INDUCTION OF METALLOTHIONEIN SYNTHESIS IN TRANSPLANTED MURINE TUMORS BY X-IRRADIATION

Although recent studies have shown that radiation can induce metalloth ionein (MT) synthesis in normal tissues, the induction of tumor MT syn thesis by irradiation has not been reported. We examined the accumulat ion of MT in the Meth-A tumor (mouse fibrosarcoma cells) transplanted into mice exposed to whole-body X irradiation. In the present study, t he MT content in the tumor cells was increased by X irradiation in a d ose-dependent manner. The MT level induced in the tumor cells by X irr adiation was elevated not only after a single exposure but also after repeated exposures. Several studies have shown that MT is one of the i mportant cellular factors in resistance to various anticancer drugs an d ionizing radiation. Thus our results suggest that the radiation-indu ced MT in the tumor cells may have to be taken into consideration when designing protocols for radio- and chemotherapy. (C) 1995 by Radiatio n Research Society