TGFB1 and cancer: However, the role of TGF-β signaling in tumorigenesis is somewhat paradoxical since it acts as a tumor suppressor at early stages of cancer development and as an oncogene at terminal stages of the disease by initiating a transcriptional program required for the activation of genes involved in cell metastasis and invasion (reviewed in Massague, 2008; Barcellos-Hoff and Akhurst, 2009; Padua and Massague, 2009).