Inhibition of Bcl-xL expression sensitizes normal human keratinocytes and epithelial cells to apoptotic stimuli.

The epidermis is continually exposed to harmful mutagens that have the potential to cause DNA damage. To protect the skin from accumulating mutated cells, keratinocytes have developed a highly regulated mechanism of eliminating damaged cells through apoptosis. Bcl-xL is a well-described cell survival protein that when overexpressed in skin can protect keratinocytes from UV radiation-induced apoptosis. To begin to unravel the complex mechanisms that keratinocytes use to survive, we wanted to characterize the role of endogenous Bcl-xL in protecting cells from death. In this study, we describe the development and characterization of an antisense inhibitor to Bcl-xL. We show that this inhibitor reduces Bcl-xL RNA and protein in a concentration-dependent, sequence-specific manner. Furthermore, treatment of keratinocytes and epithelial cells with this inhibitor sensitizes these cells to UV-B radiation and cisplatinum treatment-induced apoptosis. Thus, these results offer direct evidence that Bcl-xL is critical in the protection of skin and epithelial cells from apoptosis and provide a basis for the role of Bcl-xL in keratinocyte and epithelial cell survival.