AbstractBACKGROUNDThe occurrence of the retrovirus xenotropic murine leukemia virus (MLV)‐related virus (XMRV) has been reported in prostate tissue of patients with prostate cancer (PrCa). Considering the potential great medical and social relevance of this discovery, we investigated whether this finding could be confirmed in an independent group of Dutch sporadic PrCa cases.METHODSWe investigated the occurrence of XMRV in fresh‐frozen PrCa specimens of 74 PrCa patients from The Netherlands. Total RNA and DNA were isolated, subjected to cDNA synthesis, and analyzed by real‐time PCR targeting conserved XMRV sequences.RESULTSSpiking experiments showed that we were able to detect at least 10 copies of XMRV sequences in 100,000 cells by real‐time PCR, demonstrating high sensitivity of the assay. XMRV sequences were detected in 3 out of 74 (i.e., 4%) PrCa specimens. The number of XMRV containing cells was extremely low (1 in 600–7,000 cells). This was corroborated by the fact that XMRV could not be detected in consecutive tissue sections of the initial XMRV‐positive cases.CONCLUSIONSXMRV was rarely detected, and at extremely low levels, in sporadic PrCa samples from Dutch patients. When XMRV would play a causal role in prostate carcinogenesis, integration of the provirus could be expected to be present in, at least, a proportion of tumor cells. Therefore, our data do not support the claim that there is an association between XMRV infection and PrCa in Dutch PrCa patients. Prostate 77:415–420, 2011. © 2010 Wiley‐Liss, Inc.