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Literature Review on the Benefits of Thermotherapy to Boost Immune System and Reduce Viral Replication
... Dry heat therapy uses heating pads, electric blankets, and heat lamps. Moist heat sources penetrate deeper into tissues and include hot baths and steamed towels to ensure good relaxation of muscles [10,11]. Infrared therapy uses lamps or saunas, whereby more deeply located skin layers get heated to treat deep tissue pathologies for chronic conditions like arthritis [12]. ...
This bibliometric study analyzes the evolving field of thermotherapy, a medical treatment that utilizes heat to treat various conditions, including cancer, by applying controlled temperatures to targeted tissues. Utilizing bibliographic data from the core collection of Web of Science and analysis software Biblioshiny and VOSviewer, we analyzed several key metrics to gain insights into the development and trends in thermotherapy research. The annual scientific production revealed a significant increase in publications over the past two decades, reflecting growing interest in this field. Analysis of the most relevant authors and sources highlighted key contributors and influential journals. Trend topics demonstrated a shift from early focus areas like hyperthermia and laser-induced thermotherapy to recent advancements involving nanoparticles and combination therapies. The thematic map provided insights into core, emerging, and niche areas within the research landscape. A historiograph traced the chronological development of significant publications, while the co-occurrence of keywords and bibliographic coupling of documents identified major themes and interconnections in the literature. International collaborations were mapped, showing the global nature of thermotherapy research. The study identified several research gaps, including the need for large-scale clinical trials, interdisciplinary approaches, and standardized treatment protocols. Practical implications suggest focusing on targeted delivery systems, expanding cancer research, and fostering collaborative projects to advance the field.
Fever is a complex, coordinated autonomic, neuroendocrine, and behavioral response that is adaptive and is used by nearly all vertebrates as part of the acute-phase reaction to immune challenge. Although the febrile response can be elicited by a wide variety of infectious organisms and may also occur during noninfectious inflammatory conditions, its manifestations are stereotyped and largely independent of the causative agent. Like other integrated responses, such as the regulation of energy metabolism, blood pressure and volume, and reproduction, fever depends on humoral cues from the body, is orchestrated largely by the hypothalamus, and involves the coordination of a wide . . .
Cytotoxic T lymphocytes (CTLs) are a critical component of the immune response to tumors. Tumor-derived peptide antigens targeted by CTLs are being defined for several human tumors and are potential immunogens for the induction of specific antitumor immunity. Dendritic cells (DC) are potent antigen-presenting cells (APCs) capable of priming CTL responses in vivo. Here we show that major histocompatibility complex class I-presented peptide antigen pulsed onto dendritic APCs induces protective immunity to lethal challenge by a tumor transfected with the antigen gene. The immunity is antigen specific, requiring expression of the antigen gene by the tumor target, and is eliminated by in vivo depletion of CD8+ T cells. Furthermore, mice that have rejected the transfected tumor are protected from subsequent challenge with the untransfected parent tumor. These results suggest that immunization strategies using antigen-pulsed DC may be useful for inducing tumor-specific immune responses.
Spontaneous regression of cancer is one of the most fascinating phenomena observed in medicine. It is generally regarded as inexplicable, although there are now some laboratory studies of regressed or regressing tumours, as well as new theoretical possibilities about mechanisms. In this review, the historical background, clinical features and possible mechanisms are discussed. The clinical aspects of the malignancies most often reported to undergo spontaneous regression, namely renal cell carcinoma, neuroblastoma, carcinoma of the breast, malignant melanoma and leukaemias/lymphomas, are reviewed. The prevalent view regarding the mechanism for spontaneous regression is the involvement of immunological factors in the host. Other mechanisms include hormonal changes, tumour necrosis, trauma and changes in blood supply. Recent. reports suggest other mechanisms such as apoptosis and differentiation to a benign tumour. Decreased telomerase activity has been reported in neuroblastomas that regress, and hypomethylation of DNA in retinoblastoma is a possibility. A role for cytokines and/or growth factors is also discussed. The significance of spontaneous regression is the demonstration of endogenous control of neoplastic growth. Spontaneous regression of cancer is defined as the complete or partial disappearance of malignant tumour in the absence of therapy that is capable of inducing anti-neoplastic effects. Most patients ultimately relapse, so it is not usually associated with cure of the malignant disease. The existence of spontaneous regression is often questioned; indeed, review of the literature reveals reported cases which do not represent malignant disease, instances in which documentation of metastases is questionable and some reported cases in which therapy may have played a role. In 1966, Everson and Cole published a classic monograph on this topic which included 176 well- documented cases of spontaneous regression of cancer published from 1900 until 1964, and listed criteria for the diagnosis (1). These are: documented histologic regression of biopsy-proven metastases; radiologic regression of
Increasing the ability of tumor-reactive T cells to mediate tumor regression in vivo has been a major goal of tumor immunologists. Progress toward this goal has been aided by the identification of tumor-associated antigens on both experimental mouse tumors and human tumors. However, the self-like nature and low immunogenicity of these antigens has made it clear that other measures to enhance the effectiveness of the T cells reactive to these antigens are essential if immunotherapy is to be clinically effective. An increased understanding of antigen processing and presentation is an important step in this process, as is the use of cytokines to increase immune responsiveness. Despite recent advances, there is still much to be learned before the specificity of the immune system is safely harnessed to halt malignant cell growth effectively.
