Studies have shown that TGFβ stimulation of carcinoma-derived cell populations in culture can lead to the activation of this reversible process [45, 178, 179]. In vivo studies have further shown that expression of TGFβ1 in the skin of transgenic mice enhanced the conversion of benign skin tumors to carcinomas and highly invasive spindle-cell carcinomas [180]. Here, TGFB1 is linked to sarcomatoid carcinoma.