Enhanced growth of primary tumors in cancer-prone mice after immunization against the mutant region of an inherited oncoprotein

Both CD8 and CD4 T cells contribute to immunosurveillance preventing the development of neoantigen-expressing autochthonous sarcomas

The adaptive immune system plays an essential anti-tumor role through immunosurveillance and response to immunotherapies. Characterizing phenotypic features and mechanisms of dysfunction of tumor-specific T cell populations may uncover novel immunotherapeutic targets and biomarkers of response. To study tumor-specific T cell responses in vivo, a tumor model must express a known neoantigen. While transplant models with known neoantigen expression are widely available, autochthonous tumor models in which the tumor coevolves with the immune system are limited. In this study, we combined CRISPR/Cas9 and sleeping beauty transposase technology to develop an autochthonous orthotopic murine sarcoma model with oncogenic KrasG12D, functionally impaired p53, and expression of known MHCI and MHCII sarcoma neoantigens. Using MHC tetramer flow cytometry, we identified a tumor-specific immune response in the peripheral blood as early as 10 days after tumor induction leading to tumor clearance. Tumors developed at high penetrance after co-depletion of CD8 and CD4 T cells, but depletion of either CD8 or CD4 T cells alone was insufficient to permit tumor growth. These results suggest that CD8 and CD4 T cells can independently contribute to immunosurveillance leading to clearance of sarcomas expressing MHCI and MHCII neoantigens.

Immunization with nanovaccines containing mutated K-Ras peptides and imiquimod aggravates heterotopic pancreatic cancer induced in mice

Purpose

The growing incidence and lethality of pancreatic cancer urges the development of new therapeutic approaches. Anti-tumoral vaccines can potentiate the immune response against the tumor, targeting specific antigens expressed only on tumor cells. In this work, we designed new vaccines for pancreatic cancer, composed by chitosan nanocapsules (CS NCs) containing imiquimod (IMQ) as adjuvant, and targeting the K-Ras mutation G12V.

Experimental design

We tested the immunogenicity of our vaccines in mice, carrying different combinations of K-Ras mutated peptides. Then, we analyzed their prophylactic and therapeutic efficacy in mice bearing heterotopic pancreatic cancer.

Results

Unexpectedly, although good results were observed at short time points, the different combinations of our CS NCs vaccines seemed to potentiate tumor growth and reduce survival rate. We propose that this effect could be due to an inadequate immune response, partially because of the induction of a regulatory tolerogenic response.

Conclusion

Our results call for caution in the use of some NCs containing IMQ in the immunotherapy against pancreatic cancer.

The role of CD4 T cells in rejection of solid tumors

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Versatility of CD4 T cells enables different attack modes towards cancer cells.

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Cooperation of CD4 and CD8 T cells renders anti-tumor responses most efficient.

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Integrating CD4 T cells in cancer therapy will improve clinical outcome.

The focus in cancer immunotherapy has mainly been on CD8 T cells, as they can directly recognize cancer cells. CD4 T cells have largely been neglected, because most cancers lack MHC II expression and cannot directly be recognized by CD4 T cells. Yet, tumor antigens can be captured and cross-presented by MHC II-expressing tumor stromal cells. Recent data suggest that CD4 T cells act as a swiss army knife against tumors. They can kill cancer cells, if they express MHC II, induce tumoricidal macrophages, induces cellular senescence of cancer cells, destroy the tumor vasculature through cytokine release and help CD8 T cells in the effector phase. We foresee a great future for CD4 T cells in the clinic, grafted with tumor antigen specificity by T cell receptor gene transfer, either alone or in combination with engineered CD8 T cells.

The tumor-promoting effects of the adaptive immune system: a cause of hyperprogressive disease in cancer?

Adaptive antitumor immune responses, either cellular or humoral, aim at eliminating tumor cells expressing the cognate antigens. There are some instances, however, where these same immune responses have tumor-promoting effects. These effects can lead to the expansion of antigen-negative tumor cells, tumor cell proliferation and tumor growth, metastatic dissemination, resistance to antitumor therapy and apoptotic stimuli, acquisition of tumor-initiating potential and activation of various forms of survival mechanisms. We describe the basic mechanisms that underlie tumor-promoting adaptive immune responses and try to identify the variables that induce the switching of a tumor-inhibitory, cellular or humoral immune response, into a tumor-promoting one. We suggest that tumor-promoting adaptive immune responses may be at the origin of at least a fraction of hyperprogressive diseases (HPD) that are observed in cancer patients during therapy with immune checkpoint inhibitors (ICI) and, less frequently, with single-agent chemotherapy. We also propose the use of non-invasive biomarkers allowing to predict which patients may undergo HPD during ICI and other forms of antitumor therapy. Eventually, we suggest possibilities of therapeutic intervention allowing to inhibit tumor-promoting adaptive immune responses.

Enhanced detection of neoantigen-reactive T cells targeting unique and shared oncogenes for personalized cancer immunotherapy

Adoptive cell transfer (ACT) of tumor-infiltrating lymphocytes (TILs) targeting neoantigens can mediate tumor regression in selected patients with metastatic epithelial cancer. However, effectively identifying and harnessing neoantigen-reactive T cells for patient treatment remains a challenge and it is unknown whether current methods to detect neoantigen-reactive T cells are missing potentially clinically relevant neoantigen reactivities. We thus investigated whether the detection of neoantigen-reactive TILs could be enhanced by enriching T cells that express PD-1 and/or T cell activation markers followed by microwell culturing to avoid overgrowth of nonreactive T cells. In 6 patients with metastatic epithelial cancer, this method led to the detection of CD4+ and CD8+ T cells targeting 18 and 1 neoantigens, respectively, compared with 6 and 2 neoantigens recognized by CD4+ and CD8+ T cells, respectively, when using our standard TIL fragment screening approach. In 2 patients, no recognition of mutated peptides was observed using our conventional screen, while our high-throughput approach led to the identification of 5 neoantigen-reactive T cell receptors (TCRs) against 5 different mutations from one patient and a highly potent MHC class II-restricted KRASG12V-reactive TCR from a second patient. In addition, in a metastatic tumor sample from a patient with serous ovarian cancer, we isolated 3 MHC class II-restricted TCRs targeting the TP53G245S hot-spot mutation. In conclusion, this approach provides a highly sensitive platform to isolate clinically relevant neoantigen-reactive T cells or their TCRs for cancer treatment.

