〔Abstract〕 ObjectiveTo investigate the expression level of mammalian sterile 20-like kinase 1 (MST1) in prostate cancer (PCa) tissues, its biological functions, and its regulatory effects on androgen receptor (AR) and vascular endothelial growth factor (VEGF) expression. MethodsImmunohistochemistry was performed to detect MST1 expression in 77 prostate cancer tissues and 34 benign prostatic hyperplasia (BPH) tissues, and the relationship between MST1 expression and clinicopathological parameters was analyzed. MST1-overexpressing C4-2 and LNCaP cell lines were constructed. CCK-8 assay, Transwell migration assay, and angiogenesis assay were conducted to evaluate the effects of MST1 on cell proliferation, migration, and angiogenesis. The expression changes of AR and VEGF were detected by qRT-PCR and Western blot. ResultsMST1 expression was significantly lower in PCa tissues compared with BPH tissues ( P=0.012). Low MST1 expression was significantly associated with tumor metastasis ( P=0.033). MST1 overexpression inhibited C4-2 cell proliferation and migration, with transmembrane migrated cells reduced by 53.6% ( P<0.01). MST1 overexpression decreased the mRNA and protein expression levels of AR and VEGF ( P<0.05). Angiogenesis assay demonstrated that the length of new vessel structure was significantly reduced ( P<0.05). ConclusionMST1 shows a low expression level in PCa tissues and is associated with tumor metastasis. MST1 exerts tumor-suppressive effects in prostate cancer by inhibiting cell proliferation, migration, and angiogenesis, as well as downregulating the expression of AR and VEGF, indicating its potential as a therapeutic target for prostate cancer.