p21-ras-peptide-specific T-cell responses in a patient with colorectal cancer. CD4+ and CD8+ T cells recognize a peptide corresponding to a common mutation (13Gly-->Asp)

Immune vulnerabilities of mutant KRAS in pancreatic cancer

The 40-year desire to target the mutant Kirsten rat sarcoma (KRAS) gene (mKRAS) therapeutically is being realized with more and more broadly applicable and tumor-specific small-molecule inhibitors. Immunologically, mKRAS has equal desirability as a target. Tumor KRAS signaling plays a large role in shaping the immunosuppressive nature of the tumor microenvironment, especially in pancreatic cancer, leaving mKRAS inhibitors with potentially powerful immune modulatory capabilities that could be exploited in immunological-oncological combinations. mKRAS is itself an immunological antigen, a 'shared neoepitope' linked to the oncogenic process, validated biochemically and immunologically. Novel approaches in the clinic are taking advantage of the fact that mKRAS peptides are naturally processed and presented in tumors by the major histocompatibility complex (MHC).

Trial watch: Peptide vaccines in cancer therapy

Prophylactic vaccination constitutes one of the most prominent medical achievements of history. This concept was first demonstrated by the pioneer work of Edward Jenner, dating back to the late 1790s, after which an array of preparations that confer life-long protective immunity against several infectious agents has been developed. The ensuing implementation of nation-wide vaccination programs has de facto abated the incidence of dreadful diseases including rabies, typhoid, cholera and many others. Among all, the most impressive result of vaccination campaigns is surely represented by the eradication of natural smallpox infection, which was definitively certified by the WHO in 1980. The idea of employing vaccines as anticancer interventions was first theorized in the 1890s by Paul Ehrlich and William Coley. However, it soon became clear that while vaccination could be efficiently employed as a preventive measure against infectious agents, anticancer vaccines would have to (1) operate as therapeutic, rather than preventive, interventions (at least in the vast majority of settings), and (2) circumvent the fact that tumor cells often fail to elicit immune responses. During the past 30 y, along with the recognition that the immune system is not irresponsive to tumors (as it was initially thought) and that malignant cells express tumor-associated antigens whereby they can be discriminated from normal cells, considerable efforts have been dedicated to the development of anticancer vaccines. Some of these approaches, encompassing cell-based, DNA-based and purified component-based preparations, have already been shown to exert conspicuous anticancer effects in cohorts of patients affected by both hematological and solid malignancies. In this Trial Watch, we will summarize the results of recent clinical trials that have evaluated/are evaluating purified peptides or full-length proteins as therapeutic interventions against cancer.

Healthy Donors Harbor Memory T Cell Responses to RAS Neo-Antigens

The RAS mutations are the most frequently occurring somatic mutations in humans, and several studies have established that T cells from patients with RAS-mutant cancer recognize and kill RAS-mutant cells. Enhancing the T cell response via therapeutic cancer vaccination against mutant RAS results in a clinical benefit to patients; thus, T cells specific to RAS mutations are effective at battling cancer. As the theory of cancer immuno-editing indicates that healthy donors may clear malignantly transformed cells via immune-mediated killing, and since T cells have been shown to recognize RAS-mutant cancer cells, we investigated whether healthy donors harbor T-cell responses specific to mutant RAS. We identified strong and frequent responses against several epitopes derived from the RAS codon 12 and codon 13 mutations. Some healthy donors demonstrated a response to several mutant epitopes, and some, but not all, exhibited cross-reactivity to the wild-type RAS epitope. In addition, several T cell responses were identified against mutant RAS epitopes in healthy donors directly ex vivo. Clones against mutant RAS epitopes were established from healthy donors, and several of these clones did not cross-react with the wild-type epitope. Finally, CD45RO⁺ memory T cells from healthy donors demonstrated a strong response to several mutant RAS epitopes. Taken together, these data suggest that the immune system in healthy donors spontaneously clears malignantly transformed RAS-mutant cells, and the immune system consequently generates T-cell memory against the mutations.

Memory T cells targeting oncogenic mutations detected in peripheral blood of epithelial cancer patients

T cells targeting shared oncogenic mutations can induce durable tumor regression in epithelial cancer patients. Such T cells can be detected in tumor infiltrating lymphocytes, but whether such cells can be detected in the peripheral blood of patients with the common metastatic epithelial cancer patients is unknown. Using a highly sensitive in vitro stimulation and cell enrichment of peripheral memory T cells from six metastatic cancer patients, we identified and isolated CD4⁺, and CD8⁺ memory T cells targeting the mutated KRAS^G12D and KRAS^G12V variants, respectively, in three patients. In an additional two metastatic colon cancer patients, we detected CD8⁺ neoantigen-specific cells targeting the mutated SMAD5 and MUC4 proteins. Therefore, memory T cells targeting unique as well as shared somatic mutations can be detected in the peripheral blood of epithelial cancer patients and can potentially be used for the development of effective personalized T cell-based cancer immunotherapy across multiple patients.

Prostate cancer health disparities: An immuno-biological perspective

Prostate cancer (PCa) is the most commonly diagnosed malignancy in males, and, in the United States, is the second leading cause of cancer-related death for men older than 40 years. There is a higher incidence of PCa for African Americans (AAs) than for European-Americans (EAs). Investigations related to the incidence of PCa-related health disparities for AAs suggest that there are differences in the genetic makeup of these populations. Other differences are environmentally induced (e.g., diet and lifestyle), and the exposures are different. Men who immigrate from Eastern to Western countries have a higher risk of PCa than men in their native countries. However, the number of immigrants developing PCa is still lower than that of men in Western countries, suggesting that genetic factors are involved in the development of PCa. Altered genetic polymorphisms are associated with PCa progression. Androgens and the androgen receptor (AR) are involved in the development and progression of PCa. For populations with diverse racial/ethnic backgrounds, differences in lifestyle, diet, and biology, including genetic mutations/polymorphisms and levels of androgens and AR, are risk factors for PCa. Here, we provide an immuno-biological perspective on PCa in relation to racial/ethnic disparities and identify factors associated with the disproportionate incidence of PCa and its clinical outcomes.

