GAMMA-RAY IRRADIATION INDUCES B7.1 COSTIMULATORY MOLECULE NEOEXPRESSION IN VARIOUS MURINE TUMOR-CELLS

The use of gene-modified tumor cells as a strategy for active immunoth erapy is currently undergoing intensive fundamental and clinical resea rch. Most clinical trials use gamma-ray-irradiated tumor cells as vacc ine, although little is known about the effects of irradiation on the immunogenicity of tumor cells. In particular, no data have been report ed so far concerning the effects of gamma-ray irradiation on the expre ssion of B7 molecules in tumor cells. In this paper, we show a neoexpr ession of the B7.1 molecule after gamma-ray irradiation in tumor cell lines from different tissues, while the B7.2 molecule remains unexpres sed in all the cell lines tested. Furthermore, the induction of B7.1 m olecule membrane expression after irradiation is shown to result from the neoexpression of B7.1 mRNA, and to be reproduced with H2O2 oxidati ve stress. These data could explain the enhanced immunogenicity of man y tumor cells after irradiation, and could lead to new immunotherapy p rotocols.