The mouse renal cell carcinoma line, Renca, is insensitive to transforming growth factor-beta (TGF-β) in vitro. The present study was conducted to determine whether removal of TGF-β from these tumor cells would inhibit tumor progression in vivo.

TGF-β elimination was accomplished either by administration of neutralizing TGF-β antibody into mice receiving intravenous injection of Renca tumor cells or infection of TGF-β antisense expression vector into these tumor cells before subcutaneous injection into recipient mice.

Although a low dose of TGF-β antibody (5 mg/kg every 3 days) was without any effect, a high dose of TGF-β antibody (50 mg/kg every 3 days), administered to recipient mice, resulted in a significant reduction in lung metastasis and was accompanied by increased apoptosis in the tumor cells. When the tumor cells were transfected with a TGF-β1 antisense expressing vector, a significant reduction occurred in the tumor incidence, as well as the tumor burden. However, in nude mice, cells with reduced TGF-β1 production grew almost as well as did the unmodified Renca cells, suggesting that the host's immune system might play an antitumor role.

These results indicate that progression of Renca tumor can be inhibited by eliminating TGF-β from the tumor cells. Our results also suggest that, although insensitive to TGF-β under in vitro conditions, Renca tumors could be inhibited by TGF-β removal through the systemic host environment.