Abstract 1067: Tenascin C in colorectal cancer stroma is a predictive marker for liver metastasis and is a potent target of miR-198 as identified by microRNA analysis

Abstract

Abstract Background: Liver metastasis in colorectal cancer (CRC) is still one of the major determinants of survival. Tumor stroma has important roles in the development of colorectal cancer (CRC) metastasis. MicroRNAs (miRNAs) are known to regulate the expression of genes involved in many physiological conditions, including cancer. Previous studies reported important roles of miRNAs in cancer cells in CRC development and metastasis. However, only few studies have focused on miRNA expression in CRC stroma. In this study, we revealed the miRNA expression profiles in tumor stroma by miRNA array analysis using Laser captured microdissection (LCM) to identify miRNAs and their target genes as novel molecular markers involved in CRC liver metastasis. Methods: Tumor stroma was isolated from formalin-fixed, paraffin-embedded tissues of primary CRCs with or without liver metastasis by LCM, and miRNA expression was analyzed using TaqMan miRNA arrays. Results: Hierarchical clustering classified 16 CRCs into two groups according to the existence of synchronous liver metastasis. Combinatory target prediction identified tenascin C (TNC) as a predicted target of miR-198, one of the top 10 miRNAs downregulated in tumor stroma of CRCs with synchronous liver metastasis. Immunohistochemical analysis of TNC in 139 primary CRCs revealed that a high staining intensity was correlated with synchronous liver metastasis (P<0.001). TNC staining intensities in the tumor stroma of 83 CRC liver metastases revealed a higher staining in liver metastases than in primary CRCs independently of preoperative chemotherapy. Univariate and multivariate analyses revealed that the TNC staining intensity was an independent prognostic factor to predict postoperative overall survival (P=0.005; n=139) and liver metastasis-free survival (P=0.001; n=128). To evaluate the biological link between miR-198 and TNC, we first checked expression levels of miR-198 in the 16 samples in miRNA array data, and compared them with TNC staining intensities. The CRC samples expressing miR-198 tended to have lower levels of TNC expression in comparison with those without miR-198 expression, although the difference was not statistically significant (P=0.237). Next, we transfected a miR-198 mimic or a miR-198 inhibitor into SW620 human colon cancer cells and CCD-18Co human colon fibroblast cells and analyzed the expression change of TNC protein by western blotting. The relative protein expression of TNC was suppressed by treatment with the miR-198 mimic and increased by miR-198 inhibitor. Conclusions: Alterations of miRNAs in CRC stroma appear to form a metastasis-permissive environment that can elevate TNC to promote liver metastasis. TNC in primary CRC stroma has the potential to be a novel biomarker to predict postoperative prognosis. Citation Format: Tomohiro Murakami, Hirotoshi Kikuchi, Hisahito Ishimatsu, Sanshiro Kawata, Amane Hirotsu, Tomohiro Matsumoto, Yusuke Ozaki, Yoshihiro Hiramatsu, Kinji Kamiya, Megumi Baba, Satoshi Baba, Masatoshi Kitagawa, Takanori Sakaguchi, Hiroyuki Konno, Hiroya Takeuchi. Tenascin C in colorectal cancer stroma is a predictive marker for liver metastasis and is a potent target of miR-198 as identified by microRNA analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1067.