Oncoimmunology: Some fundamental problems of cancer immunotherapy

The review briefly discusses several central problems of modern oncoimmunology. The controversies surrounding the concept of immunological surveillance, as well as the problem of immunological tolerance to tumors, are considered. The discovery of tumor antigens is a great advance towards the identification of possible therapeutic targets. However, antigen-specific vaccinations against cancer have, so far, a very limited use, mainly for prevention of virus-associated cancers, which is essentially based on the antiviral immune response. On the other hand, antibodies to cancer antigens are widely used in cancer diagnosis, and there are remarkable examples of their therapeutic applications. The future opportunities in both theoretical and applied oncoimmunology will directly depend on further advances in basic science.     

Clinical evaluation of systemic and local immune responses in cancer: time for integration

The immune system has a dual role in cancer development and progression. On the one hand, it can eradicate emerging malignant cells, but on the other hand, it can actively promote growth of malignant cells, their invasive capacities and their ability to metastasize. Immune cells with predominantly anti-tumor functionality include cells of the innate immune system, such as natural killer cells, and cells of adaptive immunity, such as conventional dendritic cells and cytotoxic T lymphocytes. Immune cells with predominantly pro-tumor functionality include a broad spectrum of cells of the innate and adaptive immune system, such as type 2 neutrophils and macrophages, plasmacytoid DC, myeloid-derived suppressor cells and regulatory T lymphocytes. The presence of immune cells with tumor-suppressive and tumor-promoting activity in the cancer microenvironment and in peripheral blood is usually associated with good clinical outcomes and poor clinical outcomes, respectively. Significant advances in experimental and clinical oncoimmunology achieved in the last decade open an opportunity for the use of modern morphologic, flow cytometric and functional tests in clinical practice. In this review, we describe an integrated approach to clinical evaluation of the immune status of cancer patients for diagnostic purposes, prognostic/predictive purposes (evaluation of patient prognosis and response to treatment) and for therapeutic purposes.     

Dissecting tumor responsiveness to immunotherapy: the experience of peptide-based melanoma vaccines

Recent years have witnessed important breakthroughs in our understanding of tumor immunology. A variety of immunotherapeutic strategies has shown that immune manipulation can induce the regression of established cancer in humans. The identification of the genes encoding tumor-associated antigens (TAA) and the development of means for immunizing against these antigens have opened new avenues for the development of an effective anticancer immunotherapy. However, an efficient immune response against tumor requires an intricate cross-talk between cancer and immune system cells, which is still poorly understood. Only when the molecular basis underlying tumor susceptibility to an immune response is deciphered could new therapeutic strategies be designed to fit biologically defined mechanisms of cancer immune rejection. In this article, we address some of the critical issues that have been identified in cancer immunotherapy, in part from our own studies on immune therapies in melanoma patients treated with peptide-based vaccination regimens. This is not meant to be a comprehensive overview of the immunological phenomena accompanying cancer patient vaccination but rather emphasizes some emergent findings, puzzling controversies and unanswered questions that characterize this complex field of oncology. In addition to reviewing the main immunological concepts underlying peptide-based vaccination, we also review the available data regarding naturally occurring and therapeutically induced anticancer immune response, both at the peripheral and intratumoral level. The hypothesized role of innate immunity in predetermining tumor responsiveness to immunotherapeutic manipulation is also discussed.     

Pilot study of a novel combination of two therapeutic vaccines in advanced non-small-cell lung cancer patients

Cancer vaccines contain tumor antigens in a pro-inflammatory context with the purpose to generate potent antitumor immune responses. However, tumor cells develop different immunosuppressive mechanisms that limit the effectiveness of an anticancer immune response. Therefore, therapeutic vaccine treatment alone is usually not sufficient to generate tumor regression or survival improvement, especially in the advanced disease scenario in which most clinical studies have been conducted. Combining cancer vaccines with different anticancer therapies such as chemotherapy, radiotherapy and other immunotherapeutic agents has had different levels of success. However, the combination of cancer vaccines with different mechanisms of action has not been explored in clinical trials. To address this issue, the current review summarizes the main clinical and immunological results obtained with two different therapeutic vaccines used in advanced non-small-cell lung cancer patients, inducing an immune response against epidermal growth factor (CIMAvax-EGF) and NGcGM3 ganglioside (racotumomab). We also discuss preliminary findings obtained in a trial of combination of these two vaccines and future challenges with these therapies.     

