Bax-interacting factor-1 inhibits cell proliferation and promotes apoptosis in prostate cancer cells.

Prostate cancer (PCa) is one of the most common malignant tumors and the second leading cause of cancer-related death among males. Bax-interacting factor-1 (Bif-1) is a member of Endophilin family, which binds to and activates the BAX protein in response to the apoptosis signaling pathway. Loss of Bif-1 may suppress the intrinsic pathway of apoptosis and promote tumorigenesis, but there is also converse evidence that Bif-1 could in part be responsible for the tumorigenesis and the role of Bif-1 in PCa development is not clear. In the present study, we aimed to understand the relationships between Bif-1 expression and PCa development. The mRNA and protein expression levels of Bif-1 in PCa cell lines, benign prostatic hyperplasia (BPH) (n=100) and PCa tissues (n=100, including low Gleason-scored PCa n=43 and high Gleason-scored PCa n=57) were detected and the effects of Bif-1 overexpression on the apoptosis, proliferation and migration in LNCaP cells were explored. Bif-1 mRNA levels of PCa cell lines were analyzed by real-time PCR and the protein levels were detected by western blotting. Bif-1 expression in BPH and PCa samples was detected by immunohistochemistry. To build Bif-1 overexpression PCa cells, Bif-1 gene was transfected into LNCaP cells by pcDNA3.1(+)‑Bif-1 vector. Cell apoptosis was detected by flow cytometric analysis, cell proliferation measured by 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide (MTT) assay and cell migration was analyzed by wound‑healing assay. The results proved that Bif-1 is downregulated in both PCa cell lines (P<0.01) and clinical samples (P<0.05), and Bif-1 expression is suppressed with the cancer progression (BPH vs. PCa P<0.01, and low Gleason-scored PCa vs. high Gleason-scored PCa P<0.05). Overexpression of Bif-1 could significantly inhibit cell proliferation (P<0.05) and enhancing PCa cell apoptosis (P<0.05), but it did not affect the migration ability (P>0.05). Our findings give strong evidence that Bif-1 is involved in PCa tumorigenesis and acts as a suppressor in PCa progression, and may have significance in understanding the process of PCa development.