Effect of irradiation of renal cell carcinoma (RCC) cell lines on RCC tumor-associated antigen (TAA) specific CD8+ T-cell stimulation.

Abstract

542 Background: Radiation increases the immunogenicity of many cancers. We have previously shown increased immunogenicity of RCC with cell line irradiation. Herein, we describe the effect of irradiation of RCC cell lines on the expression of TAAs as well as several molecules involved in CD8+ T Cell (CTL) mediated tumor cytotoxicty and the in vitro effect of tumor irradiation on NY-ESO-1 specific CTL clones. Methods: Six RCC cell lines (ACHN, 786-0, 769-P, Caki-1, A-498, A-704) were cultured and exposed to 0, 12 or 16 Gy of ionizing radiation. Cells were isolated at 2, 24 and 48 hours after irradiation. Expression of cell surface molecules (CD95, CD54, Calreticulin, NYESO-1, CA-9, 5T4, MUC-1 and HSP-70) was assessed using multi-color flow cytometry. Results are reported as mean relative increase from control (dose 0 Gy, time 2 hours post irradiation). In a second experiment, NY-ESO-1 specific CTL clones were cultured in the presence of A-498 cells that were subjected to radiation under the above noted conditions and assessed using an ELISPOT assay. Negative control consisted of only CD8+ T Cells. Results: The ELISPOT experiment demonstrated stimulation of NY-ESO-1-specific CTL by irradiated A-498 cells. Negative control showed no stimulation, with only 4 spots. An increase in spots was observed from 79 and 82 spots at 2 hours post-irradiation to 166 and 205 spots at 48 hours post-irradiation for 0 Gy and 16 Gy, respectively. Conclusions: Sublethal irradiation of human RCC cell lines increases their immunogenicity, provoking TAA-specific T cell stimulation. [Table: see text]