Improvement of Antitumor Therapies Based on Vaccines and Immune-Checkpoint Inhibitors by Counteracting Tumor-Immunostimulation

Immune-checkpoint inhibitors and antitumor vaccines may produce both tumor-inhibitory and tumor-stimulatory effects on growing tumors depending on the stage of tumor growth at which treatment is initiated. These paradoxical results are not necessarily incompatible with current tumor immunology but they might better be explained assuming the involvement of the phenomenon of tumor immunostimulation. This phenomenon was originally postulated on the basis that the immune response (IR) evoked in Winn tests by strong chemical murine tumors was not linear but biphasic, with strong IR producing inhibition and weak IR inducing stimulation of tumor growth. Herein, we extended those former observations to weak spontaneous murine tumors growing in pre-immunized, immune-competent and immune-depressed mice. Furthermore, we demonstrated that the interaction of specifical T cells and target tumor cells at low stimulatory ratios enhanced the production of chemokines aimed to recruit macrophages at the tumor site, which, upon activation of toll-like receptor 4 and p38 signaling pathways, would recruit and activate more macrophages and other inflammatory cells which would produce growth-stimulating signals leading to an accelerated tumor growth. On this basis, the paradoxical effects achieved by immunological therapies on growing tumors could be explained depending upon where the therapy-induced IR stands on the biphasic IR curve at each stage of tumor growth. At stages where tumor growth was enhanced (medium and large-sized tumors), counteraction of the tumor-immunostimulatory effect with anti-inflammatory strategies or, more efficiently, with selective inhibitors of p38 signaling pathways enabled the otherwise tumor-promoting immunological strategies to produce significant inhibition of tumor growth.

Immunoprevention of chemical carcinogenesis through early recognition of oncogene mutations

Prevention of tumors induced by environmental carcinogens has not been achieved. Skin tumors produced by polyaromatic hydrocarbons, such as 7,12-dimethylbenz(a)anthracene (DMBA), often harbor an H-ras point mutation, suggesting that it is a poor target for early immunosurveillance. The application of pyrosequencing and allele-specific PCR techniques established that mutations in the genome and expression of the Mut H-ras gene could be detected as early as 1 d after DMBA application. Further, DMBA sensitization raised Mut H-ras epitope-specific CTLs capable of eliminating Mut H-ras(+) preneoplastic skin cells, demonstrating that immunosurveillance is normally induced but may be ineffective owing to insufficient effector pool size and/or immunosuppression. To test whether selective pre-expansion of CD8 T cells with specificity for the single Mut H-ras epitope was sufficient for tumor prevention, MHC class I epitope-focused lentivector-infected dendritic cell- and DNA-based vaccines were designed to bias toward CTL rather than regulatory T cell induction. Mut H-ras, but not wild-type H-ras, epitope-focused vaccination generated specific CTLs and inhibited DMBA-induced tumor initiation, growth, and progression in preventative and therapeutic settings. Transferred Mut H-ras-specific effectors induced rapid tumor regression, overcoming established tumor suppression in tumor-bearing mice. These studies support further evaluation of oncogenic mutations for their potential to act as early tumor-specific, immunogenic epitopes in expanding relevant immunosurveillance effectors to block tumor formation, rather than treating established tumors.

Liver metastases induce reversible hepatic B cell dysfunction mediated by Gr-1+CD11b+ myeloid cells

LM escape immune surveillance, in part, as a result of the expansion of CD11b+MC, which alter the intrahepatic microenvironment to promote tumor tolerance. HBC make up a significant proportion of liver lymphocytes and appear to delay tumor progression; however, their significance in the setting of LM is poorly defined. Therefore, we characterized HBC and HBC/CD11b+MC interactions using a murine model of LM. Tumor-bearing livers showed a trend toward elevated absolute numbers of CD19+ HBC. A significant increase in the frequency of IgM(lo)IgD(hi) mature HBC was observed in mice with LM compared with normal mice. HBC derived from tumor-bearing mice demonstrated increased proliferation in response to TLR and BCR stimulation ex vivo compared with HBC from normal livers. HBC from tumor-bearing livers exhibited significant down-regulation of CD80 and were impaired in inducing CD4(+) T cell proliferation ex vivo. We implicated hepatic CD11b+MC as mediators of CD80 down-modulation on HBC ex vivo via a CD11b-dependent mechanism that required cell-to-cell contact and STAT3 activity. Therefore, CD11b+MC may compromise the ability of HBC to promote T cell activation in the setting of LM as a result of diminished expression of CD80. Cross-talk between CD11b+MC and HBC may be an important component of LM-induced immunosuppression.

IFN-γ-mediated downregulation of LXA4 is necessary for the maintenance of nonresolving inflammation and papilloma persistence

Nonresolving inflammation is a hallmark of many types of tumors and the molecular mechanisms maintaining this inflammation are still largely unknown. In a two-stage carcinogenesis model, we observed here that the lack of IFN-γ receptor or neutralization of IFN-γ accelerated spontaneous papilloma regression in mice. The impaired maintenance of local inflammation was associated with reduced IFN-γ and enhanced biosynthesis of proresolution lipid mediator lipoxin A4 (LXA4). Interestingly, blocking LXA4 eliminated the effect of anti-IFN-γ, whereas treatment of mice with a therapeutic dose of LXA4 accelerated papilloma regression in an IFN-γ-independent manner. These results link for the first time a cytokine-dependent maintenance of inflammation with a downregulated production of proresolution lipid mediators. Strategies promoting spontaneous resolution of chronic inflammation by blocking IFN-γ and/or increasing LXA4 may be useful for the treatment of inflammation-associated tumors.