Tumor antigens discovery: perspectives for cancer therapy.

The adoptive transfer of cytotoxic T lymphocytes (CTLs) derived from tumor-infiltrating lymphocytes (TIL) along with interleukin 2 (IL-2) into autologous patients with cancer resulted in the objective regression of tumor, indicating that these CTLs recognized cancer rejection antigens on tumor cells. To understand the molecular basis of T cell-mediated antitumor immunity, several groups started to search for such tumor antigens in melanoma as well as in other types of cancers. This led to the subject I will review in this article. A number of tumor antigens were isolated by the use of cDNA expression systems and biochemical approaches. These tumor antigens could be classified into several categories: tissue-specific differentiation antigens, tumor-specific shared antigens, and tumor-specific unique antigens. However, the majority of tumor antigens identified to date are nonmutated, self proteins. This raises important questions regarding the mechanism of antitumor activity and autoimmune disease. The identification of human tumor rejection antigens provides new opportunities for the development of therapeutic strategies against cancer. This review will summarize the current status and progress toward identifying human tumor antigens and their potential applications to cancer treatment.     

Carbohydrate vaccines as immunotherapy for cancer

Carbohydrates have established themselves as the most clinically relevant antigens of those tested and subsequently developed for vaccines against infectious diseases. However, in cancer patients, many of the defined carbohydrate antigens are really altered 'self' antigens and for unclear reasons, the body does not react to them immunologically. Although these self antigens have been found to be potentially suitable targets for immune recognition and killing, the development of vaccines for cancer treatment is actually more challenging compared with those for infectious diseases mainly because of the difficulty associated with breaking the body's immunological tolerance to the antigen. These antigens lack the inherent immunogenicity associated with bacterial antigens and, therefore, methods to enhance immunological recognition and induction of immunity in vivo are under investigation. These include defining the appropriate tumour-associated antigen, successfully synthesizing the antigen to mimic the original molecule, inducing an immune response, and subsequently enhancing the immunological reactivity so that all components can work together. This has been successfully accomplished with several glycolipid and glycoprotein antigens using carriers such as keyhole limpet haemocyanin (KLH) together with a saponin adjuvant, QS-21. Not only can high titre IgM and IgG antibodies be induced, which are specific for the antigen used for immunization, but the antibodies can mediate complement lysis. The approaches for synthesis, conjugation, clinical administration and immunological potential are discussed.     

CAR-T Cell Therapy for Breast Cancer: From Basic Research to Clinical Application

Breast cancer rises as the most commonly diagnosed cancer in 2020. Among women, breast cancer ranks first in both cancer incidence rate and mortality. Treatment resistance developed from the current clinical therapies limits the efficacy of therapeutic outcomes, thus new treatment approaches are urgently needed. Chimeric antigen receptor (CAR) T cell therapy is a type of immunotherapy developed from adoptive T cell transfer, which typically uses patients'' own immune cells to combat cancer. CAR-T cells are armed with specific antibodies to recognize antigens in self-tumor cells thus eliciting cytotoxic effects. In recent years, CAR-T cell therapy has achieved remarkable successes in treating hematologic malignancies; however, the therapeutic effects in solid tumors are not up to expectations including breast cancer. This review aims to discuss the development of CAR-T cell therapy in breast cancer from preclinical studies to ongoing clinical trials. Specifically, we summarize tumor-associated antigens in breast cancer, ongoing clinical trials, obstacles interfering with the therapeutic effects of CAR-T cell therapy, and discuss potential strategies to improve treatment efficacy. Overall, we hope our review provides a landscape view of recent progress for CAR-T cell therapy in breast cancer and ignites interest for further research directions.     