Improving Prospects for Targeting RAS

RAS mutations are among the most common oncogenic drivers in human cancers, affecting nearly a third of all solid tumors and around a fifth of common myeloid malignancies, but they have evaded therapeutic interventions, despite being the focus of intense research over the last three decades. Recent discoveries lend new understanding about the structure, function, and signaling of RAS and have opened new avenues for development of much needed new therapies. We discuss the various approaches under investigation to target mutant RAS proteins. The recent development of direct RAS inhibitors specific to KRAS G12C mutations represents a landmark discovery that promises to change the perception about RAS's druggability. Multiple clinical trials targeting synthetically lethal partners and/or downstream signaling partners of RAS are underway. Novel inhibitors targeting various arms of RAS processing and signaling have yielded encouraging results in the laboratory, but refinement of the drug-like properties of these molecules is required before they will be ready for the clinic.

Vaccines for colorectal cancer and renal cell carcinoma

Vaccines have shown promise for the prevention and treatment of solid tumors. Colorectal cancer and renal cell carcinoma are common malignancies that may be amenable to vaccine strategies. This review summarizes target antigens in colorectal and renal cell carcinoma, discusses some of the vaccine approaches in development, and details the results of pivotal phase III trials evaluating therapeutic vaccines in patients with advanced colorectal and renal cell carcinoma. Finally, some of the challenges with vaccine development for colorectal and renal cell carcinoma are described.

Unconventional cytokine profiles and development of T cell memory in long-term survivors after cancer vaccination

Cancer vaccine trials frequently report on immunological responses, without any clinical benefit. This paradox may reflect the challenge of discriminating between effective and pointless immune responses and sparse knowledge on their long-term development. Here, we have analyzed T cell responses in long-term survivors after peptide vaccination. There were three main study aims: (1) to characterize the immune response in patients with a possible clinical benefit. (2) To analyze the long-term development of responses and effects of booster vaccination. (3) To investigate whether the Th1/Th2-delineation applies to cancer vaccine responses. T cell clones were generated from all nine patients studied. We find that surviving patients harbor durable tumor-specific responses against vaccine antigens from telomerase, RAS or TGFbeta receptor II. Analyses of consecutive samples suggest that booster vaccination is required to induce robust T cell memory. The responses exhibit several features of possible clinical advantage, including combined T-helper and cytotoxic functionality, recognition of naturally processed antigens and diverse HLA-restriction and fine-specificity. CD4(-)CD8(-) T cell clones display unconventional cytotoxicity and specifically kill tumor cells expressing mutated TGFbeta receptor II. Cytokine profiling on the long-term survivors demonstrates high IFN gamma/IL10-ratios, favoring immunity over tolerance, and secretion of multiple chemokines likely to mobilize the innate and adaptive immune system. Interestingly, these pro-inflammatory cytokine profiles do not follow a Th1/Th2-delineation. Most IFN gamma(high)/IL4(low)/IL10(low) cultures include high concentrations of hallmark Th2-cytokines IL-5 and IL-13. This does not reflect a mixture of Th1- and Th2-clones, but applies to 19/20 T cell clones confirmed to be monoclonal through TCR clonotype mapping. The present study identifies several factors that may promote clinical efficacy and suggests that cytokine profiling should not rely on the Th1/Th2-paradigm, but assess the overall inflammatory milieu and the balance between key cytokines.

Pilot study of mutant ras peptide-based vaccine as an adjuvant treatment in pancreatic and colorectal cancers

INTRODUCTION

There is mounting evidence describing the immunosuppressive role of bulky metastatic disease, thus countering the therapeutic effects of tumor vaccine. Therefore, adjuvant immunotherapy may have a better impact on clinical outcome. In this phase II clinical trial, we aimed to test the feasibility of using a specific mutant ras peptide vaccine as an adjuvant immunotherapy in pancreatic and colorectal cancer patients.

MATERIALS AND METHODS

Twelve patients with no evidence of disease (NED), five pancreatic and seven colorectal cancer patients were vaccinated subcutaneously with 13-mer mutant ras peptide, corresponding to their tumor's ras mutation. Vaccinations were given every 4 weeks, up to a total of six vaccines.

RESULTS

No serious acute or delayed systemic side effects were seen. We detected specific immune responses to the relevant mutant ras peptide by measuring IFN-gamma mRNA expression by quantitative real-time PCR. Five out of eleven patients showed a positive immune response. Furthermore, the five pancreatic cancer patients have shown a mean disease-free survival (DFS) of 35.2+ months and a mean overall survival (OS) of 44.4+ months. The seven colorectal cancer patients have shown a mean disease-free survival (DFS) of 27.2+ months and a mean overall survival (OS) of 41.5+ months.

CONCLUSION

In this study, we found that it is feasible to use mutant ras vaccine in the adjuvant setting. This vaccine is safe, can induce specific immune responses, and it appears to have a positive outcome in overall survival. Therefore, we believe that such an approach warrants further investigation in combination with other therapies.

Targeting epidermal growth factor receptor variant III: a novel strategy for the therapy of malignant glioma

Immunotherapy represents an exciting approach for the treatment of glioblastoma multiforme. The success of this approach depends on the identification of tumor-specific antigens that can then be exploited to target the tumor. One such antigen, the epidermal growth factor receptor variant III (EGFRvIII) is found in up to 50% of malignant gliomas. This molecule is an interesting vaccine candidate since its expression is tumor specific. Recent preclinical, as well as clinical, studies of EGFRvIII-based vaccines suggest a promising role for immunotherapy of malignant gliomas. This review focuses on vaccines that target EGFRvIII. We review preclinical and clinical data and emphasize the immunological mechanisms involved in its therapeutic effect.

