MicroRNA-143 suppresses gastric cancer cell growth and induces apoptosis by targeting COX-2

AIM:To investigate the function of microRNA-143(miR-143)in gastric cancer and explore the target genes of miR-143.METHODS:A quantitative real-time reverse transcription-polymerase chain reaction(RT-PCR)analysis was performed to evaluate miR-143 expression in gastric cancer cell lines.After transfecting gastric cancer cells with miR-143-5p and miR-143-3p precursors,Alamar blue and apoptosis assays were used to measure the respective proliferation and apoptosis rates.Cyclooxygenase-2(COX-2)expression was determined by realtime RT-PCR and Western blot assays after miR-143transfection.Reporter plasmids were constructed,and a luciferase reporter assay was used to identify the miR-143 binding site on COX-2.RESULTS:Both miR-143-5p and miR-143-3p were significantly downregulated in multiple gastric cancer cell lines.Forced miR-143-5p and miR-143-3p expression in gastric cancer cells produced a profound cytotoxic effect.MiR-145-5p transfection into gastric cancer cells resulted in a greater growth inhibitory effect(61.23%±3.16%vs 46.58%±4.28%,P<0.05 in the MKN-1cell line)and a higher apoptosis rate(28.74%±1.93%vs 22.13%±3.31%,P<0.05 in the MKN-1 cell line)than miR-143-3p transfection.Further analysis indicated that COX-2 expression was potently suppressed by miR-143-5p but not by miR-143-3p.The activity of a luciferase reporter construct that contained the 3’-untranslated region(UTR)of COX-2 was downregulated by miR-143-5p(43.6%±4.86%,P<0.01)but not by miR-143-3p.A mutation in the miR-145-5p binding site completely ablated the regulatory effect on luciferase activity,which suggests that there is a direct miR-145-5p binding site in the 3’-UTR of COX-2.CONCLUSION:Both miR-143-5p and miR-143-3p function as anti-oncomirs in gastric cancer.However,miR-143-5p alone directly targets COX-2,and it exhibits a stronger tumor suppressive effect than miR-143-3p.