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Mesothelioma is a rare thoracic malignancy with a dismal prognosis. Current treatment options are scarce and clinical outcomes are rather disappointing. Due to the immunogenic nature of mesothelioma, several studies have investigated immunotherapeutic strategies to improve the prognosis of patients with mesothelioma. In the last decade, progress in knowledge of the modulation of the immune system to attack the tumor has been remarkable, but the optimal strategy for immunotherapy has yet to be unraveled. Because of their potent antigen-presenting capacity, dendritic cells are acknowledged as a promising agent in immunotherapeutic approaches in a number of malignancies. This review gives an update and provides a future perspective in which immunotherapy may improve the outcome of mesothelioma therapy.
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IS SN 175 0 -743X10.2217/IMT.12.108 © 2012 Future Medicine Ltd Immunotherapy (2012) 4(10), 1011–1022
Dendritic cell-based immunotherapy in
Asbestos was named by the ancient Greeks, its
name meaning ‘inextinguishable’. It has been
said that the Greeks also noted its harmful
effects in the first century AD: “sickness of the
lungs” was described in asbestos quarry slaves
or slaves who wove asbestos into cloth, leading
to a recommendation not to buy these slaves as
they often “died young” [ 20 1] . The use of asbestos
declined during the Middle Ages, but it regained
popularity during the Industrial Revolution in
the late 1800s. At the turn of the 20th century,
researchers began to notice a large number of
deaths and lung problems in people living in
asbestos mining towns and during the first dec-
ades of that century, an expanding number of
articles appeared in medical journals [1 –3] , and
some authors suggested a link between inhala-
tion of asbestos fibers and carcino genesis [4 ,5] .
The term ‘mesothelioma’ entered the medical
literature in 1931 when Klemperer and Rabin
described the distinct features of these dif-
fuse pleural neoplasms [6 ]. It was, however, not
until 1960 that the link between asbestos fib-
ers and mesothelioma became incontrovertible
with an article published in The Lancet entitled
“Primary malignant mesothelioma of the pleura”
by Eisenstadt and Wilson [7] . Over the last dec-
ades, the association between asbestos exposure
and subsequent development of mesothelioma
has been extensively studied in multiple ani-
mal species via inhalation of, or subcutaneous,
intrapleural and intra peritoneal inoculation
with, asbestos fibers [8–11] . Inhaled asbestos
fibers within the lung cause infiltration of cir-
culating macrophages into the pleural space,
where the macrophages try to phagocytose the
inhaled foreign bodies [12 ] . In the effort to clear
these asbestos fibers, reactive oxygen species
are generated, causing DNA damage to nearby
cells. Subsequently, inflammatory cytokines
and recruitment of immune cells to sites of
inflammation within the pleura are induced
[13 –1 6] . Given the large size of the asbestos fib-
ers, macrophages fail to clear the asbestos fib-
ers, resulting in continued generation of reactive
oxygen species and secretion of proinflammatory
cytokines [1 6] , a process often called ‘frustrated
phagocytosis’ [17] . In addition to this procarci-
nogenic and proinflammatory substance release,
asbestos fibers can sometimes directly penetrate
the cells and damage chromosomes. Also, the
retained asbestos fibers may adsorb other car-
cinogens on their surface [1 8– 2 2] . As a result,
DNA alterations occur, such as in activation of
p16INK4a/p14ARF, NF2/Merlin and L ATS2,
and the activation of YAP [2 3, 24] .
In contrast to the increase in knowledge of
the etiology of mesothelioma, the treatment
options for mesothelioma are still scarce and
prognosis is poor, with a median survival of only
9–12 months after diagnosis.
Surgery for mesothelioma is a very contro-
versial subject, with the number of randomized
controlled trials being small. Most thoracic
surgeons would agree that a complete resec-
tion for mesothelioma is only possible in a
Mesothelioma is a rare thoracic malignancy with a dismal prognosis. Current treatment options are scarce
and clinical outcomes are rather disappointing. Due to the immunogenic nature of mesothelioma, several
studies have investigated immunotherapeutic strategies to improve the prognosis of patients with
mesothelioma. In the last decade, progress in knowledge of the modulation of the immune system to
attack the tumor has been remarkable, but the optimal strategy for immunotherapy has yet to be
unraveled. Because of their potent antigen-presenting capacity, dendritic cells are acknowledged as a
promising agent in immunotherapeutic approaches in a number of malignancies. This review gives an
update and provides a future perspective in which immunotherapy may improve the outcome of
mesothelioma therapy.
KEYWORDS: dendritic cell n immature dendritic cell n immunotherapy
n mesothelioma n myeloid-derived suppressor cell n regulatory T cell
n tumor-associated macrophage
Robin Cornelissen*1,
Lysanne A Lievense1,
Marlies E Heuvers1,
Alexander P Maat2,
Rudi W Hendriks1,
Henk C Hoogsteden1,
Joost P Hegmans1
& Joachim G Aerts1
1Depart ment of Pulmon ary Medic ine,
Erasmus MC, S V-125, PO-B ox 2040,
3000C ARoerda m,TheNether lands
2DepartmentofThora cicSurger y,
Erasmus Medic al Center – Daniel den
Hoed Cancer Center, University
MedicalCe nter,Roerdam,
*Authorforcorre spondenc e:
part of
part of
Immunotherapy (2012) 4(10)
future science group
Dendritic cell-based immunotherapy in mesothelioma ReviewReview Cornelissen, Lievense, Heuvers et al.
limited number of patients. Whether there is
a role for surgery in the other patients is not
known. Also, conflicting opinions regarding
the optimal surgical procedure exist; in effect,
extrapleural pneumonectomy or various forms
of pleurectomy/decortication, with the current
trend towards more localized resections [2 5, 26 ] .
Chemotherapy was the only treatment that
improved survival in randomized controlled tri-
als in mesothelioma patients. This is based on
a study by Vogelzang and colleagues in 2003,
in which they compared cisplatin alone with a
combination of cisplatin and pemetrexed that
resulted in a survival advantage of over 3 months
for the combination therapy arm [27] . This led to
the approval of the combination of cisplatin and
pemetrexed as ‘standard of care’ for the treat-
ment of patients with ‘unresectable’ mesothe-
lioma. It should be noted that similar outcomes
were reached with cisplatin and raltitrexed
compared with cisplatin alone, confirming that
a combination of cisplatin and an antifolate is
superior to cisplatin alone in patients with mes-
othelioma [28]. Whether the antifolate/cisplatin
combination is the most effective chemothera-
peutic option remains uncertain, since no head-
to-head chemotherapeutic comparison has been
performed in mesothelioma. For example, the
comparison between the current standard regi-
men of cisplatin plus pemetrexed versus gemcit-
abine plus cisplatin, mitomycin, vin desine plus
cisplatin or vinorelbine. However, for every
individual agent previously studied, the survival
improvement was modest.