Cytotoxic T lymphocytes and natural killer cells are essential effectors of anti-tumor immune responses in vivo. Dendritic cells (DC) 'prime' tumor antigen-specific cytotoxic T lymphocytes; thus, we investigated whether DC might also trigger the innate, NK cell-mediated anti-tumor immunity. In mice with MHC class I-negative tumors, adoptively transferred- or Flt3 ligand-expanded DC promoted NK cell-dependent anti-tumor effects. In vitro studies demonstrated a cell-to-cell contact between DC and resting NK cells that resulted in a substantial increase in both NK cell cytolytic activity and IFN-gamma production. Thus, DC are involved in the interaction between innate and adaptive immune responses.
The role of T helper type 1 (Th1) and Th2 cells in tumor immunity was investigated using Th cells induced from ovalbumin (OVA)-specific
T cell receptor transgenic mice. Although Th1 cells exhibited stronger cytotoxicity than Th2 cells, both cell types completely
eradicated tumors when transferred into mice bearing A20 tumor cells transfected with the OVA gene (A20-OVA). Th1 cells eradicated
the tumor mass by inducing cellular immunity, whereas Th2 cells destroyed the tumor by inducing tumor necrosis. Both Th1 and
Th2 cells required CD8+ T cells to eliminate tumors, and neither of these cells were able to completely eliminate A20-OVA tumors from T and B cell–deficient
RAG2−/− mice. Mice cured from tumors by Th1 and Th2 cell therapy rejected A20-OVA upon rechallenge, but CD8+ cytotoxic T lymphocytes were induced only from spleen cells prepared from cured mice by Th1 cell therapy. Moreover, we demonstrated
that Th1 and Th2 cells used distinct adhesion mechanisms during tumor eradication: the leukocyte function-associated antigen
(LFA)-1–dependent cell–cell adhesion step was essential for Th1 cell therapy, but not for Th2 cell therapy. These findings
demonstrated for the first time the distinct role of antigen-specific Th1 and Th2 cells during eradication of established
tumors in vivo.
Heat shock proteins like gp96 (grp94) are able to induce specific cytotoxic T-cell (CTL) responses against cells from which they originate and are currently studied in clinical trials for use in immunotherapy of tumors. We have recently demonstrated that gp96 binds to at least one yet unidentified receptor restricted to antigen-presenting cells (APCs) like dendritic cells (DCs) but not to T cells. Moreover we have shown, that for CTL activation by gp96-chaperoned peptides receptor-mediated uptake of gp96 by APCs is required. Lately, we have discovered a second function of gp96 when interacting with professional APCs. Gp96 is able to mediate maturation of DCs as determined by upregulation of MHC class II, CD86 and CD83 molecules, secretion of pro-inflammatory cytokines IL-12 and TNF-alpha and enhanced T-cell simulatory capacity. Furthermore, the gp96 receptor(s) are down-regulated on mature DCs, suggesting that the gp96 receptor(s) behave similar to other endocytic receptors like CD36, mannose receptor etc. Our findings now provide additional evidence for the remarkable immunogenicity of gp96: first, the existence of specific gp96 receptors on APCs and second, the capacity to activate dendritic cells which is strictly required to enable these highly sophisticated APCs to prime CTL responses.
Liposomes are the leading drug delivery systems for the systemic (iv.) administration of drugs. There are now liposomal formulations of conventional drugs that have received clinical approval and many others in clinical trials that bring benefits of reduced toxicity and enhanced efficacy for the treatment of cancer and other life-threatening diseases. The mechanisms giving rise to the therapeutic advantages of liposomes, such as the ability of long-circulating liposomes to preferentially accumulate at disease sites including tumours, sites of infection and sites of inflammation are increasingly well understood. Further, liposome-based formulations of genetic drugs such as antisense oligonucleotides and plasmids for gene therapy that have clear potential for systemic utility are increasingly available. This paper reviews the liposomal drug delivery field, summarises the success of liposomes for the delivery of small molecules and indicates how this success is being built on to design effective carriers for genetic drugs.
Over most of the 20th century, immunotherapy for cancer was based on empiricism. Interesting phenomena were observed in the areas of cancer, infectious diseases, or transplantation. Inferences were made and extrapolated into new approaches for the treatment of cancer. If tumors regressed, the treatment approaches could be refined further. However, until the appropriate tools and reagents were available, investigators were unable to understand the biology underlying these observations. In the early 1990s, the first human tumor T cell antigens were defined and dendritic cells were discovered to play a pivotal role in antigen presentation. The current era of cancer immunotherapy is one of translational research based on known biology and rationally designed interventions and has led to a rapid expansion of the field. The beginning of the 21st century brings the possibility of a new era of effective cancer immunotherapy, combining rational, immunological treatments with conventional therapies to improve the outcome for patients with cancer.
