Co-expression of Piwil2/Piwil4 in nucleus indicates poor prognosis of hepatocellular carcinoma

PURPOSE This study aimed to explore the localization and expression of P-element-induced wimpy testis-like 2 (piwil2)/Piwil4 in hepatocellular carcinoma (HCC) tissues, and analyze the correlation between co-expression pattern and prognosis of HCC. RESULTS Piwil2 showed 100% positive expression in the cell nucleus, with the intensity higher than in the cytoplasm. Piwil4 showed a lower intensity of expression in the cell nucleus than in the cytoplasm. The molecular chaperone Piwil2/Piwil4 had four co-expression patterns: nuclear co-expression, nuclear and cytoplasmic co-expression, cytoplasmic co-expression, and non-coexpression. The survival rate and the overall survival sequentially increased. The prognostic phenotype of the nuclear co-expression of Piwil2/Piwil4 was worse than that of non-coexpression, and the intracellular localization and expression of Piwil2 and Piwil4 were not significantly different. METHODS HCC pathological tissue samples with follow-up information (90 cases) and 2 normal control liver tissues were collected and made into a 92-site microarray. The expression of Piwil2 and Piwil4 was detected using the immunofluorescence double staining method. The differences in the expression and location of Piwil2 and Piwil4 in tumor cells were explored, and the influence of such differences on the long-term survival rate of HCC was studied using Kaplan-Meier survival curve and log-rank test. The clinical staging was analyzed according to the HCC international TNM staging criteria. CONCLUSIONS The nuclear co-expression of Piwil2/Piwil4 indicated that patients with HCC had a worse prognostic phenotype. The molecular chaperone Piwil2/Piwil4 seems promising as a molecular marker for prognosis judgment; a single marker (Piwil2/Piwil4) cannot be used for prognosis judgment.