Tumor-associated antigens and biomarkers in cancer and immune therapy

Cancer has currently overtaken heart disease as the major cause of mortality in the United States. The Human Genome Project, advances in informatics, miniaturization of sample collection, and increased knowledge of cell signaling pathways has revolutionized the study of disease. Genomics, proteomics, and metabolomics are currently being used to develop molecular signatures for disease diagnosis, prognosis, and therapeutic efficacy. Tumor-associated antigens discovered by these methods are being used to develop passive (humoral) as well as active immunotherapy strategies to stimulate the immune system. Development and validation of biomarkers on a parallel track with therapeutics can speed development times by accurate screening of patient populations and substituting surrogate markers that correlate well with clinical outcomes.     

光动力疗法治疗肿瘤的免疫机制研究进展

光动力疗法(photodynamic therapy,PDT)是治疗肿瘤的有效手段之一,PDT治疗可导致肿瘤细胞的死亡和凋亡,并损伤肿瘤相关血管.近年来,PDT的免疫机制越来越受到关注.肿瘤细胞的免疫逃逸是肿瘤发生发展的重要因素.PDT治疗肿瘤时,可通过免疫原性细胞死亡(immunogenic cell death,ICD)诱导肿瘤细胞表达损伤相关分子模式(damage associated molecular patterns,DAMPs),从而活化树突状细胞,诱导机体特异性抗肿瘤免疫.同时,PDT还可影响肿瘤微环境中的相关免疫细胞和因子,进而增强机体抗肿瘤反应.光动力治疗和其他免疫治疗联合应用亦能增强疗效.故光动力治疗的免疫机制研究将为肿瘤治疗提供可能的新思路.     

Forcing Tumor Cells to Present Their Own Tumor Antigens to the Immune System： a Necessary Design for an Efficient Tumor Immunotherapy

The general principle for tumor cells to escape from immune surveillance is to prevent tumor antigens from being recognized by the immune system. Many methods have been developed to increase the immunogenecity of the tumor cells. The most efficient methods are able to force tumor cells to present their own tumor antigens to the immune system. Stimulating Th cells by converting tumor cells into MHC class II /Ii- antigen presenting cells is one of the most efficient technologies. Using antisense methods, we suppress the expression of the Ii protein that normally co-expresses with MHC class II molecules and blocks the antigenic peptide binding site of MHC class II molecules during synthesis in the endoplasmic reticulum. In such tumor cells, the“unprotected“ MHC class II molecules pick up endogenous tumor antigenic peptides, which have been transported into the ER for binding to MHC class I molecules. Simultaneous presentation of tumor antigens by both MHC class I and II molecules generates a robust and long-lasting anti-tumor immune response. MHC class II /Ii- tumor cells are potent tumor cell vaccines and also cure a significant number of animals with renal and prostate tumors. We have developed analogous human gene vectors that are suitable for most patients and cancers.     

新城疫病毒HN基因对肿瘤抗原诱导的抗肿瘤免疫的增强作用

目的 了解新城疫病毒HN基因增强肿瘤抗原诱发的抗肿瘤免疫反应的作用。并对其作用机制进行探讨。方法 将构建的HN基因-癌胚抗原（CEA）cDNA共表达质粒（pcD-CEA/HN)免疫小鼠,通过淋巴细胞增殖实验,NK细胞活性检测了解HN对抗CEA免疫反应的影响,并以免疫组化的手段追踪HN质粒表达产物在体内组织的分布,以及HN质粒对荷瘤小鼠肿瘤生长,抗肿瘤免疫反应的影响。结果 （1）共表达质粒pcD-CEA/HN免疫小鼠获得了较其他对照组强的淋巴细胞增殖指数及NK细胞活性。（2）HN质粒在肌肉,肿瘤组织有明显的表达。（3）HN质粒对肿瘤长生具有一定的抑制作用。并能增强荷瘤小鼠的抗肿瘤免疫。结论 新城疫病毒HN基因对肿瘤抗原诱导的抗肿瘤免疫具有增强作用。     

Human tumor antigens for cancer vaccine development

Summary: The adoptive transfer of tumor-infiltrating lymphocytes (TH.) along with interleukin (H.)-2 into autologous patients with cancer resulted in the objective regression of tumor, indicating that T cells play an important role in tumor regression. In the last few years, efforts have been made towards understanding the molecular basis of T-cell-mediated antitumor immunity and elucidating the molecular nature of tumor antigens recognized by T cells. Tumor antigens identified thus far could be classified into several catagories: tissue-specific differentiation antigens, tumor-specific shared antigens and tumor-specific unique antigens, CD4 T cells play a central role in orchestrating the host immune response against cancer, infections diseases, and autoimmune deseases, and we thus have attempted to identify major histocompatibility complex (MHC) class II-restricted tumor antigens as well. The identification of tumor rejection antigens provides new opportunities for the development of therapeutic strategies against cancer. This review will summarize the current status of MHC class I- and class II-restricted human tumor antigens, and their potential application to cancer treatment.     