This report describes the time-dependent biodistribution of human p53 plasmid delivered in aerosol with polyethyleneimine in mice compared to the distribution of this material following intravenous injection. Area-under-the-curve values for p53 plasmid after inhalation were 2.8-fold greater than values after intravenous administration, despite the fact that the delivered aerosol dose was one-fifth the intravenous dose. After aerosol administration, pulmonary concentrations of p53 plasmid were high and other organs showed amounts not distinguishable from untreated control. High concentrations of p53 plasmid in the lungs remained with negligible reduction for at least 24 h. Shortly after intravenous injection, organs exhibited the following relative levels of exogenously administered p53: liver > spleen > blood > or = lungs > heart > kidney. These results demonstrate effective pulmonary delivery of DNA in complex with PEI by aerosol, without significant systemic dissemination. In contrast, intravenous administration caused a prompt systemic distribution of DNA with a shorter half-life of the administered gene in the lungs.
Non-viral gene delivery systems have the potential to create viable pharmaceuticals from nucleic acids. These DNA delivery systems contain lipids and/or cationic polymers. In order for these systems to be developed into commercial products, several barriers must be overcome. These include obstacles in manufacturing, formulation and stability. In vivo, problems of extracellular non-specific interactions and intracellular trafficking to the nucleus are also encountered. Recent progress has been made in overcoming these issues.
Throughout this text we have presented the results of preclinical studies which were relevant to the topics being presented. In this chapter we wish to summarize some of the literature regarding in vivo WBH studies to serve as a convenient reference point for the reader to pursue further inquiry into the literature, or as a starting point for laboratory research.
Recent advances in the understanding of the molecular pathogenesis of cancer herald breakthroughs in the treatment of this collection of diseases, which are still usually incurable in advanced stages. In particular, there is a high expectation of gene and immunogene therapy. A recent meeting
¹The 3rd European Conference on Gene Therapy of Cancer was held at Berlin, Germany, on 11–13 September 1997.
¹ surveyed new progress in this area.
There is considerable circumstantial evidence that the immune system is involved in the tumour regression and host cure that may follow curative local tumour heating in animals. There is little to indicate that a specific anti-tumour immune response is stimulated following heating or that heat per se is in any way unique in its effect on tumours. Available data suggest that the participation of the immune response involves macrophages and an increase in non-specific cellular and humoral immune competence. Total-body hyperthermia can depress these reactions, probably by direct physical damage to lymphoid tissues, and so predispose to enhanced metastasis. In man, results obtained with bacterial preparations are also consonant with a non-specific boosting effect on host defences via stimulation of the reticuloendothelial system. There is no definitive evidence for stimulation of an effective anti-tumour response in man following tumour heating, and no indication that total-body heating is deleterious to host defence mechanisms.
Current data suggest that the more defined host response to tumour heating in animals is an artifact, due to the greater chemically induced antigenicity (immunogenicity) of animal tumours used for research.
To investigate the temperature dependence of T lymphocyte activation, we have examined the IL 1-induced secretion of IL 2 by the murine T lymphoma cell line LBRM-33-1A5. During 24-hr incubations, there are modest increases in IL 2 secretion as culture temperatures are increased from 33 degrees to 37 degrees C, but IL 2 secretion declines at higher temperatures. However, the kinetics of IL 2 release during the first 8 hr of culture are highly temperature-dependent. The rate of IL 2 release increases linearly with temperature over the range from 33 degrees to 41 degrees C, demonstrating temperature coefficients (Q10) greater than 70. In contrast, IL 2-promoted proliferation of a continuous T cell line is much less temperature-dependent with Q10 values of less than 4.0.
Human gene therapy is a rapidly emerging field; therapeutic genes are engineered into adenovirus, retrovirus, or into plasmid-liposome complexes for their delivery into cells in culture or in vivo. Steps to improve for successful liposome-mediated gene delivery to somatic cells include persistence of the plasmid in blood circulation, port of entry and transport across the cell membrane, release from endosomal compartments into the cytoplasm, nuclear import by docking through the pore complexes of the nuclear envelope, expression driven by the appropriate promoter/enhancer control elements, and persistence of the plasmid in the nucleus for long periods. A number of strategies for enhancing the efficiency of uptake by the cells and release from endosomal compartments of liposome-plasmid or liposome-oligonucleotide complexes are reviewed here; emphasis is given to the direction of liposomes to caveolae vesicles.
Fever is a common response to infection and to other challenges to host defense. Temperature elevation has been associated
with effects on the recognition, recruitment, and effector phases of the immune response. Specific immunologic responses are
generally enhanced in the setting of temperature elevation within the physiologic range but not the supraphysiologic range.
In contrast, natural immune responses may be unchanged or adversely affected. Temperature elevation appears to affect primarily
the phase of recognition and sensitization or activation of mononuclear leukocytes. T lymphocyte responses (and/or the interactions
of T lymphocytes with monocytes-macrophages) are enhanced for generation of effector cells. The activities of the effector
cells, once generated, are usually not enhanced — or may even be depressed — by temperature elevation, but decreases are more
than offset by increased T helper function. Overall, the data suggest that temperature elevations of the febrile response
constitute a beneficial component of effective host defense.
