Predictive value of p53, Bcl2 and bax in the radiotherapy of head and neck cancer.
Radiation is known to induce DNA damage resulting in the onset of apoptosis. The apoptosis is modulated by p53, Bcl2 and Bax proteins. High level of wild type p53 is required for radiation induced apoptosis. The p53 status, therefore, may be a crucial determinant of radiosensitivity of tumor cells. Overexpression of Bcl2, however, inhibits apoptosis via hetero- and homodimeric interaction. Bax might function as a cell death effector molecule that is neutralized by Bcl2. The aim of the present study is to investigate the correlation between p53, Bcl2, Bax and c-myc levels and the clinical response of head and neck cancer patients to radiation. The base line and 30 GY gamma radiation induced values of p53, Bcl2, Bax and c-myc were estimated by Western blot in 40 biopsies of head and neck cancers. We found that the radiosensitivity of head and neck cancer patients depends on the ratio of p53, Bcl2 and Bax protein levels. High Bcl2 levels resulted in radioresistance of cancer patients. Overexpression of Bax and c-myc may ensure the radiosensitivity of head and neck cancer patients. Our studies indicate that prediction of radiation sensitivity of tumors could be based on the simultaneous evaluation of p53, Bax and Bcl2 levels.