PC 11. Small interfering RNA targeting at HMGN5 induces apoptosis via modulation of mitochondrial pathway and Bcl - 2 family in prostate cancer cell

Background: High-mobility group N protein 5 (HMGN5), previously known as nucleosomal binding protein 1 (NSBP1), a new member in the HMGN family, is a nuclear protein which binds to nucleosomes via nucleosomal binding domain (NBD), unfolds chromatin, and affects transcription, but its biological function remains mainly uncharacterized. Our initial research on HMGN5 indicated high level of HMGN5 in human with prostate cancer and association with the proliferation of prostate cancer cells.

Methods: The LNCaP (androgen-dependent prostate cancer) cells were transfected with small interfering RNA (siRNA) targeting at HMGN5. Apoptosis was detected through the Annexin V-PE/7-AAD double staining and terminal transferase TdT-mediated dUTP-biotin end labeling (TUNEL) assay. Miochondrial membrane potential was measured by JC-1 staining. HMGN5 and GAPDH mRNA expression were determined by Real-time PCR. Bcl-2 and other apoptosis-related proteins were determined by Western blot analysis. The caspase activity was measured by cleavage of the caspase substrate.

Results: Transfection with siRNA targeting at HMGN5 efficiently and specifically reduced the HMGN5 expression in LNCaP cells. The down-regulation of HMGN5 induced remarkable LNCaP cells apoptosis and resulted in reduction of mitochondrial membrane potential. The induction of cell apoptosis was accompanied with up-regulation of Bax, Bcl-2, Bax/Bcl-2 ration, and the activation of the caspase-3.

Conclusions: The siRNA targeting at HMGN5 was effective on down-regulating the expression of HMGN5 in androgendependent prostate cancer cells via regulation of caspase related mitochondrial pathway and Bcl-2 family proteins. This study suggests that HMGN5 may be a potential molecular target for therapeutic relevance of prostate cancer.