MUC1-specific immune therapy generates a strong anti-tumor response in a MUC1-tolerant colon cancer model

Markers of Epithelial-Mesenchymal Transition and Mucinous Histology Are Significant Predictors of Disease Severity and Tumor Characteristics in Early-Onset Colorectal Cancer

Approximately 20% of patients with colorectal cancer (CRC) are diagnosed with a mucinous subtype of this tumor, have a worse prognosis, and often show resistance to available therapies. Molecules from the mucin family are involved in the regulation of epithelial-mesenchymal transition (EMT), which significantly determines the cancer aggressiveness. This study aimed to examine the diagnostic and prognostic significance of mucinous histology and EMT markers in patients with early-onset CRC and their association with disease severity and tumor characteristics. This study included tumor tissue samples from 106 patients diagnosed with CRC before the age of 45, 53 with mucinous and 53 with non-mucinous tumors. The EMT status was determined by immunohistochemical analysis of E-cadherin and Vimentin in tissue sections. Mucinous tumors had significantly higher Mucin-1 (p < 0.001) and cytoplasmic E-cadherin (p = 0.043) scores; they were significantly less differentiated (p = 0.007), more advanced (p = 0.027), and predominately affected right the colon (p = 0.039) compared to non-mucinous tumors. Epithelial tumors were significantly better differentiated (p = 0.034) and with less prominent tumor budding (p < 0.001) than mesenchymal tumors. Mucin-1 and Vimentin were independent predictors of tumor differentiation (p = 0.006) and budding (p = 0.001), respectively. Mucinous histology and EMT markers are significant predictors of disease severity and tumor characteristics in early-onset colorectal cancer.

The tumor immune microenvironment and T-cell-related immunotherapies in colorectal cancer

The tumor microenvironment includes a complex network of immune T-cell subsets that play important roles in colorectal cancer (CRC) progression and are key elements of CRC immunotherapy. T cells develop and migrate within tumors, recognizing tumor-specific antigens to regulate immune surveillance. Current immunotherapies are divided into the following main categories based on the regulatory role of T-cell subsets in the tumor immune microenvironment (TIME): cytokines, monoclonal antibodies, peptide vaccines, CAR-T cells and more. This review describes the composition of the tumor immune microenvironment in colorectal cancer and the involvement of T cells in the pathogenesis and progression of CRC as well as current T-cell-related immunotherapies. Further studies on CRC-specific tumor antigens, the gene regulation of T cells, and the regulation of immune activity are needed.

Vaccination and Microbiota Manipulation Approaches for Colon Cancer Prevention in Rodent Models

Colorectal cancer represents the third most common cancer type worldwide and is a leading cause of cancer-related mortality in the United States and Western countries. Rodent models have been invaluable to study the etiology of colorectal cancer and to test novel chemoprevention avenues. In the past, the laboratory mouse has become one of the best preclinical models for these studies due to the availability of genetic information for commonly used mouse strains with well-established and precise gene targeting and transgenic techniques. Well-established chemical mutagenesis technologies are also being used to develop mouse and rat models of colorectal cancer for prevention and treatment studies. In addition, xenotransplantation of cancer cell lines and patient-derived xenografts has been useful for preclinical prevention studies and drug development. This review focuses on the recent use of rodent models to evaluate the utility of novel strategies in the prevention of colon cancers including immune prevention approaches and the manipulation of the intestinal microbiota.

Prevention of Inflammation-Driven Colon Carcinogenesis in Human MUC1 Transgenic Mice by Vaccination with MUC1 DNA and Dendritic Cells

The preventive efficacy of MUC1-specific DNA immunization on inflammation-driven colon carcinogenesis in human MUC1 transgenic (MUC1.Tg) mice was investigated. Mice were vaccinated with MUC1 DNA mixed with autologous bone-marrow-derived dendritic cells (BMDCs), and then colonic tumors were induced by azoxymethane (AOM) injection and oral administration of dextran sulfate sodium (DSS). Two types of tumors, squamous metaplasia and tubular adenoma, were observed. Both expressed high levels of MUC1 as indicated by the binding of anti-MUC1 antibodies with different specificities, whereas MUC1 expression was not detected in normal colonic mucosa. When mice were immunized with MUC1 DNA + BMDCs, tumor incidence, tumor number, and tumor size were significantly reduced. In contrast, vaccination with MUC1 DNA alone or BMDCs alone was ineffective in reducing tumor burden. Inflammation caused by DSS was not suppressed by the MUC1 DNA + BMDCs vaccination. Furthermore, MUC1 protein expression levels, as judged by anti-MUC1 antibody binding in tumors grown after vaccination, did not significantly differ from the control. In conclusion, an inflammation-driven carcinogenesis model was established in MUC1.Tg mice, closely resembling human colon carcinogenesis. In this model, vaccination with MUC1 DNA + BMDCs was effective in overriding MUC1 tolerance and reducing the tumor burden by a mechanism not affecting the level of colonic inflammation.

The Mucin Family of Proteins: Candidates as Potential Biomarkers for Colon Cancer

Mucins (MUC1-MUC24) are a family of glycoproteins involved in cell signaling and barrier protection. They have been implicated in the progression of numerous malignancies including gastric, pancreatic, ovarian, breast, and lung cancer. Mucins have also been extensively studied with respect to colorectal cancer. They have been found to have diverse expression profiles amongst the normal colon, benign hyperplastic polyps, pre-malignant polyps, and colon cancers. Those expressed in the normal colon include MUC2, MUC3, MUC4, MUC11, MUC12, MUC13, MUC15 (at low levels), and MUC21. Whereas MUC5, MUC6, MUC16, and MUC20 are absent from the normal colon and are expressed in colorectal cancers. MUC1, MUC2, MUC4, MUC5AC, and MUC6 are currently the most widely covered in the literature regarding their role in the progression from normal colonic tissue to cancer.

A Concise Review on the Role of Natural and Synthetically Derived Peptides in Colorectal Cancer

Colorectal cancer being the second leading cause of cancer-associated deaths has become a significant health concern around the globe. Though there are various cancer treatment approaches, many of them show adverse effects and some compromise the health of cancer patients. Hence, significant efforts are being made for the evolution of a novel biological therapeutic approach with better efficacy and minimal side effects. Current research suggests that the application of peptides in colorectal cancer therapeutics holds the possibility of the emergence of an anticancer reagent. The primary beneficial factors of peptides are their comparatively rapid and easy process of synthesis and the enormous potential for chemical alterations that can be evaluated for designing novel peptides and enhancing the delivery capacity of peptides. Peptides might be utilized as agents with cytotoxic activities or as a carrier of a specific drug or as cytotoxic agents that can efficiently target the tumor cells. Further, peptides can also be used as a tool for diagnostic purposes. The recent analysis aims at developing peptides that have the potential to efficiently target the tumor moieties without harming the nearby normal cells. Additionally, decreasing the adverse effects, and unfolding the other therapeutic properties of potential peptides, are also the subject matter of in-depth analysis. This review provides a concise summary of the function of both natural and synthetically derived peptides in colorectal cancer therapeutics that are recently being evaluated and their potent applications in the clinical field.

