The Expression And Clinical Significance Of SIRT1Protein In Hepatocellular Carcinoma And Its Association With P53and YAP2Protein

Purpose: Hepatocellular carcinoma (HCC) is one of the most common cancers inChina. Recent studies show silent mating type information regulation2homolog1(SIRT1) plays an important role in various malignant tumors, however, whetherSIRT1is a tumor promoter or tumor suppressor in HCC remains controversial. Inorder to explore the possible role of SIRT1in HCC in the process of tumordevelopment and metastasis, the present study was conducted to investigate theexpression of SIRT1protein in large samples of HCC tumor tissues and theself-matched adjacent non-tumor tissues, and to explore the association of SIRT1expression with the clinical significance and the prognostic significance of SIRT1expression. Furthermore, recent fundamental studies showed that SIRT1was closelyrelated to P53and Yes-associated protein2(YAP2) in HCC, the present study wasalso conduced to investigate the association of SIRT1with P53and YAP2in largesamples of paraffin-fixed HCC specimens and fresh HCC samples, thereby to providethe clinical evidence of their association.Methods：Under the inclusion and exclusion criteria, we included a retrospectivecohort of300consecutive HCC samples who underwent initial surgical resection inseveral hospitals in Beijing City or Tianjin City from2000to2009both the tumortissues and self-matched adjacent non-tumor tissues (NT) were collected. By the construction of tissue microarray, SIRT1, P53and YAP2expression were determinedby immunohistochemistry. The association of protein expression with clinicalfeatures was analyzed, overall survival analysis and multivariate analysis wereperformed.30pairs of fresh HCC samples were also collected,Western blotting andqPCR analysis were conducted to investigate the SIRT1, P53and YAP2expression.Results：By the immunohistochemistry of tissue microarray of the300pairs of HCCsamples, significantly overexpression of SIRT1was detected in tumor tissuescompared with the self-matched adjacent non-tumor tissues. SIRT1immunostainingcould be localized both in the nucleus (145/300,48.3%) and the cytoplasm. In HCCtumor tissues, the positive expression rate of SIRT1in the nucleus was48.3%(145/300) while in the cytoplasm was21.2%(70/300). The overexpression ofnucleus SIRT1in HCC tumor tissues was significantly related to the hepatitis Cinfection, high serum AFP level, peplos infiltration, poor cellular differentiation andthe adjacent chronic hepatitis. Overall survival analysis showed nuclear SIRT1overexpression predicted poor overall survival (P=0.017) while cytoplasmic SIRT1overexpression predicted longer overall survival (P=0.005). Multivariate analysisshowed the overexpression of nuclear SIRT1was an independent tumor promoterwhile cytoplasmic SIRT1expression as an independent tumor suppressor. By theanalysis of the30pairs of fresh HCC samples, significant overexpression of SIRT1,P53and YAP2was detected in tumor tissue compared with the self-paired adjacent non-tumor tissues while there was no difference in SIRT1mRNA level. By theimmunohistochemistry of the tissue microarray and the Western blotting of HCCfresh samples, the overexpression of SIRT1was found to be positively related to theoverexpression of P53and YAP2. Furthermore, P53and YAP2proteins weresignificantly overexpressed in HCC tumor tissue and overall survival analysis showedthe overexpressions of P53and YAP2predicted poor overall survival.Conclusion：SIRT1was overexpressed in HCC and the overexpressed was related toseveral clinical manifestations. The overexpression of SIRT1was positively related tothe overexpression P53and YAP2protein. As the nuclear SIRT1functions as a tumorpromoter and cytoplasmic SIRT1functions as a tumor suppressor, the role of SIRT1in HCC should be reconsidered.