The structure and dynamics of actin cytoskeleton are factors important for regulation of cell adhesion, spreading, and migration. TRIP6 is a LIM domain-containing protein interacting with many actin cytoskeleton- associated proteins and modulating the activity of certain transcription factors. To study the functions of TRIP6, we inhibited its expression in A549 and A431 cells with short interfering RNAs (siRNAs). TRIP6 knockdown led to an increase in the number and length of stress fibers and acquisition of the locomotor phenotype. Staining for paxillin demonstrated a decrease in the number of focal adhesion zones and their reorganization, while staining for E-cadherin revealed a loss of cell-to-cell contacts. These morphological changes were accompanied by a twofold increase in cell motility rate, as determined by the wound-healing assay. Thus, downregulation of TRIP6 in the above cell lines led to development of more malignant phenotype of epithelial cells. Possible mechanisms underlying the effects observed are discussed.