Cancer immunoprevention

Cancer immunotherapy is now a reality. The results are phenomenal but the cost is outrageous. Even if the cost eventually comes down and immunotherapy becomes more broadly available, using the knowledge derived from immunotherapy to apply to immunoprevention would be a good strategy. The most likely approach to cancer immunoprevention is cancer vaccines. To date, cancer vaccines have been tested mostly in the setting of advanced disease. Numerous immunosuppressive mechanisms have been identified in the tumor microenvironment as well as systemically that compromise the ability of cancer patients to respond to the vaccines. Multiple approaches are being tested to improve therapeutic cancer vaccine efficacy, including combinations with other immunotherapies. An alternative approach is to administer the vaccines to individuals without cancer but at high risk for cancer. Data in support of this approach and immunoprevention in general is accumulating and clinical testing has started.

The FDA guidance on therapeutic cancer vaccines: the need for revision to include preventive cancer vaccines or for a new guidance dedicated to them

Cancer vaccines based on antigens derived from self molecules rather than pathogens have been under basic and clinical investigations for many years. Up until very recently, they had been tested primarily in the setting of metastatic disease with the goal to engage the immune system in slowing down disease progression. Many therapeutic vaccine trials, either investigator initiated or led by pharmaceutical companies, have been completed and many are currently ongoing, following the FDA Guidance on therapeutic cancer vaccines published in 2011. In recent years, the target of cancer vaccines is being shifted to early cancer and even premalignant disease with the goal of preventing cancer. Although some issues addressed in the FDA Guidance on therapeutic vaccines apply to preventive vaccines, many do not. Here, we discuss a set of recommendations for revising the current Guidance to also cover preventive vaccines, or to include in a new Guidance dedicated specifically to vaccines for cancer prevention.

Abstract 2509: Human anti-MUC1 antibodies elicited by a prophylactic cancer vaccine for mAb and CAR-modified T cell immunotherapies

MUC1 is a tumor-associated protein that is abnormally expressed on human adenocarcinomas. In our recent clinical trial, individuals at-risk for colonic adenocarcinoma received a prophylactic MUC1 cancer vaccine. Many individuals responded to the vaccine by producing high titers of anti-MUC1 IgG antibodies (Kimura, 2013). We isolated a panel of these antibodies and are seeking to develop them as antibody and chimeric antigen receptor (CAR) T cell cancer immunotherapies. To this end we used a novel method combining proteomics and next-gen DNA sequencing to identify and recombinantly produce 12 high-affinity anti-MUC1 antibodies from the sera of vaccinated individuals. By ELISA we determined that the antibodies bind with high-affinity to diverse epitopes within the MUC1 vaccine peptide. We also found that several of the antibodies can stain MUC1+ pancreas, colon, and breast cancer cell lines, but not a cell line expressing normal MUC1. We then determined that the antibodies could stain MUC1+ human pancreas and colon tumor samples, but not normal tissues. Having established tumor-specificity we have begun assessing the antibodies in a series of functional assays. In preliminary in vitro testing we determined that several of the antibodies can be internalized by MUC1+ cells making them potential candidates for toxin delivery as antibody drug conjugates (ADCs). Additionally, we found that two of the antibodies are capable of efficiently performing complement-dependent cytotoxicity (CDC) on MUC1+ cells. Finally, we have constructed CAR lentiviral expression constructs using the variable regions of several of the antibodies as targeting domains and are testing their ability to mediate MUC1-specific T cell activation, cytokine production, and target cell lysis. As the antibodies are human-derived, indication of efficacy in pre-clinical testing has the potential to directly enable clinical trials and hopefully approval of these reagents for therapy of cancer patients.

