TGFB1 and osteosarcoma: Moreover, mesenchymal stem cells (MSCs) exhibit a profound connection with both the metastatic progression and therapeutic resistance of osteosarcoma.259 Specifically, EVs secreted by osteosarcoma cells, containing TGF-β, are capable of inducing MSCs to release IL-6, which in turn activates STAT3-mediated tumor progression pathways.