Antitumor effects of the MIG and IP-10 genes transferred with poly [D,L-2,4-diaminobutyric acid] on murine neuroblastoma

The number of tumor-infiltrating lymphocytes is known to be related to outcomes in patients with a variety of malignancies. Interferon (IFN) gamma-inducible protein-10 (IP-10) and monokine induced by IFNgamma (MIG) have chemotactic effects on activated T lymphocytes and natural killer (NK) cells. The aim of this study was to evaluate the antitumor effects of exogenous expression of the MIG and IP-10 genes delivered to solid tumors by poly [D,L-2,4-diaminobutyric acid] (PDBA). The murine MIG and IP-10 genes were transfected into mouse neuroblastoma cells with PDBA. MIG and IP-10 levels in supernatants of transfected cells were measured by enzyme-linked immunosorbent assay. The chemotactic activities of MIG and IP-10 in the supernatants of cell cultures were measured by chemotaxis assay. Tumors were injected in vivo with PDBA/pmMIGColon, two colonsIP-10 complexes to evaluate the effects of these genes on tumor volume and survival time of mice. Transfected PDBA/pmMIGColon, two colonsIP-10 complexes produced MIG and IP-10 protein in vitro. MIG and IP-10 proteins secreted into the culture medium showed chemotactic activity. MIG and IP-10 gene therapy with the PDBA system in vivo significantly inhibited tumor growth and prolonged survival time of mice. In conclusion, PDBA-mediated MIG and IP-10 gene therapy may be useful for treatment of solid tumors.

Clinicopathological significance of stromal variables: angiogenesis, lymphangiogenesis, inflammatory infiltration, MMP and PINCH in colorectal carcinomas

Cancer research has mainly focused on alterations of genes and proteins in cancer cells themselves that result in either gain-of-function in oncogenes or loss-of-function in tumour-suppressor genes. However, stromal variables within or around tumours, including blood and lymph vessels, stromal cells and various proteins, have also important impacts on tumour development and progression. It has been shown that disruption of stromal-epithelial interactions influences cellular proliferation, differentiation, death, motility, genomic integrity, angiogenesis, and other phenotypes in various tissues. Moreover, stromal variables are also critical to therapy in cancer patients. In this review, we mainly focus on the clinicopathological significance of stromal variables including angiogenesis, lymphangiogenesis, inflammatory infiltration, matrix metalloproteinase (MMP), and the particularly interesting new cysteine-histidine rich protein (PINCH) in colorectal cancer (CRC).

CD8+ T-cell response against MUC1-derived peptides in gastrointestinal cancer survivors

The tumor-associated antigens CEA, MUC1 and Her2/neu are broadly expressed in gastrointestinal tumors, and are attractive candidates for targeting by T-cell-based immunotherapy. However, little is known about the natural cytotoxic T-cell response of patients suffering from colorectal or gastric carcinoma against these three as well as other antigens. Using a quantitative reverse transcription-polymerase chain reaction-based assay for IFN-gamma, we analyzed the CD8+ T-cell repertoire present in the blood of HLA-A2+ gastrointestinal tumor survivors against five known epitopes derived from CEA, MUC1 and Her2/neu. The results show that most of the patients (16 from 22 tested) have detectable, peripheral CD8+ T cells directed against at least one of these three proteins. Interestingly, the majority of these patients reacts to the two MUC1-derived HLA-A*0201 epitopes tested (14 from 16), demonstrating that this protein represents one dominant target for CD8+ T cells in gastrointestinal cancer.

Tumor antigens for cancer immunotherapy: therapeutic potential of xenogeneic DNA vaccines

Preclinical animal studies have convincingly demonstrated that tumor immunity to self antigens can be actively induced and can translate into an effective anti-tumor response. Several of these observations are being tested in clinical trials. Immunization with xenogeneic DNA is an attractive approach to treat cancer since it generates T cell and antibody responses. When working in concert, these mechanisms may improve the efficacy of vaccines. The use of xenogeneic DNA in overcoming immune tolerance has been promising not only in inbred mice with transplanted tumors but also in outbred canines, which present with spontaneous tumors, as in the case of human. Use of this strategy also overcomes limitations seen in other types of cancer vaccines. Immunization against defined tumor antigens using a xenogeneic DNA vaccine is currently being tested in early phase clinical trials for the treatment of melanoma and prostate cancers, with proposed trials for breast cancer and Non-Hodgkin's Lymphoma.

Specific T-cell immunity against Ki-ras peptides in patients with pancreatic and colorectal cancers

Mutations of codon 12 in the Ki-ras gene are frequently found in pancreatic and colorectal cancers. It has been demonstrated that human T-cells have the potential to recognise tumours expressing mutated ras-derived peptides. However, it remains unclear whether T-cells from a given individual can recognise the mutant peptides, which are expressed in that individual's tumour tissues. Mutations of the Ki-ras oncogene were analysed by the mutant-allele-specific amplification (MASA) method in pancreatic and colorectal tumour tissues, and T-cell responses against mutated Ki-ras-derived peptides were measured by [(3)H]thymidine incorporation and IFN-gamma production assays. Specific T-cell responses against Ki-ras-products were found in cancer patients, whereas no immune response was observed in normal individuals (P<0.01). Six of the eight pancreatic cancer patients (75%) and nine of 26 colorectal cancer patients (35%) had T-cell responses to mutated Ki-ras-derived-peptides. T-cell response in a given individual cannot recognise the same mutated ras peptide, which is expressed in that individual's tumour tissues. However, pancreatic and colorectal cancer patients have T-cell immunity against Ki-ras-peptides, and this provides potential target for cancer immunotherapy.

