Purpose. Production of active transforming growth factor-β (TGF-β )by human osteosarcoma may contribute to malignant progression through mechanismsthat include induction of angiogenesis, immune suppression and autocrine growthstimulation of tumor cell growth.To study events associated with induction of cell proliferationby TGF-β , we have evaluated the TGF-β pathway in two murine osteosarcoma cell lines, K7and K12. The gene discussed is TGFB1; the disease is osteosarcoma.