Advances in Nanotechnology for Cancer Immunoprevention and Immunotherapy: A Review

One of the most effective cancer therapies, cancer immunotherapy has produced outstanding outcomes in the field of cancer treatment. However, the cost is excessive, which limits its applicability. A smart way to address this issue would be to apply the knowledge gained through immunotherapy to develop strategies for the immunoprevention of cancer. The use of cancer vaccines is one of the most popular methods of immunoprevention. This paper reviews the technologies and processes that support the advantages of cancer immunoprevention over traditional cancer immunotherapies. Nanoparticle drug delivery systems and nanoparticle-based nano-vaccines have been employed in the past for cancer immunotherapy. This paper outlines numerous immunoprevention strategies and how nanotechnology can be applied in immunoprevention. To comprehend the non-clinical and clinical evaluation of these cancer vaccines through clinical studies is essential for acceptance of the vaccines.

Mucinous adenocarcinoma: A unique clinicopathological subtype in colorectal cancer

Mucinous adenocarcinoma (MAC) is a unique clinicopathological subtype of colorectal cancer, which is characterized by extracellular mucinous components that comprise at least 50% of the tumor tissue. The clinical characteristics, molecular features, response to chemo-/radiotherapy, and prognosis of MAC are different from that of non-MAC (NMAC). MAC is more common in the proximal colon, with larger volume, higher T-stage, a higher proportion of positive lymph nodes, poorer tumor differentiation, and a higher proportion of peritoneal implants compared to NMAC. Although biopsy is the main diagnostic method for MAC, magnetic resonance imaging is superior in accuracy, especially for rectal carcinoma. The aberrant expression of mucins, including MUC1, MUC2 and MUC5AC, is a notable feature of MAC, which may be related to tumor invasion, metastasis, inhibition of apoptosis, and chemo-/radiotherapy resistance. The genetic origin of MAC is mainly related to BRAF mutation, microsatellite instability, and the CpG island methylator phenotype pathway. In addition, the poor prognosis of rectal MAC has been confirmed by various studies, and that of colonic MAC is still controversial. In this review, we summarize the epidemiology, clinicopathological characteristics, molecular features, methods of diagnosis, and treatments of MAC in order to provide references for further fundamental and clinical research.

MUC1-Targeted Radiopharmaceuticals in Cancer Imaging and Therapy

Mucin 1 (MUC1) is a large, transmembrane mucin glycoprotein overexpressed in most adenocarcinomas and plays an important role in tumor progression. Regarding its cellular distribution, biochemical features, and function, tumor-related MUC1 varies from the MUC1 expressed in normal cells. Therefore, targeting MUC1 for cancer immunotherapy and imaging can exploit the difference between cancerous and normal cells. Radiopharmaceuticals have a potential use as carriers for the delivery of radionuclides to tumors for a diagnostic imaging and radiotherapy. Several radiolabeled targeting molecules like peptides, antibodies, and aptamers have been efficiently demonstrated in detecting and treating cancer by targeting MUC1. This review provides a brief overview of the current status of developments and applications of MUC1-targeted radiopharmaceuticals in cancer imaging and therapy.

CpG Oligonucleotides as Vaccine Adjuvants

CpG Oligonucleotides (ODN) are immunomodulatory synthetic oligonucleotides specifically designed to stimulate Toll-like receptor 9. TLR9 is expressed on human plasmacytoid dendritic cells and B cells and triggers an innate immune response characterized by the production of Th1 and pro-inflammatory cytokines. This chapter reviews recent progress in understanding the mechanism of action of CpG ODN and provides an overview of human clinical trial results using CpG ODN to improve vaccines for the prevention/treatment of cancer, allergy, and infectious disease.

Cancer Immunoprevention: Current Status and Future Directions

Cancer is one of the most serious diseases affecting health and the second leading cause of death worldwide. Despite the development of various therapeutic modalities to deal with cancer, limited improvement in overall survival of patients has been yielded. Since there is no certain cure for cancer, detection of premalignant lesions, and prevention of their progression are vital to the decline of high morbidity and mortality of cancer. Among approaches to cancer prevention, immunoprevention has gained further attention in recent years. Deep understanding of the tumor/immune system interplay and successful prevention of virally-induced malignancies by vaccines have paved the way toward broadening cancer immunoprevention application. The identification of tumor antigens in premalignant lesions was the turning point in cancer immunoprevention that led to designing preventive vaccines for various malignancies including multiple myeloma, colorectal, and breast cancer. In addition to vaccines, immune checkpoint inhibitors are also being tested for the prevention of oral squamous cell carcinoma (SCC), and imiquimod which is an established drug for the prevention of skin SCC, is a non-specific immunomodulator. Herein, to provide a bench-to-bedside understanding of cancer immunoprevention, we will review the role of the immune system in suppression and promotion of tumors, immunoprevention of virally-induced cancers, identification of tumor antigens in premalignant lesions, and clinical advances of cancer immunoprevention.

T-cell-based immunotherapy in colorectal cancer

Colorectal cancer (CRC) is the leading cause of cancer death worldwide. CRC therapeutic strategies include surgical resection, chemotherapy, radiotherapy, and other approaches. However, patients with metastatic CRC have worse prognoses. In recent years, T-cell-based immunotherapy has elicited promising responses in B-cell malignancies, melanoma, and lung cancer, but most CRC patients are resistant to immunotherapy, chemotherapy, and targeted therapy. Immune checkpoint inhibitors have shown encouraging results in non-small cell lung cancer, melanoma, and other cancers, but immune checkpoint blockade is only effective for CRC subset with microsatellite instability. Other immunotherapies, such as cytokines, cancer vaccines, small molecules, oncolytic viruses, and chimeric antigen-receptor therapy, are currently in use against CRC. This review analyzes recent developments in immunotherapy for CRC treatment as well as the challenges in overcoming resistance.

uMUC1-Targeting Magnetic Resonance Imaging of Therapeutic Response in an Orthotropic Mouse Model of Colon Cancer

PURPOSE

Noninvasive assessment of chemotherapeutic response in colon cancer would tremendously aid in therapeutic intervention of cancer patients and improve outcomes. The aim of the study was to evaluate the feasibility of a noninvasive assessment of chemotherapeutic response by magnetic resonance imaging utilizing underglycosylated mucin 1 (uMUC1) tumor antigen as a biomarker of therapeutic response in a colon cancer mouse model.

PROCEDURES

The study was performed by applying molecular imaging approach based on targeting uMUC1 with specific dual-modality imaging probe (MN-EPPT). The probe consisted of dextran-coated iron oxide nanoparticles conjugated to the near infrared fluorescent dye Cy5.5 and to a uMUC1-specific peptide (EPPT) and was used for magnetic resonance imaging (MRI) and fluorescence optical imaging. An orthotopic murine model of colon cancer expressing human uMUC1 peptide (MC38 MUC1) was created along with the control model devoid of the antigen (MC38 neo). Animals received chemotherapy with 5-fluorouracil (5-FU) followed by MN-EPPT-enhanced MR and optical imaging.

RESULTS

In vivo imaging of animals with uMUC1 expressing tumors after 5-FU therapy showed that the average deltaT2 was reduced by 7.27 ms (p = 0.045) compared with animals in control groups indicating lower accumulation of MN-EPPT caused by uMUC1 downregulation. In vivo optical imaging, biodistribution, and fluorescence microscopy confirmed the MRI findings. Interestingly, we found that the group of animals that did not respond to chemotherapy ("progressive disease" per RECIST) showed higher accumulation of MN-EPPT compared to the group of responders ("stable disease") consistent with proliferating tumor cells and increased antigen availability.

CONCLUSIONS

We believe that in application to over 50 % of human cancers expressing uMUC1, our results could provide insight into overall assessment of therapeutic response based on its expression as defined by non-invasive MN-EPPT-enhanced MRI.

