Expression and subcellular distribution of Bcl-2 and BAX proteins in serum-starved human keratinocytes and mouth carcinoma epidermoid cultures.

Squamous cell carcinoma (SSC) is the most frequent malignant tumor of the oral cavity. Aberration of programmed cell death is thought to participate in cancer. Using specific antibodies a study of the expression and subcellular distribution of Bcl-2, BAX, caspase-3 and cytochrome c in normal human keratinocytes and mouth carcinoma slowly (HN) and rapidly growing (KB) cells has been carried out. In carcinoma cells depressed expression of BAX, presence in the cytosol of procaspase-3 and absence in this fraction of cytochrome c have been found. PGE2 treatment prevented cell growth depression induced by pro-apoptotic serum starvation both in control and carcinoma cell cultures. It is also shown that PGE2 promoted both in keratinocytes and KB cells expression of Bcl-2, which was accompanied in the first case by increase in its mitochondrial level. These results indicate that in carcinoma cells there is an apparent down regulation of the apoptotic cascade as compared to normal keratinocytes. Thus the possibility that down regulation of apoptosis is associated with promotion of tumor development in the oral mucosa cells seems to be supported by these observations.