Significance of Cytotoxic Activity of Peripheral Blood Lymphocytes against Autologous Tumor Cells in Patients with Bladder Cancer

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Abstract
Cell-mediated immunity is an important and central mechanism of host resistance to cancer. Most reported studies have used cultured tumor cell lines as targets to assess antitumor cell-mediated cytotoxicity. However, it is difficult to translate the data generated from the cytotoxic activity against cultured tumor cell lines to cytotoxicity against autologous tumors. In a recent study, we have reported on the prognostic significance of circulating cytotoxic lymphocytes against autologous tumor cells in patients with bladder cancer. In this study, we examined whether established bladder cancer cell line like T24 or NK-sensitive K562 target cells can be substituted for autologous bladder cancer cells. The cytotoxic activity of peripheral blood lymphocytes (PBL) against freshly isolated autologous tumor cells, the T24 human bladder cancer cell line and the NK-sensitive K562 human myelogenous leukemia cell line was studied in 63 patients with primary initial bladder cancer by a 12-h 51Cr release assay. The mean percent cytotoxic activity of PBL directed against autologous tumor cells, T24 cells and K562 cells were 11.3%, 18.2% and 29.4%, respectively, using an E.T of 40:1. The cytotoxic activity against T24 cells in patients with bladder cancer was higher than that in normal individuals. The anti-K562 and the anti-T24 cytotoxic activities in patients with low-stage or low-grade bladder cancer were relatively higher than those in patients with high-stage or high-grade cancer, but not statistically significant. There was no correlation between the anti-autologous tumor cytotoxic activity and either the histologie grade or stage in patients with bladder cancer. The extent of the anti-autologous tumor cytotoxic activity was not paralleled with that of either the anti-K562 or the anti-T24 cytotoxic activity. In contrast, the anti-K562 cytotoxic activity correlated positively with the anti-T24 cytotoxic activity. Separation of PBL revealed that the anti-K562 and the anti-T24 cytotoxic activities were mediated mainly by the NK cells, whereas the anti-autologous tumor cytotoxic activity was mediated by both the NK cells and the T lymphocytes. These findings demonstrate that cytotoxicity against T24 or K562 cells is not of prognostic value. The magnitude of the anti-autologous tumor cytotoxic activity of PBL derived from bladder cancer patients might represent an independent and important immunological parameter to monitor disease progression.

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