Several targeted agents have been extensively
studied in mesothelioma. EGF receptor (EGFR)
inhibitors were thought to be a promising target
for mesothelioma therapy since studies showed
that EGFR was highly expressed in malignant
mesothelioma [29,30]. However, most likely due
to absence of sensitizing mutations in the EGFR
tyrosine kinase domain, the results of these clini-
cal trials were disappointing [31 ,32]. Remarkably,
in peritoneal mesothelioma, there were reports of
novel EGFR mutations with a possible sensitivity
to erlotinib [33] , but these have been contradicted
by others [34 ]. A mong the anti-angiogenic agents,
thalidomide is the most extensively studied drug.
After numerous previous trials, the Phase III
trial NVALT 5/MATES with thalidomide as
switch maintenance in nonprogressive patients
after first-line pemetrexed chemotherapy could
unfortunately not prove a survival advantage [35] .
Phase II clinical trials of VEGF tyrosine kinase
inhibitors have shown, at best, modest activity in
mesothelioma [36, 37] . Bevacizumab, a humanized
anti-VEGF antibody, is currently being studied
for use in mesothelioma in addition to chemo-
therapy in France and Belgium in a Phase III
trial [2 02] , following several Phase II trials with
variable results [38] . An increasing amount of
preclinical data highlighting the effectiveness of
histone deacetylase inhibitors in mesothelioma
cell lines and mouse xenograft models has led to
a number of early-phase clinical trials in patients
with mesothelioma [39] . The results of these
efforts have led to a multicenter, randomized,
placebo-controlled Phase III study of the histone
deacetylase inhibitor vorinostat in patients with
advanced mesothelioma, which did not improve
survival compared with placebo as second-line
therapy for mesothelioma [4 0] . In conclusion,
there are no promising chemotherapeutic or
targeted agents on the horizon for patients with
mesothelioma. Clearly, there is a need for new
approaches in the treatment of mesothelioma.
Sporadically, a mesothelioma patient has
a tumor that regresses spontaneously. This
observation is ascribed to the immune system,
which may invoke a clinical response in mes-
othelioma patients under some circumstances
[41–43] . Mesothelioma is indeed an immunogenic
cancer and can induce immune recognition,
immune cell infiltration and immune-mediated
killing, the extent of which may define disease
prog nosis. As early as 1982, the impact of T-cell
infiltration on survival in mesothelioma patients
was demonstrated, showing a positive correla-
tion between T cells and increased survival [4 4] .
More recently, subtyping of T cells showed that
high frequencies of CD8+ tumor-infiltrating
T cells had a positive effect on progression-free
and overall survival, while increased frequencies
of CD4+CD25+ Tregs and CD45RO+ memory
T cells tended to be negative prognostic indica-
tors [45]. Higher frequencies of infiltrating CD3+
T cells correlated with worse overall survival in
patients having mesothelioma with sarcoma-
toid or biphasic histology [4 6] . In addition to
the immunogenic characteristics of the tumor,
exposure to asbestos fibers also has significant
negative direct effects on several components of
the immune system [47] . These findings indicate
that people exposed to asbestos fibers possess
reduced tumor immunity, making them more
sensitive to cancer development.
In summary, understanding the immune sys-
tem and developing mechanisms to activate it or
to overcome immune suppression could prove
beneficial to the patient; a therapeutic strategy
called immunotherapy. In this review, we discuss
the progress of immunotherapy in meso thelioma
future science group
Dendritic cell-based immunotherapy in mesothelioma
ReviewReview Cornelissen, Lievense, Heuvers et al.
over the years and focus on DC-based immuno-
therapy, since the stimulation of these powerful
APCs appears to be a very effective method of
inducing an antitumor response.
Immunotherapy in mesothelioma
The first attempts to activate the immune sys-
tem in mesothelioma were published 30 years
ago with the BCG vaccine trial that favored a
nonspecific activation of the immune response
[48 ,49] . The use of IL-2 to stimulate the immune
response was investigated more than 10 years
later [5 0 ,51] , and other activators of the immune
response, such as GM-CSF, IFN-g and IFN-a2a,
followed [52 –5 4] . However, these therapeutic
approaches have been abandoned owing to lack
of efficacy or unacceptable toxicity.
Due to its location in the pleural cavity, the
possibility of local vector administration to
apply immunotherapy via gene transfer appears
to be an attractive strategy in mesothelioma. In
a recently published pilot and feasibility trial
using an adenovirus vector expressing a homo-
logous type 1 human interferon gene (IFN‑a2b),
antitumor humoral immune responses against
mesothelioma cell lines were seen in seven of the
eight subjects evaluated. Furthermore, evidence
of disease stability or tumor regression was seen
in the remaining five patients, including one
partial tumor regression at sites not contiguous
with vector infusion [55] .
Preclinical studies targeting mesothelin,
a differentiation antigen present on normal
mesothelial cells and overexpressed in several
human tumors including mesothelioma, as
well as ovarian and pancreatic adeno carcinoma
[56 ] , with immunotoxins CAT-5001 (formerly
SS1P) and amatuximab (previously known
as MORab-009) were promising [5 6 –58 ] .
Unfortunately, in clinical trials CAT-5001
showed only modest clinical responses in meso-
thelioma patients [5 7,5 8] , and amatuximab failed
to demonstrate any radio logical responses in a
Phase I trial in meso thelioma and other cancer
types [5 9] . Preclinical studies demonstrated sig-
nificant antitumor efficacy using a combination
of amatuximab and chemotherapy treatment
[60] , justifying a multicenter Phase II clinical trial
utilizing cisplatin/pemetrexed with amatuximab
in meso thelioma patients. The preliminary out-
comes of this trial were recently presented and
showed that amatuximab in combination with
chemotherapy resulted in 90% of patients hav-
ing an objective tumor response or stable disease
[61] . However, progression-free survival was not
significantly different from historical results of
patients treated with chemotherapy only. More
recently, a Phase I study of SS1(dsFv)PE38, a
recombinant antimesothelin immunotoxin, was
commenced, which is ongoing at the time of
writing [203].
In addition to the agents mentioned above, it
is also possible to use immune cells for immu-
notherapy in mesothelioma. One approach is
to make use of lentiviral or retroviral vectors to
transduce T cells with modified T-cell receptors
engineered to attack specific tumor antigens [62] .
Preclinical results of this method are promising
[63] and this approach will proceed to a clinical
trial at the University of Pennsylvania (USA).
Adoptive transfer of lymphocytes with tumori-
cidal properties can, in theory, bypass the daunt-
ing task of breaking tolerance to tumor antigens
and generating a high frequency of high-avidity
effector T cells. In a preclinical mesothelioma
model, tumor-reactive T cells expressing chi-
meric antigen receptors were found to mediate
regression of the tumor [64] .
Another approach is to stimulate the APCs,
which in turn can induce a specific T-cell anti-
tumor response. In this field, dendritic cell
(DC)-based therapy has proven itself very prom-
ising. The present authors have recently pub-
lished the results of a clinical trial with dendritic
cell-based immunotherapy in mesothelioma [65] .
DCs were first described by Steinman, a discov-
ery for which he was awarded the Nobel Prize in
2011 [6 6] . These cells are widely acknowledged
as the central surveillance cell type and play
a pivotal role in the initiation and program-
ming of tumor-specific T-cell responses [66–69].
