Epithelial-mesenchymal transition (EMT) is an essential step for cancer 
metastasis. MicroRNAs (miRNAs) are small non-coding RNAs that regulate 
target-mRNAs post-transcriptionally. The expression and function of miRNAs in 
EMT of HT-29 colonic cells remain elusive. This study looks at expression of 
miRNAs in EMT and explores the effects of miRNAs on EMT in HT-29 cell line. 
HT-29 was treated with TGF β to establish an EMT model, in which a collection of 
miRNAs was dynamically regulated by real-time PCR (qPCR) analysis. Among them, 
miR-21 and miR-27 were significantly upregulated, while miR-22, miR-26, miR-30, 
miR-181, miR-200b, miR-200c and miR-214 were markedly downregulated. 
MiRNA-inhibitors were used to knockdown miRNAs in HT-29 and EMT markers were 
determined by qPCR to monitor the effects of miRNAs on EMT process. Results 
showed that miR-22 could not alter the expression of EMT markers, while 
knockdown of miR-200b could significantly increase that of epithelial markers, 
N-cadherin, Vimentin, α-Sma and Twist1 and decrease that of mesenchymal marker, 
E-cadherin. Bioinformatic analysis and Western blot showed that ZEB1 was 
directly suppressed by miR-200b. In conclusion, miRNAs are dynamically regulated 
in TGF β-induced EMT of HT-29 and miR-200b was essential for EMT by suppressing 
the expression of ZEB1 in HT-29.