Hexim-1 modulates androgen receptor and the TGF-β signaling during the progression of prostate cancer.

BACKGROUND: Androgen and TGF-β signaling are important components during the progression of prostate cancer. However, whether common molecular events participate in the activation of these signaling pathways are less understood.
METHOD: Hexim 1 expression was detected by immunohistochemistry of human tissue microarrays and TRAMP mouse models. The in vivo significance of Hexim-1 was established by crossing the TRAMP mouse model of prostate cancer with Hexim-1 heterozygous mice. TRAMP C2 cell line was also modified to delete one copy of Hexim-1 gene to generate TRAMP-C2-Hexim-1+/- cell lines.
RESULTS: In this report, we observed that Hexim-1 protein expression is absent in normal prostate but highly expressed in adenocarcinoma of the prostate and a characteristic sub-cellular distribution among normal, benign hyperplasia, and adenocarcinoma of the prostate. Heterozygosity of the Hexim-1 gene in the prostate cancer mice model and the TRAMP-C2 cell line, leads to increased Cdk9-dependent serine phosphorylation on protein targets such as the androgen receptor (AR) and the TGF-β-dependent downstream transcription factors, such as the SMAD proteins.
CONCLUSION: Our results suggest that changes in the Hexim-1 protein expression and cellular distribution significantly influences the AR activation and the TGF-β signaling. Thus, Hexim-1 is likely to play a significant role in prostate cancer progression.