Mucin glycoproteins block apoptosis; promote invasion, proliferation, and migration; and cause chemoresistance through diverse pathways in epithelial cancers

Overexpression of mucin glycoproteins has been demonstrated in many epithelial-derived cancers. The significance of this overexpression remains uncertain. The aim of this paper was to define the association of mucin glycoproteins with apoptosis, cell growth, invasion, migration, adhesion, and clonogenicity in vitro as well as tumor growth, tumorigenicity, and metastasis in vivo in epithelial-derived cancers by performing a systematic review of all published data. A systematic review of PubMed, Embase, and the Cochrane Central Register of Controlled Trials was performed to identify all papers that evaluated the association between mucin glycoproteins with apoptosis, cell growth, invasion, migration, adhesion, and clonogenicity in vitro as well as tumor growth, tumorigenicity, and metastasis in vivo in epithelial-derived cancers. PRISMA guidelines were adhered to. Results of individual studies were extracted and pooled together based on the organ in which the cancer was derived from. The initial search revealed 2031 papers, of which 90 were deemed eligible for inclusion in the study. The studies included details on MUC1, MUC2, MUC4, MUC5AC, MUC5B, MUC13, and MUC16. The majority of studies evaluated MUC1. MUC1 overexpression was consistently associated with resistance to apoptosis and resistance to chemotherapy. There was also evidence that overexpression of MUC2, MUC4, MUC5AC, MUC5B, MUC13, and MUC16 conferred resistance to apoptosis in epithelial-derived cancers. The overexpression of mucin glycoproteins is associated with resistance to apoptosis in numerous epithelial cancers. They cause resistance through diverse signaling pathways. Targeting the expression of mucin glycoproteins represents a potential therapeutic target in the treatment of epithelial-derived cancers.

Indomethacin enhances anti-tumor efficacy of a MUC1 peptide vaccine against breast cancer in MUC1 transgenic mice

In recent years, vaccines against tumor antigens have shown potential for combating invasive cancers, including primary tumors and metastatic lesions. This is particularly pertinent for breast cancer, which is the second-leading cause of cancer-related death in women. MUC1 is a glycoprotein that is normally expressed on glandular epithelium, but is overexpressed and under-glycosylated in most human cancers, including the majority of breast cancers. This under-glycosylation exposes the MUC1 protein core on the tumor-associated form of the protein. We have previously shown that a vaccine consisting of MUC1 core peptides stimulates a tumor-specific immune response. However, this immune response is dampened by the immunosuppressive microenvironment within breast tumors. Thus, in the present study, we investigated the effectiveness of MUC1 vaccination in combination with four different drugs that inhibit different components of the COX pathway: indomethacin (COX-1 and COX-2 inhibitor), celecoxib (COX-2 inhibitor), 1-methyl tryptophan (indoleamine 2,3 dioxygenase inhibitor), and AH6809 (prostaglandin E₂ receptor antagonist). These treatment regimens were explored for the treatment of orthotopic MUC1-expressing breast tumors in mice transgenic for human MUC1. We found that the combination of vaccine and indomethacin resulted in a significant reduction in tumor burden. Indomethacin did not increase tumor-specific immune responses over vaccine alone, but rather appeared to reduce the proliferation and increase apoptosis of tumor cells, thus rendering them susceptible to immune cell killing.

Mucin Pools Following Neoadjuvant Chemoradiotherapy for Rectal Cancer: A Marker of Response or Epiphenomenon?

Neoadjuvant chemoradiotherapy (CRT) is the standard of care for locally advanced rectal cancer. Morphologic changes such as fibrosis, inflammatory infiltrates, and the formation of extracellular mucin pools can be identified in the resection specimen after neoadjuvant CRT. The association of mucin pool formation with clinicopathologic variables and outcomes is unclear. The aim of this study was to meta-analyze all available evidence with regard to mucin pool formation and clinicopathologic outcomes following neoadjuvant CRT for rectal cancer. A comprehensive search for published studies analyzing outcomes between patients who formed mucin pools and patients who did not following neoadjuvant CRT for rectal cancer was performed. A random-effects model was used to combine the data. This study adhered to the recommendations of the MOOSE (Meta-analyses of Observational Studies in Epidemiology) guidelines. Data from 11 studies describing 1947 patients were included. Mucin pool formation was not associated with sex, T stage, N stage, tumor regression, pathologic complete response rate, lymphovascular invasion, perineural invasion, differentiation, margin status, local or distant recurrence, and disease-free or overall survival. Mucin pool formation is not associated with tumor response or downstaging; furthermore, on the basis of these data, it is not associated with local or systemic recurrence rate or survival.

Circulating Myeloid Derived Suppressor Cells (MDSC) That Accumulate in Premalignancy Share Phenotypic and Functional Characteristics With MDSC in Cancer

Myeloid derived suppressor cells (MDSC) are a heterogeneous population of immature myeloid cells that accumulate in circulation of cancer patients and at tumor sites where they suppress anti-tumor immunity. We previously reported that in a colon cancer prevention trial of a MUC1 vaccine tested in individuals at increased risk for colon cancer, those who did not mount immune response to the vaccine had higher pre-vaccination levels of circulating MDSC compared to those who did. We also reported that individuals with pancreatic premalignancy, Intraductal Papillary Mucinous Neoplasm (IPMN), had increased circulating levels of MDSC that inversely correlated with spontaneous antibody responses against the pancreatic tumor associated antigen MUC1, abnormally expressed on IPMN. Accumulation of MDSC in cancer and their immunosuppressive role had been well established but their presence in premalignancy was unexpected. In this study we compared MDSC in premalignancy with those in cancer with the hypothesis that there might be differences in the composition of various MDSC subpopulations and their immunosuppressive functions due to different lengths of exposure to disease and/or different tissue microenvironments. In cohorts of patients with premalignant polyps, colon cancer, premalignant IPMN, and pancreatic cancer, we confirmed higher levels of MDSC in premalignancy compared to healthy controls, higher levels of MDSC in cancer compared to premalignancy, but no difference in their subpopulation composition or immunosuppressive capacity. We show that levels of MDSC in premalignancy correlate negatively in vivo with spontaneous MUC1-specific antibody responses and in vitro with polyclonal T cell proliferation and IFN-γ secretion.

Oligodeoxynucleotides ODN 2006 and M362 Exert Potent Adjuvant Effect through TLR-9/-6 Synergy to Exaggerate Mammaglobin-A Peptide Specific Cytotoxic CD8+T Lymphocyte Responses against Breast Cancer Cells

