Lesion-Specific Activation of Cloned Human Tumor-Infiltrating Lymphocytes by Autologous Tumor Cells: Induction of Proliferation and Cytokine Production

Abstract

To investigate the mechanisms by which tumor-infiltrating lymphocytes exert their antitumor effects, tumor-specific tumor-infiltrating lymphocyte clones, as well as autologous tumor cell lines from primary and secondary tumors of two patients during the course of melanoma progression were established. Enrichment for tumor-infiltrating lymphocytes expressing CD25, as well as low concentrations of interleukin-2 (30 IU/ml) in the culture medium, led to a preferential outgrowth of cells that express the high-affinity interleukin-2 receptor. All of these expressed CD2, CD3, CD11, and CD25. Coculture of tumor-infiltrating lymphocyte clones with irradiated, autologous tumor cells induced an up to 480% greater proliferative responses than recombinant interleukin-2 alone. Approximately 60% of the tumor-infiltrating lymphocyte clones showed cytotoxicity against the relevant tumor in a 4-h 51Cr-release assay. When tested in an 18-h 51Cr-release assay, the number of tumor-infiltrating lymphocyte clones exhibiting cytotoxicity against the relevant tumor increased to over 85%. In response to autologous tumor cells, nine of 15 clones secreted interferon-gamma, tumor necrosis factor-alpha, or both. Cytokine production was not restricted to either CD4+ or CD8+ T cells because both CD4+ and CD8+ tumor-infiltrating lymphocyte clones secreted cytokines. Tumor-infiltrating lymphocyte tumor interaction appears to be lesion specific because induction of proliferation and cytokine production, as well as susceptibility to cytolysis, was found not only restricted to the autologous system, but also to the specific lesion. The pattern of tumor-infiltrating lymphocyte tumor interaction specificity indicates a possible loss of antigens expressed on the tumor during disease progression.