Effects of high ambient temperatures on various stages of rabies virus infection have been studied. Ambient temperature increased within the tolerated range was found to have little effect upon body temperature of normal mice, but caused marked elevation of temperature during illness. Temperatures at onset of patent illness in mice were lower than normal. Increased body temperature in the higher thermic ambience during the incubation period was associated with decreased mortality and frequent abortive infections. Exposure to high ambient temperature late in the incubation period delayed onset of illness, decreased mortality, and increased frequency of abortive infections, but exposure to high ambient temperature after onset of patent illness did not affect the course of the disease.
Inadequate presentation of tumor antigens by host professional antigen-presenting cells (APCs), including dendritic cells (DCs), is one potential mechanism for the escape of tumors from the host immune system. Here, we show that human cancer cell lines release a soluble factor or factors that dramatically affect DC maturation from precursors without affecting the function of relatively mature DCs. One factor responsible for these effects was identified as vascular endothelial growth factor (VEGF). Thus, VEGF may play a broader role in the pathogenesis of cancer than was previously thought, and therapeutic blockade of VEGF action may improve prospects for immunotherapy as well as inhibit tumor neovasculature.
Dendritic cells (DC) are a distinct population of leukocytes and specialized antigen-presenting cells for T cell responses. Prior work has shown that GM-CSF can induce the development of large numbers of DC from proliferating progenitors in mouse bone marrow. We have monitored the effects of potentially enhancing and suppressive cytokines in these cultures. In this system, many immature DC develop from proliferating precursors during the first six days of culture, and between days 6-8 maturation of typical nonadherent and nonreplicating DC takes place. The maturation is accompanied by a large increase in the expression of major histocompatibilities complex class II (MHC II) and B7-2/CD86, and in mixed leukocyte reaction stimulating activity. Tumor necrosis factor-alpha (TNF-alpha), previously shown to be required for development of human DC, was found to enhance the maturation of mouse DC in the last two days of culture. Transforming growth factor-beta 1 (TGF-beta 1), on the other hand, almost totally blocked DC maturation, but it had to be given in the first six days of culture when the DC were actively proliferating. TGF-beta 1 did not block the production of immature, MHC II-positive but B7-2/CD86-negative DC. Maturation would take place between days 6-8 as long as the cultures were depleted of Fc-receptor-bearing cells, or if TNF-alpha were added. In both instances, maturation was not blocked even when TGF-beta 1 remained in the culture. We conclude that the development of DC, in response to GM-CSF, can be modified by other cytokines. TGF-beta 1 is suppressive but only indirectly via Fc-receptor-bearing suppressive cells, presumably suppressive macrophages, while TNF-alpha enhances the final maturation of DC.
Fever's ability to manipulate the character and extent of physiological temperature gradients correlates with the unusual influence different physiological temperatures have upon model immune responses in vitro. This relationship may help to explain the remarkable evolutionary conservation of the febrile response to infection. A very restricted range of the upper physiological temperatures supports the activation of resting lymphocytes for proliferation and effector formation in the two major limbs of the immune system, cell-mediated immunity and humoral immunity. In contrast, once effectors are formed they can function in a fashion which is nearly independent of physiological temperature. This suggests that physiological temperature change acts to regulate the emergence of new immune responses but does not restrict the activity of existing effector mechanisms once they have been formed. The differential sensitivity of these processes to different physiological temperatures suggests that fever's biological purpose with respect to the immune system is the elimination of lower peripheral tissue temperatures rather than the elevation of core temperatures. However, further studies may reveal that some functions are amplified by the core temperature transitions while other functions are selectively regulated by peripheral tissue temperature transitions. The critical cell for the temperature dependence of immune responses seems to be the Th since its ability to produce cytokines is highly temperature dependent. In contrast, macrophages produce cytokines equally well at all temperatures except those of the febrile core, a feature which may serve to downregulate the production of endogenous pyrogens.
First attempts of cancer immunotherapy were made approximately 100 years ago on the assumption that tumor cells are recognized as 'foreign' by the immune system. Later on, a whole series of experimental animal tumor models were developed. They included the use of syngeneic tumors, spontaneously arising tumors and human tumor xenografts in immunodeficient mice. The experimental data contributed to our understanding of the interaction between immunocompetent cells and their products on the one hand and tumor cells on the other. On this basis, various immunotherapeutic protocols have been devised which included the use of 'nonspecific' components such as bacterial adjuvants, cytokines, NK cells and macrophages and attempts were made to raise specific T and B cell responses against tumor cells. Many human tumor-associated antigens have been characterized, and various ways of increasing the immunogenicity of human tumor cells have been described. Moreover, more insight has been achieved in defining 'high risk' populations on the basis of genetic background, the role of environmental factors and the characterization of 'precancerous' cells. Some cancer vaccines have been used in clinical trials which have resulted in partially beneficial therapeutic effects but have not provided a full solution for a rational use of immunotherapy against human neoplasia.
Cytokines are pleiotropic molecules mediating several pathologic processes. Long before the discovery of cytokines as immune
system growth factors or as bone marrow stimulants, investigators learned a great deal about cytokines when they studied them
as the endogenous mediators of fever. The terms “granulocytic” or “endogenous pyrogen” were used to describe substances with
the biologic property of fever induction. Today, we recognize that pyrogenicity is a fundamental biologic property of several
cytokines and hence the clinically recognizable property of fever links host perturbations during disease with fundamental
perturbations in cell biology. In this review, the discoveries made on endogenous pyrogens are revisited, with insights into
the importance of the earlier work to the present-day understanding of cytokines in health and in disease.