Mammaglobin-A (MamA) is overexpressed in 40–80% of all human breast cancers. Recent phase I clinical trials of the MamA DNA vaccine showed encouraging safety outcomes. However, this vaccine elicited only a modest increase in MamA specific CD8+T lymphocyte (CTL) activation. As vaccine adjuvants play a critical role in enhancing the immunotherapeutic efficiency of vaccines, we tested the potential role of three synthetic CpG oligodeoxynucleotides (ODN2216—class A ODN, ODN2006—class B ODN, and ODN M362—class C ODN) to further enhance MamA specific CTL responses. Towards this, naïve CD8+T cells were obtained from healthy HLA-A2+ human donors. The HLA-A2 specific immunodominant epitope of MamA, MamA2.1 (LIYDSSLCDL), was utilized to activate naïve CD8+T cells. The THP-1 (HLA-A2+) cells were used as antigen presenting cells to stimulate naïve CD8+T cells along with (or without) co-treatment of various ODNs mentioned above. Activation of naïve CD8+T cells with the MamA2.1 peptide along with ODNs demonstrated enhanced MamA specific CTL mediated cytotoxicity on AU565 (HLA-A⁺/MamA⁺) breast cancer cells following co-treatment with ODN2006 and M362 compared to ODN2216 or MamA2.1 peptide alone. However, no significant cytotoxicity was noted upon treatment of MamA2.1 activated CTLs on MCF7 (HLA-A⁺/MamA⁻) cells, suggesting that the activation of CTLs is specific to the MamA antigen. Functional characterization studies demonstrated specific IL-12 mediated cross-talk between TLR-6 and -9 in THP-1 cells following stimulation with ODN2006 and M362, which was critical for the final cytotoxic activation of CD8+T lymphocytes. Based on these data, we conclude that ODN2006 and ODN M362 exerted a strong adjuvant effect through induction of the initial innate immune response through TLR9 upregulation followed by enhanced MamA specific CTL dependent adaptive immune responses. Our current data provide evidence for the application of Class-B/-C-CpG-ODNs as potential vaccine adjuvants towards enhancing the success of MamA based breast cancer vaccination.

Combining the Specific Anti-MUC1 Antibody TAB004 and Lip-MSA-IL-2 Limits Pancreatic Cancer Progression in Immune Competent Murine Models of Pancreatic Ductal Adenocarcinoma

Immunotherapy regimens have shown success in subsets of cancer patients; however, their efficacy against pancreatic ductal adenocarcinoma (PDA) remain unclear. Previously, we demonstrated the potential of TAB004, a monoclonal antibody targeting the unique tumor-associated form of MUC1 (tMUC1) in the early detection of PDA. In this study, we evaluated the therapeutic benefit of combining the TAB004 antibody with Liposomal-MSA-IL-2 in immune competent and human MUC1 transgenic (MUC1.Tg) mouse models of PDA and investigated the associated immune responses. Treatment with TAB004 + Lip-MSA-IL-2 resulted in significantly improved survival and slower tumor growth compared to controls in MUC1.Tg mice bearing an orthotopic PDA.MUC1 tumor. Similarly, in the spontaneous model of PDA that expresses human MUC1, the combination treatment stalled the progression of pancreatic intraepithelial pre-neoplastic (PanIN) lesion to adenocarcinoma. Treatment with the combination elicited a robust systemic and tumor-specific immune response with (a) increased percentages of systemic and tumor infiltrated CD45+CD11b+ cells, (b) increased levels of myeloperoxidase (MPO), (c) increased antibody-dependent cellular cytotoxicity/phagocytosis (ADCC/ADCP), (d) decreased percentage of immune regulatory cells (CD8+CD69+ cells), and (e) reduced circulating levels of immunosuppressive tMUC1. We report that treatment with a novel antibody against tMUC1 in combination with a unique formulation of IL-2 can improve survival and lead to stable disease in appropriate models of PDA by reducing tumor-induced immune regulation and promoting recruitment of CD45+CD11b+ cells, thereby enhancing ADCC/ADCP.

Colorectal cancer vaccines: Tumor-associated antigens vs neoantigens

Therapeutic options for the treatment of colorectal cancer (CRC) are diverse but still not always satisfying. Recent success of immune checkpoint inhibition treatment for the subgroup of CRC patients suffering from hyper-mutated tumors suggests a permanent role of immune therapy in the clinical management of CRC. Substantial improvement in treatment outcome could be achieved by development of efficient patient-individual CRC vaccination strategies. This mini-review summarizes the current knowledge on the two general classes of targets: tumor-associated antigens (TAAs) and tumor-specific antigens. TAAs like carcinoembryonic antigen and melanoma associated antigen are present in and shared by a subgroup of patients and a variety of clinical studies examined the efficacy of different TAA-derived peptide vaccines. Combinations of several TAAs as the next step and the development of personalized TAA-based peptide vaccines are discussed. Improvements of peptide-based vaccines achievable by adjuvants and immune-stimulatory chemotherapeutics are highlighted. Finally, we sum up clinical studies using tumor-specific antigens - in CRC almost exclusively neoantigens - which revealed promising results; particularly no severe adverse events were reported so far. Critical progress for clinical outcomes can be expected by individualizing neoantigen-based peptide vaccines and combining them with immune-stimulatory chemotherapeutics and immune checkpoint inhibitors. In light of these data and latest developments, truly personalized neoantigen-based peptide vaccines can be expected to fulfill modern precision medicine’s requirements and will manifest as treatment pillar for routine clinical management of CRC.

Vaccines for colorectal cancer: an update

Colorectal cancer (CRC) is known as the third most common and fourth leading cancer associated death worldwide. The occurrence of metastasis has remained as a critical challenge in CRC, so that distant metastasis (mostly to the liver) has been manifested in about 20%-25% of patients. Several screening approaches have introduced for detecting CRC in different stages particularly in early stages. The standard treatments for CRC are surgery, chemotherapy and radiotherapy, in alone or combination. Immunotherapy is a set of novel approaches with the aim of remodeling the immune system battle with metastatic cancer cells, such as immunomodulatory monoclonal antibodies (immune checkpoint inhibitors), adoptive cell transfer (ACT) and cancer vaccine. Cancer vaccines are designed to trigger the intense response of immune system to tumor-specific antigens. In two last decades, introduction of new cancer vaccines and designing several clinical trials with vaccine therapy, have been taken into consideration in colon cancer patients. This review will describe the treatment approaches with the special attention to vaccines applied to treat colorectal cancer.

Autologous iPSC-Based Vaccines Elicit Anti-tumor Responses In Vivo

Cancer cells and embryonic tissues share a number of cellular and molecular properties, suggesting that induced pluripotent stem cells (iPSCs) may be harnessed to elicit anti-tumor responses in cancer vaccines. RNA sequencing revealed that human and murine iPSCs express tumor-associated antigens, and we show here a proof of principle for using irradiated iPSCs in autologous anti-tumor vaccines. In a prophylactic setting, iPSC vaccines prevent tumor growth in syngeneic murine breast cancer, mesothelioma, and melanoma models. As an adjuvant, the iPSC vaccine inhibited melanoma recurrence at the resection site and reduced metastatic tumor load, which was associated with fewer Th17 cells and increased CD11b+GR1hi myeloid cells. Adoptive transfer of T cells isolated from vaccine-treated tumor-bearing mice inhibited tumor growth in unvaccinated recipients, indicating that the iPSC vaccine promotes an antigen-specific anti-tumor T cell response. Our data suggest an easy, generalizable strategy for multiple types of cancer that could prove highly valuable in clinical immunotherapy.

Analysis of sialyl-Lewis x on MUC5AC and MUC1 mucins in pancreatic cancer tissues

Pancreatic adenocarcinoma (PDAC) lacks efficient biomarkers. Mucins are glycoproteins that can carry aberrant glycosylation in cancer. Our objective was to identify cancer-related glycan epitopes on MUC1 and MUC5AC mucins in PDAC as potential biomarkers. We have analysed the tumour-associated carbohydrate antigens sialyl-Lewis x (SLe^x) and sialyl-Tn (STn) on MUC1 and MUC5AC in PDAC tissues. The selected cohort for this study consisted of twenty-one PDAC tissues positive for SLe^x antigen and three normal pancreas specimens as controls. STn expression was shown in 76% of the PDAC tissues. MUC1 and MUC5AC were detected in 90% of PDAC tissues. We performed in situ proximity ligation assay combining antibodies against mucins and glycan epitopes to identify specific mucin glycoforms. MUC1-SLe^x and MUC5AC-SLe^x were found in 68% and 84% respectively, of the mucin expressing PDAC tissues, while STn hardly colocalized with any of the evaluated mucins. Further analysis by Western blot of MUC5AC and SLe^x in eight PDAC tissue lysates showed that six out of eight cases were positive for both markers. Moreover, immunoprecipitation of MUC5AC from positive PDAC tissues and subsequent SLe^x immunodetection confirmed the presence of SLe^x on MUC5AC. Altogether, MUC5AC-SLe^x glycoform is present in PDAC and can be regarded as potential biomarker.

