The functional role and specificity of tumor infiltrating lymphocytes (TIL) is generally not well characterized. Prominent lymphocyte infiltration is the hallmark of the most common form of hereditary colon cancer, hereditary nonpolyposis colon cancer (HNPCC) and the corresponding spontaneous colon cancers with the microsatellite instability (MSI) phenotype. These cancers are caused by inherited or acquired defects in the DNA mismatch-repair machinery. The molecular mechanism behind the MSI phenotype provides a clue to understanding the lymphocyte reaction by allowing reliable prediction of potential T cell epitopes created by frameshift mutations in candidate genes carrying nucleotide repeat sequences, such as TGF␤RII and BAX. These tumors therefore represent an interesting human system for studying TIL and characterizing tumor-specific T cells. We here describe T cell reactivity against several T helper cell epitopes, representing a common frameshift mutation in TGF␤RII, in TIL and peripheral blood lymphocytes from patients with MSI ؉ tumors. The peptide SLVRLSSCVPVALMSAMTTSSSQ was recognized by T cells from two of three patients with spontaneous MSI ؉ colon cancers and from all three patients with HNPCC. Because such mutations are present in 90% of cancers within this patient group, these newly characterized epitopes provide attractive targets for cancer vaccines, including a prophylactic vaccine for individuals carrying a genetic disposition for developing HNPCC.

No abstract

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 ؉ peptidespecific 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 HLAclass-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. Int.

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. Int. J. Cancer 72:784–790, 1997. © 1997 Wiley‐Liss, Inc.