Tissue damage-associated "danger signals" influence T-cell responses that promote the progression of preneoplasia to cancer

T-cell responses may be shaped by sterile "danger signals" that are constituted by damage-associated molecular patterns (DAMP). However, whether and what type of adaptive immune responses are triggered in vivo by DAMPs induced by tumor progression are not well characterized. In this study, we report that the production of HMGB1, an established DAMP released by dying cells, was critical for tumor progression in an established mouse model of prostate cancer. HMGB1 was required for the activation and intratumoral accumulation of T cells that expressed cytokine lymphotoxinα(1)β(2) (LT) on their surface. Intriguingly, these tumor-activated T cells recruited macrophages to the lesion and were essential to promote the preneoplasia to invasive carcinoma in an LTβ receptor (LTβR)-dependent manner. Taken together, our findings suggest that the release of HMGB1 as an endogenous danger signal is important for priming an adaptive immune response that promotes malignant progression, with implications for cancer prevention and therapy.

"First do no harm" and the importance of prediction in oncology

Present cancer treatment strategies are based on the assumption that a therapy may work (“response”) or not work (“no-response”). However, the existing evidence suggests that current cancer treatment modalities may also have a cancer-promoting effect in part of the patients. In this paper, some relevant data are reviewed suggesting that surgery, irradiation, chemotherapy and immunotherapy can stimulate tumor growth / metastatic spread and decrease survival of patients in certain subgroups. Thus, results of cancer treatment may be improved by detection and use of biomarkers that correlate with positive or negative therapeutic effects. Small trials based on groups with differing biomarkers rather than large phase III trials may aid the development and efficacy testing of new anticancer drugs. Moreover, ignoring biomarkers that correlate with positive or negative therapeutic effect may not be compatible anymore with the ethical principle “First Do No Harm”.

FcRgamma activation regulates inflammation-associated squamous carcinogenesis

Chronically activated leukocytes recruited to premalignant tissues functionally contribute to cancer development; however, mechanisms underlying pro- versus anti-tumor programming of neoplastic tissues by immune cells remain obscure. Using the K14-HPV16 mouse model of squamous carcinogenesis, we report that B cells and humoral immunity foster cancer development by activating Fcgamma receptors (FcgammaRs) on resident and recruited myeloid cells. Stromal accumulation of autoantibodies in premalignant skin, through their interaction with activating FcgammaRs, regulate recruitment, composition, and bioeffector functions of leukocytes in neoplastic tissue, which in turn promote neoplastic progression and subsequent carcinoma development. These findings support a model in which B cells, humoral immunity, and activating FcgammaRs are required for establishing chronic inflammatory programs that promote de novo carcinogenesis.

Lineage-specific T-cell responses to cancer mucosa antigen oppose systemic metastases without mucosal inflammatory disease

Cancer mucosa antigens are emerging as a new category of self-antigens expressed normally in immunologically privileged mucosal compartments and universally by their derivative tumors. These antigens leverage the established immunologic partitioning of systemic and mucosal compartments, limiting tolerance opposing systemic antitumor efficacy. An unresolved issue surrounding self-antigens as immunotherapeutic targets is autoimmunity following systemic immunization. In the context of cancer mucosa antigens, immune effectors to self-antigens risk amplifying mucosal inflammatory disease promoting carcinogenesis. Here, we examined the relationship between immunotherapy for systemic colon cancer metastases targeting the intestinal cancer mucosa antigen guanylyl cyclase C (GCC) and its effect on inflammatory bowel disease and carcinogenesis in mice. Immunization with GCC-expressing viral vectors opposed nascent tumor growth in mouse models of pulmonary metastasis, reflecting systemic lineage-specific tolerance characterized by CD8(+), but not CD4(+), T-cell or antibody responses. Responses protecting against systemic metastases spared intestinal epithelium from autoimmunity, and systemic GCC immunity did not amplify chemically induced inflammatory bowel disease. Moreover, GCC immunization failed to promote intestinal carcinogenesis induced by germ-line mutations or chronic inflammation. The established role of CD8(+) T cells in antitumor efficacy, but CD4(+) T cells in autoimmunity, suggests that lineage-specific responses to GCC are particularly advantageous to protect against systemic metastases without mucosal inflammation. These observations support the utility of GCC-targeted immunotherapy in patients at risk for systemic metastases, including those with inflammatory bowel disease, hereditary colorectal cancer syndromes, and sporadic colorectal cancer.

Spontaneous immune responses to sporadic tumors: tumor-promoting, tumor-protective or both?

Cancer cells cannot develop into invasive cancers without interactions with cells and soluble mediators present in the tumor microenvironment. Accumulating evidence indicates that the immune system is a critical determinant of malignant outgrowth; however, the tumor-modulating effects of spontaneous immune responses towards nascent malignancies are rather paradoxical. Both cancer-protective and cancer-promoting features of the immune system have been described. This review will discuss the role of the dynamic inflammatory tumor microenvironment during cancer development and progression, and will focus on the intriguing question: "Do malignancies develop in spite of-or because of-spontaneous immune responses?" Special emphasis will be put on recent progress in our understanding of the immune system's double-edged sword function during de novo carcinogenesis.

