Abstract 3882: Downregulation of PRRX1 confers cancer stem cell-like properties and poor prognosis in hepatocellular carcinoma

Abstract

Abstract Background: Recent studies have been focused on the relationship between cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT). Unlike classical EMT inducers, PRRX1 is involved in the acquisition of CSC-like properties when its down-regulation induces mesenchymal-epithelial transition in breast cancer. Meanwhile, hepatocellular carcinoma (HCC) is one of the most intractable malignancies, and it is required to identify a bona-fide molecular target to regulate tumor progression and the treatment resistance. The purpose of this study is to investigate the role of PRRX1 expression on clinical significance and CSC-like properties in HCC. Methods: (1) PRRX1 expression was analyzed in 62 resected primary HCC cases by quantitative RT-PCR (qRT-PCR). Clinicopathological factors and overall survival (OS) according to PRRX1 expression were analyzed. (2) The gene set enrichment analysis (GSEA) on the published clinical data set of 242 HCC samples (GSE14520) was applied to investigate the association of PRRX1 expression levels and the stem cell-like properties. (3) PRRX1 stably expressing HCC cell lines (HuH7) were established using a lentiviral vector. The expression levels of the hepatic CSC surface markers (CD13, CD133 and EpCAM) were analyzed by flowcytometry and qRT-PCR. Furthermore, the ability of sphere formation and in vitro chemosensitivity to 5-FU were evaluated to assess the CSC-like properties. Results: (1) Univariate analysis showed that 5-year OS of the low PRRX1 expression group was significantly shorter than that of the high PRRX1 expression group (49.8% vs. 80.3%, P=0.014). On multivariate analysis, low PRRX1 expression was an independent prognostic factor for HCC (P=0.026). (2) GSEA analysis on the 247 HCC data set indicated that the down-regulation of PRRX1 was significantly correlated with the stem cell signature (P=0.039). Furthermore, using gene sets of polycomb repressive complex 2 (PCR2) targets and H3 lysine-27 trimethylation mediated by PCR2, HCC with low PRRX1 expression showed parallel enrichment patterns with human embryonic stem cells (P=0.002 and P<0.001, respectively). These results suggested that down-regulation of PRRX1 in HCC induces the acquisition of CSC-like properties through modification of chromatin structure. (3) The level of CSC markers (CD13, CD133 and EpCAM) and the number of spheres were significantly decreased in PRRX1-expressing HuH7 cells compared with the controls. Moreover, PRRX1 impaired resistance to 5-FU in HCC cells. Conclusions: The down-regulation of PRRX1 expression contributes to the poor prognosis through the acquisition of CSC-like properties in HCC patients. We might apply the aberrant expression of PRRX1 as a novel clinical biomarker for prediction of the malignant potential in HCC cases. Citation Format: Hidenari Hirata, Keishi Sugimachi, Ryutaro Uchi, Junji Kurashige, Tae Matsumura, Yuki Takano, Hiroki Ueo, Masami Ueda, Shotaro Sakimura, Yoshiaki Shinden, Hidetoshi Eguchi, Tomoya Sudo, Masakazu Hirakawa, Hiroshi Honda, Koshi Mimori. Downregulation of PRRX1 confers cancer stem cell-like properties and poor prognosis in hepatocellular carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3882. doi:10.1158/1538-7445.AM2014-3882