DCs are the most potent APCs specialized in
inducing activation and proliferation of CD8+
cytotoxic T lymphocytes (CTLs) and helper
CD4+ lymphocytes. DCs originate from bone
marrow precursors and migrate to peripheral
tissues, where they differentiate into immature
DCs. Immature DCs capture tumor-associated
antigens (TAAs) and start migrating via lym-
phatic vessels to regional lymphoid organs. This
migration is coordinated by chemokines and
their receptors, matrix molecules and adhesion
molecules on DCs, as well as the surrounding
tissues. DCs mature en route; activating their
ability to convert antigens to 10–15-mer pep-
tides bound to MHC class I and II molecules.
Mature DCs upregulate production of sur-
face costimulatory molecules (e.g., CD80 and
CD86) and cytokines needed to stimulate lym-
phocytes in the tumor-draining lymph nodes.
Immunotherapy (2012) 4(10)
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Dendritic cell-based immunotherapy in mesothelioma ReviewReview Cornelissen, Lievense, Heuvers et al.
DCs present tumor antigens to naive CTLs,
among other cells [70 –73] , inducing antitumor
immune responses.
However, tumors induce a microenvironment
that interferes with the natural development and
function of DCs by a number of mechanisms
(Figu re 1)
A growing tumor may outgrow its blood sup-
ply, leaving portions of the tumor milieu
deprived of adequate oxygen supply (hypoxia).
Under these conditions the expression of
matrix metalloproteases and the migratory
activity of DCs is suppressed [74, 75] ;
Tumor metabolites, such as lactic acid, arach-
idonic acid metabolites (prostanoids) and
gangliosides, contribute to DC dysfunction
[76–7 8];
The list of tumor-derived cytokines and
chemo kines is constantly growing and
includes, but is not limited to, IL-1, IL-2,
IL-4, IL-6, IL-8, IL-10, IL-15, VEGF, TFG-b,
TNF-a, EGF, FGF, HGF and MIP [79] , of
which IL-10 and TGF-b seem to be the best
characterized tumor-derived cytokines with
well-defined immunosuppressive function;
Besides the induction of defective DC func-
tion, tumor-induced factors can also skew the
differentiation of monocytes/DCs toward
alternatively activated macrophages and
endothelial-like cells [80– 82] ;
Tregs – immune cells that are abundantly pre-
sent in the tumor microenvironment – can
impede DC function.
Cumulatively, these mechanisms result in
DCs that express substantially lower levels of
MHC class II molecules, adhesion molecules
and costimulatory molecules than under nor-
mal conditions, and that are consistent with the
phenotype of nonactivated DCs [83 ,8 4] . These
tolerogenic DCs are impaired in their ability
to phagocytose antigens and stimulate T cells.
They also contribute to the recruitment, expan-
sion and function of Tregs, leading to a defective
induction of antitumor responses [85,86].
In larger tumors, competent
DCs can become
phenotypically and functionally
defective by a number
of mechanisms:
- Hypoxia
- Tumor metabolites
- Cytokines/chemokines
- Skewing of differentiation towards
macrophages and endothelial cells
- Inhibition by regulatory T cells
These impaired DCs secrete immunosuppressive cytokines
and upregulate the cell surface expression of T-cell
suppressive molecules.
Tumor regression
Tumor progression
Figure 1. Impairment of dendritic cell number and activity by tumor environment. mDCs are
capable of inducing an antitumor response in small tumors. However, when tumors grow and
establish a tumor microenvironment, several factors impair the functions of the tDCs.
DC: Dendritic cell; FB: Fibroblast; mDC: Mature dendritic cell; tDC: Tolerogenic dendritic cell.
future science group
Dendritic cell-based immunotherapy in mesothelioma
ReviewReview Cornelissen, Lievense, Heuvers et al.
First preclinical DC-based
In 2004, the research group of Gregoire pub-
lished a pioneering article in which they used
DC-based immunotherapy in a human mesothe-
lioma model [87] . By using dead cells (necrotic or
apoptotic lysate) for the loading of DCs, the cells
were exposed to a full array of antigenic peptides
that rapidly gain access to both MHC class I
(cross-presentation) and II pathways, therefore
leading to a diversified immune response involv-
ing CTLs as well as CD4+ T-helper cells. In their
paper, the authors successfully demonstrated
in vitro culture and antigen loading of DCs in a
human mesothelioma model, resulting in a spe-
cific cytotoxic T-cell response. Heat shocking
the tumor cells before apoptosis induction was
required to induce potent cross-priming of CTLs
with antitumor activity.
In 2005, the present authors’ group published
the first trial on DC-based immunotherapy of
mesothelioma in a murine model [88] . This was
a peritoneal tumor model using the AB-1 tumor
cell line. DCs were cultured and loaded with
tumor lysate and vaccinations were given at dif-
ferent time points in relation to tumor inocula-
tion. Immunization with tumor lysate-pulsed
DCs before a lethal tumor implantation pre-
vented mesothelioma outgrowth; mice receiv-
ing tumor lysate-pulsed DCs were protected for
months and even resisted a secondary challenge
with tumor, illustrating the induction of long-
lived immunity by using DC-based immuno-
therapy. Also, immunization with tumor lysate-
pulsed DCs after tumor implantation reduced
mesothelioma growth, depending on the method
of DC maturation and tumor load. In contrast
with the curative effect when tumor lysate-
pulsed DCs were given before or 1 and 8 days
after tumor challenge, immunization with tumor
lysate-pulsed DCs on the day of tumor implan-
tation promoted mesothelioma outgrowth and
poor prognosis occurred. The observation of a
paradoxical tumor-enhancing effect of simul-
taneous administration of DCs may be caused
by several factors. First, high levels of cytokines
or soluble mediators produced by mesotheli-
oma cells could downregulate cellular immune
responses induced by DCs. Next, tumor cells
might cluster with DCs, which, through their
highly motile nature, might lead to more wide-
spread dissemination and attachment of cancer
cells to the mesothelial surface. Finally, if DCs
are mixed with tumor cells in vivo, it has been
shown that DCs can transform into endothe-
lial cells, thus enhancing tumor vasculogenesis
and tumor growth [89] . Successful tumor lysate-
pulsed DC immunotherapy was associated with
cytotoxic T-cell induction and even transfer of
splenocytes or CD8+ T cells from surviving mice
receiving DC immunotherapy transfers tumor
protection for tumor-bearing mice. DC vacci-
nations had a better outcome when DCs were
injected early in tumor development, indicating
that tumor load played an important role in sur-
vival. Although the potency of immunotherapy
treatment decreased when DCs were injected
later, mice still showed an improved prognosis
compared with mice receiving no treatment,
but eventually tumors escaped immune surveil-
lance and all of the mice died. It is now well
established that larger tumor mass is associated
with an immuno suppressive milieu that has the
capacity to suppress the effector arm of the anti-
tumoral immune response (CTL response inside
the tumor) and the inductive arm of the immune
response (i.e., the potential of antigen-presenting
DCs to induce CTL responses) [90] .
