Abstract 1078: Micro RNAs as promising therapeutic targets for anti-metastatic therapy in colorectal cancer

Abstract

Abstract Background: Colorectal cancer (CRC) is the third most common cancer and is a leading cause of cancer related death worldwide and arises by accumulation of genetic and epigenetic alterations. Recently, it has been demonstrated that microRNAs (miRNAs) play critical roles in tumor progression in various cancers. In this study, we tried to find miRNAs associated with distant metastasis and poor outcome and evaluate those miRNAs as therapeutic target for advanced CRC. Methods: MiRNA array was done on CRC specimens derived from tumors with various gene status (KRAS/BRAF/microsatellite instability [MSI] status) with reference of their normal mucosal specimens. The array analysis revealed that a set of miRNAs was specifically down-regulated in CRC with BRAF V600E mutation without MSI, considered to be the poorer outcome. To examine whether the set of miRNAs causes distant metastasis or not, we investigated malignant potential of cell lines transfected and knock-downed the set of miRNAs by siRNA. Expression status of ZEB2 and Epithelial-Mesenchymal Transition (EMT) markers, E-cadherin, were evaluated. In addition, we analyzed expression level of the set of miRNAs in a cohort of 67 stage IV CRCs (TNM staging system by UICC 7th) by quantitative reverse transcription PCR using a comparative Ct method and examined association of target-miRNA fold change (tumor/normal tissue) and their clinocopathilogical findings. Patient survival analysis were performed by Cox proportional hazard model and Kaplan-Meier analysis. Results: In vitro, cell lines transfected the set of miRNAs significantly reduced their malignant potentials. In contrast cell lines knock-downed the set of miRNAs by siRNA obviously increased their malignant potentials. Finally, to confirm our results obtained from in vitro assays, we analyzed expression level of the set of miRNAs in a cohort of stage IV CRCs. Of 67 patients with stage IV CRCs, 15 patients showed KRAS mutation, 4 patients showed BRAF mutation. CRCs with the lower expression level of the set of miRNAs showed poor outcome compared with those with the higher expression level by Cox proportional hazard model and Kaplan-Meier analysis. Conclusions: Our data indicate that miRNAs associated with BRAF mutant CRCs is promising prognostic biomarkers and therapeutic targets for anti-metastatic therapy in CRC. Citation Format: Takashi Kawai, Takeshi Nagasaka, Yoshiko Mori, Tomokazu Fuji, Fumitaka Taniguchi, Keisuke Kimura, Toshiaki Toshima, Kazuya Yasui, Yuzo Umeda, Hiroshi Tazawa, Ajay Goel, Toshiyoshi Fujiwara. Micro RNAs as promising therapeutic targets for anti-metastatic therapy in colorectal cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1078.