Expression and androgen regulation of C-CAM cell adhesion molecule isoforms in rat dorsal and ventral prostate

C-CAM is an epithelial cell adhesion molecule with two major splice variant s that differ in the length of the cytoplasmic domain. C-CAM1 (long (L)-for m) strongly suppresses the tumorigenicity of human prostate carcinoma cells . In contrast, C-CAM2 (short (S)-form) does not exhibit tumor-suppressive a ctivity. In the present study we have investigated the functional significa nce of L-form and S-form C-CAM in rat prostate by examining their expressio n and distribution in different prostate lobes and their response to androg en deprivation, RNase protection assays with a probe for both C-CAM isoform s detected high levels of C-CAM messages in the rat dorso-lateral prostate (DLP), L- and S-form proteins, localized by indirect immunofluorescence usi ng isoform-specific antipeptide antibodies, were co-expressed on the apical surface of prostate epithelial cells in normal DLP, Androgen depletion did not significantly change the steady state levels of C-CAM message and prot ein expression in the DLP, although there was a change in the pattern of pr otein expression in these lobes, In contrast, C-CAM isoform messages and pr oteins were undetectable in normal ventral prostate (VP) but increased mark edly in this lobe in response to castration, producing isoform ratios simil ar to those in DLP, These results demonstrate that coordinate expression of C-CAM isoforms is maintained in the VP following androgen depletion and su ggest that androgen suppresses C-CAM expression in VP but not in DLP, These results suggest that balanced expression of L- and S-form C-CAM is importa nt for normal prostate growth and differentiation.