First clinical trial
The research group of Robinson published a
trial in 2006 in which they used an autologous
tumor lysate vaccine that was manufactured
from surgically resected tumor and adminis-
tered subcutaneously together with GM-CSF
[91]. GM-CSF stimulates APCs in vivo, which in
turn present TAAs and thereby generate tumor-
specific immunity. A total of 22 patients were
enrolled in the trial. Of these, five developed
positive delayed type hypersensitivity skin tests
and five showed evidence of altered antibody
specificities by western blotting, proving that
tumor lysate plus GM-CSF could induce tumor-
specific immunity, both cellular and humoral.
Of the patients, 32% developed at least one
type of immune response against mesothelioma
[91]. In vivo stimulation of APCs is an attrac-
tive method; however, it remains important to
determine whether the activation signals might
actually polarize the DCs in the desired manner.
For example, engaging DC asialoglycoprotein
receptor [92] induces DCs to secrete IL-10, which
polarizes T cells into IL-10-secreting suppressor
T cells, which in turn might negatively affect
tumor-specific effector T cells. Furthermore,
the tumor microenvironment interferes with
the stimulation of DCs, as is discussed above.
Therefore, ex vivo culture and antigen-loading of
DCs, while demanding more labor, seems pref-
erable. In this way DCs can be cultured and
matured in vitro without the immunosuppres-
sive effect of the tumor. Also, the loading of the
Immunotherapy (2012) 4(10)
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Dendritic cell-based immunotherapy in mesothelioma ReviewReview Cornelissen, Lievense, Heuvers et al.
TAAs can be performed in a controlled situation
to make use of the full potential of these cells.
On the basis of their preclinical animal stud-
ies, the present authors have performed the first
clinical trial in which autologous tumor lysate-
pulsed DCs were administered to mesothelioma
patients [65] . In this clinical trial, patients were
eligible for the study when sufficient tumor
cells could be obtained from pleural effusion
or tumor biopsy material at the time of diag-
nosis. DC-based immunotherapy was planned
after completion of the cytoreductive therapy
provided that no major side effects occurred
during chemotherapy and there was no progres-
sive disease. DCs were obtained using concen-
trated leukocyte fractions that were generated
through peripheral blood leukapheresis [93] .
Large numbers of DCs were generated ex vivo,
in the absence of the suppressing tumor milieu,
and subsequently loaded with a preparation of
autologous tumor antigens and keyhole limpet
hemocyanin as positive control. Mature DCs
were injected three-times with a 2-week inter-
val both intravenously (distribution to the liver,
spleen and bone marrow) and intradermally
from where they migrate to the regional lymph
(Fi gur e 2)
. In this way, they maximally
stimulate the cytotoxic T cells, B cells, NK cells
and NKT cells that are essential for tumor lysis.
Overall, the vaccination regimen with loaded
DCs was well tolerated in all patients and no
common toxicity criteria grade 3 or 4 toxicities
were reported. A local skin rash occurred at the
site of the intradermal injection after the first vac-
cination in eight of the ten patients. Subsequent
vaccinations (second and third) gave a quicker
and increased induration and erythema in all
patients suggesting that some form of immunity
was induced. Most patients developed mild-to-
severe flu-like symptoms after the vaccination,
particularly fever, muscle aches, chills and tired-
ness; however, these symptoms normalized after
1 day. Since this was a proof-of-principle study,
no conclusions can be drawn regarding improve-
ment of the progression-free survival or overall
survival. To assess the T-cell capacity for cell lysis,
flow cytometric detection of CD3+CD8+ T cells
expressing granzyme B was used. Nine patients
showed a significantly increased percentage of
granzyme B + CD8+ T cells after vaccination and
granzyme B expression per CD8+ cell increased
in most patients. Furthermore, radioactive chro-
mium release assays were performed in six of ten
patients from whom pleural fluid was obtained.
In four patients, a clear induction of cytotoxicity
against autologous tumor cells was measured.
The cytotoxicity levels of one patient increased
after every vaccination; for the other three
patients three vaccinations were necessary to
induce cytotoxicity. In addition, serum samples
from all patients showed a significant increase of
antibodies reactive to keyhole limpet hemocya-
nin post vaccination, both of the IgG and IgM
isotype. The response remained at the same level
for several months after the last DC injection
and gradually decreased after 6–12 months. This
proves that a successful immunoreaction was
induced by the DC vaccinations. In conclusion,
administration of DCs loaded with autologous
tumor cell lysate to patients was safe and feasible,
and no significant adverse effects were observed.
Future developments in DC-based
There is still room for improvement in DC pro-
duction, either ex vivo or in vivo. The most com-
monly used approach to harvest DCs for immu-
notherapy is to use the differentiated DCs from
peripheral blood mononuclear cells obtained
from whole blood or by a leukapheresis pro-
cedure. However, DCs can also be propagated
from CD34+ precursors. CD34+ precursors are
first mobilized from the bone marrow by treat-
ment of patients with GM-CSF prior to leuka-
pheresis procedures [94] . In addition, DCs can
also be directly isolated from circulating DCs.
Circulating DC subsets comprise less than 1%
of peripheral blood mononuclear cells. In vivo
expansion of these rare cells can be achieved by
administration of hemopoietic growth factors
such as Flt3L followed by leukapheresis [95] . For
a more elaborate description of DC subsets, the
review by Liu and Nussenzweig is recommended
[96] . All of these methods for gener ating DCs are
currently used in clinical trials, but there is no
consensus on the optimal method of generating
DCs for immunotherapy use [9 7, 98] .
A novel strategy for loading antigens involves
the direct targeting of antigens to DCs in vivo
to induce tumor-specific immune responses [9 9] .
Although the limitations have been mentioned
above, in vivo targeting of DCs represents an
option for DC immunotherapy as it bypasses the
expensive and labor-intensive ex vivo DC gen-
eration process. Vaccines may be produced on a
larger scale and at a lower cost than an ex vivo
cultured DC vaccine. In vivo targeting also
allows for the stimulation of natural DC sub-
sets at multiple sites in vivo. Newer approaches
involve the targeting of DC-specific molecules.
Candidate receptors for stimulation and matu-
ration of DCs include Fc receptors, CD40 and
future science group
Dendritic cell-based immunotherapy in mesothelioma
ReviewReview Cornelissen, Lievense, Heuvers et al.
C-type lectin receptors [97] . However, further
studies are still required to translate this new
strategy to clinical applications in humans.
Improving maturation of DCs also has the
potential to improve the efficacy of the immuno-
response; recently, it has been shown that in vitro
sequential DC maturation can be beneficial [10 0] .
This method tries to mimic the in vivo situa-
tion in which DCs exposed at the periphery to
maturation stimuli migrate to lymph nodes,
where they receive secondary signals from CD4+
T-helper cells. It was shown that a sequential
activation with activated CD4+ T cells dramati-
cally increased the maturation of DCs in terms
of their phenotype and cytokine secretion com-
pared with DCs activated with maturation stim-
uli delivered simultaneously [10 0 ] . Furthermore,
this sequential maturation led to the induction
of CTLs with long-term effector and central
memory phenotypes.
Either ex vivo or in vivo, the most optimal
method of DC production has to be established;
the question remains whether efficacy will be
enhanced due to optimization of this method,
because immunomonitoring of the present
authors’ clinical trial and those using other DC
vaccines has demonstrated that these cells are
now sufficiently powerful to be used in clinical
trials [101 ] .
