Interference with TGF-beta1 and -beta3 in tumor stroma lowers tumor interstitial fluid pressure independently of growth in experimental carcinoma.

A high tumor interstitial fluid pressure (TIFP) is a pathologic characteristic distinguishing the stroma of carcinomas from normal interstitial loose connective tissues. The role of TGF-beta1 and -beta3 in generating a high TIFP was investigated in xenografted experimental anaplastic thyroid carcinoma (ATC) derived from the human ATC cell line KAT-4. A single intravenous injection of a soluble recombinant TGF-beta receptor type II-murine Fc:IgG(2A) chimeric protein that specifically inhibits TGF-beta1 and -beta3, significantly lowered TIFP in a time and concentration dependent manner but did not change total tissue water content in the tumors. Tumor growth rate was higher in tumors treated with the TGF-beta1 and -beta3 inhibitor compared to control tumors during the first 10 days after administration of the inhibitor. The apoptotic index of carcinoma cells, and expression of the cell cycle inhibitor p27(Kip1), were, however, increased in TGF-beta1 and -beta3 inhibitor-treated tumors. Prolonged treatment periods and administration of a second dose of the inhibitor decreased tumor growth rate. The TGF-beta1 and -beta3 inhibitor did not affect proliferation or expression of phosphorylated Smad2 protein in KAT-4 cells cultured in vitro. Our results indicate that members of the TGF-beta family are potential targets for novel anti-cancer treatment directed to the stroma. First by controlling TIFP and by that potentially the uptake of anticancer drugs into tumors and second by their suggested role in maintaining a supportive tumor stroma.