In an attempt to disclose mechanisms of hepatocarcinogenesis and discover novel target molecules for the diagnosis and treatment of hepatocellular carcinomas (HCCs), we previously analyzed expression profiles of HCC tissues by means of human cDNA microarray. Among the genes upregulated in tumor tissues compared with their nontumor counterparts, we focused on a novel gene, termed WDRPUH, and characterized its biologic function. WDRPUH encodes a predicted 620-amino acid protein containing 11 highly conserved WD40-repeat domains. Multiple-tissue Northern blot analysis revealed its specific expression in the testis among 16 normal tissues examined. Transfection of plasmids designed to express WDRPUH-specific siRNA significantly reduced its expression in HCC cells and resulted in growth suppression of transfected cells. Interestingly, we found that WDRPUH associated with HSP70, proteins of the chaperonin-containing TCP-1 (CCT1) complex, as well as BRCA2. These findings have disclosed a novel insight into hepatocarcinogenesis and suggested that WDRPUH may be a molecular target for the development of new strategies to treat HCCs.