TWIST1 and cancer: These results complement contemporary reports that CTCs are more “mesenchymal” than matched primary tumors or metastases [22, 37, 38], and that activation of Twist-1, which similarly represses E-Cadherin, also enabled cancer cells to enter the circulation, while subsequent down-regulation of Twist1 accompanied growth at metastatic sites using a carcinogen-induced rodent model [10].