Bax protein expression correlates with radiation-induced apoptosis in radiation therapy for cervical carcinoma

Abstract

Bax protein serves as a positive regulator of apoptosis by forming heterodimers with bcl-2 protein, thereby promoting cell survival. It is unclear whether the regulation of apoptosis reported in many studies is applicable to the apoptotic phenomenon observed in conventional fractionated radiation therapy for cervical carcinoma. The authors assessed the relation between apoptosis and the expression of Bax and bcl-2 protein in fractionated radiation therapy for cervical carcinoma by using in situ nick end labeling (ISEL) and immunohistochemical methods. Specimens were excised from the cervical tumors of 20 patients before and after administration of a total irradiation dose of 9 gray (Gy). The apoptotic cell index (AI) in tumor cells was 0.22% before irradiation and 1.20% after the administration of the 9 Gy, which represented a significant increase (P=0.0004). The positive rate of Bax protein increased from 15% (in 3 of 20 patients) before irradiation to 60% (in 12 of 20 patients) after the 9 Gy was administered, a statistically significant change (P=0.0126). In addition, there was a significant correlation between Bax protein expression and apoptosis positivity after the 9 Gy was administered (P=0.018). These results suggest that Bax protein is associated with apoptosis induced by fractionated radiation therapy.