Combination Immunotherapy of MUC1 mRNA Nano-vaccine and CTLA-4 Blockade Effectively Inhibits Growth of Triple Negative Breast Cancer

Triple negative breast cancer (TNBC), which constitutes 10%-20% of all breast cancers, is associated with aggressive progression, a high rate of metastasis, and poor prognosis. The treatment of patients with TNBC remains a great clinical challenge. Preclinical reports support the combination immunotherapy of cancer vaccines and immune checkpoint blockades in non-immunogenic tumors. In this study, we constructed nanoparticles (NPs) to deliver an mRNA vaccine encoding tumor antigen MUC1 to dendritic cells (DCs) in lymph nodes to activate and expand tumor-specific T cells. An anti-CTLA-4 (cytotoxic T-lymphocyte-associated protein 4) monoclonal antibody was combined with the mRNA vaccine to enhance the anti-tumor benefits. In vivo studies demonstrated that the NP-based mRNA vaccine, targeted to mannose receptors on DCs, could successfully express tumor antigen in the DCs of the lymph node; that the NP vaccine could induce a strong, antigen-specific, in vivo cytotoxic T lymphocyte response against TNBC 4T1 cells; and that combination immunotherapy of the vaccine and anti-CTLA-4 monoclonal antibody could significantly enhance anti-tumor immune response compared to the vaccine or monoclonal antibody alone. These data support both the NP as a carrier for delivery of mRNA vaccine and a potential combination immunotherapy of the NP-based mRNA vaccine and the CTLA-4 inhibitor for TNBC.

Immunogenicity of a Fully Synthetic MUC1 Glycopeptide Antitumor Vaccine Enhanced by Poly(I:C) as a TLR3-Activating Adjuvant

Fully synthetic MUC1 glycopeptide antitumor vaccines have a precisely specified structure and induce a targeted immune response without suppression of the immune response when using an immunogenic carrier protein. However, tumor-associated aberrantly glycosylated MUC1 glycopeptides are endogenous structures, "self-antigens", that exhibit only low immunogenicity. To overcome this obstacle, a fully synthetic MUC1 glycopeptide antitumor vaccine was combined with poly(inosinic acid:cytidylic acid), poly(I:C), as a structurally defined Toll-like receptor 3 (TLR3)-activating adjuvant. This vaccine preparation elicited extraordinary titers of IgG antibodies which strongly bound human breast cancer cells expressing tumor-associated MUC1. Beside the humoral response, the poly(I:C) glycopeptide vaccine induced a pro-inflammatory environment, very important to overcome the immune-suppressive mechanisms, and elicited a strong cellular immune response crucial for tumor elimination.

Targeting MUC1-C inhibits the AKT-S6K1-elF4A pathway regulating TIGAR translation in colorectal cancer

Background

Colorectal cancer is third most common malignancy and is the second most common cause of cancer-related death. The MUC1 heterodimeric protein is aberrantly overexpressed in colorectal cancer and has been linked to poor outcomes in this disease. Here, we investigate the effects of the MUC1-C subunit inhibitor (GO-203), which disrupts MUC1-C homo-oligomerization, on human colorectal cancer cells.

Methods

TIGAR mRNA level was determined using qRT-PCR. Western blotting was used to measure TIGAR protein level and AKT-mTOR-S6K1 pathways. Reactive oxygen species and apoptosis were measured by flow cytometry. Effect of MUC1-C peptide, GO-203 was studied on colorectal xenograft tumors. Immunohistochemistry was utilized for TIGAR staining.

Results

Treatment of MUC1-overexpressing SKCO-1 and Colo-205 colon cancer cells with GO-203 was associated with downregulation of the TP53-inducible glycolysis and apoptosis regulator (TIGAR) protein. TIGAR promotes the shunting of glycolytic intermediates into the pentose phosphate pathway and thus is of importance for maintaining redox balance. We show that GO-203-induced suppression of TIGAR is mediated by inhibition of AKT and the downstream mTOR pathway. The results also demonstrate that targeting MUC1-C blocks eIF4A cap-dependent translation of TIGAR. In concert with these results, GO-203-induced suppression of TIGAR was associated with decreases in GSH levels. GO-203 treatment also resulted in increases in reactive oxygen species (ROS) and loss of mitochondrial transmembrane potential. Consistent with these results, GO-203 inhibited the growth of colon cancer cells in vitro and as xenografts in nude mice. Inhibition of MUC1-C also downregulated TIGAR expression in xenograft tissues.

Conclusions

These findings indicate that MUC1-C is a potential target for the treatment of colorectal cancer. Colorectal cancer patients who overexpress MUC1-C may be candidates for treatment with the MUC1-C inhibitor alone or in combination therapy with other agents.

The emerging role of immunotherapy in colorectal cancer

Modulation of the interaction between the immune system and the tumor microenvironment has long been a target of cancer research, including colorectal cancer (CRC). Approaches explored to date include vaccines (autologous, peptide, dendritic cell, viral and bacterial), cytokine therapy, toll-like receptors (TLRs), autologous cell therapy and checkpoint inhibition. Until recently these approaches have been shown to have only modest efficacy in reducing tumor burden. However, significant breakthroughs have been made, with the use of checkpoint inhibitors targeting programmed cell death protein-1 (PD-1), programmed cell death ligand-1 (PD-L1), and cytotoxic T lymphocyte antigen-4 (CTLA-4). Immunotherapy now represents a possible avenue of curative treatment for those with chemo-otherwise refractory tumors. Success with this approach to immunotherapy has largely been confined to tumors with high mutational burdens such as melanoma, renal cell carcinoma (RCC) and non-small cell lung cancer. This observation led to the exploration and successful use of checkpoint inhibitors in those with mismatch repair colorectal cancer which have a relatively high mutational burden. Ongoing trials are focused on further exploring the use of checkpoint inhibitors in addition to investigating the various combinations of immunotherapeutic drugs.

Chimeric peptide containing both B and T cells epitope of tumor-associated antigen L6 enhances anti-tumor effects in HLA-A2 transgenic mice

Synthetic peptides are attractive for cancer immunotherapy because of their safety and flexibility. In this report, we identified a new B cell epitope of tumor-associated antigen L6 (TAL6) that could induce antibody-dependent cellular cytotoxicity (ADCC) in vivo. We incorporated the B cell epitope with a cytotoxic T lymphocyte (CTL) and a helper T (Th) epitope to form a chimeric long peptide. We formulated the chimeric peptide with different adjuvants to immunize HLA-A2 transgenic mice and evaluate their immunogenicity. The chimeric peptide formulated with an emulsion type nanoparticle (PELC) adjuvant and a toll-like receptor 9 agonist (CpG ODN) (PELC/CpG) induced the greatest ADCC and CTL responses. The induced anti-tumor immunity inhibited the growth of TAL6-positive cancer cells. Moreover, we observed that immunization with the chimeric peptide inhibited cancer cell migration in vitro and metastasis in vivo. These data suggest that a chimeric peptide containing both B and T cell epitopes of TAL6 formulated with PELC/CpG adjuvant is feasible for cancer immunotherapy.

