Aim: 5-FU chemoresistance is a major challenge in gastric cancer patient's post-operation treatment. CMPK1 is a key metabolism enzyme associated with 5-FU phosphorylation activation, which is also functioned by epigenetic regulation-microRNA. We characterized the role of CMPK1 and potential regulated target-miR-193a in 5-FU chemotherapy response in gastric cancers.

Methods: The roles of miR-193a on prognosis were assessed in a cohort of gastric cancer samples (n=90, tested by microarray assay) and reconfirmed in expanded samples (n=385, tested by q-PCR assay) with Kaplan-Meier and log-rank analysis. We used luciferase and Western-blot assays to test the regulation effect of miR-193a on CMPK1, and in vitro experiments including comet assay and 3-D spheroid assays to study whether miR-193a is associated with 5-FU chemoresistance. All statistical tests were two-sided.

Results: MiR-193a high expression was associated with worse response to therapy and shorter progression-free survival in two cohorts (PFS: Primary microarray samples: [HR] = 1.28, 95% CI= 1.04 to 1.67, P = 0.005; Expanded samples: [HR] =1.08, 95% CI = 1.00 to 1.17, P = 0.050). In the expanded samples, patients received 5-FU-based therapeutic regimen which have high miR-193a expression was more likely to relapse (PFS<24 months VS PFS>60 months: 0.38±1.17 VS -0.89±1.41,p=0.001;24<PFS<60 months VS PFS>60 months: -0.20±1.59 VS -0.89±1.41,p=0.021 ). Comet assay showed that knock-down of CMPK1 impeded 5-FU caused DNA damage, induced a diminished cell cycle arrest and cell apoptosis. MiR-193a bound directly to the 3'-UTR of CMPK1 and downregulated CMPK1 expression in gastric cancer cells, showed parallel results about 5-FU sensitivity alike to CMPK1. Spheroid assays indicated that miR-193a-mediated attenuation of CMPK1 resulted in significant resistance of gastric cancer cells to 5-FU caused DNA damage and cell death (mean diameters of cell clones ± SD, miR-NC plus 5-FU vs miR-193a plus 5-FU: 78.5±14.8 VS 124.5±16.3, P<0.001; miR-NC plus 5-FU vs si-CMPK1 plus 5-FU: 78.5±14.8 VS 116.0±18.4, P=0.002 ), but not in cisplatin treatment (miR-NC plus 5-FU vs miR-193a plus 5-FU: 75.1±11.3 VS 82.2±12.7, P=0.274; miR-NC plus 5-FU vs si-CMPK1 plus 5-FU: 75.1±11.3 VS 82.0±17.4, P=0.316). Rescue experiments with augmented CMPK1 expression abolished the effect of miR-193a demonstrating the key function of this miRNA in this pathway.

Conclusions: The discovery of a miR-193a-CMPK1-5-FU damage axis supports the methods that combining low miR-193a expression with 5-FU agents may substantially benefit gastric cancer management. MiR-193a might be a valuable predictive biomarker for the chemotherapy response in gastric cancer patients, and provided a therapeutic drug proposal for neoadjuvant chemotherapy.

Citation Format: Hao Chen, Wei Wang, Ben Liu, Lu Han, Xinlei Chu, Hong Zheng, Yanrui Zhao, Xiangchun Li, Lian li, Fengju Song, Wei Zhang, Kexin Chen. Elevated miR-193a attenuates 5-fluorouricil metabolism enzyme CMPK1, resulting in therapeutic resistance and poor survival in gastric cancer [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 4412.