TWIST1 is involved in tumor invasion and metastasis by promoting epithelial-to-mesenchymal transition. However, the molecular target of TWIST1 involving this mechanism is poorly understood. To identify the TWIST1-regulated genes, we established the Saos-2 cells stably expressing TWIST1 gene by transfecting TWIST1 cDNA into the cells and performed a differential display approach by using annealing control primers. Here, we report that one of the genes that were down-regulated in TWIST1 expressing cells is predicted to be TIMP1. TIMP1 has been reported as the naturally occurring specific inhibitor of matrix metalloproteinases (MMPs). Overexpression of TWIST1 gene suppressed the expression of TIMP1 mRNA but had no effect on TIMP2 and MMP-2 expression, as determined by semi-quantitative RT-PCR. We showed that TWIST1 was up-regulated in SCCBHY cells, which have a strong capacity of invasion into mandibular bone compared with SCCHN cells. Our present results suggest that TWIST1 is involved in tumor invasion by regulating the expression of TIMP1.