Immune based therapies in cancer

Immunotherapy of cancer has become a more promising approach in the past decade. Developments in both basic immunology and tumor biology have increased our knowledge of the interactions between the tumor cells and the immune system. The molecular identification of tumor-associated antigens and understanding of immunological pathways have cleared the way for development of different strategies for anti-tumor vaccines. The success of any cancer vaccine relies on the induction of an effective tumor-specific immune response to break tolerance and to elicit a long lasting anti-tumor immunity. It is also increasingly clear that the interactions of host-tumor are quite complicated leading to tumor escape mechanisms, which add another level of difficulty to this interaction. This review will summarize the recent developments in tumor immunotherapy as well as the clinical trials addressing novel immunotherapeutic approaches to cancer.     

Toll-like receptor expression and function in human dendritic cell subsets: implications for dendritic cell-based anti-cancer immunotherapy

Dendritic cells (DCs) are central players of the immune response. To date, DC-based immunotherapy is explored worldwide in clinical vaccination trials with cancer patients, predominantly with ex vivo-cultured monocyte-derived DCs (moDCs). However, the extensive culture period and compounds required to differentiate them into DCs may negatively affect their immunological potential. Therefore, it is attractive to consider alternative DC sources, such as blood DCs. Two major types of naturally occurring DCs circulate in peripheral blood, myeloid DCs (mDCs) and plasmacytoid (pDCs). These DC subsets express different surface molecules and are suggested to have distinct functions. Besides scavenging pathogens and presenting antigens, DCs secrete cytokines, all of which is vital for both the acquired and the innate immune system. These immunological functions relate to Toll-like receptors (TLRs) expressed by DCs. TLRs recognize pathogen-derived products and subsequently provoke DC maturation, antigen presentation and cytokine secretion. However, not every TLR is expressed on each DC subset nor causes the same effects when activated. Considering the large amount of clinical trials using DC-based immunotherapy for cancer patients and the decisive role of TLRs in DC maturation, this review summarizes TLR expression in different DC subsets in relation to their function. Emphasis will be given to the therapeutic potential of TLR-matured DC subsets for DC-based immunotherapy.     

Tumor-associated antigen arrays for the serological diagnosis of cancer

The recognition that human tumors stimulate the production of autoantibodies against autologous cellular proteins called tumor-associated antigens (TAAs) has opened the door to the possibility that autoantibodies could be exploited as serological tools for the early diagnosis and management of cancer. Cancer-associated autoantibodies are often driven by intracellular proteins that are mutated, modified, or aberrantly expressed in tumor cells and hence are regarded as immunological reporters that could help uncover molecular events underlying tumorigenesis. Emerging evidence suggests that each type of cancer might trigger unique autoantibody signatures that reflect the nature of the malignant process in the affected organ. The advent of novel genomic, proteomic, and high throughput approaches has accelerated interest in the serum autoantibody repertoire in human cancers for the discovery of candidate TAAs. The use of individual anti-TAA autoantibodies as diagnostic or prognostic tools has been tempered by their low frequency and heterogeneity in most human cancers. However, TAA arrays comprising several antigens significantly increase this frequency and hold great promise for the early detection of cancer, monitoring cancer progression, guiding individualized therapeutic interventions, and identification of novel therapeutic targets. Our recent studies suggest that the implementation of TAA arrays in screening programs for the diagnosis of prostate cancer and other cancers should be preceded by the optimization of their sensitivity and specificity through the careful selection of the most favorable combinations of TAAs.     