Lymphocytic infiltration surrounding liver metastases from colorectal cancer

BACKGROUND AND OBJECTIVES

Tumor infiltrating lymphocytes (TILs) have been recognized as a tumor-host reaction in various primary neoplasms. Although several studies reported TILs surrounding metastatic liver tumors, to the authors' knowledge few evaluations of the clinical significance of such features in patients with colorectal liver metastases have been carried out.

METHODS

Forty-one patients who underwent initial hepatic resection for liver metastases from colorectal cancer were studied. Lymphocytic infiltration surrounding metastatic liver tumor was graded as weak or dense according to the mean number of TILs from 10 high-power microscopic fields (< or =50 or >50/HPF).

RESULTS

Dense lymphocytic infiltration between the metastatic tumor and hepatic parenchyma was seen in 18 of 41 patients (44%). Histologically, tumor invasion of the portal vein was rare in patients with dense TILs (12%) compared with patients with weak TILs (36%). Patients with dense TILs survived longer than patients with weak TILs after hepatic resection (P = 0.013). Multivariate analysis using the Cox proportional hazard model identified this pathological variable as a significant independent prognostic factor after hepatic resection.

CONCLUSIONS

The extent of lymphocytic infiltration between the metastatic nodule and hepatic parenchyma may reflect host defensive activity in the liver and is closely related to prognosis in patients who underwent hepatic resection for liver metastases from colorectal cancer.

Emerging biological therapies for pancreatic carcinoma

AIMS

The incidence of pancreatic carcinoma remains approximately equal to its mortality, with the vast majority of patients having advanced disease at presentation. This review is an update of the promising novel approaches involving biological therapy that may be used in conjunction with new chemotherapeutic agents in the near future.

METHODS

A literature review was performed using the National Library of Medicine's Pubmed database, combined with recently published data from the AGA and ASCO conferences.

RESULTS

Rapid progress is being made in gene and molecular technology potentially enabling us to inhibit pancreatic carcinogenesis and to reduce disease progression. Different targets include signal transduction inhibitors, gene therapy, genetic prodrug activation therapy, antisense therapy, immunotherapy, matrix metalloproteinase and cyclo-oxygenase-2 inhibition and hormonal manipulation.

CONCLUSION

A variety of biological agents are currently undergoing clinical trials, targeting different areas of the pancreas'neoplastic process. .

Spinning molecular immunology into successful immunotherapy

Until recently, immunotherapies have been of limited success, particularly against cancer. However, recent insights into the cells, molecules and signalling pathways that regulate immune responsiveness are providing new approaches for immunotherapy. In this article, I review some of the most promising molecular and cellular targets for immunotherapy and discuss approaches that use these targets to amplify immune responses and potentially break antigen-specific tolerance. These strategies provide a blueprint for the development of successful immunotherapy over the next decade.

Mucinous differentiation in colonic adenocarcinoma is associated with a reduction in tumour-infiltrating lymphocytes

AIMS

The aim of this study was to examine the density of tumour-infiltrating lymphocytes (TILs) in colorectal carcinomas showing mucinous differentiation.

METHODS

We examined 33 adenocarcinomas showing variable mucinous differentiation and compared the density of TILs with that of 65 adenocarcinomas of no special type (NOS) showing no mucinous differentiation.

RESULTS

Mucinous differentiation is associated with a significantly lower density of TILs compared to adenocarcinoma NOS (P=0.0016; chi-squared test with continuity correction). This reduction in TILs is present also in adjacent foci of adenocarcinoma NOS within mucinous tumours.

CONCLUSIONS

There is a reduction in the number of TILs in all areas of colorectal adenocarcinomas that show mucinous differentiation, which may help explain the increased biological aggressiveness associated with this pattern of differentiation.

Intradermal ras peptide vaccination with granulocyte-macrophage colony-stimulating factor as adjuvant: Clinical and immunological responses in patients with pancreatic adenocarcinoma

K-RAS mutations are frequently found in adenocarcinomas of the pancreas, and induction of immunity against mutant ras can therefore be of possible clinical benefit in patients with pancreatic cancer. We present data from a clinical phase I/II trial involving patients with adenocarcinoma of the pancreas vaccinated by i.d. injection of synthetic mutant ras peptides in combination with granulocyte-macrophage colony-stimulating factor. Forty-eight patients (10 surgically resected and 38 with advanced disease) were treated on an outpatient basis. Peptide-specific immunity was induced in 25 of 43 (58%) evaluable patients, indicating that the protocol used is very potent and capable of eliciting immune responses even in patients with end-stage disease. Patients followed-up for longer periods showed evidence of induction of long-lived immunological memory against the ras mutations. CD4(+) T cells reactive with an Arg12 mutation also present in the tumor could be isolated from a tumor biopsy, demonstrating that activated, ras-specific T cells were able to selectively accumulate in the tumor. Vaccination was well tolerated in all patients. Patients with advanced cancer demonstrating an immune response to the peptide vaccine showed prolonged survival from the start of treatment compared to non-responders (median survival 148 days vs. 61 days, respectively; p = 0.0002). Although a limited number of patients were included in our study, the association between prolonged survival and an immune response against the vaccine suggests that a clinical benefit of ras peptide vaccination may be obtained for this group of patients.