MUC1 Vaccines, Comprised of Glycosylated or Non-Glycosylated Peptides or Tumor-Derived MUC1, Can Circumvent Immunoediting to Control Tumor Growth in MUC1 Transgenic Mice

It remains challenging to produce decisive vaccines against MUC1, a tumor-associated antigen widely expressed by pancreas, breast and other tumors. Employing clinically relevant mouse models, we ruled out such causes as irreversible T-cell tolerance, inadequate avidity, and failure of T-cells to recognize aberrantly glycosylated tumor MUC1. Instead, every tested MUC1 preparation, even non-glycosylated synthetic 9mer peptides, induced interferon gamma-producing CD4⁺ and CD8⁺ T-cells that recognized glycosylated variants including tumor-associated MUC1. Vaccination with synthetic peptides conferred protection as long as vaccination was repeated post tumor challenge. Failure to revaccinate post challenge was associated with down-regulated tumor MUC1 and MHC molecules. Surprisingly, direct admixture of MUC1-expressing tumor with MUC1-hyperimmune T-cells could not prevent tumor outgrowth or MUC1 immunoediting, whereas ex vivo activation of the hyperimmune T-cells prior to tumor admixture rendered them curative. Therefore, surrogate T-cell preactivation outside the tumor bed, either in culture or by repetitive vaccination, can overcome tumor escape.

A safety and feasibility study of an allogeneic colon cancer cell vaccine administered with a granulocyte-macrophage colony stimulating factor-producing bystander cell line in patients with metastatic colorectal cancer

BACKGROUND

Despite recent advances in earlier detection and improvements in chemotherapy, the 5-year survival rate of patients with metastatic colorectal carcinoma remains poor. Immunotherapy is a potentially effective therapeutic approach to the treatment of colorectal carcinoma. Preclinical studies have supported the antitumor activity of immunization with a granulocyte-macrophage colony-stimulating factor (GM-CSF) producing murine colon tumor cell vaccine.

METHODS

A novel colorectal cancer vaccine composed of irradiated, allogeneic human colon cancer cells and GM-CSF-producing bystander cells was developed and tested in combination with a single intravenous low dose of cyclophosphamide in a phase 1 study of patients with metastatic colorectal cancer.

RESULTS

A total of nine patients were enrolled onto and treated in this study. Six patients had a history of colorectal adenocarcinoma hepatic metastases and underwent curative metastasectomy, while three other patients had unresectable stage IV disease. This study demonstrates the safety and feasibility of this vaccine administered in patients with metastatic colorectal cancer. At last follow-up, the six patients who underwent curative metastasectomy survived longer than 36 months, and four of these six patients were without disease recurrence. Immunologic correlate results suggest that the GM-CSF-producing colon cancer vaccine enhances the production of anti-MUC1 antibodies.

CONCLUSIONS

This vaccine is feasible and safe. Future investigation of the efficacy and antitumor immunity of this vaccine is warranted.

MUC1 and maltose‑binding protein recombinant fusion protein combined with Bacillus Calmette‑Guerin induces MUC1‑specific and nonspecific anti‑tumor immunity in mice

Human mucin 1 (MUC1) is a target for immunotherapy. The major problem associated with MUC1‑based cancer vaccines is the weakness of the immunogenicity of MUC1. The present study aimed to develop an efficient cancer vaccine through generating a recombinant fusion protein consisting of MUC1 and maltose‑binding protein (MBP) by inserting seven tandem repeats encoding the human MUC1 gene into the pMAL‑c2 expression vector. Bacillus Calmette‑Guerin (BCG) was used as an adjuvant. MUC1 was found to predominantly induce T helper type 2 (Th2) cell responses. MUC1/BCG and MUC1‑MBP were found to generate T helper (Th) type 1 and 2 responses, while MUC1‑MBP/BCG induced a Th1 immune profile and stimulated MUC1‑specific cytotoxic T lymphocyte killing activity. MUC1‑MBP, as well as MBP and BCG alone were found to induce natural killer (NK) cell activity, with MUC1‑MBP/BCG observed to synergistically induce NK cell activity. Furthermore, MUC1‑MBP/BCG significantly inhibited MUC1+ B16 cell growth in mice. These findings show that MBP augments the immunogenicity of MUC1 and that BCG enhances the efficacy of the MUC1‑MBP vaccine. Thus, MUC1‑MBP/BCG may have potential as a cancer vaccine for clinical application.

Immune and anticancer responses elicited by fully synthetic aberrantly glycosylated MUC1 tripartite vaccines modified by a TLR2 or TLR9 agonist

The mucin MUC1 is overexpressed and aberrantly glycosylated by many epithelial cancer cells manifested by truncated O-linked saccharides. Although tumor-associated MUC1 has generated considerable attention because of its potential for the development of a therapeutic cancer vaccine, it has been difficult to design constructs that consistently induce cytotoxic T-lymphocytes (CTLs) and ADCC-mediating antibodies specific for the tumor form of MUC1. We have designed, chemically synthesized, and immunologically examined vaccine candidates each composed of a glycopeptide derived from MUC1, a promiscuous Thelper peptide, and a TLR2 (Pam3 CysSK4 ) or TLR9 (CpG-ODN 1826) agonist. It was found that the Pam3 CysSK4 -containing compound elicits more potent antigenic and cellular immune responses, resulting in a therapeutic effect in a mouse model of mammary cancer. It is thus shown, for the first time, that the nature of an inbuilt adjuvant of a tripartite vaccine can significantly impact the quality of immune responses elicited against a tumor-associated glycopeptide. The unique adjuvant properties of Pam3 CysSK4 , which can reduce the suppressive function of regulatory T cells and enhance the cytotoxicity of tumor-specific CTLs, are likely responsible for the superior properties of the vaccine candidate 1.

A novel emulsion-type adjuvant containing CpG oligodeoxynucleotides enhances CD8+ T-cell-mediated anti-tumor immunity

PELC is a novel emulsion-type adjuvant that contains the bioresorbable polymer poly (ethylene glycol)-block-poly (lactide-co-ε-caprolactone) (PEG-b-PLACL), Span®85 and squalene. To investigate whether PELC is able to enhance CTL responses of antigens for treating tumor, peptides or protein antigens derived from HPV16 E7 were formulated with PELC nanoparticles and CpG oligodeoxynucleotide. We identified that PELC formulation could delay the release of antigens in vitro and in vivo. We assessed the immunogenicity of an H-2D(b)-restricted CTL epitope RAHYNIVTF (RAH) formulated with PELC or PELC/CpG and investigated the ability of these formulations to promote tumor regression. Following a single-dose subcutaneous injection in mice, we found that the RAH peptide formulated with PELC/CpG (RAH/PELC/CpG) resulted in increased numbers of IFN-γ-secreting cells and RAH-specific CD8(+) T cells and an enhanced cytotoxic T cell response compared with RAH formulated with PELC or CpG alone. The tumor-bearing mice received a single-dose injection of RAH/PELC/CpG, which induced complete tumor regression. These results demonstrated that peptide antigen formulated with PELC/CpG nanoparticles is feasible for cancer immunotherapy.