Citation Format: Jason J. Lohmueller, Shuji Sato, Wan Cheung Cheung, Isabel Chu, Lana Popova, Christopher A. Manning, Katherine Crosby, Christopher Grange, James D. Ham, Roberto D. Polakiewicz, Olivera J. Finn. Human anti-MUC1 antibodies elicited by a prophylactic cancer vaccine for mAb and CAR-modified T cell immunotherapies. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2509. doi:10.1158/1538-7445.AM2015-2509

Vaccines for cancer prevention: a practical and feasible approach to the cancer epidemic

Concerted efforts of tumor immunologists over more than two decades contributed numerous well-defined tumor antigens, many of which were promptly developed into cancer vaccines and tested in animal models and in clinical trials. Encouraging results from animal models were seldom recapitulated in clinical trials. The impediment to greater success of these vaccines has been their exclusive use for cancer therapy. What clinical trials primarily revealed were the numerous ways in which cancer and/or standard treatments for cancer could suppress the patient's immune system, making it very difficult to elicit effective immunity with therapeutic vaccines. In contrast, there is an extensive database of information from experiments in appropriate animal models showing that prophylactic vaccination is highly effective and safe. There are also studies that show that healthy people have immune responses against antigens expressed on tumors, some generated in response to viral infections and others in response to various nonmalignant acute inflammatory events. These immune responses do not appear to be dangerous and do not cause autoimmunity. Epidemiology studies have shown that these immune responses may reduce cancer risk significantly. Vaccines based on tumor antigens that are expressed differentially between tumors and normal cells and can stimulate immunity, and for which safety and efficacy have been proved in animal models and to the extent possible in therapeutic clinical trials, should be considered prime candidates for prophylactic cancer vaccines.

Altered glycosylation of MUC1 influences its association with CIN85: the role of this novel complex in cancer cell invasion and migration

MUC1 is a transmembrane glycoprotein abnormally expressed in human adenocarcinomas. The extracellular domain of MUC1 contains a variable number of tandem repeats (VNTR) region that is extensively O-glycosylated in normal epithelia and underglycosylated in tumor cells. This change in posttranslational modification of MUC1 leads to changes in its normal functions including, we hypothesized, its interaction with other molecules. We identified CIN85, an adaptor protein involved in multiple cellular processes including signal transduction, cytoskeletal remodeling and cancer cell invasion, as one of several proteins that associate with MUC1 in tumor cells. CIN85 associates with both the cytosolic tail and the extracellular VNTR of MUC1. Co-immunoprecipitation and confocal immunofluorescence confirmed that MUC1 and CIN85 co-localize primarily at the plasma membrane but the complex can be found also in the cytosol and on the cytoskeleton. MUC1 and CIN85 are both over-expressed in early as well as advanced clinical stages of breast cancer and co-localize on invadopodia-like structures implicated in cell invasion. siRNA-mediated silencing of CIN85 and/or MUC1 revealed that MUC1 enhances CIN85-dependent breast cancer cell migration and invasion in vitro. However, ectopic expression of MUC1 enhances the motility induced by CIN85. When tested in vivo in a tumor metastasis model of B16 melanoma, mice injected with CIN85-depleted melanoma cells exhibited few or no lung metastasis and, similarly to the in vitro results, overexpression of MUC1 recovered the shCIN85-reduced metastatic process. Our findings implicate this newly identified CIN85/MUC1 complex associated with invadopodia-related molecules in promoting the invasive and metastatic potential of breast cancer.

Global Inhibition of DC Priming Capacity in the Spleen of Self-Antigen Vaccinated Mice Requires IL-10

Dendritic cells (DC) in the spleen are highly activated following intravenous vaccination with a foreign-antigen, promoting expansion of effector T cells, but remain phenotypically and functionally immature after vaccination with a self-antigen. Up-regulation or suppression of expression of a cohort of pancreatic enzymes 24–72 h post-vaccination can be used as a biomarker of stimulatory versus tolerogenic DC, respectively. Here we show, using MUC1 transgenic mice and a vaccine based on the MUC1 peptide, which these mice perceive as a self-antigen, that the difference in enzyme expression that predicts whether DC will promote immune response or immune tolerance is seen as early as 4–8 h following vaccination. We also identify early production of IL-10 as a predominant factor that both correlates with this early-time point and controls DC function. Pre-treating mice with an antibody against the IL-10 receptor prior to vaccination results in DC that up-regulate CD40, CD80, and CD86 and promote stronger IFNγ+ T cell responses. This study suggests that transient inhibition of IL-10 prior to vaccination could improve responses to cancer vaccines that utilize self-tumor antigens.

