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
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.