Twist, a newly found EMT-inducer, has been reported to be up-regulated in those of diffuse-type gastric carcinomas with high N-cadherin level. We show here MKN45, a cell line derived from undifferentiated carcinomas cells, expresses high levels of Twist. Down-regulation of Twist, using an antisense Twist vector in MKN45 cells, inhibits cell migration and invasion, companied with a morphologic changes associated with MET. Suppression of Twist also decreases the expressions of N-cadherin and fibronectin, but not of E-cadherin in MKN45. In contrast, overexpression of Twist in MKN28, a cell line derived from moderate differentiated carcinomas, results in up-regulation of N-cadherin and fibronectin, companied with down-regulation of E-cadherin. Taken together, our results suggest that Twist regulates cell motility and invasion in gastric cancer cell lines, probably through the N-cadherin and fibronectin production.