Novel mechanisms underlying the immediate and transient global tolerization of splenic dendritic cells after vaccination with a self-antigen

Dendritic cells (DCs) are important orchestrators of the immune response, ensuring that immunity against pathogens is generated, whereas immunity against healthy tissues is prevented. Using the tumor Ag MUC1, we previously showed that i.v. immunization of MUC1 transgenic mice, but not wild-type, with a MUC1 peptide resulted in transient tolerization of all splenic DCs. These DCs did not upregulate costimulatory molecules and induced regulatory T cells rather than effector T cells. They were characterized by suppressed expression of a cohort of pancreatic enzymes not previously reported in DCs, which were upregulated in DCs presenting the same MUC1 peptide as a foreign Ag. In this article, we examined the self-antigen-tolerized DC phenotype, function, and mechanisms responsible for inducing or maintaining their tolerized state. Tolerized DCs share some characteristics with immature DCs, such as a less inflammatory cytokine/chemokine profile, deficient activation of NF-κB, and sustained expression of zDC and CCR2. However, tolerized DCs demonstrated a novel inducible expression of aldehyde dehydrogenase 1/2 and phospho-STAT3. Suppressed expression of one of the pancreatic enzymes, trypsin, in these DC impeded their ability to degrade extracellular matrix, thus affecting their motility. Suppressed metallopeptidases, reflected in low expression of carboxypeptidase B1, prevented optimal Ag-specific CD4(+) T cell proliferation suggesting their role in Ag processing. Tolerized DCs were not refractory to maturation after stimulation with a TLR3 agonist, demonstrating that this tolerized state is not terminally differentiated and that tolerized DCs can recover their ability to induce immunity to foreign Ags.

Influenza virus infection elicits protective antibodies and T cells specific for host cell antigens also expressed as tumor-associated antigens: a new view of cancer immunosurveillance

Most tumor-associated antigens (TAA) are self-molecules that are abnormally expressed in cancer cells and become targets of antitumor immune responses. Antibodies and T cells specific for some TAAs have been found in healthy individuals and are associated with lowered lifetime risk for developing cancer. Lower risk for cancer has also been associated with a history of febrile viral diseases. We hypothesized that virus infections could lead to transient expression of abnormal forms of self-molecules, some of which are TAAs; facilitated by the adjuvant effects of infection and inflammation, these molecules could elicit specific antibodies, T cells, and lasting immune memory simultaneously with immunity against viral antigens. Such infection-induced immune memory for TAA would be expected to provide life-long immune surveillance of cancer. Using influenza virus infection in mice as a model system, we tested this hypothesis and demonstrated that influenza-experienced mice control 3LL mouse lung tumor challenge better than infection-naive control mice. Using 2D-difference gel electrophoresis and mass spectrometry, we identified numerous molecules, some of which are known TAAs, on the 3LL tumor cells recognized by antibodies elicited by two successive influenza infections. We studied in detail immune responses against glyceraldehyde-3-phosphate dehydrogenase (GAPDH), histone H4, HSP90, malate dehydrogenase 2, and annexin A2, all of which were overexpressed in influenza-infected lungs and in tumor cells. Finally, we show that immune responses generated through vaccination against peptides derived from these antigens correlated with improved tumor control.

Preventing cancer by targeting abnormally expressed self-antigens: MUC1 vaccines for prevention of epithelial adenocarcinomas

Prophylactic vaccines based on tumor-associated antigens (TAAs) have elicited concerns due to their potential toxicity. Because TAAs are considered self-antigens, the prediction is that such vaccines will induce autoimmunity. While this has been observed in melanoma, where an antitumor immune response leads to vitiligo, autoimmunity has almost never been seen following vaccination with numerous other TAAs. We hypothesized that antigen choice determines outcome and have been working to identify TAAs whose expression differs between normal and tumor tissue, and thus could elicit antitumor immunity without autoimmunity. Studies on the epithelial TAA MUC1 have revealed that, compared to MUC1 on normal cells, tumors, premalignant lesions, and noncancerous pathologies affecting epithelial cells express abnormal MUC1, which is not a self-antigen but rather an abnormal disease-associated antigen (DAA). This distinction, which can be made for many known TAAs, has broad implications for the design and acceptance of preventative cancer vaccines.