Besides DC production, the method of antigen
loading is one of great debate; the ideal target for
cancer immunotherapy would be a TAA that is
exclusively expressed in all tumor cells but not in
normal tissues in order to avoid potential induc-
tion of autoimmunity. In addition, the TAA
should be important for tumor growth and sur-
vival, so that down regulation to escape the immu-
notherapeutic effect of the vaccine is impossible.
Most TAAs are self-derived proteins and thus,
in vivo, poorly immunogenic, certainly keeping
in mind the concept of the immuno suppressive
environment of the tumor. Nevertheless, DCs
loaded with these antigens can be used to initiate
antigen-specific T-cell responses. In recent years,
a large number of strategies have been developed
to deliver TAAs to DCs, using defined epitopes,
specific TAAs, apoptotic whole-cell suspen-
sions, necrotic cell lysates or cellular DNA or
mRNA, and employing both viral and nonviral
techniques [102,103].
In the present authors’ study, and in others
in mesothelioma, whole-cell material is used.
The need for patients’ tumor material for anti-
gen loading of the DCs unfortunately results
Ex vivo generated and
matured DCs
Figure 2. Administration of ex vivo maturated autologous dendritic cells into a patient,
resulting in antigen presentation in the lymph node and a specific cytotoxic antitumor
B: B cell; DC: Dendritic cell; mDC: Mature dendritic cell; NK: NK cell; T: T cell.
Immunotherapy (2012) 4(10)
future science group
Dendritic cell-based immunotherapy in mesothelioma ReviewReview Cornelissen, Lievense, Heuvers et al.
in patients being excluded from these trials if
there is an inability to collect sufficient tissue
samples. The University Hospital of Antwerp
(Belgium) has started a trial of DC immuno-
therapy in mesothelioma and several other solid
tumors, using WT-1 as antigen loading for the
DCs [20 4] , circumventing the need for patient’s
tumor material. In the present authors’ view, this
approach limits the antitumor response to a sin-
gle peptide, making it obligatory for the tumor to
significantly express this peptide in order for the
immunotherapy to be effective. In addition, it is
becoming clear that most tumors consist of dif-
ferent clones of tumor cells expressing different
TAAs. Elimination of one clone does not prevent
outgrowth of another.
But even when the preferable method of
DC preparation and antigen loading has been
established, immunotherapy has to overcome an
immunosuppressive environment caused by the
tumors’ recruitment of suppressive cell types that
inhibit an effective antitumor response, among
which are myeloid-derived suppressor cells,
tumor-associated macrophages (TAMs) and
Tregs. Dampening of this immuno suppression
through various methods of cell modulation
might be an important key to increasing the
efficacy of DC-based immunotherapy.
Myeloid-derived suppressor cells are increased
in cancer patients and play a suppressive role
in the innate and adaptive immune responses
to cancer. The present authors have recently
shown the role of myeloid-derived suppressor
cells in DC immuno therapy recently and sev-
eral strategies are being studied to counteract this
immuno suppression, for example gemcitabine,
5-fluorouracil, celecoxib or sunitinib [104–106 ].
TAMs are a major component of the leukocyte
infiltrate in the tumor microenvironment and are
described as key orchestrators of cancer-related
inflammation [10 7] . Evidence is accumulating on
their role in tumor initiation, progression and
metastasis [1 08 ] . TAMs are considered as ‘alter-
natively activated’ macrophages and have a dif-
ferent phenotype compared with the ‘classically
activated’ macrophages. Classically activated
macrophages are characterized by the expres-
sion of high levels of proinflammatory cytokines
and reactive oxygen species and have antitumor
activity. By contrast, alternatively activated mac-
rophages are considered to be involved in tissue
remodeling and wound healing and are able to
suppress the adoptive immune response through
various mechanisms and contribute to angio-
genesis and tumor invasiveness [1 0 9] . Suppressing
these TAMs might prove crucial to improving
the efficacy of immunotherapy; zoledronic acid,
the anti-IL-6 antibody siltuximab, antibod-
ies against CD40 and antagonists of CSF-1
receptor are candidates for suppression of these
TAMs [110–114] .
Tregs are a population of CD4+ T cells with a
central role in the prevention of autoimmunity
and the promotion of tolerance via their suppres-
sive function on a broad repertoire of cellular
targets; they have several pathways that limit the
antitumor response [115] . An engineered recom-
binant fusion protein of IL-2 and diphtheria
toxin and other CD25-directed immunotoxins,
low-dose cyclophosphamide, a p300-inhibiting
molecule, sorafinib and anti-CCL2/CCL12
mono clonal antibodies have been investigated
for Treg depletion [116 –12 3 ] .
Another method that is being extensively
studied is to enhance the antitumor immune
response by blockading immune checkpoints.
Immune checkpoints refer to a plethora of inhibi-
tory pathways hardwired into the immune system
that are crucial for maintaining self-tolerance and
modulating the duration and amplitude of physi-
ological immune responses in peripheral tissues
in order to minimize collateral tissue damage. It
is now clear that tumors co-opt certain immune
checkpoint pathways as a major mechanism of
immune resistance, particularly against T cells
that are specific for tumor antigens. Because
many of the immune checkpoints are initiated by
ligand–receptor interactions, they can be readily
blocked by antibodies or modulated by recombi-
nant forms of ligands or receptors. CTLA4 anti-
bodies were the first of this class of immunothera-
peutics to achieve a survival benefit in a Phase III
trial in melanoma [124], but several blockers of
additional immune checkpoint proteins, such as
PD1, are now being studied [1 25 ] .
The role of the immune system in mesotheli-
oma is vast. In malignant diseases, progress in
modulating the immune system has been slow
at first but, more recently, immunotherapy has
taken flight. In mesothelioma, multiple strate-
gies are currently being tested and many com-
binations of therapeutic options await research,
with DC-based therapy being one of the most
exciting options in our view.
Future perspective
In the coming years, we expect that a num-
ber of mechanisms that reduce the efficacy of
immunotherapy will be clarified and possible
therapeutic strategies will find their way into
future science group
Dendritic cell-based immunotherapy in mesothelioma
ReviewReview Cornelissen, Lievense, Heuvers et al.
Papers of special note have been highlighted as:
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Executive summary
Mesothelioma is an immunogenic cancer and can induce immune recognition, immune cell infiltration and immune-mediated killing,
the extent of which defines disease prognosis.
Immunotherapy in mesothelioma has been studied for over 30 years, with significant progress mainly being made in the last decade.
Dendritic cells (DCs) are the most potent APCs, specialized in inducing activation and proliferation of cytotoxic CD8+ and helper CD4+
T lymphocytes.
DC-based immunotherapy of mesothelioma in a murine model was capable of preventing mesothelioma development when applied
before tumor inoculation and slows down mesothelioma growth if given after tumor implantation.
In mesothelioma patients, immunotherapy with autologous DC vaccines after chemotherapy is feasible and well tolerated, and capable
of inducing specific immune responses.