In situ hybridization of Epstein-Barr virus in tumor cells and tumor-infiltrating lymphocytes of the gastrointestinal tract

Unlike gastric carcinoma, associations of the Epstein-Barr virus (EBV) with carcinomas of other sites in the gastrointestinal tract have not yet been clarified. To elucidate these associations, we investigated the presence of EBV in 142 cases of esophageal carcinoma, 107 cases of ampulla of Vater carcinoma, and 274 cases of colorectal carcinoma in Korean patients using EBV-encoded small RNAs (EBER)-in situ hybridization (ISH). In all cases, none of the tumor cells showed a positive signal, indicating that EBV is not generally related to the carcinogenesis of these cancers. Some EBV-positive tumor-infiltrating lymphocytes (TILs) were found in 8 of 142 cases (5.6%) of esophageal carcinoma, 8 of 107 cases (7.5%) of ampulla of Vater cancer, and 35 of 274 cases (12.8%) of colorectal carcinoma. For comparison, EBER-ISH was performed in consecutive gastric carcinomas; the EBER signal on tumor cells was observed in 17 of 306 cases (5.6%), and EBV-positive TILs were seen in 31 of the 289 cases (10.7%). There was no statistically significant difference in the frequencies of cases with EBV-positive TILs among the gastrointestinal tract cancers. We suggest that the reservoir lymphocytes carrying EBV, like other inflammatory cells, are able to reach anywhere, and that the chance for an epithelial cell to be exposed to EBV is similar at different sites of the gastrointestinal tract, regardless of its carcinogenic effect on the epithelial cell. HUM PATHOL 32:297-301.

Molecular technology and pancreatic cancer

BACKGROUND

Pancreatic cancer is the fifth leading cause of cancer death in the Western world. Despite improvement in operative mortality rates, little impact has been made on overall 5-year survival. This review discusses the molecular changes peculiar to pancreatic cancer and how the use of molecular technology might affect detection, screening, diagnosis and treatment of the disease.

METHODS

A literature review was performed using the National Library of Medicine's Pubmed database; this was combined with ongoing work within the Queen Elizabeth Hospital, Birmingham.

RESULTS

Over the past 20 years great strides have been made in our understanding of the molecular basis of disease. Advances in molecular biology are now reshaping how diseases are screened for, diagnosed, investigated and treated. In recent years collaboration between clinicians and basic scientists has revealed a unique pattern of genetic and molecular events in pancreatic cancer. This review discusses how these advances may impact on patients with this disease.

CONCLUSION

The past decade has seen some improvement in outlook for patients with pancreatic cancer, but the 'molecular age' promises to deliver even better results.

Novel non-operative treatment and treatment strategies in pancreatic cancer

Patients with advanced pancreatic cancer have traditionally been treated with palliative care only. The last decade has seen significant improvements in the surgical treatment of this disease but until the late 1990s there was no effective non-surgical treatment for these tumours. The introduction of gemcitabine has given clinicians treating patients with pancreatic cancer a new option. The published randomised data of gemcitabine in patients with pancreatic cancer has shown both a small survival advantage and significant improvements in quality of life indicators in these patients. These data have stimulated a resurgence of interest in pancreatic tumours and several studies have been or are currently investigating novel treatments or treatment strategies. The explosion in the molecular knowledge of cancer has led to the development of several 'molecular designer drugs' that have been tested in pancreatic cancer. The furthest advanced of these is a matrix metalloproteinase (MMP) inhibitor called marimastat. The first randomised data using this new class of agents is increasing and suggests that marimastat may have a role in the future treatment of patients with pancreatic cancer. Other agents such as gastrimmune, are about to enter Phase III studies and several other molecular treatment strategies are progressing from the in vitro stage towards the clinical arena. Each of these treatments and treatment regimens are discussed along with their current progress.

Mutated Ras peptides as vaccines in immunotherapy of cancer

Mutations in codon 12 and 13 of K-RAS are frequently found in human cancer, including pancreatic- and colorectal adenocarcinomas. T cell responses specific for individual RAS mutations can be elicited in vitro by stimulation with synthetic peptides and in vivo following vaccination with antigen presenting cells pulsed ex vivo with synthetic peptides. The peptide-responding T cells are capable of responding to intact p21 ras, and can recognise and kill tumour cell lines and isolated tumour cells harbouring the corresponding RAS mutation. The responding cells can be of both CD4+ and CD8+ phenotype, and these T cell subsets recognise nested epitopes within the vaccine peptides. Mutant ras peptides are therefore possibly an important vaccine for specific immunotherapy in patients with pancreatic and colorectal carcinomas, and are currently being tested in vivo together with GM-CSF as an adjuvant in these cancer patients.

Identification of a human CD8+ T lymphocyte neo-epitope created by a ras codon 12 mutation which is restricted by the HLA-A2 allele

Point mutations in the ras proto-oncogenes, notably at codon 12, are found in high frequency of human malignancies and, thus, may be appropriate targets for the induction of tumor-specific T cell responses in cancer immunotherapy. In this study, we examined the mutant ras protein sequence reflecting the substitution of Gly to Val at position 12 as a putative point-mutated determinant for potential induction of an HLA-A2-reactive, CD8+ cytotoxic T lymphocyte (CTL) response. We identified the ras 4-12(Val12) sequence as a minimal 9-mer peptide, which displayed specific binding to HLA-A2 by T2 bioassays. Peptide binding to HLA-A2 on T2 cells was weak and required coincubation with exogenous beta(2)-microglobulin to facilitate and enhance complex formation. In contrast, the wild-type ras 4-12(Gly12) peptide failed to bind to HLA-A2 even in the presence of beta(2)-microglobulin, consistent with the hypothesis that the point mutation creates a C-terminus anchor residue. A CD8+ CTL line against the ras 4-12(Val12) peptide was derived in vitro from a normal HLA-A2+ donor using a model culture system consisting of T2 cells as antigen presenting cells pulsed with exogenous mutant ras peptide and beta(2)-microglobulin plus cytokines (interleukin-2 and 12). Functional characterization of CD8+ CTL line revealed (1) peptide-specific and HLA-A2-restricted cytotoxicity against a panel of peptide-pulsed targets; (2) no specific lysis using the normal ras peptide sequence; (3) half-maximal lysis with exogenous peptide of approximately 0.3 microM; (4) lysis of HLA-A2+ B cell lines infected with a recombinant vaccinia virus construct encoding the point-mutated human K-ras gene; and (5) specific lysis of the HLA-A2+ SW480 colon carcinoma cell line expressing the naturally occurring K-ras Val12 mutation. Maximal lysis of SW480 cells occurred following interferon (IFN)-gamma pretreatment, which correlated with enhanced HLA-A2 and ICAM-1 (CD54) expression. Specificity of lysis was revealed by the absence of lysis against a HLA-A2+ melanoma cell line (+/- IFN-gamma), which lacked the mutant Val12 mutation, and the inability of an irrelevant CD8+ CTL line to lyse SW480 (+/- IFN-gamma) unless the appropriate exogenous peptide was added. These findings demonstrated that tumor cells may endogenously process and express mutant ras epitopes, such as the 4-12(Val12) sequence, albeit in limiting amounts that may be potentiated by IFN-gamma treatment. These data support the biological relevance of this sequence and, thus, may have important implications for the generation of ras oncogene-specific CTL responses in clinical situations.