TNFR1 signaling and IFN-gamma signaling determine whether T cells induce tumor dormancy or promote multistage carcinogenesis

Immune responses may arrest tumor growth by inducing tumor dormancy. The mechanisms leading to either tumor dormancy or promotion of multistage carcinogenesis by adaptive immunity are poorly characterized. Analyzing T antigen (Tag)-induced multistage carcinogenesis in pancreatic islets, we show that Tag-specific CD4+ T cells home selectively into the tumor microenvironment around the islets, where they either arrest or promote transition of dysplastic islets into islet carcinomas. Through combined TNFR1 signaling and IFN-gamma signaling, Tag-specific CD4+ T cells induce antiangiogenic chemokines and prevent alpha(v)beta(3) integrin expression, tumor angiogenesis, tumor cell proliferation, and multistage carcinogenesis, without destroying Tag-expressing islet cells. In the absence of either TNFR1 signaling or IFN-gamma signaling, the same T cells paradoxically promote angiogenesis and multistage carcinogenesis. Thus, tumor-specific T cells can directly survey multistage carcinogenesis through cytokine signaling.

Inflammation and breast cancer. Balancing immune response: crosstalk between adaptive and innate immune cells during breast cancer progression

Recent insights into the molecular and cellular mechanisms underlying cancer development have revealed that immune cells functionally regulate epithelial cancer development and progression. Moreover, accumulated clinical and experimental data indicate that the outcome of an immune response toward an evolving breast neoplasm is largely determined by the type of immune response elicited. Acute tumor-directed immune responses involving cytolytic T lymphocytes appear to protect against tumor development, whereas immune responses involving chronic activation of humoral immunity, infiltration by Th2 cells, and protumor-polarized innate inflammatory cells result in the promotion of tumor development and disease progression. Herein we review this body of literature and summarize important new findings revealing the paradoxical role of innate and adaptive leukocytes as regulators of breast carcinogenesis.

The adaptive immune response to sporadic cancer

Most of the current experimental cancer models do not reflect the pathophysiology of real-life cancer. Cancer usually occurs sporadically and is clonal in origin. Between tumor initiation and progression, clinically unapparent pre-malignant cells may persist for years or decades in humans. Recently, mouse models of sporadic cancer have been developed. The mouse germ-line can be engineered with high precision so that defined genes can be switched on and off in the adult organism in a targeted manner. Analysis of the immune response against sporadic tumors requires the knowledge of a tumor antigen. Ideally, a silent oncogene, for which the mice are not tolerant, is stochastically activated in individual cells. This approach offers the opportunity to analyze the adaptive immune response throughout the long process of malignant transformation and most closely resembles cancer in humans. In such a model with the highly immunogenic SV40 large T antigen as a dormant oncogene, we discovered that sporadic cancer is recognized by the adaptive immune system at the pre-malignant stage, concomitant with the induction of tumor antigen-specific tolerance. These results demonstrated that even highly immunogenic sporadic tumors are unable to induce functional cytotoxic T lymphocytes. Based on this model, we conclude that immunosurveillance plays little or no role against sporadic cancer and that tumors must not escape immune recognition or destruction.

Dynamic cross-talk between tumor and immune cells in orchestrating the immunosuppressive network at the tumor microenvironment

Accumulating evidence indicates that a dynamic cross-talk between tumors and the immune system can regulate tumor growth and metastasis. Increased understanding of the biochemical nature of tumor antigens and the molecular mechanisms responsible for innate and adaptive immune cell activation has revolutionized the fields of tumor immunology and immunotherapy. Both the protective effects of the immune system against tumor cells (immunosurveillance) and the evasion of tumor cells from immune attack (tumor-immune escape) have led to the concept of cancer immunoediting, a proposal which infers that a bidirectional interaction between tumor and inflammatory/regulatory cells is ultimately responsible for orchestrating the immunosuppressive network at the tumor site. In this context, a major challenge is the potentiation or redirection of tumor antigen-specific immune responses. The success in reaching this goal is highly dependent on an improved understanding of the interactions and mechanisms operating during the different phases of the cancer immunoediting process. In this review, we discuss the multiple defense and counterattack strategies that tumors have devised in order to evade immune attack and to thwart the effectiveness of several immunotherapeutic approaches.

Decreased tumor surveillance after adoptive T-cell therapy

The effect of cancer immunotherapy on the endogenous immune response against tumors is largely unknown. Therefore, we studied immune responses against murine tumors expressing the glycoprotein (GP) and/or nucleoprotein of lymphocytic choriomeningitis virus (LCMV) with or without adoptive T-cell therapy. In nontreated animals, CTLs specific for different epitopes as well as LCMV-GP-specific antibodies contributed to tumor surveillance. Adoptive immunotherapy with monoclonal CTLs specific for LCMV-gp33 impaired the endogenous tumor-specific antibody and CTL response by targeting antigen cross-presenting cells. As a consequence and in contrast to expectations, immunotherapy enhanced tumor growth. Thus, for certain immunogenic tumors, a reduction of tumor-specific B- and T-cell responses and enhanced tumor growth may be an unwanted consequence of adoptive immunotherapy.

A systematic review of the safety of topical therapies for atopic dermatitis

BACKGROUND

The safety of topical therapies for atopic dermatitis (AD), a common and morbid disease, has recently been the focus of increased scrutiny, adding confusion as how best to manage these patients.

OBJECTIVES

The objective of these systematic reviews was to determine the safety of topical therapies for AD.

METHODS

Databases searched included: OVID Medline, Medline In-Process and Other Non-Indexed Citations, Embase, and the Cochrane Central Register of Controlled Trials. In addition to the articles identified by this search, investigators were also referred to a list of links (most recently updated 25 September 2005) to recent Food and Drug Administration (FDA) studies, reports and meetings regarding the topical calcineurin inhibitors for further potential references. Only fully published papers available in English and data obtained from FDA sites were included. Furthermore, the criteria for inclusion and exclusion for each systematic review were further evaluated at a meeting of all of the content and evidence-based medicine experts participating in this process and alteration of the inclusion criteria was done at that time when it was felt necessary to avoid inclusion of lower-quality data in the review. Qualitative review of the abstracted data was performed and reviewed at a meeting of all of the content and evidence-based medicine experts.

