BCG (bacille Calmette-Guérin)-activated lymphocytes (BAK cells) induce apoptosis in urinary bladder carcinoma cell line T24 in vitro

Abstract

Background. We previously reported the basic characteristics of BCG (bacille Calmette-Guerin)-activated killer (BAK) cells, which exhibited antitumor effects against the bladder cancer cell line T24. Our study suggested that both BCG and BAK cells were responsible for the inhibition of tumor cell proliferation; however, the basic mechanism of BCG or BAK cells in this inhibition was not clear. We here report the antitumor effects of BAK cells, which correlated with the induction of apoptosis in T24 cells. Methods. Lymphocytes were cultured with BCG to examine 3H-thymidine uptake, and the subpopulation was evaluated by immunocytometry. T24 cells were then cultured with BAK cells for the analysis of 3H-thymidine uptake and apoptosis induction by DNA electrophoresis; pathology study, and cell-cycle analysis were also done. Culture supernatants of BAK and T24 cells were also investigated to detect interferon-γ (IFN-γ), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α). Results. The 3H-thymidine uptake study of lymphocytes showed that BCG activated the lymphocytes. Evaluation by immunocytometry revealed that CD4+ and CD8+ T cells were induced by BCG. The 3H-thymidine uptake study of T24 cells revealed that BAK cells inhibited tumor cell proliferation. DNA electrophoresis, the morphological study, and cell-cycle analysis by immunocytometry demonstrated that apoptosis in T24 cells was induced when they were cultured with BAK cells. IFN-γ, IL-6, and TNF-α were detected in the culture supernatants of BAK and T24 cells. Conclusions. Cytokine production and the induction of apoptosis may, together, be the major mechanisms of the antitumor action seen when BAK cells were employed against T24 cells; BAK cells could be employed as clinical effectors against bladder cancer.