Potential for novel MUC1 glycopeptide-specific antibody in passive cancer immunotherapy

MUC1 is an important target for antibodies in passive cancer immunotherapy. Antibodies against mucin glycans or mucin peptide backbone alone may give rise to cross reactivity with normal tissues. Therefore, attempts to identify antibodies against cancer-specific MUC1 glycopeptide epitopes havebeen made. We recently demonstrated that a monoclonal antibody against the immunodominant Tn-MUC1 (GalNAc-α-MUC1) antigen induced ADCC in breast cancer cell lines, suggesting the feasibility of targeting combined glycopeptide epitopes in future passive cancer immunotherapy.

Colorectal cancer immunotherapy

Antitumor immunotherapy for colorectal cancer has been studied at the bench and bedside for decades. Some clinical trials of cancer immunotherapy have demonstrated a potential benefit for patients with colorectal cancer, yet immunotherapy remains only an experimental option for this disease. Here, we review the major immunotherapeutic approaches currently under investigation for colorectal cancer, including cancer vaccines and adoptive cell therapy. Weakness and advantages of each strategy and progress in clinical trials will be described. Examination of previous and ongoing research in colorectal cancer therapy should define a path towards identification, approval, and mainstream adoption of colorectal cancer immunotherapeutics.

Peptide Vaccine Therapy in Colorectal Cancer

Colorectal cancer is the third most common cause of cancer-related deaths and the second most prevalent (after breast cancer) in the western world. High metastatic relapse rates and severe side effects associated with the adjuvant treatment have urged oncologists and clinicians to find a novel, less toxic therapeutic strategy. Considering the limited success of the past clinical trials involving peptide vaccine therapy to treat colorectal cancer, it is necessary to revise our knowledge of the immune system and its potential use in tackling cancer. This review presents the efforts of the scientific community in the development of peptide vaccine therapy for colorectal cancer. We review recent clinical trials and the strategies for immunologic monitoring of responses to peptide vaccine therapy. We also discuss the mechanisms underlying the therapy and potential molecular targets in colon cancer.

Immune recognition of tumor-associated mucin MUC1 is achieved by a fully synthetic aberrantly glycosylated MUC1 tripartite vaccine

The mucin MUC1 is typically aberrantly glycosylated by epithelial cancer cells manifested by truncated O-linked saccharides. The resultant glycopeptide epitopes can bind cell surface major histocompatibility complex (MHC) molecules and are susceptible to recognition by cytotoxic T lymphocytes (CTLs), whereas aberrantly glycosylated MUC1 protein on the tumor cell surface can be bound by antibodies to mediate antibody-dependent cell-mediated cytotoxicity (ADCC). Efforts to elicit CTLs and IgG antibodies against cancer-expressed MUC1 have not been successful when nonglycosylated MUC1 sequences were used for vaccination, probably due to conformational dissimilarities. Immunizations with densely glycosylated MUC1 peptides have also been ineffective due to impaired susceptibility to antigen processing. Given the challenges to immuno-target tumor-associated MUC1, we have identified the minimum requirements to consistently induce CTLs and ADCC-mediating antibodies specific for the tumor form of MUC1 resulting in a therapeutic response in a mouse model of mammary cancer. The vaccine is composed of the immunoadjuvant Pam(3)CysSK(4), a peptide T(helper) epitope and an aberrantly glycosylated MUC1 peptide. Covalent linkage of the three components was essential for maximum efficacy. The vaccine produced CTLs, which recognized both glycosylated and nonglycosylated peptides, whereas a similar nonglycosylated vaccine gave CTLs which recognized only nonglycosylated peptide. Antibodies elicited by the glycosylated tripartite vaccine were significantly more lytic compared with the unglycosylated control. As a result, immunization with the glycosylated tripartite vaccine was superior in tumor prevention. Besides its own aptness as a clinical target, these studies of MUC1 are likely predictive of a covalent linking strategy applicable to many additional tumor-associated antigens.

CpG or IFN-α are more potent adjuvants than GM-CSF to promote anti-tumor immunity following idiotype vaccine in multiple myeloma

Idiotype (Id) protein in combination with GM-CSF has been used as vaccines for immunotherapy of patients with myeloma and B-cell tumors and the results have been disappointing. To search for better immune adjuvants to improve the efficacy of Id-based immunotherapy in myeloma, we evaluated and compared the efficacy of vaccination of Id protein in combination with CpG or IFN-α, or GM-CSF as a control, in the 5TGM1 myeloma mouse model. Our results showed that Id vaccine combined with CpG or IFN-α, but not GM-CSF, not only efficiently protected mice from developing myeloma but also eradicated established myeloma. The therapeutic responses were associated with an induction of strong humoral immune responses including anti-Id antibodies, and cellular immune responses including Id- and myeloma-specific CD8+ cytotoxic T lymphocytes (CTLs), CD4+ type-1 T-helper (Th1) cells and memory T cells in mice receiving Id vaccine combined with CpG or IFN-α. Furthermore, Id vaccine combined with CpG or IFN-α induced Id- and tumor-specific memory immune responses that protected surviving mice from tumor rechallenge. Thus, our study clearly shows that CpG or IFN-α are better immune adjuvants than GM-CSF. This information will be important for improving the strategies of Id-based immunotherapy for patients with myeloma and other B-cell tumors.

Identification of HLA-A*0201- and A*2402-restricted epitopes of mucin 5AC expressed in advanced pancreatic cancer

OBJECTIVES

Mucin 5AC (MUC5AC) was previously identified as being expressed in most pancreatic ductal adenocarcinomas. We studied the significance of MUC5AC expression for the development of pancreatic ductal adenocarcinoma and the possibility of using MUC5AC as a target for immunotherapy for pancreatic cancer.

METHODS

We immunohistochemicaly tested MUC5AC expression in 134 specimens. To assess the possibility of using the MUC5AC protein to develop an anticancer vaccine, we examined MUC5AC for possible peptide epitopes to elicit cytotoxic T lymphocytes (CTLs).

RESULTS

In immunohistochemical analysis, MUC5AC was absent from all cell types of the normal pancreas but was expressed de novo in 79% of invasive ductal adenocarcinoma. Clinicopathologically, primary tumors with lymph node metastasis had a significantly higher expression of MUC5AC. Next, we successfully established CTL clones stimulated by the MUC5AC-A02-1398 (FLNDAGACV) and MUC5AC-A24-716 (TCQPTCRSL) peptides, which have specific cytotoxicity against the corresponding HLA-A*0201- and A*2402-positive target cells pulsed with the candidate peptide. Each CTL clone also demonstrated its cytotoxic activity toward pancreatic cancer cells endogenously expressing MUC5AC.

CONCLUSIONS

Our results suggest that MUC5AC is a novel tumor-associated antigen that has potential application as a vaccine against pancreatic cancer.

CpG DNA as a vaccine adjuvant

Synthetic oligodeoxynucleotides (ODNs) containing unmethylated CpG motifs trigger cells that express Toll-like receptor 9 (including human plasmacytoid dendritic cells and B cells) to mount an innate immune response characterized by the production of Th1 and proinflammatory cytokines. When used as vaccine adjuvants, CpG ODNs improve the function of professional antigen-presenting cells and boost the generation of humoral and cellular vaccine-specific immune responses. These effects are optimized by maintaining ODNs and vaccine in close proximity. The adjuvant properties of CpG ODNs are observed when administered either systemically or mucosally, and persist in immunocompromised hosts. Preclinical studies indicate that CpG ODNs improve the activity of vaccines targeting infectious diseases and cancer. Clinical trials demonstrate that CpG ODNs have a good safety profile and increase the immunogenicity of coadministered vaccines.

