Mechanisms of thiol mediated modulation of radiation induced apoptosis in lymphoma cells

Research project P 13811 Radiation induced apoptosis in lymphoma cells Reinhard KODYM 28.06.1999 From the radiotherapeutic point of view apoptosis or programmed cell death is an fascinating modality of radiation induced cell kill. Its partially characterized signal transduction pathways offer the possibility of intervention aiming at the increase of tumor cell radiosensitivity and at the reduction of the sensitivity of normal cells to ionizing radiation. It has been reported by several research groups that depleting lymphoid cells of thiols leads to an increase in radiosensitivity caused by a greater susceptibility to radiation induced apoptosis. These findings are especially interesting as the thiol depletion increases the apoptotic propensity of these cells despite the overexpression of well known anti-apoptotic proteins like Bcl-2. Until now it is not clear which cellular thiol is responsible for the observed modulation of the susceptibility of lymphoma cell to radiation induced apoptosis and it is unknown which mechanism leads to this phenomenon. It is therefore the aim of the proposed project to identify the relevant cellular thiol and to elucidate its mechanism of action. To achieve this goal lymphoma cells will be treated with several thiol modifying agents. Some of these are known to influence the apoptotic propensity of the cells while others do not. Thereafter the changes, induced in the mRNA expression pattern will be detected by differential display PCR. From the proteins, the mRNAs of which are up or downregulated in response to treatment with thiol modifying agents, it can be concluded which metabolic pathways are involved in the modulation of the apoptotic propensity. Once candidates for the pathways and for the involved enzymes have been found these will be verified and further investigated by transfection experiments and by the use of pharmacological inhibitors, if such substances already exist. The expected results of the proposed project might offer new possibilities for the modulation of tumor cell radiosensitivity with therapeutic applications in mind.