Spontaneous adenocarcinoma mouse models for immunotherapy

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.

Widespread Non-Canonical Epigenetic Modifications in MMTV-NeuT Breast Cancer

Breast tumors in (FVB × BALB-NeuT) F1 mice have characteristic loss of chromosome 4 and sporadic loss or gain of other chromosomes. We employed the Illumina GoldenGate genotyping platform to quantitate loss of heterozygosity (LOH) across the genome of primary tumors, revealing strong biases favoring chromosome 4 alleles from the FVB parent. While allelic bias was not observed on other chromosomes, many tumors showed concerted LOH (C-LOH) of all alleles of one or the other parent on sporadic chromosomes, a pattern consistent with cytogenetic observations. Surprisingly, comparison of LOH in tumor samples relative to normal unaffected tissues from these animals revealed significant variegated (stochastic) deviations from heterozygosity (V-LOH) in every tumor genome. Sequence analysis showed expected changes in the allelic frequency of single nucleotide polymorphisms (SNPs) in cases of C-LOH. However, no evidence of LOH due to mutations, small deletions, or gene conversion at the affected SNPs or surrounding DNA was found at loci with V-LOH. Postulating an epigenetic mechanism contributing to V-LOH, we tested whether methylation of template DNA impacts allele detection efficiency using synthetic oligonucleotide templates in an assay mimicking the GoldenGate genotyping format. Methylated templates were systematically over-scored, suggesting that the observed patterns of V-LOH may represent extensive epigenetic DNA modifications across the tumor genomes. As most of the SNPs queried do not contain standard (CpG) methylation targets, we propose that widespread, non-canonical DNA modifications occur during Her2/neuT-driven tumorigenesis.

Preclinical modeling of hematopoietic stem cell transplantation - advantages and limitations

Hematopoietic stem cell transplantation, which was first successfully performed in the 1950s, remains a critical therapeutic modality for treatment of a diverse array of diseases, including a multitude of hematological malignancies, autoimmune disorders, amyloidosis and inherited genetic hematological disorders. Although great advances have been made in understanding and application of this therapy, significant complications still exist, warranting further investigation. Of critical importance, graft-versus-host disease (GVHD), in both acute and chronic forms, remains a major complication of hematopoietic stem cell transplantation, responsible for both the development of chronic illness and morbidity, as well as mortality. Use of an appropriate preclinical model may provide significant insight into the mechanistic pathways leading to the development and progression of graft-versus-host disease, as well as cancer in general. However, existing preclinical modeling systems exhibit significant limitations, and development of models that recapitulate the complex and comprehensive clinical scenario and provide a tool by which therapeutic intervention may be developed and assessed is of utmost importance. Here, we review the present status of the field of graft-versus-host disease research. We discuss and summarize the preclinical models currently in use, as well as their advantages and limitations.

Induction of HER2 Immunity in Outbred Domestic Cats by DNA Electrovaccination

Domestic cats share human living environments and genetic traits. They develop spontaneous feline mammary carcinoma (FMC) with similar histopathology to human breast cancer. HER2 and AKT phosphorylation was demonstrated in primary FMC by immunoblot analysis, indicating HER2 as a therapeutic target. FMC lines K12 and K248 expressing HER1, HER2, and HER3 were sensitive to receptor tyrosine kinase (RTK) inhibitors gefitinib and lapatinib. To test HER2 vaccine response in cats, purpose-bred, healthy cats were electrovaccinated with heterologous (xenogeneic) or point-mutated feline HER2 DNA. T-cell reactivity to feline self-HER2 was detected in 4 of 10 cats that received bear HER2, human-rat fusion HER2 (E2Neu) or mutant feline HER2 (feHER2-K), which contains a single amino acid substitution. The variable T-cell responses may resemble that in the genetically heterogeneous human population. All immune sera to heterologous HER2 recognized feline HER2 expressed in 3T3 cells (3T3/HER2), but not that in FMC K12 or K248. Immune sera to mutant pfeHER2-K bound 3T3/HER2 cells weakly, but they showed better recognition of K12 and K248 cells that also express HER1 and HER3, suggesting distinct HER2 epitopes displayed by FMC that may be simulated by feHER2-K. In summary, HER2 DNA electroporation overcomes T-cell immune tolerance in approximately 40% of healthy cats and induces antibodies with distinct specificity. Vaccination studies in domestic cats can expedite vaccine iteration to guide human vaccine design and better predict outcome, with the added benefit of helping feline mammary tumor patients.