An enormous effort using a great variety of approaches has been undertaken in the last decade to translate basic and clinical research into successful cancer therapies. This review summarizes recent results of experiments and trials using cellular and cytokine therapy, as well as gene therapy, to exploit immune responses to tumors.
Gene therapy has attracted much interest since the first submissions of phase I clinical trials in the early 1990s, for the treatment of inherited genetic diseases. Preliminary results were very encouraging and prompted many investigators to submit protocols for phase I and phase II clinical trials for the treatment of inherited genetic diseases and cancer. The possible application of gene transfer technology to treat AIDS, cardiopathies, and neurologic diseases is under evaluation. Some viral vectors have already been used to deliver HIV-1 subunits to immunize volunteers who are participating in the AIDS vaccine programs in the USA. However, gene delivery systems still need to be optimized in order to achieve effective therapeutic interventions. The purpose of this review is to summarize the latest achievements in improving gene delivery systems, their current application in preclinical studies and in therapy, and the most pressing issues that must be addressed in the area of vector design.
A major goal for gene therapy is to obtain targeted vectors that transfer genes efficiently to specific cell types. In theory, this can be achieved by targeting entry of the vector or by building gene expression cassettes that restrict gene expression to certain cell types. This review summarizes recent strategies to alter vector tropism for targeted gene delivery.
Immunotherapy of cancer is entering into a new phase of active investigation both at the pre-clinical and clinical level. This is due to the exciting developments in basic immunology and tumour biology that have allowed a tremendous increase in our understanding of mechanisms of interactions between the immune system and tumour cells. This review briefly summarizes the state of the art in basic tumour immunology before discussing the clinical applications of the new concepts in the clinical setting. Clinical approaches are diverse but can now be based on strong scientific rationales. The analysis of the available clinical results suggests that, despite some disappointments, there is room for optimism that both active immunotherapy (vaccination) and adoptive immunotherapy may soon become part of the therapeutic arsenal to combat cancer in a more efficient way.
Biopsies of tumors responding to interleukin 2 (IL-2) based immunotherapy have been reported to show a leukocytic infiltration. Clinical responses to IL-2-based immunotherapy, however, are limited, suggesting a failure of leukocyte localization at tumor sites. Leukocyte infiltration at inflammatory sites requires local activation of leukocytes and endothelial cells in a coordinated and defined temporal sequence. There is evidence supporting the theory that infiltration of leukocytes at tumor sites is suboptimal due to a failure of coordination of these localizing events. In this review, factors involved in leukocyte recruitment at sites of inflammation and the coordination of these factors in a successful model of inflammation, i.e., wound healing, are discussed. This example is contrasted with events at tumor sites where alterations in expression of cell adhesion molecules or in the production of activating agents may be present. Additionally, the systemic administration of an activating cytokine such as IL-2 may fail to duplicate events that normally occur within a local environment. These observations may facilitate the design of future immunotherapy trials.
Infectious disease, heart disease, cancer, autoimmunity, genetic defects and even traumatic injury may someday be treated with gene therapy and gene transfer strategies. The potential impact of this new technology on human disease has produced optimism and expectation for scientists and lay people alike. As more effort is directed at harvesting the potential of this technology it has become clear that the success or failure of gene therapy will hinge on our ability to manipulate and control the process of gene transfer in somatic cells. Today, somatic gene transfer is accomplished using either viral or non-viral gene transfer methods. The benefits and limitations of each system are aggressively being investigated to determine which characteristics are most compatible with safe and reliable gene transfer.
Conventional treatment approaches for malignant tumors are highly invasive and sometimes have only a palliative effect. Therefore, there is an increasing demand to develop novel, more efficient treatment options. Increased efforts have been made to apply immunomodulatory strategies in antitumor treatment. In recent years, immunizations with naked plasmid DNA encoding tumor-associated antigens have revealed a number of advantages. By DNA vaccination, antigen-specific cellular as well as humoral immune responses can be generated. The induction of specific immune responses directed against antigens expressed in tumor cells and displayed e.g., by MHC class I complexes can inhibit tumor growth and lead to tumor rejection. The improvement of vaccine efficacy has become a critical goal in the development of DNA vaccination as antitumor therapy. The use of different DNA delivery techniques and coadministration of adjuvants including cytokine genes may influence the pattern of specific immune responses induced. This brief review describes recent developments to optimize DNA vaccination against tumor-associated antigens. The prerequisite for a successful antitumor vaccination is breaking tolerance to tumor-associated antigens, which represent "self-antigens." Currently, immunization with xenogeneic DNA to induce immune responses against self-molecules is under intensive investigation. Tumor cells can develop immune escape mechanisms by generation of antigen loss variants, therefore, it may be necessary that DNA vaccines contain more than one tumor antigen. Polyimmunization with a mixture of tumor-associated antigen genes may have a synergistic effect in tumor treatment. The identification of tumor antigens that may serve as targets for DNA immunization has proceeded rapidly. Preclinical studies in animal models are promising that DNA immunization is a potent strategy for mediating antitumor effects in vivo. Thus, DNA vaccines may offer a novel treatment for tumor patients. DNA vaccines may also be useful in the prevention of tumors with genetic predisposition. By DNA vaccination preventing infections, the development of viral-induced tumors may be avoided.
