The long noncoding RNA HOTTIP promotes breast cancer cell migration, invasiveness, and epithelial-mesenchymal transition via the Wnt-β-catenin signaling pathway

Long noncoding RNA HOTTIP (HOXA transcript at the distal tip) has recently been reported to have a role in the proliferation of various cancer cells, yet its role in cell migration, invasiveness, and the EMT (epithelial-mesenchymal transition) in breast cancer and the potential mechanisms remain unknown. Breast cancer cell lines MDA-MB-231 and MDA-MB-468 were transfected with shRNA (short hairpin RNA) that specifically targeting HOTTIP. We observed a remarkable decrease in migration and invasiveness in these two breast cancer cell lines after knock-down of HOTTIP by shHOTTIP. We also demonstrated that the EMT of these two breast cell lines was suppressed after HOTTIP knock-down, as evidenced by increased E-cadherin levels, and decreased levels of N-cadherin, Snail, and Twist. Moreover, HOTTIP silencing also suppressed tumor metastasis in nude mice in vivo. In addition, we found that the expression of beta-catenin was significantly decreased in breast cancer cells after knock-down of HOTTIP. In a further rescue experiment using overexpression of beta-catenin, the rates of cell migration, invasiveness, and EMT of HOTTIP-silenced breast cancer cells were promoted, disclosing a potential role of the Wnt-beta-catenin signaling pathway in this process. Overall, we discovered the positive regulatory function of HOTTIP in the migration, invasiveness, and EMT of breast cancer cells, via regulating the Wnt-beta-catenin pathway.