Over-expression of ST3Gal-I promotes mammary tumorigenesis

Changes in glycosylation are common in malignancy, and as almost all surface proteins are glycosylated, this can dramatically affect the behavior of tumor cells. In breast carcinomas, the O-linked glycans are frequently truncated, often as a result of premature sialylation. The sialyltransferase ST3Gal-I adds sialic acid to the galactose residue of core 1 (Galβ1,3GalNAc) O-glycans and this enzyme is over-expressed in breast cancer resulting in the expression of sialylated core 1 glycans. In order to study the role of ST3Gal-I in mammary tumor development, we developed transgenic mice that over-express the sialyltransferase under the control of the human membrane-bound mucin 1 promoter. These mice were then crossed with PyMT mice that spontaneously develop mammary tumors. As expected, ST3Gal-I transgenic mice showed increased activity and expression of the enzyme in the pregnant and lactating mammary glands, the stomach, lungs and intestine. Although no obvious defects were observed in the fully developed mammary gland, when these mice were crossed with PyMT mice, a highly significant decrease in tumor latency was observed compared to the PyMT mice on an identical background. These results indicate that ST3Gal-I is acting as a tumor promoter in this model of breast cancer. This, we believe, is the first demonstration that over-expression of a glycosyltransferase involved in mucin-type O-linked glycosylation can promote tumorigenesis.

Altered immune function during long-term host-tumor interactions can be modulated to retard autochthonous neoplastic growth

Ag-specific and generalized forms of immunosuppression have been documented in animal tumor models. However, much of our knowledge on tumor-induced immunosuppression was acquired using tumor implant models, which do not reiterate the protracted nature of host-tumor interactions. Therefore, a transgenic mouse model of autochthonous mammary tumor development and progression was chosen to investigate the long-term consequences of neoplastic growth on the immune system. In vitro proliferation of unfractionated splenocytes from tumor-bearing mice, as assessed by [(3)H]thymidine uptake, was inhibited by the presence of suppressor cells within these splenocyte preparations, because purifying the T cells restored their biological activity. However, the level of inhibition did not correlate with either tumor load or the percentage of myeloid-derived CD11b+Gr1+ cells. To evaluate tumor-specific immune dysfunction, transgenic mice were challenged with autologous tumor cells. Mice with extensive, but not minimal autochthonous tumor burdens demonstrated a significantly enhanced rate of autologous tumor growth compared with age-matched controls. In contrast, an allogeneic tumor challenge was efficiently rejected from both groups of transgenic mice. It was also noted that allogeneic tumor challenge of mice with minimal disease significantly inhibited autochthonous primary tumor growth. We therefore demonstrated that 1) a generalized form of immunosuppression occurred, but not as a result of permanent alterations to T cell function, because purified T cell subsets retained normal biological activity following polyclonal or allostimulation; and 2) tumor-specific immunosuppression emerged as a consequence of tumor progression, but could be modulated to enhance antitumor responses against autochthonous primary neoplastic growth.

Cancer vaccines: preclinical studies and novel strategies

The development of cancer vaccines, aimed to enhance the immune response against a tumor, is a promising area of research. A better understanding of both the molecular mechanisms that govern the generation of an effective immune response and the biology of a tumor has contributed to substantial progress in the field. Areas of intense investigation in cancer immunotherapy will be discussed here, including: (1) the discovery and characterization of novel tumor antigens to be used as targets for vaccination; (2) the investigation of different vaccine-delivery modalities such as cellular-based vaccines, protein- and peptide-based vaccines, and vector-based vaccines; (3) the characterization of biological adjuvants to further improve the immunogenicity of a vaccine; and (4) the investigation of multimodal therapies where vaccines are being combined with other oncological treatments such as radiation and chemotherapy. A compilation of data from preclinical studies conducted in vitro as well as in animal models is presented here. The results from these studies would certainly support the development of new vaccination strategies toward cancer vaccines with enhanced clinical efficacy.

Immunoprevention of cancer

This article discusses the current understanding of the interactions between tumors and cells of the immune system, particularly at the early stages of carcinogenesis. A growing body of data suggests that these interactions help shape the eventual development of tumors. Inflammation is a common feature of several cancers, and the immune system can serve as a two-edged sword against cancer, capable of supporting and suppressing cancer. Data from human studies show that the immune system is capable of detecting the smallest expansions of transformed cells, well before the development of clinical cancer. These advances suggest a need to change the current emphasis for harnessing antitumor immunity from therapy to prevention of cancers.

