Differential Loss of T Cell Signaling Molecules in Metastatic Melanoma Patients’ T Lymphocyte Subsets Expressing Distinct TCR Variable Regions

In this study we tested the hypothesis that loss of T cell signaling molecules in metastatic melanoma patients’ T cells may affect differently T cell subsets characterized by distinct TCR variable regions. By a two-color immunofluorescence technique, expression of ζ-chain, lck , and ZAP-70 was evaluated in CD3 + T cells and in three representative T cell subsets expressing TCRAV2, TCRBV2, or TCRBV18. Partial loss of lck and ZAP-70 was found in CD3 + T cells from PBL of most melanoma patients, but not of healthy donors. The extent of ζ-chain, lck, and ZAP-70 loss depended on the TCRV region expressed by the T cells, and this association was maintained or increased during progression of disease. Coculture of patients’ or donors’ T cell with melanoma cells, or with their supernatants, but not with normal fibroblasts or their supernatants, down-modulated expression of ζ-chain, lck, and ZAP-70 in a TCRV region-dependent way. Immunodepletion of soluble HLA class I molecules present in tumor supernatants, but not of soluble ICAM-1, blocked the suppressive effect on T cell signaling molecule expression. T cell activation with mAbs to a single TCRV region and to CD28 led to significant and TCRV region-specific re-induction of ζ-chain expression. These findings indicate that extent of TCR signaling molecules loss in T lymphocytes from metastatic melanoma patients depends on the TCRV region and suggest that tumor-derived HLA class I molecules may contribute to induce such alterations.