RESULTS

While systemic exposure to these topical agents does occur, physiological changes appear to be uncommon and systemic complications rare and have only been found with use of topical corticosteroids.

CONCLUSIONS

Based on the data that are available the overall safety of AD therapies appears to be good with the only documented systemic side-effects of therapy those occasionally seen with use of topical corticosteroids.

Characterizing tumor-promoting T cells in chemically induced cutaneous carcinogenesis

There is a longstanding but poorly understood epidemiologic link between inflammation and cancer. Consistent with this, we previously showed that alphabeta T cell deficiency can increase resistance to chemical carcinogenesis initiated by 7,12-dimethylbenz[a]anthracene and promoted by phorbol 12-myristate 13-acetate. This provoked the hypothesis that alphabeta T cell deficiency removed T regulatory cells that limit the anti-tumor response or removed a specific tumor-promoting (T-pro) T cell population. Here we provide evidence for the latter, identifying a novel CD8(+) subset that is a candidate for T-pro cells. We demonstrate that CD8 cell-deficient mice show substantially less tumor incidence and progression to carcinoma, whereas susceptibility is restored by CD8(+) cell reconstitution. To characterize the putative T-pro cells, tumor-infiltrating lymphocytes were isolated from normal and CD4(-/-) mice, revealing an activated population of T cell receptor alphabeta(+)CD8(+)CD44(+)CD62L(-) cells expressing the inflammatory mediators IFNgamma, TNFalpha, and cyclooxygenase-2, but deficient in perforin, relative to recirculating cells of equivalent phenotype. This novel population of CD8(+) T cells has intriguing similarities with other lymphocytes that have been associated with tissue growth and invasiveness and has implications for inflammation-associated carcinogenesis, models of cancer immunosurveillance, and immunotherapeutic strategies.

Cancer immunotherapy and preclinical studies: why we are not wasting our time with animal experiments

Experimental research on the immune response to transplanted tumors has led to pioneering discoveries that laid many of the foundations for the current field of immunology. Experimental research in oncology has proven that murine and human tumors have antigens that are truly cancer specific. This article discusses research investigating how can antigens on cancer cells be used to help eradicate cancer.

Tumor growth or regression: powered by inflammation

Malignant cells thrive in a highly specialized, stromal environment, which harbors support cells, blood vessels, and diverse leukocyte populations. There is increasing evidence that "by default", intratumoral inflammation fosters angiogenic and vasculogenic processes and simultaneously creates an immunosuppressive micromilieu. This self-amplifying loop of proangiogenic inflammation represents a serious obstacle for adaptive anticancer immune responses. However, angiogenesis is a highly dynamic process, which can be reversed in the "right" inflammatory context; this in turn facilitates immune effector cell entry and tumor rejection. Thus, we propose that a shift from proangiogenic to antiangiogenic inflammation creates a tumor environment permissive for immune destruction. This is a new concept, which integrates antiangiogenic and immune therapeutic treatment modalities.

Tumor-infiltrating T lymphocytes: friends or foes?

The prognostic significance of tumor-infiltrating lymphocytes (TILs) has been a longstanding topic of debate. In cases where TILs have improved patient outcome, T lymphocytes are recognized as the main effectors of antitumor immune responses. However, recent studies have revealed that a subset of CD4(+) T cells, referred to as CD4(+)CD25(+) regulatory T cells (Treg), may accumulate in the tumor environment and suppress tumor-specific T-cell responses, thereby hindering tumor rejection. Hence, predicting tumor behavior on the basis of an indiscriminate evaluation of tumor-infiltrating T cells may result in inconsistent prognostic accuracy. The presence of infiltrating CD4(+)CD25(+) Treg may be detrimental to the host defense against the tumor, while the presence of effector T lymphocytes, including CD8(+) T cells and non-regulatory CD4(+) helper T cells may be beneficial. Enhanced recruitment of antitumor effector T lymphocytes to tumor tissue in addition to inhibition of local Treg, may therefore be an ideal target for improving cancer immunotherapy. This article reviews the antitumor functions of T-lymphocytes, with special attention given to CD4(+) regulatory T-cells within the tumor environment.

The role of stroma in immune recognition and destruction of well-established solid tumors

Well-established solid tumors (at least 14 days old and >1cm in average diameter) are extremely difficult to eradicate immunologically in mice. Most cancer patients that seek medical attention bear primary or metastatic tumors that have grown for longer and that are larger than the tumors we call established. Therefore, focusing research on the problems of rejecting well-established mouse tumors might help in the development of novel concepts and protocols for destroying tumors in patients. A particular problem with established cancers is that even when treatments induce temporary regression, cancer often recurs. Recent studies suggest that manipulation of the stromal microenvironment of these tumors can induce immune recognition and regression. Furthermore, targeting cancer cells as well as tumor stroma for immune destruction might be needed to prevent recurrence.

Paradoxical roles of the immune system during cancer development

The main function of the mammalian immune system is to monitor tissue homeostasis, to protect against invading or infectious pathogens and to eliminate damaged cells. Therefore, it is surprising that cancer occurs with such a high frequency in humans. Recent insights that have been gained from clinical studies and experimental mouse models of carcinogenesis expand our understanding of the complex relationship between immune cells and developing tumours. Here, we examine the paradoxical role of adaptive and innate leukocytes as crucial regulators of cancer development and highlight recent insights that have been gained by manipulating immune responses in mouse models of de novo and spontaneous tumorigenesis.

The interplay between innate and adaptive immunity regulates cancer development

There is increasing clinical and experimental evidence that inflammation and cancer are causally linked. Much progress has been made in understanding how inflammatory cells contribute to cancer development; however, it is still largely unknown which molecular mechanisms are responsible for initiation and maintenance of chronic inflammation associated with developing neoplasms. This review will discuss how the adaptive and innate immune systems interact during physiological and chronic inflammation, with a focus on studies revealing new insights into the role of adaptive immune cells as important regulators of chronic inflammation-associated carcinogenesis. We will speculate on whether current knowledge about the dysregulated interplay between adaptive and innate immunity during chronic inflammatory disorders might be useful in understanding and targeting the underlying mechanisms of chronic inflammation-associated neoplastic progression.

