et al. 2000 [116] I
Trask et al. 2000 [129] I
Klatzman et al. 1998 [64] I/II
Prados et al. 2003 [100] I/II
Ram et al. 1997 [106] I/II
Shand et al. 1999 [117] I/II
Smitt et al. 2003 [123] I/II
Rainov et al. 2000 [103] III
Oncolytic therapy Ad (ONYX-015) Chiocca et al. 2004 [16] I
HSV (G207) Markert et al. 2000 [79] I
HSV (1716) Harrow et al. 2004 [48] I
Papanastassiou et al. 2002 [93] I
Rampling et al. 2000 [107] I
Immunotherapy DC-tumor lysate (sc) Yu et al. 2004 [140] I
DC-tumor lysate (id) Rutkowski et al. 2004 [114] I
DC-tumor lysate (id) Yamanaka et al. 2005 [139] I/II
Irradiated tumor and BCG Plautz et al. 2000 [99] I
Irradiated tumor and GM-CSF Holladay et al. 1996 [54] I
IL-4-PE Weber et al. 2003 [137] I
IL-13-PE Kunwar et al. 2006 [69] I/II
Tumor-infiltrating lymphocytes Quattrocchi et al. 1999 [102] I
131
I Anti-tenascin
Reardon et al. 2002 [109] II
Anti-tenascin Grana et al. 2002 [40] II
125
I Anti-EGFRvIII
Brady et al. 1998 [11] III
EGFRvIII (Pep3) Heimberger et al. 2003 [50] III
Multimodal B7-2 + GM-CSF Parney et al. 2006 [95] I
Gefitinib + rapamycin Rich et al. 2005 [111] I
HSV-tk/GCV + IL2 Colombo et al. 2005 [19] I/II
DC-glioma (id) + IL12 Kikuchi et al. 2004 [63] I/II
Erlotinib + temozolomide + radiation Brewer et al. 2005 [12] II
Imatinib + hydroxyurea Reardon et al. 2005 [110] II
Neurosurg Rev
. Author manuscript; available in PMC 2012 August 14.
