SENSITIVITY TO RADIATION TREATMENT AND CHANGES IN METALLOTHIONEIN SYNTHESIS IN A TRANSPLANTED MURINE TUMOR

A protective role for metallothionein (MT) in cellular injury caused b y ionizing radiation has been proposed, To elucidate the role of MT in the sensitivity of tumors to radiation, we examined the effectiveness of radiation treatment of tumors with altered synthesis of MT after i njection of tumor-bearing mice with zinc and/or propargyl glycine (PPG ). The mice were inoculated with Meth-A fibrosarcoma cells and the ant itumor activity of X radiation was tested in mice with and without ind uced synthesis of MT. Exposure to X radiation decreased the tumor weig ht markedly. In mice pretreated with zinc to induce MT, the tumor weig ht did not change compared to the controls. However, injection of PPG, an inhibitor of cystathionase, decreased the zinc-induced MT synthesi s in the tumors and also decreased the tumor weight after exposure to X radiation. These results suggest that in radiation therapy one of th e factors involved in radiosensitivity may be the expression of MT in certain tumors. (C) 1997 bg Radiation Research Society.