Human tumor antigens recognized by T-cells

T-cells play an important role in in vivo tumor rejection in many animal tumor models and in human melanoma. Many human tumor antigens recognized by autologous T-cells have now been identified. These are found to be nonmutated and mutated peptides derived from various self proteins as well as viral proteins. A variety of mechanisms involved in generating these T-cell epitopes on growing cancers have also been identified. However, the role of these identified antigens remains to be evaluated. Passive or active immunotherapies using these identified tumor antigens are being conducted in many institutions. The results obtained from these clinical trials may give us better insight into the role of T-cell responses to each antigen in tumor rejection as well as the development of new antigen-specific immunotherapies for patients with cancer.

Prognostic value of tumour-infiltrating lymphocytes (TILs) in colorectal cancer

Clinical follow-up data of 276 colorectal adenocarcinoma patients treated in Kuopio University Hospital between 1976 and 1986 and followed up for a mean of 14 years were analysed. The clinical findings were correlated with tumour-infiltrating lymphocytes (TILs) and with histological and quantitative factors including nuclear parameters and volume-corrected mitotic index. In univariate survival analysis, TNM classification, Dukes' stage, histological grade, and TILs were significant predictors of survival. TNM classification, Dukes' stage, and TILs also predicted recurrence-free survival. In multivariate analysis, TILs were an independent prognostic factor of survival in all cases, as well as in patients with T1-4N0-3M0 and T1-4N1-3M1. TILs also independently predicted recurrence-free survival. TILs can provide important prognostic information in colorectal cancer to be used in evaluating for adjuvant therapy in different tumour stages.

A newly identified pattern of K-ras mutations at codons 12 and 13 is associated with long-term survival in colorectal cancer

BACKGROUND

Although K-ras mutations reportedly occur in 40% to 60% of all colorectal carcinomas, the relationship between specific mutations and clinical outcome is unclear. The purpose of this study was to assess the frequency and types of K-ras mutations in 89 colorectal cancer patients, comparing groups with short-term (less than 5 years) and long-term (more than 10 years) survival.

METHODS

The group was divided into four cohorts by survival and modified Dukes classification (Dukes B2 and C2). DNA was extracted from formalin-fixed paraffin-embedded archival material. Mutational status was analyzed using a modification of allele-specific-polymerase chain reaction.

RESULTS

Mutations in codon 12 were found in 11.2% of tumors, and 83% of tumors had mutations in codon 13. Gly > Asp accounted for 85.2% of the mutations. Tumors with mutations in both codon 12 and codon 13 occurred significantly more frequently in the long-term (21.3%) versus the short-term (2.4%) survival group. Gly > Asp mutations in either codon were related to long-term survival, and 80% of long-term survivors with mutations in both codons had Gly > Asp mutations in both.

CONCLUSIONS

Simultaneous mutation in codons 12 and 13 of the K-ras gene appears to be a positive prognostic indicator in colorectal cancer.

Serological identification of human tumor antigens

Using the antibody repertoire of cancer patients for the systematic search for human tumor antigens, a plenitude of new human tumor antigens has been identified demonstrating that many human tumors elicit multiple immune responses in the autologous host. The abundance of serologically defined human tumor antigens facilitates the identification of T cell dependent antigens and provides a basis for peptide and gene therapy vaccine strategies in a wide variety of human cancers.

Cytotoxic CD4+ and CD8+ T lymphocytes, generated by mutant p21-ras (12Val) peptide vaccination of a patient, recognize 12Val-dependent nested epitopes present within the vaccine peptide and kill autologous tumour cells carrying this mutation

Mutant p21-ras proteins contain sequences that distinguish them from normal ras, and represent unique epitopes for T-cell recognition of antigen-bearing tumour cells. Here, we examined the capacity of CD4+ and CD8+ T cells, generated simultaneously by mutant-ras-peptide vaccination of a pancreatic-adenocarcinoma patient, to recognize and lyse autologous tumour cells harbouring corresponding activated K-ras epitopes. The patient was vaccinated with a purified 17mer ras peptide (KLVVVGAVGVGKSALTI), containing the Gly12 --> Val substitution. Responding T cells were cloned following peptide stimulation, and CD4+ and CD8+ peptide-specific cytotoxic T lymphocytes(CTL) were obtained. Transient pancreatic-adenocarcinoma cell lines(CPE) were established in cell culture from malignant ascites of the patient, and were shown to harbour the same K-ras mutation as found in the primary tumour. These cells were efficiently killed by the T-cell clones and CD8+-mediated cytotoxicity was HLA-class-I-restricted, as demonstrated by inhibition of lysis by anti-class-I monoclonal antibodies. By employing as targets different class-I-matched tumour cell lines expressing a 12Val mutation, we were able to demonstrate HLA-B35 as the restriction molecule, and further use of peptide-sensitized EBV-B cells as target cells identified VVVGAVGVG as the nonamer peptide responsible for CD8+-T-cell recognition. These data demonstrate that peptide vaccination with a single mutant p21-ras-derived peptide induces CD4+ and CD8+ CTL specific for nested epitopes, including the Gly --> Val substitution at codon 12, and that both these T-cell sub-sets specifically recognize tumour cells harbouring the corresponding K-ras mutation.

