Small interfering RNA targeting HMGN5 induces apoptosis via modulation of a mitochondrial pathway and Bcl-2 family proteins in prostate cancer cells

Abstract

We investigated the importance of HMGN5, a nuclear protein that binds to nucleosomes, unfolds chromatin, and affects transcription, in the LNCaP prostate cancer cell line. We also examined the molecular mechanisms that promote apoptosis of LNCaP cells after infection with small interfering RNA (siRNA) targeting HMGN5 (siRNA-HMGN5). The androgen-dependent LNCaP human prostate cancer cells were infected with siRNA-HMGN5. Apoptosis was detected using the Annexin V-PE/7-AAD double staining and the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assays. Mitochondrial membrane potential was measured by JC-1 staining. HMGN5 and GAPDH mRNA expression were determined using real-time PCR. Bcl-2 and other apoptosis-related protein levels were determined by Western blot analysis. Caspase activity was measured by cleavage of the caspase substrate. Infection with siRNA targeting HMGN5 efficiently and specifically reduced the HMGN5 expression in LNCaP cells. The downregulation of HMGN5 induced remarkable apoptosis of LNCaP cells and resulted in the reduction of mitochondrial membrane potential. The induction of cell apoptosis was accompanied by the upregulation of Bax, the Bax/Bcl-2 ratio and the activation of caspase3. The HMGN5-targeted siRNA was effective in downregulating the expression of HMGN5 in androgen-dependent prostate cancer cells and inducing cell apoptosis via the regulation of a caspase-related mitochondrial pathway and Bcl-2 family proteins. This study suggests that HMGN5 may be a potential molecular target with therapeutic relevance for the treatment of prostate cancer.

Suppression of nucleosome-binding protein 1 by miR-326 impedes cell proliferation and invasion in non-small cell lung cancer cells

“…Knockdown of NSBP1 causes cell cycle arrest and promotes cell apoptosis of prostate cancer cells possibly by inhibiting cyclin B1 and Bcl-2 expression levels (15). Similarly, Zhang et al showed that NSBP1 gene silencing results in increased mitochondria-mediated cell apoptosis in prostate cancer cells (22). Furthermore, NSBP1 is overexpressed in glioma clinical tissues, and knockdown of NSBP1 induces cell cycle arrest in the G1 phase, inhibits cell proliferation and promotes cell apoptosis in glioma cells in vitro (16).…”

Expression of oncogenic HMGN5 increases the sensitivity of prostate cancer cells to gemcitabine

“…HMGN5 plays an important role during development and tumorigenesis (8,12,13), and HMGN5 expression is upregulated in prostate (14), bladder (15), clear cell renal cell carcinoma (16), breast (17), cutaneous squamous (18) and ovarian cancer (19), suggesting an association between high HMGN5 expression and tumorigenesis. In our previous studies, we found that HMGN5 was overexpressed in prostate cancer tissues and prostate cancer cell lines, and downregulation of HMGN5 with shRNA caused cell cycle arrest, growth inhibition and apoptosis in vitro and in vivo (20,21). We also found that gemcitabine downregulated the expression of HMGN5 (22).…”

HMGB1 in health and disease

“…In addition, HMGN5 expression is upregulated with the development of several cancers, including squamous cell carcinoma, breast and bladder cancer, renal cell carcinoma, and gliomas (Gerlitz, 2010; Ji et al, 2012b; Li et al, 2006a; Qu et al, 2011; Tang et al, 2008b; Wahafu et al, 2011). Knockout of HMGN5 by RNAi inhibits cell proliferation and increases apoptosis in cancer cells (Chen et al, 2012b; Ji et al, 2012b; Zhang et al, 2012c). …”