Improvements to DC-based immunotherapy include further optimization of DC harvesting and tumor-associated antigen loading,
modulation of immunosuppressive cells and immune checkpoints, and combining immunotherapy with chemotherapy and/or surgery.
clinical trials. Furthermore, the combination
of immunotherapy with traditional treatments
(e.g., chemotherapy, targeted therapy, radiother-
apy and [debulking] surgery) is currently being
studied to elucidate which therapeutic combi-
nation is most effective in individual patients.
DC-based therapy and other immunothera-
peutical approaches will see their critical test in
Phase II and III clinical trials to prove their place
in cancer treatment.
Financial & competing interests disclosure
The authors have no relevant affiliations or financial
involvement with any organization or entity with a finan
cial interest in or financial conflict with the subject matter
or materials discussed in the manuscript. This includes
employment, consultancies, honoraria, stock ownership or
options, expert testimony, grants or patents received or
pending, or royalties.
No writing assistance was utilized in the production of
this manuscript.
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NC T00 651456
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NCT01445392 ?term=NCT00575770&rank=1
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solid tumors.
NCT012914 20?term = NCT01291420&rank=1
... Dendritic cells are antigen-presenting cells that present tumor-associated antigens (TAAs) to the immune system by trafficking from tumors to lymph nodes. They are essential in priming proliferation and activation of CD8 + cytotoxic Tlymphocytes and CD4 + helper T-lymphocytes resulting in a potent and specific anti-tumor response (104). Dendritic cell function is hampered in cancer patients by tumor-derived soluble factors that suppress their immune-stimulatory ability (105,106). ...
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Malignant pleural mesothelioma (MPM) is an uncommon but aggressive and treatment resistant neoplasm with low survival rates. In the last years we assisted to an exponential growth in the appreciation of mesothelioma pathobiology, leading several new treatments to be investigated both in the early stage of the disease and in the advanced setting. In particular, expectations are now high that immunotherapy will have a leading role in the next years. However, caution is required as results from phase II studies in MPM were often not replicated in larger, randomized, phase III trials. In this review, we describe the most promising emerging therapies for the treatment of MPM, discussing the biological rationale underlying their development as well as the issues surrounding clinical trial design and proper selection of patients for every treatment.
... The first DCBI for mesothelioma was developed in the Erasmus MC, Rotterdam, and has been tested in murine models with peritoneal mesothelioma and in clinical phase I/II studies for patients with pleural mesothelioma. [5][6][7][8][9][10][11] These studies have shown that DCBI induces durable responses and higher survival rates compared with the general mesothelioma population. Dendritic cell (DC) therapy was well tolerated in these patients without grade 3 or 4 toxicities. ...
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Introduction Malignant peritoneal mesothelioma (MPM) is an uncommon but aggressive neoplasm and has a strong association with asbestos exposure. MPM has low survival rates of approximately 1 year even after (palliative) surgery and/or systemic chemotherapy. Recent advances in treatment strategies focusing on cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) have resulted in improved median survival of 53 months and a 5 year survival of 47%. However, recurrence rates are high. Current systemic chemotherapy in the adjuvant setting is of limited efficacy, while immunotherapy with dendritic cell based immunotherapy (DCBI) has yielded promising results in murine models with peritoneal mesothelioma and in patients with pleural mesothelioma. Methods and analysis The MESOPEC trial is an open-label single centre phase II study. The study population are adult patients with histological/cytological confirmed diagnosis of epithelioid malignant peritoneal mesothelioma. Intervention: 4 to 6 weeks before CRS-HIPEC a leukapheresis is performed of which the monocytes are used for differentiation to dendritic cells (DCs). Autologous DCs pulsed with allogeneic tumour associated antigens (MesoPher) are re-injected 8 to 10 weeks after surgery, three times biweekly. Additional booster vaccinations are given at 3 and 6 months. Primary objective is to determine the feasibility of administering DCBI after CRS-HIPEC in patients with malignant peritoneal mesothelioma. Secondary objectives are to assess safety of DCBI in patients with peritoneal mesothelioma and determine whether a specific immunological response against the tumour occurs as a result of this adjuvant immunotherapy. Ethics and dissemination Permission to carry out this study protocol has been granted by the Central Committee on Research Involving Human Subjects (CCMO in Dutch) and the Research Ethics Committee (METC in Dutch). The results of this trial will be submitted for publication in a peer-reviewed journal. Trial registration number NTR7060. EudraCT: 2017-000897-12; Pre-Results.
... A few target drugs were evaluated in mesothelioma treatment. As angiogenesis is a key event in carcinogenesis its inhibitors were considered a good potential for MM treatment [13]. Clinical trials of angiogenesis inhibitors with different mechanisms of action were performed to evaluate their efficacy. ...
Immunotherapy of malignant peritoneal mesothelioma and pseudomixoma peritonei is a promising method and is actively developed to treat patients with these malignancies. The approach includes methods of adoptive cellular immunotherapy with local infusions of autologic activated or genetically modified lymphocytes and target drugs based on monoclonal antibodies, including immune checkpoint inhibitors.
... The highly immunosuppressive tumour microenvironment of MPM indicates a potential clinical benefit from novel immunotherapeutic approaches with anti-checkpoint mAbs [10,11]. Based on this notion, the investigator-initiated phase 2 study MESOT-TREM-2008 (Clinical trial ID: NCT01649024) was designed to explore the activity of the anti-CTLA-4 mAb tremelimumab in the second-line treatment of MPM and peritoneal mesothelioma patients. ...
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Treatment of malignant pleural mesothelioma (MPM) represents a highly unmet medical need. Here, we discuss the results and therapeutic potential of first- and second-generation immunomodulatory antibodies targeting distinct immune checkpoints for the treatment of MPM, as well as their prospective therapeutic role in combination strategies. We also discuss the role of appropriate radiological criteria of response for MPM and the potential need of ad hoc criteria of disease evaluation in MPM patients undergoing treatment with immunotherapeutic agents.
... DC therapy has a favorable safety profile comparable to that of vaccines, but is more laborious and costly to produce. In other malignancies, DC therapy is evolving, with different DC subsets and treatment regimens being tested in order to achieve the strongest antitumor responses [70][71][72]. ...
Non-small cell lung cancer (NSCLC) is still the leading cause of cancer death worldwide, with a poor prognosis. In the era of immunotherapies, the field is rapidly changing, and the clinician needs to be aware of the current state and future perspectives of immunotherapeutic strategies. In this review, we discuss the current status of immune checkpoint inhibitors, cancer vaccines and cellular therapies specifically in NSCLC. Last but not least, we will discuss rational combination strategies that are promising for the near future.
... Wu et al. demonstrated that the blockade of CTLA-4 signaling had effective anticancer effect, which also brought us a new hope in the treatment of MPM through modulation of T cell immunity (56). DC-based immunotherapy has shown promising in a wide variety of cancers including mesothelioma (57). Lack of specific antigen made it difficult to develop antigen-specific immunotherapy on mesothelioma; however, it would shed a light of targeting tumor cells through intratumoral DC vaccination. ...