Generation and immunosuppressive functions of p53-induced human adaptive regulatory T cells

Inducible regulatory T cells (iTregs, also called Tr1 cells) are generated in the periphery (circulation or tissue) of cancer patients upon the encounter of naïve CD4⁺ T cells with tumor-associated antigens. As p53 is often inactivated by genetic or epigenetic events during oncogenesis, p53-induced Tr1 cells might play a key role in establishing immunosuppressive networks in cancer patients. Tr1 cells were generated by co-culturing circulating CD4⁺CD25⁻ T cells with autologous immature dendritic cells pulsed with a wild-type (WT) p53-derived peptide or an unrelated peptide derived from mucin 1 (MUC1). The Tr1 phenotype and the specificity for p53 of these cells were confirmed by multicolor flow cytometry. Moreover, the Tr1 cell-mediated suppression of T-cell proliferation was evaluated by CFSE-based flow cytometry, while their ability to alter the T-cell cytokine profile by ELISA and Luminex assays. The capacity of p53-induced Tr1 cells to suppress the generation and function of cytotoxic T lymphcoytes (CTLs) was assessed by flow cytometry and ELISPOT. Of note, low doses of the p53-derived peptide (p53_low) induced greater numbers of Tr1 cells than the same peptide employed at high doses (p53_high). Moreover, Tr1/p53_low cells not secreted higher levels of interleukin-10 and transforming growth factor β1, but also mediated more robust suppressive effects on CTL proliferation than Tr1/p53_high cells. Tr1/p53_low cells, Tr1/p53_high cells, as well as Tr1 cells generated with low doses of an unrelated MUC1-derived peptide were equally effective in suppressing the expansion and antitumor activity of p53-reactive CTLs. p53_low induced the expansion of highly suppressive p53-reactive Tr1 cells. However, the capacity of these Tr1 cells to suppress the generation and function of p53-reactive CTLs was independent of their antigen-specificity.

Early in vivo signaling profiles in MUC1-specific CD4+ T cells responding to two different MUC1-targeting vaccines in two different microenvironments

Vaccines are beginning to be explored for as measures to prevent cancer. Since determining the efficacy of vaccines by evaluating disease outcome requires a long time, there is an urgent need for early predictive biomarkers. To this end, immunological endpoints that can be assessed weeks or months post-vaccination are currently being evaluated. However, when multiple vaccines are available, waiting for the development of humoral and cellular immunity could still cause delays, whereas early assessments would allow for a timely shift to more effective prevention modalities. Applying the phospho-flow technique to primary T cells, we examined the phosphorylation status of various proteins that shape the activation, proliferation, and differentiation of mucin 1 (MUC1)-specific CD4+ T cells within the first 24 hours post-immunization. It is known that a vaccine composed of a MUC1-derived peptide loaded on dendritic cells is more effective in eliciting T-cell responses than a vaccine including the same peptide plus an adjuvant. Both these vaccines stimulate T cells more effectively in wild-type (WT) than in MUC1-transgenic mice. We examined if the signaling events downstream of the TCR or linked to various proliferative and survival pathways, monitored in two different hosts as early as 3, 6, 12 and 24 hours post-immunization, could predict the differential potential of these two MUC1-targeting vaccines. The signaling signatures that we obtained primarily reflect differences between the vaccines rather than between the hosts. We demonstrate the feasibility of using a phospho-flow-based approach to evaluate the potential of a given vaccine to elicit a desired immune response.

Antigen choice determines vaccine-induced generation of immunogenic versus tolerogenic dendritic cells that are marked by differential expression of pancreatic enzymes

Dendritic cells (DC) elicit immunity to pathogens and tumors while simultaneously preserving tolerance to self. Efficacious cancer vaccines have been a challenge because they are based on tumor Ags, some of which are self-Ags and thus subject to self-tolerance. One such Ag is the tumor-associated mucin MUC1. Preclinical testing of MUC1 vaccines revealed existence of peripheral tolerance to MUC1 that compromises their efficacy. To identify mechanisms that act early postvaccination and might predict vaccine outcome, we immunized human MUC1 transgenic mice (MUC1.Tg) i.v. with a MUC1 peptide vaccine against which they generate weak immunity and wild-type (WT) mice that respond strongly to the same peptide. We analyzed differences in splenic DC phenotype and function between the two mouse strains at 24 and 72 h postvaccination and also performed unbiased total gene expression analysis of the spleen. Compared to WT, MUC1.Tg spleens had significantly fewer DC, and they exhibited significantly lower expression of costimulatory molecules, decreased motility, and preferential priming of Ag-specific Foxp3(+) regulatory T cells. This tolerogenic DC phenotype and function was marked by a new putative biomarker revealed by the microarray: a cohort of pancreatic enzymes (trypsin, carboxypeptidase, elastase, and others) not previously reported in DC. These enzymes were strongly upregulated in the splenic DC from vaccinated WT mice and suppressed in the splenic DC of vaccinated MUC1.Tg mice. Suppression of the enzymes was dependent on regulatory T cells and on signaling through the IL-10R and correlated with global downregulation of DC immunostimulatory phenotype and function.

