Among a variety of factors that promote EMT, the involvement of PDPN and its cell-type specific function in the EMT process, as well as the role of other regulatory proteins associated and/or activated with the process were also demonstrated in vitro [11, 25, 42] Therefore, we studied the expression of CD44, RhoA, Snail, Twist1, Vimentin, Paxillin and PTK2 proteins involved in the E/R/M or EMT pathway in TPC1 and BcPAP thyroid cell lines knock-down, which suggests that alternative signaling pathways were responsible for the observed changes in the cell motility and morphology. This evidence concerns the gene PTK2 and thyroid gland disorder.