The role of transforming growth factor beta I (TGF-beta 1) in carcinogenesi
s is a controversial issue. Certain results suggest a promoter role of this
growth factor whilst in other experimental models TGF-beta 1 seems to inhi
bit the process of tumorigenesis. In an attempt to resolve this problem, we
have performed chemical hepatocarcinogenesis experiments on transgenic mic
e expressing a high level of active TGF-beta 1 in their liver. Transgenic p
roduction of TGF-beta 1 did not result in spontaneous tumour formation duri
ng our observation period. However, two carcinogens, thioacetamide and N-OH
acetylaminofluorene, were more potent in transgenic than in wild-type mice
, whereas aflatoxin B1 was equally effective in both groups. Our observatio
ns suggest that an increased level of TGF-beta 1 in the liver does not prov
ide protection against the effect of chemical carcinogens. (C) 1999 Elsevie
r Science Ltd. All rights reserved.