Prognostic value of tumour-infiltrating lymphocytes (TILs) in colorectal cancer

Clinical follow-up data of 276 colorectal adenocarcinoma patients treated in Kuopio University Hospital between 1976 and 1986 and followed up for a mean of 14 years were analysed. The clinical findings were correlated with tumour-infiltrating lymphocytes (TILs) and with histological and quantitative factors including nuclear parameters and volume-corrected mitotic index. In univariate survival analysis, TNM classification, Dukes' stage, histological grade, and TILs were significant predictors of survival. TNM classification, Dukes' stage, and TILs also predicted recurrence-free survival. In multivariate analysis, TILs were an independent prognostic factor of survival in all cases, as well as in patients with T1-4N0-3M0 and T1-4N1-3M1. TILs also independently predicted recurrence-free survival. TILs can provide important prognostic information in colorectal cancer to be used in evaluating for adjuvant therapy in different tumour stages.

Differential binding to frequent HLA-A alleles of p21 RAS derived peptides bearing oncogenic substitutions at position 12 or 13

RAS oncogenic proteins are frequently found mutated in human cancers, where they are known to be implicated in the tumoral process. Mutations occur preferentially at positions 12, 13 or 61. Identification of potential T cell epitopes is the first step to determine it RAS mutated proteins can generate tumor specific antigens which could be further used as targets for cancer immunotherapy protocols. We have investigated the capacity of synthetic wild-type and mutant RAS derived peptides encompassing positions 12 and 13 to bind to three frequent HLA-A alleles: HLA-A*0201, HLA-A*0301 and HLA-A*1101. Binding was evaluated by two methods using TAP-defective cell lines: a cytometric assay based on HLA molecules stabilization at the cell surface, and an assembly assay detecting interactions between solubilized HLA molecules and peptides. Positive HLA binding was observed for two sets of synthetic peptides, one specific for HLA-A*0201 allele (RAS 5-14), and the other one specific for HLA-A*0301 and HLA-A*1101 alleles (RAS 8-16). Interestingly, the different substitutions at positions 12 and 13 were not equivalent for HLA binding. These observations will be useful for the in vitro generation of restricted CD8+ T lymphocytes specific for mutated RAS proteins and recognizing tumoral cells expressing such RAS mutations.

Cytotoxic T-cell clone against rectal carcinoma induced by stimulation of a patient's peripheral blood mononuclear cells with autologous cultured tumor cells

In an effort to establish cytolytic T lymphocytes (CTLs) against colorectal carcinoma (CRC) by stimulating patients' lymphocytes with autologous tumor cells, we used peripheral blood mononuclear cells (PBMC) from a patient with minimal residual rectal carcinoma following removal of the primary lesion and involved regional lymph nodes as a source to generate CTLs in culture. A CTL line and clone were established from the patient's PBMC following stimulation of PBMC with autologous, cultured tumor cells and interleukin-2. The CTL line and the clone consisted predominantly of CD4+ lymphocytes. The CTL clone expressed two T-cell receptor variable alpha chains (V alpha11 and V alpha22) and one beta chain (Vbeta14). The cytokine secretion pattern of the CTL line was of the Th1-type. Both the CTL line and the clone lysed the autologous rectal carcinoma cells, but not the allogeneic, partially human lymphocyte antigen (HLA)-matched or nonmatched CRC cells, autologous Epstein-Barr virus-transformed B cells, K562 (natural killer target) cells or Daudi (lymphokine-activated killer target) cells. Lysis of autologous tumor cells most likely was HLA class I-restricted. Our unique success in generating CTLs against this tumor type may rest in the inclusion of a patient with minimal residual, rather than advanced, disease.

Augmentation of immune response by an analog of the antigenic peptide in a human T-cell clone recognizing mutated Ras-derived peptides

T-cells that recognize mutated p21 Ras are relevant to immune surveillance systems against cancer. We report here evidence that immune responses of a T-cell clone recognizing mutated p21 Ras can be augmented by an analog peptide. Using spleen cells from a gastric cancer patient, we established the CD4+ alpha beta Th1-like clone C27 that recognizes wild-type (3EYKLVVVGAGGVGKS17) and mutated p21 Ras protein molecules and peptides, in an HLA-DR1-restricted manner. C27 responded prominently to mutated Ras peptides carrying Val or Ala at position 12, as compared to wild-type and other mutated peptides. C27 also exhibited a much stronger response to a mutated p21 Ras whole-protein molecule-carrying Val at position 12, as compared with the wild-type protein. The proliferative response and production of GM-CSF, TNF-alpha, and IFN-gamma by C27 were further augmented by replacing the possible first DR anchor 4Tyr of the mutated Ras peptide with Trp, a more potent anchor residue for the DR1 molecule. Enhancement of peptide antigenicity by substituting the HLA anchor residue of an antigenic peptide recognized by tumor-reactive T-cells may prove to be a novel strategy for antigen-specific cancer immunotherapy.

Characterisation of immune responses in pancreatic carcinoma patients after mutant p21 ras peptide vaccination

This is a study of immune responses generated by mutant ras peptide vaccination of patients with pancreatic adenocarcinoma. Responding T cells from one patient were cloned and two CD4+ T-lymphocyte clones (TLC) specific for the 12 Val peptide and restricted by HLA-DR6 or DQ2 were obtained. These class II molecules have not previously been found to bind or present mutant ras peptides to T cells. The DR6-restricted TLC showed marked cytotoxicity against autologous target cells pulsed with the 12 Val peptide. Target cells pulsed with the control peptide were not killed. Responding T cells from another patient showed cross-reactivity towards the homologous ras peptides. Investigation by limiting dilution analysis (LDA) revealed different T-cell precursor frequencies for the immunising, mutant ras peptide (1:28000), compared with the normal ras peptide (1:110000).

