CKLF (chemokine-like factor)-like MARVEL (MAL and related proteins for vesicle trafficking and membrane link domain) transmembrane domain containing (CMTM) is a novel gene family. One member of this family, CMTM2, also named chemokine-like factor superfamily 2 (CKLFSF2), is expressed highly in the testis and moderately in the prostate, marrow and peripheral blood cells. However, the function of human CMTM2 remains unknown. Here, we found that CMTM2 was upregulated in 5α-dihydrotestosterone (DHT)-treated LNCaP cells. We investigated the relationship between CMTM2 and the androgen receptor. Our results showed that CMTM2 enhanced DHT-mediated androgen receptor (AR) transactivation and the expression of prostate specific antigen (PSA). We also observed that CMTM2 enhanced the AR protein level, which was reversed by silencing endogenous CMTM2 expression, which suggested that CMTM2 might play an important role in maintaining the AR protein level. We also found that CMTM2 suppressed Akt activation. A previous study showed that Akt could phosphorylate AR at Ser210 and Ser790 and lead to AR ubiquitylation and degradation as well as suppression of AR activity. Taken together, suppressing Akt activation and increasing the AR protein level might be one of the mechanisms for the CMTM2-mediated enhancement of AR transactivation. © 2009 Science in China Press and Springer-Verlag GmbH.