T cell responses in colorectal cancer patients: evidence for class II HLA-restricted recognition of shared tumor-associated antigens.

Few cases of anti-colon cancer specific T lymphocytes have been described so far. Moreover, the majority of these effectors were generated in vitro by stimulating PBMC from patients or healthy donors with peptides that were derived from proteins expressed and/or secreted by colon cancer tissue such as CEA, Mucin or Her-2/neu. The aim of our study was to evaluate the immunogenicity of colorectal carcinomas in an autologous setting. We exploited the antigen processing and presentation capacity of dendritic cells (DC) to establish an in vitro autologous system that can bypass the need of obtaining cultured tumor cells. DC were generated from the adherent monocyte fraction of PBMC taken from stage II/III colorectal cancer patients. A single cell suspension was prepared by mechanical and enzymatic disruption of the surgical specimens immediately after resection. DC were loaded with autologous tumor lysate, obtained by repeated freezing and thawing, before being used as stimulators for autologous PBL. HLA-class II restricted T cells that recognize the autologous tumor could be generated in a proportion of patients. The fine specificity of the anti-tumor T cells indicates that differentiation as well as tumor restricted antigens are expressed in colon cancer and that these antigens can evoke a class II HLA-restricted response in an autologous setting. Altogether these findings may open a new perspective for a DC based vaccination of colon cancer patients.

Which kinds of lymph node metastases can FDG PET detect? A clinical study in melanoma.

UNLABELLED: The purposes of this study were to establish the diagnostic accuracy of FDG PET for lymph node metastases and to determine the smallest detectable volume of disease. METHODS: Using FDG PET, we preoperatively studied 56 lymph node basins in 38 patients with a clinical or instrumental diagnosis of lymph node metastases from melanoma. All lymph node basins underwent node dissection. The FDG PET results were compared with the postoperative histopathology results. PET images were obtained using a GE 4096 WB scanner, after injection of a mean activity of 496 MBq (range, 366-699 MBq) of FDG. RESULTS: The efficacy of FDG PET in the diagnosis of involved lymph node basins was good. Sensitivity was 95% (35/37); specificity, 84% (16/19); accuracy, 91% (51/56); positive predictive value, 92% (35/38); and negative predicative value, 89% (16/18). Metastases were shown histologically in 114 of 647 surgically removed lymph nodes. FDG PET detected 100% of metastases > or = 10 mm, 83% of metastases 6-10 mm, and 23% of metastases < or = 5 mm. Moreover, FDG PET had high sensitivity (> or = 93%) only for metastases with more than 50% lymph node involvement or with capsular infiltration. CONCLUSION: Our study shows that FDG PET has a reasonable sensitivity and specificity for detecting the presence or absence of lymph node metastases in patients with melanoma. However, even if able to detect small volumes of subclinical macroscopic disease, FDG PET cannot detect subclinical microscopic disease with acceptable sensitivity. The specificity of FDG PET is good, but some false-positive results may occur.

Novel HLA-Cw8-restricted T cell epitopes derived from tyrosinase-related protein-2 and gp100 melanoma antigens.

The identification of T cell epitopes presented by alternative HLA-B and -C alleles may provide a means to counteract the tumor escape mechanism based on the selection of tumor cells no longer susceptible to HLA-A-restricted T cell recognition. Several T cell clones and lines were obtained from T lymphocytes purified from melanoma-infiltrated or noninfiltrated lymph nodes of a patient who remained disease free 8 yr after surgery. Selected T cells recognized the autologous melanoma as evaluated by direct cytolysis and production of cytokines. These effectors were directed against the tyrosinase-related protein-2 (TRP-2) and gp100 melanoma epitopes restricted by HLA-Cw8. The nonamer and decamer peptides containing the sequence ANDPIFVVL (residues 387-395) of TRP-2 and the octamer, nonamer, and decamer peptides containing the sequence SNDGPTLI (residues 71-78) of gp100 reconstituted the epitope for TRP-2- and gp100-specific T cell lines and clones, respectively. However, only the nonameric form of TRP-2 and the nonameric and octameric forms of gp100 were able to induce peptide-specific T cells recognizing the autologous tumor in an HLA-class I-restricted fashion from PBMC of the melanoma patient studied. Together these data indicate that HLA-Cw8 can restrict the recognition of gp100 and TRP-2 epitopes by CTL, and that such peptides could stimulate a patient's PBL, suggesting that these Ags could have contributed to a systemic immunity against melanoma.