Cytotoxic T-lymphocyte responses against mutated p21 ras peptides: an analysis of specific T-cell-receptor gene usage

Generation of cytotoxic-T-lymphocyte (CTL) responses against mutated ras peptides from peripheral-blood mononuclear cells (PBMC) was attempted in a group of HLA-A2.1+ healthy donors. Bulk PBMC cultures were stimulated in vitro with a mixture of peptides encompassing 12 Gly --> Val, 61 Gln --> Lys or 61 Gln --> Leu ras mutations and displaying HLA-A2.1 binding motifs, selected by a computer program. A promiscuous tetanus toxoid peptide was also added. Weekly thereafter, PBMC were re-stimulated with peptide pulsed autologous Epstein-Barr virus (EBV)-transformed B cells. After 8 rounds of re-stimulation, reproducible cytotoxic activity against peptide-pulsed target cells was detectable in one donor. The CTL line recognized 2 nonamers encompassing ras 61 Gln --> Leu mutation. Killing was mediated by CD8+ T cells displaying alphabeta TCR and was inhibited by anti-HLA-A2.1 monoclonal antibodies. No killing of tumor cells expressing the specific mutation could be observed. More than 60 CTL clones were generated. Fine specificity studies revealed effective, though differing cytotoxic activity against both 53-LDILDTAGL-61 and 55-ILDTAGLEE-63, but not against 54-DILDTAGLE-62 mutated peptides, in all but one of the clones. None was able to exert effective cytotoxic activity against tumor cells expressing the specific mutation. T-cell-receptor (TCR) usage was then analyzed phenotypically, by reverse-transcription-polymerase-chain-reaction (RT-PCR) and by sequence analysis. This study revealed the monoclonal nature of the CTL response against mutated nonamers, with TCR expressing Vbeta14 gene product in combination with, Jbeta2.7 and Cbeta2.

K-ras mutations and HLA-DR expression in large bowel adenomas

A total of 72 sporadic colorectal adenomas in 56 patients were studied for the presence of point mutations in codons 12 and 13 of the K-ras gene and for HLA-DR antigen expression related to clinicopathological variables. Forty K-ras mutations in 39 adenomas were found (54%): 31 (77%) in codon 12 and nine (23%) in codon 13. There was a strong relationship between the incidence of K-ras mutations and adenoma type, degree of dysplasia and sex. The highest frequency of K-ras mutations was seen in large adenomas of the villous type with high-grade dysplasia. Fourteen out of 15 adenomas obtained from 14 women above 65 years of age carried mutations. HLA-DR positivity was found in 38% of the adenomas, large tumours and those with high-grade dysplasia having the strongest staining. Coexpression of K-ras mutations and HLA-DR was found significantly more frequently in large and highly dysplastic adenomas, although two-way analysis of variance showing size and grade of dysplasia to be the most important variable. None of the adenomas with low-grade dysplasia showed both K-ras mutation and HLA-DR positivity (P = 0.004). K-ras mutation is recognised as an early event in colorectal carcinogenesis. The mutation might give rise to peptides that may be presented on the tumour cell surface by class II molecules, and thereby induce immune responses against neoplastic cells.

Binding of mutated Ras- and p53-derived peptides to HLA-DR molecules

We investigated binding of p53- and Ras-derived peptides with frequently observed missense mutations, to various L cell transfectants expressing a single species of HLA-DR complex, and found that: (i) all the synthetic peptides bound to various DR complexes with a variable affinity; (ii) some DR allelic products had a high affinity for both p53- and Ras-derived peptides (e.g., DRB1*1502), whereas others almost no affinity (e.g., DRB1*1101); and (iii) DR-binding motifs described in the literature can explain some of the allele-specific interactions between mutated peptides and DR complexes. Therefore, some mutated Ras- and p53-derived peptides could be tumor-specific antigens recognized by CD4+ T cells in an HLA-DR allele-specific manner.

Ex vivo ras peptide vaccination in patients with advanced pancreatic cancer: results of a phase I/II study

In a pilot I/II study we have tested synthetic ras peptides used as a cancer vaccine in 5 patients with advanced pancreatic carcinoma. The treatment principle used was based on loading professional antigen-presenting cells (APCs) from peripheral blood with a synthetic ras peptide corresponding to the ras mutation found in tumour tissue from the patient. Peptide loading was performed ex vivo and the next day APCs were re-injected into the patients after washing to remove unbound peptide. Patients were vaccinated in the first and second week and thereafter every 4-6 weeks. In 2 of the 5 patients treated, an immune response against the immunising ras peptide could be induced. None of the patients showed evidence of a T-cell response against any of the ras peptides before vaccination. The treatment was well tolerated and could be repeated multiple times in the same patient. Side effects were not observed even if an immunological response against the ras peptide was evident. We conclude that ras peptide vaccination according to the present protocol is safe and may result in a potentially beneficial immune response even in patients with advanced malignant disease.

Vaccination with mutant ras peptides and induction of T-cell responsiveness in pancreatic carcinoma patients carrying the corresponding RAS mutation

Mutations in codon 12 of K-RAS are frequently found in pancreatic adenocarcinomas. T-cell responses specific for individual RAS mutations can be elicited in vitro by stimulation of peripheral blood mononuclear cells with synthetic peptides. Mutant ras peptides are therefore a candidate vaccine for specific immunotherapy in pancreatic carcinoma patients. When vaccinated with a synthetic ras peptide representing the K-RAS mutation in their tumours, a transient ras-specific T-cell response was induced in two of five patients treated. The vaccination protocol involved multiple infusions of large amounts of peptide-pulsed antigen-presenting-cells obtained by leucapheresis. These results indicate that specific T-cell responses against mutations uniquely harboured in tumour cells can be induced in cancer patients by vaccination.