Role of BEN domain protein 4 (BEND4) in prostate cancer (PCa) and the effect of silencing BEND4 in PCa cell lines

Prostate cancer (PCa) is diagnosed in approximately 13% of men in their lifetime and is the second most diagnosed cancer in men. The existing treatments for PCa cause many severe side effects, including erectile dysfunction, hair loss, and anemia, while their effects may be reduced due to the development of treatment resistance. Due to these drawbacks associated with traditional treatments, research on targeted cancer therapy is conducted in the field of molecular oncology to develop efficient and safer treatment approaches for PCa. Many of the targets explored are involved in DNA Damage Response (DDR). One such potential cancer target is the BEN domain (BEND) protein, which is a chromatin boundary marker that recruits chromatin-modifying factors and regulates transcription. It has many functions in cancer cells related to DDR and cell proliferation. Recent studies have suggested that silencing BEND4 expression in pancreatic ductal adenocarcinoma (PDAC) promotes the accumulation of DNA damage and sensitizes cells to ATM/ATR inhibitors, thereby increasing cancer cell apoptosis. Moreover, it has been shown to be hypermethylation target in diffuse large B-cell carcinoma (DLBCL) and colorectal cancer. Therefore, these results demonstrate the potential of targeting BEND4 in the treatment and diagnosis of PCa. However, limited research has been conducted on BEND4 in PCa. The expression profile of BEND4 in PCa cell lines (androgen-dependent and androgen-independent) suggests, according to online prediction tools such as Betastasis and PCA tools, that androgen receptor-dependent (AR+) PCa cells express high levels of BEND4, indicating AR-dependent regulation of BEND4. They also imply that as the Gleason score increases, BEND4 expression decreases. To validate these findings in vitro, western blot and RT-qPCR were conducted, revealing that BEND4 expression is high in AR+ PCa cells, such as MDA-PCa-2b, LNCaP, and VCaP , and is lower in NCI-H660 and LASCPC (AR-negative and aggressive PCa cell lines). DepMap analysis assigned negative gene effect scores to AR+ cell lines such as VCaP and LNCaP, suggesting that BEND4 silencing has differential effects on PCa cells based on their androgen dependency. Follow-up studies of siRNA silencing of BEND4 reduced proliferation with an increase in siRNA concentration in AR+ cells, such as VCaP and MDA-PCa-2b. Taken together, our results suggest that BEND4 may have a role in promoting AR-driven PCa and may serve as a potential therapeutic target for AR-dependent PCa.