Therapeutic genes for cancer gene therapy

Cancer still represents a disease of high incidence and is therefore one major target for gene therapy approaches. Gene therapy for cancer implies that ideally selective tumor cell killing or inhibition of tumor cell growth can be achieved using nucleic acids (DNA and RNA) as the therapeutic agent. Therefore, the majority of cancer gene therapy strategies introduce foreign genes into tumor cells which aim at the immunological recognition and destruction, the direct killing of the target cells or the interference with tumor growth. To achieve this goal for gene therapy of cancer, a broad variety of therapeutic genes are currently under investigation in preclinical and in clinical studies. These genes are of very different origin and of different mechanisms of action, such as human cytokine genes, genes coding for immunstimulatory molecules/antigens, genes encoding bacterial or viral prodrug-activating enzymes (suicide genes), tumor suppressor genes, or multidrug resistance genes.     

Immunobiology and signaling pathways of cancer stem cells: implication for cancer therapy

Cancer stem cells (CSCs) need to survive cancer treatments with a specific end goal to provide new, more differentiated, metastatic-prone cancerous cells. This happens through diverse signals delivered within the tumor microenvironment where ample evidence indicates that altered developmental signaling pathways play an essential role in maintaining CSCs and accordingly the survival and the progression of the tumor itself. This review summarizes findings on the immunobiological properties of CSCs as compared with cancerous non-stem cells involving the expression of immunological molecules, cytokines and tumor antigens as well as the roles of the Notch, Wnt and Hedgehog pathways in the brain, breast and colon CSCs. We concluded that if CSCs are the main driving force behind tumor support and growth then understanding the molecular mechanisms and the immunological properties directing these cells for immune tolerance is of great clinical significance. Such knowledge will contribute to designing better targeted therapies that could prevent tumor recurrence and accordingly significantly improve cancer treatments and patient survival.     

Peptide‐based therapeutic cancer vaccine: Current trends in clinical application

The peptide‐based therapeutic cancer vaccines have attracted enormous attention in recent years as one of the effective treatments of tumour immunotherapy. Most of peptide‐based vaccines are based on epitope peptides stimulating CD8⁺ T cells or CD4⁺ T helper cells to target tumour‐associated antigens (TAAs) or tumour‐specific antigens (TSAs). Some adjuvants and nanomaterials have been exploited to optimize the efficiency of immune response of the epitope peptide to improve its clinical application. At present, numerous peptide‐based therapeutic cancer vaccines have been developed and achieved significant clinical benefits. Similarly, the combination of peptide‐based vaccines and other therapies has demonstrated a superior efficacy in improving anti‐cancer activity. We delve deeper into the choices of targets, design and screening of epitope peptides, clinical efficacy and adverse events of peptide‐based vaccines, and strategies combination of peptide‐based therapeutic cancer vaccines and other therapies. The review will provide a detailed overview and basis for future clinical application of peptide‐based therapeutic cancer vaccines.     

Therapeutic targets and new directions for antibodies developed for ovarian cancer

Antibody therapeutics against different target antigens are widely used in the treatment of different malignancies including ovarian carcinomas, but this disease still requires more effective agents. Improved understanding of the biological features, signaling pathways, and immunological escape mechanisms involved in ovarian cancer has emerged in the past few years. These advances, including an appreciation of the cross-talk between cancer cells and the patient's immune system, have led to the identification of new targets. In turn, potential antibody treatments with various mechanisms of action, including immune activation or toxin-delivery, that are directed at these targets have been developed. Here, we identify established as well as novel targets for antibodies in ovarian cancer, and discuss how they may provide fresh opportunities to identify interventions with enhanced therapeutic potential.     

The reverse proteomics for identification of tumor antigens

The identification of tumor antigens is essential for the development of anticancer therapeutic vaccines and clinical diagnosis of cancer. SEREX (serological analysis of recombinant cDNA expression libraries) has been used to identify such tumor antigens by screening sera of patients with cDNA expression libraries. SEREX-defined antigens provide markers for the diagnosis of cancers. Potential diagnostic values of these SEREX-defined antigens have been evaluated. SEREX is also a powerful method for the development of anticancer therapeutics. The development of anticancer vaccines requires that tumor antigens can elicit antigen-specific antibodies or T lymphocytes. More than 2000 antigens have been discovered by SEREX. Peptides derived from some of these antigens have been evaluated in clinical trials. This review provides information on the application of SEREX for identification of tumor-associated antigens (TAA) for the development of cancer diagnostics and anticancer therapeutics.     