Cytotoxic T lymphocytes (CTL) are essential effectors of the cell-mediated immune response. The ability of CTL to specifically recognise and lyse malignant cells expressing the relevant surface antigens under optimal in vitro conditions justifies attempts to boost their number and activity through various forms of immunotherapy. Considering the high prevalence of colorectal cancer and poor survival rates for patients with advanced-stage disease, the development of new protocols based on CTL stimulation represents a genuine and promising treatment option. Significant advances in recombinant DNA technology and molecular biology have led to the identification of a number of tumour-associated antigens (TAA). These have served as vaccine constituents and/or stimuli for obtaining CTL used for adoptive immunotherapy after in vitro stimulation and expansion. The present review describes the properties and functions of CTL as effectors of the immune response against tumours, and summarises the known TAA recognised by CTL and the current status of CTL-related immunotherapeutic interventions in colorectal cancer patients.
Gene-engineered dendritic cells (DC) are being tested in cancer immunotherapy. DC are the best equipped antigen-presenting cells (APC) to overcome tolerance/ignorance to self antigens presented by cancer cells. Genetic immunotherapy with DC engineered to express tumor antigens has the potential advantages of endogenous epitope presentation by both major histocompatibility complex (MHC) class I and II molecules. DC can also be gene-modified to express immunostimulatory molecules that further enhance their antigen-presenting function. Review of the literature provided 52 manuscripts where gene-modified DC were being tested in murine models of immunotherapy for cancer. Review of the antitumor effects of gene-modified DC in these preclinical studies provides valuable information on the optimal methods of gene transfer into DC, the schedule of administration, the route, dose and the underlying immunological mechanisms of the antitumor effects. These data may help in the translation of this promising approach to the clinic.
Recent genetic studies have resurrected the concept that the adaptive and innate immune systems play roles in tumor surveillance. Natural killer (NK) cells recognize many tumor cells but not normal self cells, and they are thought to aid in the elimination of nascent tumors. Two main strategies are employed by NK cells to recognize tumor targets. Many tumor cells down-regulate class I major histocompatibility complex (MHC) molecules, thus releasing the NK cell from the inhibition provided by class I MHC-specific inhibitory receptors ('missing self recognition'). More recently, it has become clear that a stimulatory receptor expressed by NK cells, T cells and macrophages (NKG2D) recognizes ligands (MHC class I chain related [MIC], H6O, retinoic acid early inducible [Rae1] and UL16 binding proteins [ULBP]) that are up-regulated on tumor cells and virally infected cells but are not expressed well by normal cells. Ectopic expression of these ligands on tumor cells leads to the potent rejection of the tumors in vivo. Importantly, mice that previously rejected the ligand+ tumor cells develop T-cell immunity to the parental (ligand-) tumor cells. The recognition of induced-self ligands as a strategy to recognize abnormal self sets a precedent for a new immune recognition strategy of the innate immune system.
Among other heat shock proteins (HSPs), the ER-resident chaperone Gp96 has been described as a potent tumour vaccine in animal models. A growing list of data underlines that Gp96 triggers both arms of pathogen defence-innate and specific immunity-in a synergistic and most efficient way: It enables specific immune responses by transferring immunogenic peptides that have been acquired in the ER to the MHC class I pathway of antigen presenting cells (APCs). For this, two important features of Gp96 are required. First, its ability to bind immunogenic peptides. Secondly, its acquisition by specialized antigen presenting cells capable of inducing cellular immune responses. Due to specific receptors on the surface of APCs, this uptake from the extracellular space occurs very efficiently and rapidly. Serving the innate branch of immunity, Gp96 unspecifically activates APCs, which then provide a pro-inflammatory cytokine milieu and co-stimulation to cytotoxic T cells. Thus, Gp96 uses all resources of the immune system to trigger cytotoxic T cell responses against associated peptides.
Dendritic cells (DCs) serve as professional antigen-presenting cells and are pivotal in the host immune response to tumor antigens. To define the pathways limiting DC function in the tumor microenvironment, we assessed the impact of tumor cyclooxygenase (COX)-2 expression on DC activities. Bone marrow-derived DCs were cultured in either tumor supernatant (TSN) or TSN from COX-2-inhibited tumors. After culture, DCs were pulsed with tumor-specific peptides, and their ability to generate antitumor immune responses was assessed following injection into established murine lung cancer. In vitro, DC phenotype, alloreactivity, antigen processing and presentation, and interleukin (IL)-10 and IL-12 secretion were evaluated. DCs cultured in TSN failed to generate antitumor immune responses and caused immunosuppressive effects that correlated with enhanced tumor growth. However, genetic or pharmacological inhibition of tumor COX-2 expression restored DC function and effective antitumor immune responses. Functional analyses indicated that TSN causes a decrement in DC capacity to (a) process and present antigens, (b) induce alloreactivity, and (c) secrete IL-12. Whereas TSN DCs showed a significant reduction in cell surface expression of CD11c, DEC-205, MHC class I antigen, MHC class II antigen, CD80, and CD86 as well as a reduction in the transporter-associated proteins, transporter associated with antigen processing 1 and 2, the changes in phenotype and function were not evident when DCs were cultured in supernatant from COX-2-inhibited tumors. We conclude that inhibition of tumor COX-2 expression or activity can prevent tumor-induced suppression of DC activities.