De novo carcinogenesis promoted by chronic inflammation is B lymphocyte dependent

Chronic inflammation predisposes tissue to cancer development; however, regulatory mechanisms underlying recruitment of innate leukocytes toward developing neoplasms are obscure. We report that genetic elimination of mature T and B lymphocytes in a transgenic mouse model of inflammation-associated de novo epithelial carcinogenesis, e.g., K14-HPV16 mice, limits neoplastic progression to development of epithelial hyperplasias that fail to recruit innate immune cells. Adoptive transfer of B lymphocytes or serum from HPV16 mice into T and B cell-deficient/HPV16 mice restores innate immune cell infiltration into premalignant tissue and reinstates necessary parameters for full malignancy, e.g., chronic inflammation, angiogenic vasculature, hyperproliferative epidermis. These findings support a model in which B lymphocytes are required for establishing chronic inflammatory states that promote de novo carcinogenesis.

The role of the immune system in early epithelial carcinogenesis: B-ware the double-edged sword

Cancer is commonly described as a disease of genetic mutations. However, epidemiologic and clinical evidence points to the important but multifaceted role of the host. The immune system has something to say about cancer evolution through promotion of malignancy by inflammatory myeloid cells of the innate immune system. In a report in this issue of Cancer Cell, B cells are implicated as key players in the regulation of chronic inflammation that promotes early events in epithelial carcinogenesis. These are surprising observations, linking antibodies of the adaptive immune system to innate immune responses that drive epithelial carcinogenesis.

The integration of conventional and unconventional T cells that characterizes cell-mediated responses

This review builds on evidence that cell-mediated immune responses to bacteria, viruses, parasites, and tumors are an integration of conventional and unconventional T-cell activities. Whereas conventional T cells provide clonal antigen-specific responses, unconventional T cells profoundly regulate conventional T cells, often suppressing their activities such that immunopathology is limited. By extrapolation, immunopathologies and inflammatory diseases may reflect defects in regulation by unconventional T cells. To explore the function of unconventional T cells, several extensive gene expression analyses have been undertaken. These studies are reviewed in some detail, with emphasis on the mechanisms by which unconventional T cells may exert their regulatory functions. Highlighting the fundamental nature of T-cell integration, we also review emerging data that the development of conventional and unconventional T cells is also highly integrated.

Characterizing the protective component of the alphabeta T cell response to transplantable squamous cell carcinoma

There is increasing promise that cellular immune response may be manipulated to combat cancer; however, it is also clear that the immune response to cutaneous malignancy comprises different T cell activities that variably inhibit or promote tumor development. Thus, a better understanding of each of these activities is crucial to more effective clinical manipulation. To better characterize the protective anti-tumor effects of alphabeta T cells, we examined the growth of the transplantable squamous cell carcinoma (SCC) line, PDV, which is markedly inhibited in immunocompetent versusalphabeta T cell-deficient mice. We show that the protective response is composed of CD8(+) and interferon-gamma (IFNgamma)-producing CD4(+) cells, and that the most overt effects of these components on tumor growth in situ are to provoke overt focal necroses and to decrease the stromal bed. Tumors growing in the presence of any of these components also show reduced expression of Rae-1, a ligand for the activating NK receptor, NKG2D. Collectively, these data illustrate which components of the alphabeta T cell response against SCC have protective potential, and indicate which aspects of tumor physiology may be most susceptible to their activities.

Strong synergy between mutant ras and HPV16 E6/E7 in the development of primary tumors

E6/E7 oncogenes of high-risk human papilloma virus (HPV) subtypes are essential for the development of certain types of cancers. However, these oncogenes are insufficient to transform normal cells into an immortalized or malignant state. Mutant Ha-ras cooperates with E6/E7 of HPV subtype 16 in transformation of cells in vitro and may contribute to some HPV-associated cancers in humans. This study investigates whether HPV16 E6/E7 and v-Ha-ras synergize in vivo. FVB/n mice transgenic for v-Ha-ras gene (R+) were crossed with transgenic C57BL/6 mice that harbor E6/E7 of HPV16 (E+). Beginning at about 3 months of age, the bitransgenic E(+)R(+)(C57BL/6 x FVB/n) F1 mice developed mouth, eye and ear tumors. By 6 months, the prevalence of these types of mouth, eye and ear tumors was 100, 71 and 79% respectively in the E(+)R+ mice. Most tumors grew progressively until the mice had to be killed. The median times for the appearance of the first mouth, eye and ear tumor were 3.6, 4.3 and 4.2 months, respectively. For the two singly transgenic groups of mice, the prevalence of mouth, eye and ear tumors was 0, 0 and 6% (E(-)R+) and 0, 0 and 0% (E(+)R-), respectively, and the median time to first tumor was greater than 12 months for singly transgenic mice (E(-)R+, E(+)R-). Thus, a remarkable synergy occurred between the v-Ha-ras and HPV16 E6/E7 oncogenes in the development of primary tumors in mice.

Tumour escape: antitumour effectors too much of a good thing?