Protein tumor antigens.

Immunogenic tumor antigens have been sought through a variety of paradigms for several past decades. Recent developments in antigen presentation have radically changed the prism through which we view these enigmatic antigens. This article discusses the small but growing treasure chest of these antigens--stress-induced proteins, the P1AB antigen of the P815 mastocytoma, the p53 tumor suppressor protein, the gp95/p97 antigen of human melanoma, mucins and others.     

Individual mouse analysis of the cellular immune response to tumor antigens in peripheral blood by intracellular staining for cytokines

Among the experimental animal models, mice remain the most widely used for the evaluation of immunotherapeutic strategies. Vaccines against parasites and viral antigens are commonly administered to the appropriate mouse strain which also allows testing of the therapeutic effect. Similarly, in mice transgenic for human tumor associated antigens (TAA), cancer vaccines must lead to breakage of immune tolerance to elicit a significant effect on the tumor. However, one of the major drawbacks in the monitoring of cellular immune responses induced by vaccination is that functional immunological assays require suppression of the animals to collect the spleen or lymph nodes for analysis. Here, we report the application of a rapid intracellular staining (ICS) method to quantify antigen-specific T cells responses in small volumes of murine blood. Genetic vaccination with plasmid DNA followed by electroporation (DNA-EP) and the use of adenoviral vectors (Ad) encoding CEA as a model target antigen were applied to different strains of mice. Optimal blood volume, number of lymphocytes, sensitivity and reproducibility of intracellular staining for IFN-gamma were determined both in non-tolerant/wild type mice as well as in tolerant CEA transgenic mice upon restimulation of PBMCs with CEA peptides. Groups of vaccinated mice were then sacrificed and PBMCs and splenocytes from individual animals were compared for intracytoplasmic detection of IFN-gamma and TNF-alpha. A significant correlation was observed between splenic and blood immune responses. Finally, the cellular immune response was followed over time in groups of vaccinated mice. The kinetics of IFN-gamma producing effectors were measured after priming and successive boosting with adenoviral vectors. We show that intracellular staining for mouse PBMCs is a rapid and simple method to measure antigen-specific immune responses. It does not require animal euthanasia and mirrors the response observed in lymphoid organs such as the spleen.     

Enhancing antitumor immune responses: intracellular peptide delivery and identification of MHC class II-restricted tumor antigens

Summary: The importance of T‐cell‐mediated antitumor immunity has been demonstrated in both animal models and human cancer therapy. The identification of major histocompatibility complex (MHC) class I‐restricted tumor antigens has generated a resurgence of interest in immunotherapy for cancer. However, recent studies suggest that therapeutic strategies that have mainly focused on the use of CD8⁺ T cells (and MHC class I‐restricted tumor antigens) may not be effective in eliminating cancer cells in patients. Novel strategies have been developed for enhancing T‐cell responses against cancer by prolonging antigen presentation of dendritic cells to T cells and the inclusion of MHC class II‐restricted tumor antigens. identification of MHC class II‐restricted tumor antigens, which are capable of stimulating CD4⁺ T cells, not only aids our understanding of the host immune responses against cancer antigens, but also provides opportunities for developing effective cancer vaccines.     

Novel tumor antigens elicit anti-tumor humoral immune reactions in a subset of patients with polycythemia vera

We attempted to determine whether the immune reactions elicited by aberrantly expressed testis antigens contribute to the beneficial responses to interferon (IFN)-alpha therapy and other therapies in patients with polycythemia vera (PV). We screened a human testis cDNA library using SEREX (serological analysis of tumor antigens by screening an expression cDNA library with sera from three patients with PV who had undergone IFN-alpha-induced or other therapeutics-induced remission). We identified two novel PV associated tumor antigens, PV65 (eIF-2alpha) and PV13 (protamine 2). These 2 antigens elicited IgG antibody reactions in a subset of PV patients but not in healthy donors, suggesting that they are authentic tumor antigens. Increased phosphorylation of PV65 in response to stimulation of IFN-alpha, and upregulation of PV13 in tumor cells might enhance their abilities in elicitation of immune reactions in patients. These findings provide new insights into the mechanism underlying the regulation of the self-antigen repertoire in eliciting anti-tumor immune reactions in patients with polycythemia vera, and suggest their potential as the targets of novel immunotherapy.     

