SB431542 is widely used in cell biology research for its ability to inhibit specific signaling pathways. It effectively blocks the TGF-β (transforming growth factor-beta) pathway by inhibiting the ALK4, ALK5, and ALK7 receptor kinases. This inhibition prevents the phosphorylation of Smad2/3 proteins, which are key mediators in TGF-β signaling. One of its primary applications is in stem cell research, where it helps maintain pluripotency in human embryonic stem cells by suppressing differentiation signals induced by TGF-β. It is also used to facilitate the reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) when combined with other factors. In cancer research, SB431542 is employed to study epithelial-to-mesenchymal transition (EMT), a process linked to tumor progression and metastasis. By inhibiting TGF-β-induced EMT, it allows researchers to investigate the role of this pathway in cell migration and invasion. Additionally, it has been used in regenerative medicine studies to direct cell fate, particularly in differentiating stem cells into specific lineages by modulating signaling environments. Its selectivity and effectiveness make it a valuable tool in mechanistic studies of development, fibrosis, and cellular plasticity.