Although even "spontaneous" tumours are immunogenic and are commonly infiltrated by tumour antigen-specific T cells (at least in melanoma), most tumours are not completely rejected by the host, and cancer progresses. There is a growing realisation that many responses defined as antitumour effector mechanisms act as double-edged swords and under different conditions either become ineffective or even protumorigenic. Examples are interleukin 2 (also proapoptotic for activated T cells), interferon gamma (by induction of ligands for T and NK cell inhibitory receptors), angiogenesis inhibition (by hypoxia-mediated induction of growth factors promoting metastasis), and macrophage free radical-mediated cytotoxicity (by inhibiting T cells). Immune selection pressure itself, resulting in outgrowth of resistant tumour variants could also be viewed in this light. On the other hand, knowledge of the many tumour escape pathways offers the theoretical possibility of reconstituting antitumour immunity. Tumour escape from immunosurveillance represents the last series of hurdles to be overcome in formulating truly effective cancer immunotherapy, but given the immense plasticity of the tumour cell, and the complex balance between pro- and antitumour activity of the very same effector pathways, this remains a major challenge.

Vigorous premalignancy-specific effector T cell response in the bone marrow of patients with monoclonal gammopathy

Most approaches targeting the immune system against tumors have focused on patients with established tumors. However, whether the immune system can recognize preneoplastic stages of human cancer is not known. Here we show that patients with preneoplastic gammopathy mount a vigorous T cell response to autologous premalignant cells. This preneoplasia-specific CD4⁺ and CD8⁺ T cell response is detected in freshly isolated T cells from the BM. T cells from myeloma marrow lack this tumor-specific rapid effector function. These data provide direct evidence for tumor specific immune recognition in human preneoplasia and suggest a possible role for the immune system in influencing the early growth of transformed cells, long before the development of clinical cancer.

The distinct contributions of murine T cell receptor (TCR)gammadelta+ and TCRalphabeta+ T cells to different stages of chemically induced skin cancer

Epithelial tissues in which carcinomas develop often contain systemically derived T cell receptor (TCR)alphabeta+ cells and resident intraepithelial lymphocytes that are commonly enriched in TCRgammadelta+ cells. Recent studies have demonstrated that gammadelta cells protect the host against chemically induced cutaneous malignancy, but the role of alphabeta T cells has been enigmatic, with both protective and tumor-enhancing contributions being reported in different systems. This study aims to clarify the contributions of each T cell type to the regulation of squamous cell carcinoma induced in FVB mice by a two-stage regimen of 7,12-dimethylbenz[a]anthracene initiation followed by repetitive application of the tumor promoter 12-O-tetradecanoylphorbol 13-acetate. This protocol permits one to monitor the induction of papillomas and the progression of those papillomas to carcinomas. The results show that whereas gammadelta cells are strongly protective, the nonredundant contributions of alphabeta T cells to the host's protection against papillomas are more modest. Furthermore, at both high and low doses of carcinogens, alphabeta T cells can contribute to rather than inhibit the progression of papillomas to carcinomas. As is likely to be the case in humans, this study also shows that the contribution of T cells to tumor immunosurveillance is regulated by modifier genes.

Genetic changes occurring in established tumors rapidly stimulate new antibody responses

Cancer patients and tumor-bearing mice possess serum antibodies that recognize antigens expressed by cancer cells at the time of diagnosis. After diagnosis, cancers progress to more aggressive stages, most often by acquiring new genetic changes that can give rise to new proteins, some of which are antigenic. However, at these relatively later stages of tumor growth, it remains unclear whether, when, and how a host can generate de novo antibody responses against these newly appearing tumor antigens. To this end, we used a tamoxifen-regulated Cre-loxP system, MerCreMer, to induce genetic recombination in cancer cells of well-established tumors, resulting in increased enhanced green fluorescence protein (EGFP) expression. These late tumor-bearing mice generated specific IgG antibodies against EGFP within 3 wk after antigen induction. Mice generated these antibody responses in the presence of preexisting anti-tumor antibody responses. Preexisting CD4(+) T cell responses to already expressed tumor antigens likely enhanced antibody responses to the induced EGFP antigen. By analogy, new antibody responses in cancer patients may identify genetic changes occurring in a growing tumor and indicate imminent tumor progression.

Immune enhancement of skin carcinogenesis by CD4+ T cells

In a transgenic model of multi-stage squamous carcinogenesis induced by human papillomavirus (HPV) oncogenes, infiltrating CD4+ T cells can be detected in both premalignant and malignant lesions. The lymph nodes that drain sites of epidermal neoplasia contain activated CD4+ T cells predominantly reactive toward Staphylococcal bacterial antigens. HPV16 mice deficient in CD4+ T cells were found to have delayed neoplastic progression and a lower incidence of tumors. This delay in carcinogenesis is marked by decreased infiltration of neutrophils, and reduced activity of matrix metalloproteinase-9, an important cofactor for tumor progression in this model. The data reveal an unexpected capability of CD4 T cells, whereby, proinflammatory CD4+ T cells, apparently responding to bacterial infection of dysplastic skin lesions, can inadvertently enhance neoplastic progression to invasive cancer.

Inhibition of methylcholanthrene-induced carcinogenesis by an interferon gamma receptor-dependent foreign body reaction

The foreign body reaction is one of the oldest host defense mechanisms against tissue damage which involves inflammation, scarring, and encapsulation. The chemical carcinogen methylcholanthrene (MCA) induces fibrosarcoma and tissue damage in parallel at the injection site. Tumor development induced by MCA but not due to p53-deficiency is increased in interferon-gamma receptor (IFN-gammaR)-deficient mice. In the absence of IFN-gammaR, MCA diffusion and DNA damage of surrounding cells is increased. Locally produced IFN-gamma induces the formation of a fibrotic capsule. Encapsulated MCA can persist virtually life-long in mice without inducing tumors. Together, the foreign body reaction against MCA prevents malignant transformation, probably by reducing DNA damage. This mechanism is more efficient in the presence of IFN-gammaR. Our results indicates that inflammation and scarring, both suspected to contribute to malignancy, prevent cancer in certain situations.