Gene therapy was initially thought of as a means to correct single gene defects in hereditary disease. Since then, cancer has become the most important indication for gene therapy in clinical trials. In the foreseeable future, the best way to achieve reasonable intratumoral concentrations of a transgene with available vectors will be direct intratumoral injection with or without the help of various techniques such as endoscopy or computed tomography guidance. At present, viral and nonviral methods of gene transfer are used either in vivo or ex vivo/in vitro. The most important viral vectors currently used in clinical trials are retroviruses, adenoviruses, adeno-associated viruses and herpes viruses. However, none of them satisfies all the criteria of an ideal gene therapeutic system, and vectors with only minimal residues of their parent viruses (gutless vectors) and completely synthetic viral vectors are gaining importance. Nonviral methods of gene therapy include liposomes, injection of vector-free (naked) DNA, protein-DNA complexes, delivery by gene gun, calcium-phosphate precipitation, electroporation and intracellular microinjection of DNA. The first clinical trial of human gene therapy was performed in 1990 and since then more than 5000 patients have been treated worldwide in over 400 clinical protocols. Side effects were rare and mostly mild in all of these studies and expression of the transgene was demonstrated in patients in vivo. Despite anecdotal reports of therapeutic responses in some patients, there is still no unequivocal proof of clinical efficacy of most approaches to gene therapy in cancer, primarily due to very low transduction and expression efficacy in vivo of available vectors. Strategies for gene therapy of cancer can be subdivided into four basic concepts: 1) strengthening of the immune response against a tumor, 2) repair of cell cycle defects caused by loss of tumor suppressor genes or inappropriate activation of oncogenes, 3) suicide gene strategies and 4) inhibition of tumor angiogenesis. Gene marker studies and gene protection of normal tissue are also discussed.
The long-term survival of lung cancer patients treated with conventional therapies (surgery, radiation therapy and chemotherapy) remains poor and has changed little in decades. The need for novel approaches remains high and gene therapy holds promise in this area. A number of genes have been shown in vitro, in animal studies and most recently, in human clinical trials, to have antitumor actions. However, a number of problems still exist and success in human patients to date has been marginal. Among the numerous considerations are the efficiency of delivery of the gene to the tumor or, if an indirect effect is the aim, possibly nontumor tissues, the efficiency and persistence of expression of the therapeutic gene, the specificity of the gene action against the tumor, potential toxic or pathogenic consequences of either the genes or the delivery vectors used, convenience of the therapy and how likely the therapy will compliment or complicate other conventional anticancer therapies. After the cloning of the cystic fibrosis gene, there was great interest in the noninvasive delivery of genes directly to the pulmonary surfaces by aerosol. Clearly, this approach could have application to some pulmonary cancers as well and most early efforts focused mainly on the use of nonviral vectors, primarily cationic lipids. Unfortunately, nebulization shear forces and inefficient pulmonary uptake and expression of plasmid DNA-cationic lipid formulations have generally resulted in a lack of therapeutic effect, so much of this work has diminished in recent years. Polyethyleneimine (PEI)-based formulations have proven stable during nebulization and result in nearly 100% efficient transfection throughout the airways and lung parenchyma. Therapeutic responses have been obtained in several animal lung tumor models when PEI-based formulations of p53 and other antitumor genes were delivered by aerosol. In addition, this mode of delivery seems to be associated with low toxicity and results in little or none of the immunostimulatory response typically associated with the delivery of bacterially produced plasmid DNA containing unmethylated CpG motifs, which has presented a challenge to repeated gene therapy via other modes of delivery. Other potential applications of PEI aerosol gene delivery include the treatment of asthma, lung alveolitis and fibrosis and a variety of monogeneic diseases such as cystic fibrosis and alpha-1-antitrypsin deficiency. In addition, a wide range of conditions treatable via genetic immunization could benefit from this approach to gene delivery as well.
There are currently over 150 medical centers worldwide enrolling patients in randomized, controlled Phase III clinical trials testing autologous cancer-derived heat-shock protein (HSP)-peptide complexes for the treatment of renal cell carcinoma and melanoma. In addition, autologous HSP-peptide complexes have been or are being tested in Phase I and II trials of chronic myelogenous leukemia, lymphoma and pancreatic, gastric and colorectal cancers. The door has more recently opened to clinical testing of off-the-shelf HSP-based treatments for infectious diseases. This review recounts the long history of basic research on HSPs in immune response. A keen understanding of how these ancient molecules orchestrate the immune response to cancer and infections has been gained, providing a clear rationale for translating this knowledge into clinical medicine.