Immuno-oncology: understanding the function and dysfunction of the immune system in cancer

The immune system has the greatest potential for the specific destruction of tumours with no toxicity to normal tissue and for long-term memory that can prevent cancer recurrence. The last 30 years of immuno-oncology research have provided solid evidence that tumours are recognised by the immune system and their development can be stopped or controlled long term through a process known as immunosurveillance. Tumour specificity of the immune response resides in the recognition of tumour antigens. Viral proteins in tumours caused by viruses and mutated proteins from oncogenes or other genes, as well as nonmutated but abnormally expressed self proteins found on all tumours, have been shown to be good antigens and good targets for immunosurveillance. In many cancers, however, malignant progression is accompanied by profound immune suppression that interferes with an effective antitumour response and tumour elimination. Initially, most of the escape from immunosurveillance was ascribed to changes in the tumour cells themselves (loss of tumour antigens, loss of human leukocyte antigen molecules, loss of sensitivity to complement, or T cell or natural killer (NK) cell lysis), making them a poor target of an immune attack. However, it has become clear that the suppression comes from the ability of tumours to subvert normal immune regulation to their advantage. The tumour microenvironment can prevent the expansion of tumour antigen-specific helper and cytotoxic T cells and instead promote the production of proinflammatory cytokines and other factors, leading to the accumulation of suppressive cell populations that inhibit instead of promote immunity. The best described are regulatory T cells and myeloid-derived suppressor cells. Great conceptual and technical advances in the field of immuno-oncology over the past 30 years have provided us with the knowledge and techniques to develop novel immunotherapeutic approaches for the treatment of cancer. These include methods that enhance tumour immunity by blocking inhibitory pathways and inhibitory cells in the tumour microenvironment (e.g. antibodies against cytotoxic T-lymphocyte-associated antigen-4, programmed death 1 or its ligand programmed death ligand 1, or low-dose chemotherapy). Of equal importance, they include methods that can enhance the specificity of antitumour immunity by inducing the expansion of T cells and antibodies directed to well-defined tumour antigens (e.g. cancer vaccines, potent adjuvants, immunostimulatory cytokines). Even as monotherapies, these approaches are having a substantial impact on the treatment of some patients with advanced, previously untreatable, malignancies. Most exciting of all, these successes provide a rationale to expect that used in various combinations or earlier in disease, current and future immunotherapies may transform cancer treatment, improving a prognosis for many patients.

Abstract A66: IL-33 promotes CD8 T cell effector function and has a potent antitumor activity in vivo

Interleukin-33 is a member of the IL-1 family of cytokines and is released by stressed cells, necrotic cells or activated innate immune cells such as macrophages during trauma or infection. Thus, IL-33 is thought to serve as an endogenous “danger signal” to trigger inflammation and promote cell mediated immune responses. Prior studies have supported the role of IL-33 in promoting type 2 immune responses but little was known for its role in type 1 immune responses such as the anti-tumor immune response. We have found that that ST2, a receptor for IL-33, is highly expressed in activated CD8 T cells. We have further revealed that, T-bet, a critical transcriptional factor for Th1 differentiation and effector functions, is required for ST2 expression by CD8 T cells, suggesting that ST2 is an integral part of the Th1 gene network in CD8 T cells. Furthermore, we have demonstrated that IL-33 synergized with TCR or IL-12 in increasing both human and mouse CD8 T cell functions such as IFN-γ production. Thus IL-33 can greatly enhance type 1 cell-mediated immune responses in both human and mice. The in vivo relevance of this pathway is examined in a preclinical model of tumor immunity. Our results support a potent function of IL-33 in inhibiting tumor growth and provide a novel therapeutic approach for tumor immunity.