A ras-mutated peptide targeted by CTL infiltrating a human melanoma lesion

Ags derived from commonly mutated oncogenic proteins seem ideally suited as targets for tumor immunotherapy. Nonetheless, only a few mutated epitopes efficiently presented by human tumors have thus far been identified. We describe here an approach to identify such epitopes. This approach involves: 1) identifying tumors expressing a ras mutation and isolating the tumor-infiltrating lymphocytes (TIL); 2) transfecting COS cells to induce expression of unknown mutated peptides in the context of a patient's HLA class I molecules; and 3) screening epitope recognition by using TIL from the tumors expressing a ras mutation. By using this approach, there appeared to be a N-ras mutation (a glutamine-to-arginine exchange at residue 61 (Q61R)), detected in a melanoma lesion, which was recognized specifically by the autologous TIL in the HLA-A*0101 context. The ras peptide 55-64(Q61R) was the epitope of these TIL and was regularly presented by Q61R-mutated HLA-A*0101(+) melanoma cell lines. This peptide and its wild-type homolog (55-64(wt)) bound to HLA-A*0101 with similar affinities. However, only the mutated peptide could induce specific CTL expansion from PBL. All the CTL clones specific to the mutated peptide, failed to recognize the wild-type sequence on both COS and melanoma cells. These data thus show that oncogenic protein mutations can create shared tumor-specific CTL epitopes, efficiently presented by tumor cells, and that screening for oncogene-transfected COS cell recognition by TIL (from tumors containing mutations) is a powerful approach for the identification of these epitopes.

Challenges in the development of effective peptide vaccines for cancer

The ability of the immune system to recognize malignant cells has opened the door to development of tumor vaccines to treat or prevent various types of cancer. In the era of molecular biology, the tumor antigens recognized by the immune system have been identified, allowing the generation of subunit vaccines that may improve safety and efficacy compared with more crude vaccines such as irradiated tumor cells and tumor cell lysates. Synthetic peptides corresponding to defined antigenic epitopes for tumor-reactive lymphocytes represent one of the new types of vaccines currently being developed to treat or prevent various types of malignant disorders. The design of peptide-based vaccines to stimulate antitumor T-cell responses has many attractive features such as ease of manufacturing and characterization (ie, quality control), as well as an excellent safety profile in past clinical studies. However, ambiguous results from initial clinical trials indicate that these vaccines are far from optimal and that considerable efforts for their optimization lie ahead. We attempt to address the 8 most important challenges we currently face for developing peptide-based vaccines that would effectively induce immune responses leading to antitumor effects.

Prophylactic cancer vaccines

Increasingly, data from distinct experimental systems show that immunity can be activated to prevent tumors. The rationale for prevention is strong because, in that setting, one deals with an immune system that is neither impaired by tumor- and treatment-induced suppression nor tolerant to tumor-associated antigens that have been encountered in the absence of correct presentation and costimulatory/danger signals. The use of overexpressed or mutated proteins, or mutated oncogenic growth factor receptors, as tumor-associated antigens yields rational targets for specific immunoprevention. Transgenic mouse models are providing encouraging indications of future usefulness of vaccines that are based on these molecules.

Induction of MHC class I presentation of exogenous antigen by dendritic cells is controlled by CD4+ T cells engaging class II molecules in cholesterol-rich domains

We investigated interactions between CD4+ T cells and dendritic cells (DC) necessary for presentation of exogenous Ag by DC to CD8+ T cells. CD4+ T cells responding to their cognate Ag presented by MHC class II molecules of DC were necessary for induction of CD8+ T cell responses to MHC class I-associated Ag, but their ability to do so depended on the manner in which class II-peptide complexes were formed. DC derived from short-term mouse bone marrow culture efficiently took up Ag encapsulated in IgG FcR-targeted liposomes and stimulated CD4+ T cell responses to Ag-derived peptides associated with class II molecules. This CD4+ T cell-DC interaction resulted in expression by the DC of complexes of class I molecules and peptides from the Ag delivered in liposomes and permitted expression of the activation marker CD69 and cytotoxic responses by naive CD8+ T cells. However, while free peptides in solution loaded onto DC class II molecules could stimulate IL-2 production by CD4+ T cells as efficiently as peptides derived from endocytosed Ag, they could not stimulate induction of cytotoxic responses by CD8+ T cells to Ag delivered in liposomes into the same DC. Signals requiring class II molecules loaded with endocytosed Ag, but not free peptide, were inhibited by methyl-beta-cyclodextrin, which depletes cell membrane cholesterol. CD4+ T cell signals thus require class II molecules in cholesterol-rich domains of DC for induction of CD8+ T cell responses to exogenous Ag by inducing DC to process this Ag for class I presentation.

DNA vaccination against v-src oncogene-induced tumours in congenic chickens

DNA vaccination is particularly efficient for induction of cytotoxic T-lymphocyte (CTL) response. In our experiments, we used MHC(B) congenic chicken lines CB and CC (regressors and progressors of v-src-induced tumours, respectively) and a mutated, non-oncogenic v-src gene construct as the DNA vaccine. A high degree of vaccine protection against oncogenic v-src challenge was achieved in the CB line chickens. CTL response was demonstrated in vitro and by adoptive transfer of immune cells to the syngeneic host and to the CC line chickens rendered tolerant to CB cells. In the CC line chickens we observed tumour growth retardation after a low-dose DNA vaccination administered to immature recipients while higher amounts of DNA vaccine in immunocompetent chickens exerted an enhancing effect.

Immunological enhancement of primary tumor development and its prevention

While it has been known for decades that the growth of tumor transplants can be enhanced immunologically, the potential significance of these previous findings to the development of primary tumors and the mechanisms of tumor enhancement has remained obscure. This review will summarize recent experiments indicating that primary tumor development can be enhanced by active immunization. The evidence suggests that antibodies, B cells and CD4+ T cells can play a critical role in enhancing the development of primary, tumors, whereas endogenous interferon-gamma (IFNgamma) can counteract enhancement. Thus, we envision two possible functions of IFNgamma: (i) preventing B cell and antibody enhancement and (ii) counteracting tumor promotion independent of T and B cells.