Gene transfer technology has many potential applications in medicine. Phase I and phase II gene-based clinical trials have been conducted for the treatment of cancer, monogenic disorders, some neurodegenerative illnesses, cardiopathies and infectious diseases. A phase I gene therapy clinical trial has recently been approved for the treatment of Parkinson's disease, while preclinical studies are in progress to develop gene-based interventions for the treatment of Alzheimer's disease and Huntington's disease, amyotrophic lateral sclerosis, spinal cord injury, and diabetes type 1 and type 2. A number of gene transfer models have been generated for gene therapy and genetic immunization programs. Vector design is addressing several pressing issues in the matter of gene delivery improvement, stabilization of transgene expression and safety. This is necessary in order to achieve efficient gene-based therapeutic interventions. Indeed, considerable progress has been reported in the field of vector design, which has produced some encouraging results in clinical trials and preclinical studies. However, vector design should be further developed to allow for the successful application of gene transfer technology in therapy. This review summarizes the latest achievements and controversies in clinical trials and preclinical studies in the field of gene therapy.
Heat shock proteins (HSP) from tumor cells contain the gp96 polypeptide associated with cancer-specific antigenic peptides. Mice that are immunized with HSP/peptide-complex (HSPPC) derived from cancer tissue reject tumor from which HSPs are purified. We tested in humans whether vaccination with HSPPC-gp96 (Oncophage) from autologous liver metastases of colorectal carcinoma induces cancer-specific T-cell responses in patients rendered disease free by surgery. Experimental Design: Twenty-nine consecutive patients underwent radical resection of liver metastases [Memorial Sloan-Kettering Cancer Center (MSKCC) score 1-3 (good prognosis), 18 patients; score 4-5 (bad prognosis), 11 patients] and received autologous tumor-derived HSPPC-96. Two vaccine cycles were administered (four weekly injections followed by four biweekly injections after 8 weeks). Class-I HLA-restricted, anti-colon cancer lines T-cell response was measured by ELISPOT assay on peripheral blood mononuclear cells (PBMCs) obtained before and after vaccination. Feasibility, safety, and possible clinical benefits were also evaluated.
Either a de novo induced or a significant increase of preexisting class I HLA-restricted T-cell-mediated anti-colon cancer response was observed in 15 (52%) of 29 patients. Frequency of CD3+, CD45RA+, and CCR7- T lymphocytes increased in immune responders. No relevant toxicity was observed. As expected, patients with good prognosis had a significantly better clinical outcome than those with poor prognosis [2-year overall survival (OS), 89 versus 64%, P = 0.001; disease-free survival (DFS), 46 versus 18%, P = 0.001]. Patients with immune response had a statistically significant clinical advantage over nonresponding subjects (2-year OS, 100% versus 50%, P = 0.001; DFS, 51% versus 8%, P = 0.0001). Occurrence of immune response led to better tumor-free survival, whatever the predicted prognosis was (hazard ratio, 0.11-0.12 with/without stratification; P = 0.0012-0.0003).
HSPPC-96 vaccination after resection of colorectal liver metastases is safe and elicits a significant increase in CD8+ T-cell response against colon cancer. In this limited number of patients, two-year OS and DFS were significantly improved in subjects with postvaccination antitumor immune response, independently from other clinical prognostic factors.
Circulating naı̈ve T cells do not recognize tumor-associated antigens (TAA) directly but need to interact with dendritic cells that have had the chance to process TAA for presentation to T cells. According to recent evidence, TAA from tumor cells circulating in the blood reach the spleen and bone marrow, where resident dendritic cells can process and cross-present them to prime T cells. This in turn leads to the generation of effector and memory cells, which can either destroy tumor cells or control them in a state of tumor dormancy. For therapeutic purposes, memory T cells can be boosted by the application of tumor vaccines that express TAA, together with danger signals. Immunization of cancer patients with such a tumor vaccine has resulted in improved survival in several Phase II studies. It is proposed that such immunization leads to long-lasting protective anti-tumor memory.
Human natural killer (NK) cells are potent effectors involved in destruction of virus infected cells and tumours. Their cytolytic function is regulated by surface receptors that either inhibit or increase the NK-mediated cytotoxicity. Under physiological conditions, NK cells recognize major histocompatibility complex (MHC)-class I molecules through surface receptors delivering signals that inhibit NK cells function. Nonetheless, the "missing self hypothesis", i.e. the release of an inhibitory signal by the interaction between HLA I-specific inhibitory receptors and their ligands, is not sufficient to entirely explain the regulation of NK cytotoxicity. Activating and co-receptors also play a central role in NK cell activation. In the haematology field, several lines of evidence suggest that NKs participate to the anti-leukaemia immune response: (1) leukaemic cells have down-regulated HLA-class I molecule expression and putative allele loss, (2) several reports have indicated an inverse relationship between NK cell number or activity and prognosis in acute leukaemia, (3) NK-cell activity dependent immunodeficiency syndromes are associated with an increased frequency of lymphoid haematological malignancies, (4) recent data support a role for NK cells in the graft-versus-leukaemia effect observed in allogeneic bone marrow transplantation. All these data raise several questions. How NK cells kill leukaemic targets, and how can leukaemia escape from innate immunity surveillance? What are the therapeutic possibilities to manipulate NK receptor-ligand interaction in order to increase leukaemia cell destruction? The responses to these questions will contribute to immunotherapy advancements in leukaemia and more generally in cancer.