Genetically induced pancreatic adenocarcinoma is highly immunogenic and causes spontaneous tumor-specific immune responses

Treatment options for pancreatic cancer are limited and often ineffective. Immunotherapeutic approaches are one possible option that needs to be evaluated in appropriate animal models. The aim of the present study was to analyze tumor-specific immune responses in a mouse model of pancreatic cancer, which mimics the human disease closely. C57BL/6 EL-TGF-alpha x Trp53-/- mice, which develop spontaneous ductal pancreatic carcinoma, were generated. EL-TGF-alpha x Trp53-/- mice developed spontaneous pancreatic tumors with pathomorphologic features close to the human disease. Tumor-specific CD8+ T-cell responses and IgG responses were analyzed in EL-TGF-alpha x Trp53-/- mice during tumor development and compared with mice with s.c. growing pancreatic tumors. In contrast to spontaneous pancreatic tumors, cell lines generated from these tumors were rejected after s.c. injection into wild-type mice but not in nude or RAG knockout mice. Direct comparison of spontaneous and s.c. injected tumors revealed an impaired infiltration of CD8+ T cells in spontaneous pancreatic tumors, which was also evident after adoptive transfer of tumor-specific T cells. Intratumoral cytokine secretion of tumor necrosis factor-alpha, IFN-gamma, IL-6, and MCP-1 was lower in spontaneous tumors as well as the number of adoptively transferred tumor-specific T cells. Our data provide clear evidence for tumor-specific immune responses in a genetic mouse model for pancreatic carcinoma. Comparative analysis of s.c. injected tumors and spontaneous tumors showed significant differences in tumor-specific immune responses, which will help in improving current immune-based cancer therapies against adenocarcinoma of the pancreas.

Expression of nerve growth factor messenger RNA in pancreatic cancer tissues in Sprague Dawley rats

AIM: To establish a model of pancreatic cancer in Sprague-Dawley(SD)rats and to explore the expression and its significance of nerve growth factor(NGF)mRNA in pancreatic cancer and non-cancer tissues.

METHODS: Ninety rats were randomly divided into A (n = 40), B (n = 40) and C (n = 10) group. For group A and B, dimethylbenzanthrancene (DMBA) was directly implanted into the parenchyma of the rat pancreas to establish pancreatic cancer model. The rats in group B were treated with trichostatin(TSA). The rats in group C served as the controls. The rats were executed within 3-5 mo, and the carcinogenesis of the rats was observed by pathological methods. In situ hybridization was used to detect the expression of NGF mRNA in the formalin-fixed and routinely paraffin-embedded sections of pancreatic cancer and non-cancer tissues.

RESULTS: The prevalence rate of pancreatic cancer in group A was 48.7%(18/37) within 3-5 mo, 28.6%(2/7) at mo, 40.0%(4/10) at 4 mo and 60%(12/20) at 5 mo (P > 0.05), and that in group B was 33.3%(12/36), 16.7%(1/6), 30.0%(3/10) and (40.0%)8/20, respectively (P > 0.05). The prevalence rate in group A was higher than that of group B (P > 0.05). The diameters of tumor mass in group A were significantly larger than those in group B (group A: 0.5-1.0 cm 7 cases, 1.0-2.0 cm 10 cases, > 2 cm 1 case vs group B: 0.5-1.0 cm 9 case, 1.0-2.0 cm 2 cases, >2.0 cm 1 case, P < 0.05). No tumor formed in the pancreas of the rats in group C or in other main organs of the rats in group A and B. The positive rate of NGF mRNA expression in the pancreatic ductal cancer tissues was significantly higher than that in non-cancer tissues (67.9% vs 18.6%, P < 0.01), and severely atypical hyperplasia was observed in the positive non-cancer pancreatic tissues of ductal epithelium. The positive rate of NGF mRNA expression in ductal adenocarcinoma was markedly higher in group A than that in group B (P = 0.052). The positive rate of NGF mRNA in the rats with tumor maximal diameter ≤ 1.0 cm was lower than that in the ones with tumor maximal diameter > 1.0 cm (P > 0.05).

CONCLUSION: Direct implantation of DMBA in the parenchyma of pancreas can induce pancreatic cancer with a high occurrence rate in a short time. NGF may play an important role in the carcinogenesis of pancreatic cancer. TSA can inhibit the occurrence and progression of pancreatic cancer by inhibiting NGF expression.

