SMAD1 and cancer: ACVR1, a constituent of the transforming growth factor-beta (TGF-β) family, has been recognized for its involvement in tumor initiation and progression across various cancer types.40–43 Wang and colleagues found that stress-induced phosphoprotein 1 (STIP1), a protein adaptor and modulator of heat shock proteins HSP70 and HSP90, was secreted by ovarian cancer cells and detected in the blood of ovarian cancer patients.44 STIP1 was observed to directly interact with ACVR1, activating it and enhancing SMAD1/5 phosphorylation downstream of ACVR1.