Malignant pleural mesothelioma (MPM) is a rare cancer originated from pleural mesothelial cells. MPM has been associated with long-term exposure to asbestos. The prognosis of MPM is poor due to the difficulty of making diagnosis in the early stage, the rapid progression, the high invasiveness and the lack of effective treatment. Although the incidence of MPM is low in China to date, it has a tendency to increase in the coming years. The variety of clinical features may cause the delay of diagnosis and high rate of misdiagnosis. The diagnosis of MPM is based on biopsy of the pleura and immunohistochemistry. As China has become the largest country in the consumption of asbestos, it would give rise to a new surge of MPM in the future. The current treatment of MPM is multimodality therapy including surgery, radiotherapy, chemotherapy and immunotherapy. Two surgical procedures are commonly applied: extrapleural pneumonectomy (EPP) and pleurectomy/decortication (P/D). Three dimensional conformal radiotherapy is used to denote a spectrum of radiation planning and delivery techniques that rely on the 3D imaging to define the tumor. Cisplatin combined with pemetrexed (PEM) is the first-line chemotherapy for MPM. The principal targets in immunotherapy include T cells (Treg), CTLA-4 and PD-1. The diagnosis, treatment and prognosis still remain a major challenge for clinical research and will do so for years to come.
... This immunosuppressive effect has also been described in thoracic malignancies [6] [7] [8] [9] [10]. Intriguingly, immunotherapeutic approaches have recently shown that modulation of the patients' immune system is possible and can be of benefit in lung cancer and mesothelioma [11] [12] [13] [14]. ...
Tumor-associated macrophages (TAMs) can be abundantly present in numerous cancer types. Under influence of various stimuli in the tumor microenvironment TAMs develop into a tumor-inhibitory (M1) or tumor-promoting (M2) phenotype. Recently, the role of TAMs in tumor biology and their prognostic value in cancer has become a major topic of interest. In this review we will discuss the importance of TAMs in the pathogenesis and clinical outcome of lung cancer and mesothelioma patients. In addition, the potential of TAMs as therapeutic targets will be discussed.
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Emerging data suggests that host immune cells with a suppressive phenotype represent a significant hurdle to successful therapy for metastatic cancer. Among the suppressor cells, T regulatory cells (Treg) and myeloid-derived suppressor cells (MDSC) are significantly increased in hosts with advanced malignancies. MDSC mediate the suppression of the tumor antigen-specific T cell response through the induction of T cell anergy and the development of Treg in tumor-bearing mice. These results provide robust evidence of an in vivo immunoregulatory function of MDSC in the establishment of tumor antigen-specific tolerance and the development of Treg in tumor-bearing hosts. To achieve effective anti-tumor immunity, tumor-induced immunosuppression must be reversed. Our preliminary results indicate that c-kit ligand (stem cell factor) expressed by tumor cells may be required for MDSC accumulation in tumor-bearing mice, and that blocking the c-kit ligand/c-kit receptor interaction can prevent the development of Treg and reverse immune tolerance induced by MDSC. Since c-kit can be readily inhibited by several small molecule inhibitors including imatinib, sunitinib and dasatinib, targeting immune suppressing cells can be readily accomplished in the clinic.
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Dendritic cells (DCs) are professional antigen-presenting cells involved in the control and initiation of immune responses. In vivo, DCs exposed at the periphery to maturation stimuli migrate to lymph nodes, where they receive secondary signals from CD4+ T helper cells. These DCs become able to initiate CD8+ cytotoxic T lymphocyte (CTL) responses. However, in vitro investigations concerning human monocyte-derived DCs have never focused on their functional properties after such sequential maturation. Here, we studied human DC phenotypes and functions according to this sequential exposure to maturation stimuli. As first signals, we used TNF-α/polyI:C mimicking inflammatory and pathogen stimuli and, as second signals, we compared activated CD4+ T helper cells to a combination of CD40-L/ IFN-γ. Our results show that a sequential activation with activated CD4+ T cells dramatically increased the maturation of DCs in terms of their phenotype and cytokine secretion compared to DCs activated with maturation stimuli delivered simultaneously. Furthermore, this sequential maturation led to the induction of CTL with a long-term effector and central memory phenotypes. Thus, sequential delivery of maturation stimuli, which includes CD4+ T cells, should be considered in the future to improve the induction of long-term CTL memory in DC-based immunotherapy.
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Immunization to multiple defined tumor antigens for specific immune therapy of human cancer has thus far proven difficult. Eighteen HLA A*0201 patients with metastatic melanoma received injections s.c. of CD34 progenitor-derived autologous dendritic cells (DCs), which in- cluded Langerhans cells. DCs were pulsed with peptides derived from four melanoma antigens ((MelAgs) MelanA/MART-1, tyrosinase, MAGE-3, and gp100), as well as influenza matrix peptide (Flu-MP) and keyhole limpet hemocyanin (KLH) as control antigens. Overall immunological effects were assessed by comparing response profiles using marginal likelihood scores. DC injections were well tolerated except for progressive vitiligo in two patients. DCs induced an immune response to control antigens (KLH, Flu-MP) in 16 of 18 patients. An enhanced immune response to one or more MelAgs was seen in these same 16 patients, including 10 patients who responded to >2 MelAgs. The two patients failing to respond to both control and tumor antigens experienced rapid tumor progression. Of 17 patients with evaluable disease, 6 of 7 patients with immunity to two or less MelAgs had progressive disease 10 weeks after study entry, in contrast to tumor progression in only 1 of 10 patients with immunity to >2 MelAgs. Regression of >1 tumor metastases were observed in seven of these patients. The overall immunity to MelAgs after DC vaccination is associated with clinical outcome (P 0.015).
Full-text available
Dendritic cells (DCs) are professional antigen-presenting cells involved in the control and initiation of immune responses. In vivo, DCs exposed at the periphery to maturation stimuli migrate to lymph nodes, where they receive secondary signals from CD4+ T helper cells. These DCs become able to initiate CD8+ cytotoxic T lymphocyte (CTL) responses. However, in vitro investigations concerning human monocyte-derived DCs have never focused on their functional properties after such sequential maturation. Here, we studied human DC phenotypes and functions according to this sequential exposure to maturation stimuli. As first signals, we used TNF-α/polyI:C mimicking inflammatory and pathogen stimuli and, as second signals, we compared activated CD4+ T helper cells to a combination of CD40-L/ IFN-γ. Our results show that a sequential activation with activated CD4+ T cells dramatically increased the maturation of DCs in terms of their phenotype and cytokine secretion compared to DCs activated with maturation stimuli delivered simultaneously. Furthermore, this sequential maturation led to the induction of CTL with a long-term effector and central memory phenotypes. Thus, sequential delivery of maturation stimuli, which includes CD4+ T cells, should be considered in the future to improve the induction of long-term CTL memory in DC-based immunotherapy.
