Secretion of a soluble T cell promoting factor by the human prostate adenocarcinoma cell line DU-145

Introduction: A variety of cancers suppress host immune defenses by secreti on of soluble factors. Conditioned media (CM) from numerous cancer cell lin es possess the ability to suppress proliferation of activated T cells. The effects of CM from the prostate cancer cell line DU-145 on T cell activatio n was investigated. Materials and Methods: Human PBMC, purified T cells and Jurkat T cells were treated with DU-145 CM Proliferation, cell cycle, apop tosis, Fas expression/and cytokine secretion were assessed by thymidine inc orporation, flow cytometry and ELISA. Results: DU-145 CM increased prolifer ation of concanavalin-tl (Cowl) activated peripheral blood mononuclear cell s (PBMC) increasing the percentage of cells in the S/G(2) phase of cell cyc le. Treatment of the Jurkat T cell line with DU-145 CM induced a potent pro liferative response. ConA-induced proliferation of purified T cells from hu man PBMC and murine splenocytes was augmented in a dose-dependent manner by addition of DU- 145 CM. DU- 145 CM treatment of ConA-activated T cells ind uced an increase in interleukin-2 (IL-2) production. The soluble factor(s) responsible for promoting T cell proliferation was dependent on protein syn thesis by the DU- 145 cells and possessed a molecular weight greater than 1 0 kDa. Conclusion: DU-145 cells secrete a soluble factor(s) >10 kDa, whose production is dependent on protein synthesis and which acts as a promoter o f T cell activation.