Purpose: Previous studies indicated that cancer patients lack functional anti-tumor cytotoxic lymphocytes. However, anti-tumor cytotoxic lymphocytes may coexist with immunoresistant tumor cells. We reasoned that anti-tumor cytotoxic activity of lymphocytes may be revealed if the tumor cells are sensitized to killing. It has been reported that adriamycin (ADR) exhibits various immunomodulating activities. In the present study, we investigate the effect of ADR on the susceptibility of freshly isolated bladder cancer cells to lysis by autologous non-activated peripheral blood lymphocytes (PBL) and tumor infiltrating lymphocytes (TIL).
Materials and methods: Cytotoxicity was determined by a 1-day microculture tetrazolium dye assay.
Results: Treatment of ADR-resistant fresh bladder cancer cells with ADR at 0.1 microg./ml. or more for 3 hours or more enhanced their susceptibility to lysis by autologous PBL. This ADR-induced enhancement of susceptibility of fresh bladder cancer cells to lysis by PBL was also observed when lymphokine activated killer cells, purified natural killer cells and T lymphocytes were used as effector cells. Furthermore, while cytotoxicity of freshly derived TIL against autologous bladder cancer cells was minimal, significant cytotoxicity was observed with ADR-treated bladder cancer cells. The ADR analogs, epirubicin and pirarubicin, also enhanced the susceptibility of bladder cancer cells to lysis by autologous PBL. Treatment of bladder cancer cells with ADR had no effect on the expression of MHC class I on the cancer cells or the frequency of bladder cancer target cell conjugates to autologous PBL. Treatment of bladder cancer cells with ADR augmented their sensitivity to anti-Fas monoclonal antibody and tumor necrosis factor-a. Pretreatment of effector cells with ADR had no effect on their cytotoxic function.
Conclusions: These findings demonstrate that PBL and TIL in patients with bladder cancer exhibit anti-tumor cytotoxic function, but their function is not manifested due to development or acquisition of tumor cell resistance to killing. However, the resistance of bladder cancer cells to killing by cytotoxic lymphocytes is overcome if cancer cells are sensitized by subtoxic concentrations of ADR. These findings suggest that treatment of bladder cancer patients with low doses of ADR may sensitize the cancer cells to killing by autologous circulating and tumor infiltrating lymphocytes and may be a novel immunotherapeutic modality for the treatment of drug-resistant and/or immune-resistant bladder cancer.