Exogenous DNA transcription in cells with their native DNA inhibited. 4. Demonstration of specific antigens codified by exogenous DNA

It is possible to obtain antisera to cancer-specific antigens of mouse Ehrlich ascites cancer (EAC) cells when chimera rabbits previously made unresponsive to immunological stimulation by normal mouse cells antigens are immunized with mouse cancer cells. Employing this specifically anti-cancerous immunoserum this work shows that EAC cells and TC-SV40 cells contain cross-reacting cancer-specific antigens. Exogenous DNA from EAC cells is demonstrated as being able to display its coded information when it is incorporated to endogenous TC-SV40 cell DNA whose activity has been previously inhibited by 5'-bromodeoxyuridine.     

Food Allergy,Oral Tolerance and Immunomodulation—Their Molecular and Cellular Mechanisms

This paper describes the molecular and cellular mechanisms of food allergy and oral tolerance including immunomodulation. Food allergy is triggered by an aberrant immune response elicited by oral administration of dietary antigens. Oral tolerance is a state of immunological unresponsiveness induced by oral administration of dietary antigens and is thought to serve to suppress food allergy. This review first describes the characteristic properties of T and B cells relating to milk allergy and also the location of binding sites to T and B cells on allergen molecules. The immunogenicity of allergens is shown to be reduced by the modulations of the T cell binding site, using sophisticated methods such as site-specific mutagenesis. Furthermore, this review focuses on oral tolerance with special reference to the identification of lymphocyte compartment subsets and the immunological mechanism relating to oral tolerance. Finally, the application of oral tolerance for the treatment of allergy is speculated on.     

Vaccine strategies against melanoma

Melanoma incidence increases and conventional antitumor therapies are often ineffective, encouraging the design of novel therapies. Several lines of evidence support the notion of an immunological control of melanoma growth. Based on this information, active immunotherapy (vaccination) and adoptive immunotherapy trials (T cell therapy) were conducted in metastatic melanoma patients. The proof of principle of effective immunotherapy was brought up by pionnering trials using tumor infiltrated lymphocytes in lymphodepleted recipients or anti-CTLA4 Ab leading to tumor eradication but also autoimmune diseases. With the identification and characterization of tumor antigens recognized by cytotoxic T lymphocytes, the utilization of tumor rejection antigens along with adjuvants become available as tumor vaccines. The last five years have witnessed the emergence of dendritic cell based-vaccines that were efficient in priming and/or boosting T cell responses in normal volunteers and patients. This review highlights preclinical bases of cancer vaccines, their clinical development and discusses their limits. Correlations between immunomonitoring and tumor regressions await larger trials.     

The questionable immunogenicity of certain neoplasms

Summary The possibilities of immunological intervention in neoplastic diseases are discussed in light of the accumulating findings that many spontaneously arising tumors of animals are not immunogenic in the host of origin or are not susceptible to immunological attack, and of the doubts as to the existence of tumor-associated antigens for many human neoplasms. Although some spontanous tumors do in fact display immunogenic properties and are subject to cytotoxic immune reactions, there are persuasive arguments for anticipating that a large proportion of naturally appearing malignant growths will be found to lack both immunogenicity and sensitivity to immunological effector mechanisms in the course of the host-tumor association. Even in the case of such tumors, however, significant opportunities for therapy and prophylaxis by extrinsic immunological manipulation remain cogent, as do eventualities of immunodiagnosis. These possibilities are discussed. It is concluded that whereas the simplistic assumptions which for some years set expectations in the field of tumor immunology must now be abandoned, reassessment of the nature of immunological parameters of host-tumor relationships and of the scope of immunological intervention on the basis of the information now available suggests that the immunological approach to the control of cancer continues to be a profitable area of investigation.