Apoptotic program is initiated but not completed in LNCaP cells in response to growth in charcoal-stripped media

Morphological, proliferative, and genetic changes were studied in androgen-responsive LNCaP cells in response to growth in charcoal-stripped (CS) media.

Within 5 days of treatment, there were dramatic changes in the morphology and organization of LNCaP cells. The cells unclumped and acquired a distinct neuronal-like appearance with small cell bodies and multiple long, thin processes. Despite this appearance, the cells stained negative to monoclonal antibodies to neuronal markers such as microtubule-associated protein-2 (MAP-2) and glial fibrillary acidic protein (GFAP). In situ end-labeling assay indicated that the number of cells showing signs of apoptosis (DNA fragmentation) increased dramatically in CS media compared to the control. However, ultrastructural changes and the fragmented DNA ladder that are used to define apoptosis were not observed. Instead of cell death, the cells became cytostatic, which can be reversed, although not completely, by exogeneous addition of dihydrotestosterone in a dose-dependent manner. Presence of mRNA of several genes involved in the apoptotic process, i.e., Bcl-2, Bcl-X, ICE, Ich-1, and DAD-1, was studied in response to normal and CS media. We detected mRNA of Bcl-2, Bcl-XL, Bcl-XS, Ich-1L and DAD-1, while ICE and Ich-1S were not expressed in LNCaP cells.

This suggests that certain signals that may be essential for complete execution of the apoptotic program may be missing in this in vitro model. This may explain our observation that the growth of LNCaP cells in CS media does not fully mimic castration-mediated regression of the prostate gland in vivo.