Transforming growth factor (TGF)-β regulates a wide variety of cellular responses,including cell growth arrest,apoptosis,cell differentiation,motility,invasion,extracellular matrix production,tissue fibrosis,angiogenesis,and immune function.Although tumor-suppressive roles of TGF-β have been extensively studied and well-characterized in many cancers,especially at early stages,accumulating evidence has revealed the critical roles of TGF-β as a pro-tumorigenic factor in various types of cancer.This review will focus on recent findings regarding epithelial-mesenchymal transition (EMT) induced by TGF-β,in relation to crosstalk with some other signaling pathways,and the roles of TGF-β in lung and pancreatic cancers,in which TGF-β has been shown to be involved in cancer progression.Recent findings also strongly suggested that targeting TGF-β signaling using specific inhibitors may be useful for the treatment of some cancers.TGF-β plays a pivotal role in the differentiation and function of regulatory T cells (Tregs).TGF-β is produced as latent high molecular weight complexes,and the latent TGF-β complex expressed on the surface of Tregs contains glycoprotein A repetitions predominant (GARP,also known as leucine-rich repeat containing 32 or LRRC32).Inhibition of the TGF-β activities through regulation of the latent TGF-β complex activation will be discussed.