Objective To investigate the functions of microRNA-1 43 (miR-1 43)in esophageal cancer cell line ECA1 09.Methods ECA1 09 cells were transfected with negative control (NC),miR-1 43 mimics or miR-1 43 inhibitors.3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT)assay was per-formed to evaluate the growth of ECA1 09 cells after transfection.Annexin V-FITC /PI apoptosis test kit was used to detect early apoptosis rate in ECA1 09 cells.Transwell migration and invasion assays were conducted to compare the migration and invasion capacity of ECA1 09 among different groups.Real-time PCR and Western blotting were used to analyze the mRNA and protein alteration after transfection.Results Three and four days after transfection,compared with NC (absorbance value:0.90 ±0.02 and 1 .09 ±0.07),miR-1 43 mimics inhibited ECA1 09 cell proliferation (absorbance value:0.66 ±0.05 and 0.80 ±0.04),while miR-1 43 inhibi-tors promoted cell proliferation (absorbance value:1 .1 3 ±0.09 and 1 .51 ±0.08),with statistical signifi-cances (F =49.1 6,P =0.000;F =1 00.34,P =0.000).Early-stage apoptosis rates of ECA1 09 transfected with NC,miR-1 43 mimics and miR-1 43 inhibitors were 3.42% ±0.72%,1 1 .63% ±1 .1 5% and 0.94% ± 0.1 0%,respectively,with statistical significance (F =1 51 .61 ,P =0.000).Meanwhile,compared with NC (migration cell number:336 ±1 3,invasion cell number:1 47 ±1 6),miR-1 43 mimics inhibited cell migration (1 48 ±1 6)and invasion (75 ±1 0),while miR-1 43 inhibitors promoted cell migration (51 0 ±1 4)and inva-sion (238 ±1 6),with statistical significances (F =470.99,P =0.000;F =90.04,P =0.000).Compared with NC (1 .00 ±0.00),miR-1 43 mimics down-regulated mRNA (relative expression level 0.22 ±0.08)and protein expression (relative expression level 0.46 ±0.08)of K-ras,whereas miR-1 43 inhibitors up-regulated mRNA (1 .55 ±0.1 2)and protein expression (1 .33 ±0.05)of K-ras (F =1 31 .36,P =0.000;F =88.1 7, P =0.000).Conclusion miR-1 43 functions as a tumor suppressor in esophageal cancer cell line ECA1 09, probably by down-regulating K-ras expression.