Induction of antitumor immunity by dendritic cells loaded with membrane-translocating mucin 1 Peptide antigen

To investigate the role of enhanced antigen presentation in dendritic cell (DC)-based immunotherapy. Here, we describe the development of a cell-penetrating mucin 1 (MUC1) antigen and its immunotherapeutic potential against tumors. After animal groups received two immunizations of MUC1-MPA(11)P-pulsed DCs, we observed a marked tumor regression compared with the mice treated with DCs alone or DCs pulsed with MUC1 peptide. We confirmed the migration and homing of DCs in the popliteal lymph node using magnetic resonance imaging during the study. In summary, enhanced antigen uptake using an MPA(11)P delivery molecule improves cell therapy.

Induction of homologous rather than heterologous antigen-specific CD4 T cell responses is critical for functional CD8 T cell responses in mice transgenic for a foreign antigen

The development of a successful cancer vaccine requires the ability to break immunological tolerance to self-Ags expressed on tumor cells. The transgenic rat insulin promoter (RIP) OVA(LOW) mouse model has been reported to be hyporesponsive for both OVA-specific CD4 and CD8 T cell responses. The experiments described in the current study show that this hyporesponsiveness can be overcome by inclusion of GM-CSF and the TLR7 agonist imiquimod as adjuvants in a DNA immunization regimen with OVA-encoding plasmids. High frequencies of OVA-specific CD8 and CD4 T cells, including a response to a CD4 T cell epitope seen only in the RIP OVA(LOW) mice, were generated by this regimen. These responses were associated with the development of autoimmunity and increased protection to tumor challenge in the RIP OVA(LOW) mice. Heterologous CD4 T cell help has been shown to improve functional CD8 T cell responses, and we confirmed that inclusion of the CD4 T cell epitope pan HLA-DR-binding epitope improved CD8 T cell responses compared with self-Ag alone. Addition of GM-CSF and imiquimod, however, resulted in dominance of the pan HLA-DR-binding epitope-specific response over the OVA-specific CD4 T cell responses, decreased OVA-specific CD8 T cell numbers and function in tolerant RIP OVA(LOW) mice, and failure to induce diabetes. The results of this study suggest that the use of heterologous help needs to be evaluated carefully in the context of specific immunization regimes and that a preferable approach may be adjuvantization of DNA vaccines.

CpG oligodeoxynucleotides as TLR9 agonists: therapeutic applications in cancer

Toll-like receptors (TLRs) are part of the innate immune system, and they belong to the pattern recognition receptors (PRR) family. The PRR family is designed to recognize and bind conserved pathogen-associated molecular patterns, which are not generated by the host and are restricted and essential to micro-organisms. TLR9, which recognizes unmethylated CpG (cytosine guanosine dinucleotide), is a very promising target for therapeutic activation. Stimulation of TLR9 activates human plasmacytoid dendritic cells and B cells, and results in potent T helper-1 (T(h)1)-type immune responses and antitumor responses in mouse tumor models and in patients. Several pharmaceutical companies, such as Pfizer, Idera, and Dynavax, are developing CpG oligodeoxynucleotides (ODNs) for the treatment of cancer, along with other conditions, such as infections and allergy. CpG ODNs have shown promising results as vaccine adjuvants and in combination with cancer immunotherapy. Several TLR9 agonists are being developed and have entered clinical trials to evaluate their safety and efficacy for the treatment of several hematopoietic and solid tumors. In this review, we discuss the use of CpG ODNs in several phase I and II clinical trials for the treatment of NHL, renal cell carcinoma, melanoma, and non-small cell lung cancer, either alone or in combination with other agents.

Current status of mucins in the diagnosis and therapy of cancer

Mucins are the most abundant high molecular weight glycoproteins in mucus. Their nature and glycosylation content dictates the biochemical and biophysical properties of viscoelastic secretions, pointing out an important role in diverse biological functions, such as differentiation, cell adhesions, immune responses, and cell signaling. Mucins are expressed in tubular organs by specialized epithelial cells in the body. Their aberrant expression is well documented in a variety of inflammatory or malignant diseases. From a prognosis point of view, their expression and alterations in glycosylation are associated with the development and progression of malignant diseases. Therefore, mucins can be used as valuable markers to distinguish between normal and disease conditions. Indeed, this alteration in glycosylation patterns generates several epitopes in the oligosaccharide side chains that can be used as diagnostic and/or prognostic markers. Furthermore, these characteristic tumor-associated epitopes are extensively used as appropriate immunotargets of malignant epithelial cells. Therefore, in an effort to detect and treat cancer at the earliest stage possible, mucins are analyzed as potential markers of disease for diagnosis, progression, and for therapeutic purposes. In this review, we focused on the current status of the distribution of mucins in normal and pathologic conditions and their clinical use both in cancer diagnosis and therapeutics treatments.

Immunotherapy for cancer: synthetic carbohydrate-based vaccines

Aberrant glycosylation of glycoproteins and glycolipids of cancer cells, which correlates with poor survival rates, is being exploited for the development of immunotherapies for cancer. In particular, advances in the knowledge of cooperation between the innate and adaptive system combined with the implementation of efficient synthetic methods for assembly of oligosaccharides and glycopeptides is providing avenues for the rationale design of vaccine candidates. In this respect, fully synthetic vaccine candidates show great promise because they incorporate only those elements requires for relevant immune responses, and hence do not suffer from immune suppression observed with classical carbohydrate-protein conjugate vaccines. Such vaccines are chemically well-defined and it is to be expected that they can be produced in a reproducible fashion. In this feature article, recent advances in the development of fully synthetic sub-unit carbohydrate-based cancer vaccines will be discussed.

Construction of an MUC-1 promoter driven, conditionally replicating adenovirus that expresses the sodium iodide symporter for gene therapy of breast cancer

Introduction

The sodium iodide symporter (NIS) directs the uptake and concentration of iodide in thyroid cells. This in turn allows radioiodine imaging and therapy for thyroid cancer. To extend the use of NIS-mediated radioiodine therapy to other types of cancer, we successfully transferred and expressed the sodium-iodide symporter (NIS) gene in prostate, colon, and breast cancer cells both in vivo and in vitro by using non-replicating adenoviral vectors.

Methods

To improve virotherapy efficiency, we developed a conditionally replicating adenovirus (CRAd) in which the transcriptional cassette RSV promoter-human NIScDNA-bGH polyA was also inserted at the E3 region. The E1a gene is driven by the tumor-specific promoter MUC-1 in the CRAd Ad5AMUCH_RSV-NIS.

Results

In vitro infection of the MUC-1-positive breast cell line T47D resulted in virus replication, cytolysis, and release of infective viral particles. Conversely, the MUC-1-negative breast cancer cell line MDA-MB-231 was refractory to the viral cytopathic effect and did not support viral replication. The data indicate that Ad5AMUCH_RSV-NIS activity is stringently restricted to MUC-1-positive cancer cells. Radioiodine uptake was readily measurable in T47 cells infected with Ad5AMUCH_RSV-NIS 24 hours after infection, thus confirming NIS expression before viral-induced cell death.

Conclusions

This construct may allow multimodal therapy, combining virotherapy with radioiodine therapy to be developed as a novel treatment for breast and other MUC1-overexpressing cancers.