AbstractThe hydrolysis of endocannabinoids has profound effects on the function of the endocannabinoid signaling system in the regulation of prostate carcinoma cells. Prostate carcinoma cells exhibit a wide range of hydrolysis activity for 2‐arachidonoylglycerol (2‐AG), the major endocannabinoid. However, enzyme(s) responsible for 2‐AG hydrolysis and their functions in prostate cancer have not been characterized. In this study, we demonstrated that fatty acid amide hydrolase (FAAH) was differentially expressed in normal and prostate carcinoma cells. In PC‐3 cells, overexpression of FAAH resulted in increased FAAH protein, 2‐AG hydrolysis, cell invasion and cell migration. Conversely, small‐interfering RNA (siRNA) knockdown of FAAH in LNCaP cells decreased FAAH protein, 2‐AG hydrolysis and cell invasion. Furthermore, CAY10401, a FAAH inhibitor, decreased cell invasion and it enhanced the reduction of invasion in FAAH siRNA‐transfected LNCaP cells. Immunohistochemistry staining of commercial tissue microarrays (TMAs) demonstrated FAAH staining in 109 of 157 cores of prostate adenocarcinomas but weak staining in 1 of 8 cores of normal prostate tissues. These results suggest that FAAH regulates 2‐AG hydrolysis and invasion of prostate carcinoma cells and is potentially involved in prostate tumorigenesis. © 2008 Wiley‐Liss, Inc.