HIWI is associated with prognosis in patients with hepatocellular carcinoma after curative resection

BACKGROUND: PIWI protein family was found to play an important role in stem cell self‐renewal. Overexpression of HIWI, the human homolog of PIWI family proteins, was found in several solid tumors, although the role of HIWI in hepatocellular carcinoma (HCC) and its prognostic value remain unclear. METHODS: HIWI expression was measured in stepwise metastatic HCC cell lines (HCCLM3, MHCC97H, MHCC97L, SMMC7721, and HepG2), the normal liver cell line (L02), and HCC tissue samples (n = 20). Proliferation and invasion were investigated in HCC cell lines undergoing HIWI target small interfering RNA transfection. Also explored was HIWI expression in HCC tissue microarrays (n = 168) for survival analysis. RESULTS: Levels of HIWI protein and mRNA were up‐regulated in highly metastatic HCC cell lines (HCCLM3, MHCC97H, and MHCC97L), whereas their proliferation and invasion significantly decreased after depletion of HIWI. Intratumoral HIWI expression was higher than that of peritumoral tissue (P < .001) and positively associated with proliferating cell nuclear antigen expression (P < .001). Positive expression of intratumoral HIWI was associated with larger tumor size (P = .047) and intrahepatic metastasis (P = .027) and was an independent risk factor for overall survival (P = .007) and recurrence‐free survival (P = .036), particularly in patients with low serum α‐fetoprotein and low Edmondson‐Steiner grade. CONCLUSIONS: HIWI may play a key role in HCC proliferation and metastasis and can be a potential prognostic factor for HCC after curative resection, particularly with well‐differentiated HCC. Cancer 2011. © 2011 American Cancer Society. HIWI may be a useful prognostic factor for hepatocellular carcinoma (HCC)—particularly with well‐differentiated HCC—after curative resection and may be involved in tumor proliferation and metastasis.