Dysregulated expression of bcl-2 and bax in oral carcinomas: evidence of post-transcriptional control

A study was conducted to investigate the gene expression of bcl-2 and bax in oral squamous cell carcinomas. We used reverse-transcriptase-polymerase chain reaction (RT-PCR) to evaluate the expression of bcl-2 and bax mRNAs and the ratio of bcl-2/bax mRNA, and employed immunohistochemistry to investigate the bcl-2- and bax-encoded proteins. It was observed that the expression level of bcl-2 mRNA or bax mRNA was not consistent with their protein level in some cases. Higher expression of bcl-2 mRNA and stronger immunostaining of bcl-2 protein were found in oral squamous cell carcinomas than in the adjacent histologically normal oral epithelium. These findings were more prominent in poorly differentiated carcinomas. No significant differences in bax mRNA and protein were observed between carcinomas and the adjacent histologically normal oral epithelium. However, poorly differentiated carcinomas showed very weak immunostaining for bax. The ratio of bcl-2/bax mRNA was higher in carcinomas than in the adjacent histologically normal oral epithelium, and higher ratios were seen in most of poorly differentiated carcinomas. This study supplies indirect evidence of post-transcriptional control of bcl-2 and bax expression, and suggests that dysregulated expression of bcl-2 and bax may be related to the differentiation of oral squamous cell carcinomas.