Citation Format: Xin Gao, Gang Li, Bo Teng, Qianting Yang, Yibei Zhu, Xueguang Zhang, Olivera J. Finn, Binfeng Lu. IL-33 promotes CD8 T cell effector function and has a potent antitumor activity in vivo. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr A66.

MUC1 vaccine for individuals with advanced adenoma of the colon: a cancer immunoprevention feasibility study

Cancer vaccines based on human tumor-associated antigens (TAA) have been tested in patients with advanced or recurrent cancer, in combination with or following standard therapy. Their immunogenicity and therapeutic efficacy has been difficult to properly evaluate in that setting characterized by multiple highly suppressive effects of the tumor and the standard therapy on the patient's immune system. In animal models of human cancer, vaccines administered in the prophylactic setting are most immunogenic and effectively prevent cancer development and progression. We report results of a clinical study that show that in patients without cancer but with a history of premalignant lesions (advanced colonic adenomas, precursors to colon cancer), a vaccine based on the TAA MUC1 was highly immunogenic in 17 of 39 (43.6%) of vaccinated individuals, eliciting high levels of anti-MUC1 immunoglobulin G (IgG) and long-lasting immune memory. Lack of response in 22 of 39 individuals was correlated with high levels of circulating myeloid-derived suppressor cells (MDSC) prevaccination. Vaccine-elicited MUC1-specific immune response and immune memory were not associated with significant toxicity. Our study shows that vaccines based on human TAAs are immunogenic and safe and capable of eliciting long-term memory that is important for cancer prevention. We also show that in the premalignant setting, immunosuppressive environment (e.g., high levels of MDSC) might already exist in some individuals, suggesting an even earlier premalignant stage or preselection of nonimmunosuppressed patients for prophylactic vaccination.

Host response in tumor diagnosis and prognosis: importance of immunologists and pathologists alliance

Pathologists and immunologists have collaborated over many years in their efforts to understand and properly diagnose cancer. The ability of pathologists to correctly diagnose this disease was facilitated by the development of immunohistology that utilized specificity of antibodies to distinguish between normal cells and cancer cells. Further boost was provided through the advent of monoclonal antibodies. The two disciplines are now together on the brink of a paradigm shift resulting from a better understanding of the importance for cancer diagnosis and prognosis to consider not only the characteristics of the cancer cells, but also the cancer microenvironment reflecting the host response to the disease. This new immunology and pathology alliance named "Immunoscore" will advance research in both disciplines as well as benefit patients.

H-2 antigen expression: Loss in vitro, restoration in vivo, and correlation with cell-mediated cytotoxicity in a mouse lymphoma cell line

The susceptibility to cell-mediated cytolysis of cells of the recently developed C57BL/Ka(H-2 ( b )) lymphoma cell line, BL/VL(3), was investigated in allogeneic assays with thymus-dependent lymphocytes (T cells). Compared to EL4, the widely used C57BL/6(H-2 ( b )) lymphoma cell line, BL/VL(3) cells were found to be insensitive to T-cell-mediated lysis as detected by the use of(51)Crrelease methods. When used as immunogens in alloreactive combinations with BALB/c(H-2 ( d )) splenocytes as responder cells, BL/VL(3) cells failed to elicit sensitization. Serological tests showed that this cell line had profoundly reduced levels of H-2(b) antigens on its surface. When BL/VL(3) cells were reinjected into C57BL/Ka and BALB/c mice, full recovery of H-2(b) antigen expression at the cell surface was observed in both syngeneic and allogeneic hosts after only 11 days of in vivo growth. Concomitantly, they acquired the ability to induce cytotoxic responses in allogeneic T cells and became susceptible to their lytic activity. The expression of H-2 antigens on the surface of BL/VL(3) cells is a reversibly modulated function that depends on in vivo growth conditions and is lost in vitro in the absence of immunoselective pressure.

MUC1 immunotherapy is here to stay

INTRODUCTION

Success of HBV vaccines in reducing the incidence of liver cancer, and HPV vaccines in reducing preneoplastic cervical lesions, demonstrate the potential of cancer reduction by harnessing the immune system. For most human cancers, infectious etiology is not known but other tumor antigens, candidates for vaccines, have been identified.