Depletion of CD25+ regulatory cells uncovers immune responses to shared murine tumor rejection antigens

Although it is known that the immune system can mount responses to a variety of tumors it is clear that most tumors exhibit weak or even undetectable immunogenicity. Recent findings suggest that the lack of tumor immunogenicity is partly due to a population of cells called CD4+ CD25+ regulatory T cells since depletion of these cells in mice can result in tumor rejection. These cells have also been shown to inhibit the development of organ-specific autoimmune diseases suggesting that they inhibit immune responses to tissue-specific self-antigens. Such immune responses may also mediate tumor rejection. Alternatively, immune responses in mice depleted of regulatory cells may target tumor antigens that are not tissue-specific, but which are shared by tumors of diverse origins. In experiments performed to discriminate between these possibilities we found, using the murine colorectal tumor CT26, that tumor immunity stimulated in the absence of regulatory cells is not restricted to tumors of colorectal origin, but is effective against tumors of different histological types such as B cell lymphomas and a renal cell carcinoma. By comparing this to CT26-induced immunity through the use of adjuvant we show that the generation of cross-reactive tumor immunity is a specific manifestation of CD25+ regulatory cell depletion. The generation of CD4+ T cells capable of mediating tumor rejection is another important feature of tumor immunity induced in the absence of CD25+ cells.     

Enhancing immune responses for cancer therapy

Although the immune system possesses the means to respond to cancer, it often fails to control the spread of malignancy. Nonetheless, equipping endogenous immunity to release a strong antitumor response has significant advantages over conventional therapies. This review explores some of the options available to accomplish this, focusing first on vaccinations with tumor antigens to stimulate the immune system and empower stronger antitumor responses. We then compare and contrast the so-far limited clinical success of vaccination with the well-documented curative potential of adoptive therapy using T lymphocytes transfer. Finally, we highlight novel approaches using T call receptor （TCR） gene transfer strategy to exploit allogeneic T cell repertoires in conjunction with receptors selected in vitro for defined MHC/peptide combinations, as a basis for antigen-specific gene therapy of cancers. Cellular ＆ Molecular Immunology.     

Gene therapy for primary immune deficiencies

Primary immunodeficiency diseases have been important targets of corrective gene transfer approaches since the very early days of gene therapy. The potential for selective survival advantage of gene-corrected cells over populations carrying the mutated, causative gene translates into the possibility of obtaining clinical meaningful results in patients with primary immunodeficiency diseases even if levels of gene transfer are low. This critical prospect has fueled the interest of researchers since the mid-1980s and has recently determined the success of a clinical trial of gene therapy for X-linked severe combined immunodeficiency.     

Acid-treated, naked bacteria as immune carriers for protein antigens

Salmonella minnesota R595 bacteria were stripped of their natural antigenic determinants to yield acid-treated, naked bacteria. The proteins, human apolipoprotein A1 and carcino-embryonic antigen, were adsorbed to naked bacteria and these complexes were used to immunise rabbits. Although the antibody titres obtained were comparable to those achieved using Freund's adjuvant emulsions, much less antigen was needed for immunisation. This technique could be of great value where the amount of protein available for immunisation is very small.     

Human tumor antigens: implications for cancer vaccine development

The adoptive transfer of tumor-infiltrating lymphocytes along with interleukin 2 into autologous patients resulted in the objective regression of tumor in about 30% of patients with melanoma, indicating that these T cells play a role in tumor rejection. To understand the molecular basis of the T cell-cancer cell interaction we and others started to search for tumor antigens expressed on cancer cells recognized by T cells. This led to the identification of several major histocompatibility complex (MHC) class I restricted tumor antigens. These tumor antigens have been classified into several categories: tissue-specific differentiation antigens, tumor-specific shared antigens, and tumor-specific unique antigens. Because CD4+ T cells play a central role in orchestrating the host immune response against cancer, infectious diseases, and autoimmune diseases, a novel genetic approach has recently been developed to identify these MHC class II restricted tumor antigens. The identification of both MHC class I and II restricted tumor antigens provides new opportunities for the development of therapeutic strategies against cancer. This review summarizes the current status of tumor antigens and their potential applications to cancer treatment.     

Adaptive immune education by gut microbiota antigens

Host–microbiota mutualism has been established during long‐term co‐evolution. A diverse and rich gut microbiota plays an essential role in the development and maturation of the host immune system. Education of the adaptive immune compartment by gut microbiota antigens is important in establishing immune balance. In particular, a critical time frame immediately after birth provides a ‘window of opportunity’ for the development of lymphoid structures, differentiation and maturation of T and B cells and, most importantly, establishment of immune tolerance to gut commensals. Depending on the colonization niche, antigen type and metabolic property of different gut microbes, CD4 T‐cell responses vary greatly, which results in differentiation into distinct subsets. As a consequence, certain bacteria elicit effector‐like immune responses by promoting the production of pro‐inflammatory cytokines such as interferon‐γ and interleukin‐17A, whereas other bacteria favour the generation of regulatory CD4 T cells and provide help with gut homeostasis. The microbiota have profound effects on B cells also. Gut microbial exposure leads to a continuous diversification of B‐cell repertoire and the production of T‐dependent and ‐independent antibodies, especially IgA. These combined effects of the gut microbes provide an elegant educational process to the adaptive immune network. Contrariwise, failure of this process results in a reduced homeostasis with the gut microbiota, and an increased susceptibility to various immune disorders, both inside and outside the gut. With more definitive microbial–immune relations waiting to be discovered, modulation of the host gut microbiota has a promising future for disease intervention.