摘要Background A disintegrin and metalloprotease 9 (ADAM9) is a membrane-anchored enzyme which is considered to be involved in some diseases including tumor.However,the role of ADAM9 in castration resistant prostate cancer (CRPC) is not clear.This study aimed to explore the different expressions on protein and messenger RNA (mRNA) level of ADAM9 between hormonal sensitive prostate cancer (HSPC) and CRPC tissue,and find the correlation with prognosis.Methods Clinicopathologic characteristics of 106 HSPC and 76 CRPC cases were collected.The ADAM9 expressions were analyzed using immunohistochemistry.ADAM9 mRNA of 32 additional cases (16 HSPC and 16 CRPC patients)were analyzed via quantitative real-time polymerase chain reaction (RT-PCR).The prediction values of variables for overall survival (OS) of CRPC patients were analyzed using Cox regression.Results ADAM9 protein expression was significantly downregulated in CRPC compared with HSPC tissue (31.6％ vs.81.1％,P＜0.001).The relativity transcription level of ADAM9 mRNA was 0.45 for CRPC tissue and 1.0 for HSPC tissue (P=0.002).In the CRPC group,patients with low ADAM9 protein expression were significantly associated with shorter OS than patients with high expression (38.6 months vs.57.8 months,hazard rate (HR)=2.638,P=0.023).Conclusion ADAM9 expression was low in CRPC,correlated with poor prognosis and might be involved in the succession from HSPC to CRPC by various functions.