Background: Patients with BRAF-mutated colorectal cancer (CRC) have a poor prognosis despite recent therapeutic advances such as combination therapy with BRAF, MEK, and EGFR inhibitors.

Aim: Our aim was to clarify the functions of the microRNAs (miRNAs) involved in oncogenesis and sensitivity to BRAF inhibitors and MEK inhibitors in BRAF-mutated CRC.

Methods and Results: To identify miRNAs that sensitize a BRAF inhibitor dabrafenib (DAB) and a MEK inhibitor trametinib (TRA), we screened 240 miRNAs in BRAF-mutated CRC cell line RKO. Among the screened miRNAs, we tried to elucidate the novel functional roles of miR-193a-3p in CRC cell lines. We found that miR-193a-3p overexpression inhibited cell proliferation in CRC cell lines. The protein array analysis revealed that protein phosphorylation levels were altered by miR-193a-3p overexpression in various pathways such as cell-cycle-related pathways and PI3K-AKT pathways. The enhanced cytotoxicity by miR-193a-3p in addition to DAB and TRA was validated in multiple BRAF-mutated cell lines. Furthermore, the enhanced cytotoxicity by miR-193a-3p in addition to DAB and TRA was shown to be through inhibiting reactivation of MAPK signaling. This enhanced cytotoxicity by miR-193a-3p was even observed under treatment of DAB, TRA, and an anti-EGFR antibody.

Conclusions: Our study shows that miR-193a-3p regulates multiple proteins involved in oncogenesis, and proposes that the combination therapy of miR-193a-3p and BRAF/MEK inhibitors could be a promising treatment strategy in BRAF-mutated CRC.

Citation Format: Sakura Hiraide, Masanobu Takahashi, Yuya Yoshida, Keigo Komine, Chikashi Ishioka. The functional roles of miRNA-193a-3p in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2361.