AREAS COVERED

The authors discuss knowledge accumulated the last two decades on the tumor antigen MUC1 that has put it at the top of the list as an immunotherapy reagent. They examine evidence that anti-MUC1 immunity affects tumor development and prognosis. Finally, they review two decades of immunotherapy trials targeting MUC1, focusing primarily on vaccines but also adoptive antibody and T-cell therapies.

EXPERT OPINION

Most approaches targeting MUC1 have been immunotherapies administered to date to more than 1200 patients in clinical trials. Even though these trials focused on advanced cancer, encouraging results were reported particularly for less immunosuppressed patients. Furthermore, spontaneous anti-MUC1 immune responses are associated with better prognosis or with a reduced lifetime risk of developing MUC1+ cancers. MUC1 is abnormally expressed in over 80% of all cancers. Successfully targeting this molecule could benefit over a million patients diagnosed yearly with MUC1+ tumors just in the USA.

Preventive immunization of aged and juvenile non-human primates to β-amyloid

Background

Immunization against beta-amyloid (Aβ) is a promising approach for the treatment of Alzheimer’s disease, but the optimal timing for the vaccination remains to be determined. Preventive immunization approaches may be more efficacious and associated with fewer side-effects; however, there is only limited information available from primate models about the effects of preclinical vaccination on brain amyloid composition and the neuroinflammatory milieu.

Methods

Ten non-human primates (NHP) of advanced age (18–26 years) and eight 2-year-old juvenile NHPs were immunized at 0, 2, 6, 10 and 14 weeks with aggregated Aβ₄₂ admixed with monophosphoryl lipid A as adjuvant, and monitored for up to 6 months. Anti-Aβ antibody levels and immune activation markers were assessed in plasma and cerebrospinal fluid samples before and at several time-points after immunization. Microglial activity was determined by [¹¹C]PK11195 PET scans acquired before and after immunization, and by post-mortem immunohistochemical and real-time PCR evaluation. Aβ oligomer composition was assessed by immunoblot analysis in the frontal cortex of aged immunized and non-immunized control animals.

Results

All juvenile animals developed a strong and sustained serum anti-Aβ IgG antibody response, whereas only 80 % of aged animals developed detectable antibodies. The immune response in aged monkeys was more delayed and significantly weaker, and was also more variable between animals. Pre- and post-immunization [¹¹C]PK11195 PET scans showed no evidence of vaccine-related microglial activation. Post-mortem brain tissue analysis indicated a low overall amyloid burden, but revealed a significant shift in oligomer size with an increase in the dimer:pentamer ratio in aged immunized animals compared with non-immunized controls (P < 0.01). No differences were seen in microglial density or expression of classical and alternative microglial activation markers between immunized and control animals.

Conclusions

Our results indicate that preventive Aβ immunization is a safe therapeutic approach lacking adverse CNS immune system activation or other serious side-effects in both aged and juvenile NHP cohorts. A significant shift in the composition of soluble oligomers towards smaller species might facilitate removal of toxic Aβ species from the brain.

IL-33 promotes type 1 cell-mediated immunity and has a potent antitumor function (46.25)

Interleukin-33 is a member of the IL-1 family of cytokines and is released by stressed cells, necrotic cells or activated innate immune cells such as macrophages during trauma or infection. Thus, IL-33 is thought to serve as an endogenous “danger signal” to trigger inflammation and promote cell-mediated immune responses. Prior studies have supported the role of IL-33 in promoting type 2 immune responses but little was known for its role in type 1 immune responses such as the anti-tumor immune response. We have found that that ST2, a receptor for IL-33, is highly expressed in CD8 T cells cultured in Th1 conditions. We have further revealed that, T-bet, a critical transcriptional factor for Th1 differentiation and effector functions, is required for ST2 expression by CD8 T cells, suggesting that ST2 is an integral part of the Th1 gene network in CD8 T cells. Furthermore, we have demonstrated that IL-33 synergized with TCR or IL-12 in increasing both human and mouse CD8 T cell functions such as IFN-γ production. Thus IL-33 can greatly enhance type 1 cell-mediated immune responses in both human and mice. The in vivo relevance of this pathway is examined in a preclinical model of tumor immunity. Our results support a potent function of IL-33 in inhibiting tumor growth and provide a novel therapeutic approach for tumor immunity.