Characterization of double transgenic mice expressing hepatocye growth factor and transforming growth factor alpha.

Hepatocyte growth factor (HGF) and transforming growth factor alpha (TGF alpha) are potent mitogens for mature hepatocytes in primary culture (Nakamura, et al. 1984, Mead et al., 1989). However, these cytokines have completely different effects on tumor cell growth (Jhappan et al., 1990, Shiota et al, 1992). To clarify dual effects of these cytokines in liver, we developed double transgenic mice of HGF and TGF alpha using albumin promoter-HGF cDNA transgenic mice (AlbHGF) and metallothionein promoter-TGF alpha transgenic mice (MthTGF alpha). Double transgenic mice were examined on DNA synthesis, c-myc mRNA and occurrence of hepatocelular carcinoma (HCC). Higher labeling indices using BrDU were observed, in sequence, in AlbHGF mice, AlbHGF/MthTGF alpha, MthTGF alpha and wild type mice. Hepatic expression of c-myc mRNA in AlbHGF mice was elevated, compared to that in AlbHGF/MthTGF alpha or MthTGF alpha mice. After long-term observation, MthTGF alpha mice developed HCC in 6/10 (60%), whereas AlbHGF/MthTGF alpha mice developed HCC in 3/9 (33%). These data suggest that HGF is the potent mitogen, stimulating DNA synthesis and up-regulating c-myc mRNA. In addition, HGF may excert some inhibitory effect on occurrence of HCC by TGF alpha.