, Inc, Daiichi Sankyo., Co., Inc, Dainippon Sumitomo, Co., Inc, Aji-nomoto Co., Inc, MDS, Co., Inc, Chugai Pharma., Co., Inc, Toray Co., Inc, Daiichi Sankyo., Co., Inc, Dainippon Sumitomo, Co., Inc, Ajinomoto Co., Inc, Bayer Japan The following people have nothing to disclose: Yoshimoto Nomura, Taro Yamashita, Naoki Oishi, Kouki Nio, Sha Sha Zeng, Takehiro Hayashi, Tomoyuki learn more Hayashi, Hikari Okada, Hajime Sunagozaka, Hajime Takatori, Masao Honda Background & Aims:
Our previous work has identified a frequent loss of Protocadherin 9 (PCDH9) in hepatocellular carcinoma (HCC) by using array-based comparative genomic hybridization (aCGH). However, the biochemical function of this potential tumor suppressor gene in HCC development has not been addressed. Therefore, we aimed to identify the genetic/epigenetic inactivation of PCDH9 and it’s role in HCC. Methods: A total of 120 paired tumour and their corresponding non-tumour liver tissues from AZD0530 HCC patients with serum HBsAg positive were collected. Expression of PCDH9 and its functional targets was tested by real-time quantitative RT-PCR, western blot or immunohistochemistry anylisis. The DNA copy number variations of HCC tissues were detected by using aCGH assay. The methylation status of PCDH9 gene promoter in each paired tumor and non-tumor specimens was quantitatively analyzed, by a method
composed of DNA methylation-sensitive endonu-clease digestion followed by quantitative PCR. The effect of PCDH9 on cell proliferation and tumor growth was detected by MTT, soft-agar, and xenograft tumorigenicity assays. The function of PCDH9 on cell migration was analyzed by scratch-wound healing and transwell assays. Results:
Down-regulation of PCDH9 expression was detected in about 61% (73/120) of primary HCC tissues. The low expression of PCDH9 was significantly correlated with present portal vein invasion (p=0.0354). Based on aCGH data, losses of chromosome 13q21.32 where PCDH9 gene mapped was found in 6 of 25 tumor specimens (24%) and gain in 1 (4%) of cases. PCHD9 promoter hypermethylation was Aspartate detected in 22% (24/109) of HCC tissues. Interestingly, PCDH9 hypermethylation was significantly correlation with larger tumor size (p=0.0139) and worse intrahepatic dissemination (p=0.0312). Demethylation treatment in PCDH9-hypermethylated HCC cells could restore its expression. Furthermore, ectopic PCDH9 expression in HCC cells significantly inhibited cell proliferation, anchorage independent growth, tumorigenicity and cell megration. PCDH9 overexpression could induce a mesenchymal-epithelial transition (MET) in HCC cell lines which was characterized by down-regulation of mesenchymal cell markers including N-cadherin, Vimentin and Fibronectin, and reactivation of epithelial cell markers such as E-cadherin and Occludin. In addition, the activation of GSK-3β signaling induced by PDCH9 was required for PCDH9-induced MET. Conclusions: PCDH9 acts as a novel tumor suppressor candidate gene in HCC.