Tumor-associated carbohydrate antigens: a possible avenue for cancer prevention

Here we examine the use of glycopeptides containing tumour-associated carbohydrate antigens (TACA) as potential preventive vaccines for carcinomas. Our recent results suggest that CD8+ T cells (CTL) are capable of recognizing TACA in a conventional class I MHC-restricted fashion. The ThomsenFriedenreich antigen (TF), a disaccharide, and Tn, its immediate precursor, are TACA largely expressed in carcinomas. TF and Tn can be successfully used as Th-independent vaccines when conjugated to designer peptides with optimal binding affinity for class I MHC molecules. TF- and Tn-specific CTL generated using this strategy are capable of recognizing TACA-expressing tumours in vitro, suggesting that glycopeptides are as effectively presented by class I MHC molecules as non-glycosylated peptides. Because the exact sequences of endogenously synthesized glycopeptides are unknown, the TACA-specific T cell repertoire elicited by carbohydrate-based vaccines is assumed to be degenerate. Here we report that mice genetically manipulated to develop TACA-expressing mammary tumours are not tolerant to glycopeptide vaccination. Moreover, we tested the immunogenicity of designer glycopeptides capable of binding multiple HLA alleles as a novel approach for the development of vaccines potentially useful for vaccination of a large fraction of the general population. Our results have suggested that CTL derived from normal donors respond with high efficiency to glycopeptides in vitro, opening a new avenue for the design of prospective vaccines for cancer prevention.

Short-term human prostate primary xenografts: an in vivo model of human prostate cancer vasculature and angiogenesis

Transgenic spontaneously occurring and transplantable xenograft models of adenocarcinoma of the prostate (CaP) are established tools for the study of CaP progression and metastasis. However, no animal model of CaP has been characterized that recapitulates the response of the human prostate vascular compartment to the evolving tumor microenvironment during CaP progression. We report that primary xenografts of human CaP and of noninvolved areas of the human prostate peripheral zone transplanted to athymic nude mice provide a unique model of human angiogenesis occurring in an intact human prostate tissue microenvironment. Angiogenesis in human kidney primary xenografts established from human renal cell carcinoma and noninvolved kidney tissue, a highly vascular organ and cancer, was compared with angiogenesis in xenografts from the relatively less vascularized prostate. Immunohistochemical identification of the human versus mouse host origin of the endothelial cells and of human endothelial cell proliferation in the human prostate and human kidney xenografts demonstrated that: (a) the majority of the vessels in primary xenografts of benign and malignant tissue of both organs were lined with human endothelial cells through the 30-day study period; (b) the mean vessel density was increased in both the CaP and benign prostate xenografts relative to the initial tissue, whereas there was no significant difference in mean vessel density in the renal cell carcinoma and benign kidney xenografts compared with the initial tissue; and (c) the number of vessels with proliferating endothelial cells in primary xenografts of CaP and benign prostate increased compared with their respective initial tissue specimens, whereas the number of vessels with proliferating endothelial cells decreased in the benign kidney xenografts. Short-term primary human prostate xenografts, therefore, represent a valuable in vivo model for the study of human angiogenesis within a human tissue microenvironment and for comparison of angiogenesis in CaP versus benign prostate.

Cancer vaccines: between the idea and the reality

Whether vaccines are designed to prepare the immune system for the encounter with a pathogen or with cancer, certain common challenges need to be faced, such as what antigen and what adjuvant to use, what type of immune response to generate and how to make it long lasting. Cancer, additionally, presents several unique hurdles. Cancer vaccines must overcome immune suppression exerted by the tumour, by previous therapy or by the effects of advanced age of the patient. If used for cancer prevention, vaccines must elicit effective long-term memory without the potential of causing autoimmunity. This article addresses the common and the unique challenges to cancer vaccines and the progress that has been made in meeting them. Considering how refractory cancer has been to standard therapy, efforts to achieve immune control of this disease are well justified.

Cancer immunoprevention: tracking down persistent tumor antigens

The immune response can effectively hamper the progression of preclinical stages of tumor growth. Medicine in the postgenomic era offers an increasing possibility of detecting healthy individuals at risk of developing cancer who could benefit from tumor-preventive vaccines. The identification of novel tumor antigens that fulfill two conditions will be crucial for the development of cancer immunoprevention. First, an ideal antigen should have a crucial pathogenetic role in tumor growth to avoid the selection of antigen-loss variants. Second, the antigen should be recognizable by the immune system even in MHC-loss variants and should therefore be recognized both by antibodies and T cells. Identifying such antigens will also provide new targets for cancer immunotherapy.