Association of MicroRNA-31-5p with Clinical Efficacy of Anti-EGFR Therapy in Patients with Metastatic Colorectal Cancer

Background Gene mutations in the pathway downstream of epidermal growth factor receptor (EGFR) are considered to induce resistance to anti-EGFR therapy in colorectal cancer (CRC). We recently reported that microRNA-31 (miR-31)-5p may regulate BRAF activation and play a role in the signaling pathway downstream of EGFR in CRC. Therefore, we hypothesized that miR-31-5p can be a useful biomarker for anti-EGFR therapy in CRC. Methods We evaluated miR-31-5p expression and gene mutations [ KRAS (codon 61 or 146), NRAS (codon 12, 13, or 61), and BRAF ( V600E )] in the EGFR downstream pathway in 102 CRC patients harboring KRAS (codon 12 or 13) wild-type who were treated with anti-EGFR therapeutics. Progression-free survival (PFS) and overall survival (OS) were evaluated. Results KRAS (codon 61 or 146), NRAS , and BRAF mutations were detected in 6.9, 6.9, and 5.9 % patients, respectively. Compared with CRCs with at least one mutation ( n = 20), significantly better PFS ( P = 0.0003) but insignificantly better OS were observed in CRCs harboring all wild-type genes ( KRAS , NRAS , and BRAF ). High miR-31-5p expression was identified in 11 % ( n = 11) patients and was significantly associated with shorter PFS ( P = 0.003). In CRCs carrying all wild-type genes, high miR-31-5p was associated with shorter PFS ( P = 0.027). Conclusions High miR-31-5p expression was associated with shorter PFS in patients with CRC treated with anti-EGFR therapeutics. Moreover, in CRCs carrying all wild-type genes, high miR-31-5p was associated with shorter PFS, suggesting that it may be a useful and additional prognostic biomarker for anti-EGFR therapy.