7030 Background: Amatuximab (MORAb-009) is a chimeric monoclonal antibody to mesothelin, a cell surface glycoprotein highly expressed in many cancers including malignant mesothelioma (MM). Based on safety of amatuximab in phase I clinical trial and pre-clinical studies showing synergy in combination with chemotherapy, a single arm phase II study of amatuximab plus pemetrexed (P) and cisplatin (C) was initiated in pts. with MM. Methods: Eligibility criteria included pts. with unresectable epithelial or biphasic pleural MM, no prior chemotherapy and KPS > 70%. Pts. received amatuximab 5 mg/kg on days 1 and 8 with P 500 mg/m ² and C 75 mg/m ² (PC) given on day 1, of each 21 day cycle for 6 cycles. Pts. with objective response or stable disease received amatuximab monotherapy until disease progression. Primary endpoint was progression-free survival (PFS) at 6 months. Secondary endpoints were overall survival (OS), objective response rate and safety of amatuximab with PC. Results: From 2/2009 to 10/2010, 89 pts. were enrolled at 26 sites. Pt. characteristics: median age 67 yrs. (range 46-80), 78% male, 70% with KPS >90%, 89% epithelial MM, 11% biphasic MM and 88% had stage III/IV disease. Median number of PC plus amatuximab cycles was 5 (range 1-6) and 56 (63%) pts. received single agent amatuximab. In addition to the expected toxicity from PC, hypersensitivity reactions (12.4%; Grade 3/4=4.5%) from amatuximab were noted. By independent radiological review 30 (39%) pts. had partial response and 39 (51%) had stable disease. PFS at 6 months was 52% (95% CI: 39.5-63.5) with a median PFS of 6.1 months (95% CI: 5.4-6.5). As of 1/10/12 the median OS was 14.5 months (95% CI: 12.4-18.5) with 31 pts. still alive and 7 pts. receiving maintenance amatuximab. Conclusions: Amatuximab in combination with PC was generally well-tolerated in this study with 90% of pts. having an objective tumor response or stable disease by independent radiological review. Although PFS is not significantly different from historical results of PC alone, the median OS is 14.5 months with 35% of pts. still alive. Updated OS and biomarker data will be presented at the meeting.
Systemic cytokine therapy in cancer has major side effects, and we reasoned that the local infusion of cytokines into tumors could induce local immunologic responses with minimal toxicity and potentially strong systemic anticancer effects. This study investigated the toxicity and effectiveness of intralesional granulocyte/macrophage-colony-stimulating factor (GM-CSF) infusion in solid-tumor masses. We studied 14 patients (12 men, two women) with malignant mesothelioma (MM), aged 60 years (range, 46-70 years), with stage 2 disease, in whom the tumor was of sufficient size and accessibility for an intralesional catheter to be inserted. Re-combinant human GM-CSF (Molgramostim; Schering Plough) was infused intralesionally for 8 weeks, by using a portable pump, at a dose of 2.5-10 [mu]g/kg/day. One patient using GM-CSF developed histologically confirmed necrosis of tumor surrounding the distal catheter, one developed a marked lymphocytic infiltrate in the tumor and had a partial response measured by chest computed tomography (CT) scan, 10 progressed, and three had no response. Neutrophilia with morphologic evidence of neutrophil activation and clinical features suggestive of neutrophil plugging of blood vessels occurred at doses >5 [mu]g/kg/day. In vitro, GM-CSF doubled human neutrophil/CD11b/CD18 expression, suggesting that neutrophil clumping as seen in vivo might be due to integrin upregulation. Intralesional infusion of cytokines is feasible but can be associated with systemic toxicity and has considerable technical problems. It produces a localized immune reaction with tumor regression in a minority of patients.
Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL The long-held view that tumors were not sufficiently immunogenic to promote host immune responses has now been revised to the assessment that at least for some tumors, Foxp3+ T-regulatory (Treg) cells actively suppress anti-tumor immunity. Seeking to build on our ongoing assessment of the regulation of Foxp3+ Treg biology by HDAC and HAT enzymes, we have begun to use combined genetic and pharmacologic approaches to identify and modulate key mechanism within Tregs that limit host immunity. Microarray studies of gene expression in WT, p300-/- and CBP-/- Tregs showed that p300 or CBP deletion led to down-regulation of Foxp3 expression, as well as that of a number of signature Treg genes. Cells co-transfected with Foxp3 and increasing amounts of p300 expression vectors showed that Foxp3 acetylation was enhanced by increasing levels of p300 levels, whereas a p300 small molecule inhibitor, C646 (p300i), impaired Foxp3 acetylation and inhibited Treg function using in vitro suppression assays. In vivo use of C646 showed negligible effects on CD4, CD8 or Treg cell numbers, but qPCR studies showed C646 decreased Treg expression of CTLA-4, GITR, IL-10 and TGF-b, in vitro assays again showed impaired Treg suppression. Additional studies showed, critically, that use of the p300i impaired Treg but not T effector cells in allograft recipients. Thus, parent-to-F1 assays involving alloactivation and proliferation of CD4 an dCD8 T cells were unaffected by C646, and this p300i restored allograft rejection in Treg-dependent models of allograft survival. Turning to tumor models, TC1 lung cancer cells were injected in the flanks of WT B6 mice, B6 mice in which p300 was deleted in CD4+ T cells (Treg plus Teff using CD4-Cre) or just in Tregs (Foxp3-Cre) (n=10/grp), p300 was inhibited using C646 (Alzet pumps, 14 d, 0.9 mg/kg/d) from day 6 post-tumor injection; in both genetic and pharmacologic approaches, p300 targeting suppressed tumor cell growth. qPCR analysis of tumors in C646-treated mice showed increased CD4 and granzyme B mRNA but decreased Foxp3; these data were confirmed by immunohistology, along with increased IFN-g production by purified CD8 cells (ELISPOT), along with reductions in tumor volumes and weights in these C646-treated mice. C646 use did not impair tumor growth in immunodeficient (RAG-/-) mice, in which tumors were exposed to drug in RAG-/- mice as seen by decreased acetylation of histone 3 in tumor extracts (Western blot); no effects on acetylation of certain p300-independent targets within tumor extracts was seen (e.g. acetylation of alpha-tubulin was unimpaired). The p300i also had no direct effect on tumor cell proliferation in vitro. We conclude that our comprehensive genetic and pharmacologic studies show that p300 is an important target for modulation of host Foxp3+ Treg functions, such that Treg suppression can be incrementally reduced and host anti-tumor responses promoted without inducing concomitant autoimmunity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4842. doi:1538-7445.AM2012-4842
The involvement of immune mechanisms in tumor angiogenesis is unclear. Here we describe a new mechanism of tumor vasculogenesis mediated by dendritic cell (DC) precursors through the cooperation of β-defensins and vascular endothelial growth factor-A (Vegf-A). Expression of mouse β-defensin-29 recruited DC precursors to tumors and enhanced tumor vascularization and growth in the presence of increased Vegf-A expression. A new leukocyte population expressing DC and endothelial markers was uncovered in mouse and human ovarian carcinomas coexpressing Vegf-A and β-defensins. Tumor-infiltrating DCs migrated to tumor vessels and independently assembled neovasculature in vivo. Bone marrow–derived DCs underwent endothelial-like differentiation ex vivo, migrated to blood vessels and promoted the growth of tumors expressing high levels of Vegf-A. We show that β-defensins and Vegf-A cooperate to promote tumor vasculogenesis by carrying out distinct tasks: β-defensins chemoattract DC precursors through CCR6, whereas Vegf-A primarily induces their endothelial-like specialization and migration to vessels, which is mediated by Vegf receptor-2.