TGFB1 and neoplasm: Our data indicate that: (1) gastric cancer cell derived exosomes are internalized by hucMSCs; (2) gastric cancer cell derived exosomes trigger hucMSCs differentiation to CAFs and (3) TGF-β/Smad pathway mediates the transition of hucMSCs to CAFs. Our findings suggest that TGF-β in tumor exosomes may interact with the TGF-β R1 on hucMSCs, resulting in the activation of Smad pathway in hucMSCs and the subsequent differentiation of hucMSCs to CAFs.