Abstract 4660: Double combination array analysis detected A kinase anchor protein 12 (AKAP12) gene as a new tumor suppressor gene of hepatocellular carcinoma

Abstract

Abstract Background Hepatocellular carcinoma (HCC) is the fifth most common malignancy and is caused environmental and genetic factors. However, little is known about the genetic characteristics of HCC cells. In this study, we investigated a novel tumor suppressor gene in HCC by double combination array method, consisting of both expression array analysis and karyotyping analysis of single-nucleotide polymorphism (SNP) array, using the same surgical specimen. Methods We performed double combination array analysis of the HCC sample from a 68-year-old woman with chronic hepatitis type C. The Affymetrix HGU133A and HGU133B was used for expression profiling and the Affymetrix GeneChip Mapping 500K array was used for SNP array. We verified the identified gene by using HCC cell lines and 48 primary HCC tissues of patients who had undergone hepatectomy at our hospital. Results AKAP12 gene expression was decreased in tumor tissue by the expression array analysis. This gene is said to produce a structurally diverse protein associated with protein kinase A, which blocks tumor cell growth and invasion. The copy number at locus 6q24-q25 did not show chromosomal deletion by the SNP array analysis. This gene was also revealed to have a CpG rich promoter region. We could recognize promoter hypermethylation by sequence analysis of the HCC cell lines. Furthermore, AKAP12 gene expression was reactivated after 5-aza-2′-deoxycytidine (5-aza-dC) treatment. As for the 48 HCC samples, 41 cases (85%) showed promoter hypermethylation by methylation specific PCR. In these cases, the values of AKAP12 gene expression in tumor tissues, which were examined by quantitative real-time PCR, were significantly lower (P = 0.0001) than those in adjacent non-cancerous tissues. Finally, we evaluated the downregulated status of AKAP12 and the clinico-pathological findings. The downregulated cases were correlated with poor overall survival rate, although the diffenrence was not significant (P = 0.115). Conclusion Our double combination array method successfully detected a tumor suppressor gene of HCC which has yet to be identified. The downregulation of AKAP12 gene occurred by promoter hypermethylation and correlated with poor prognosis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4660.