Negative regulators of hepatocyte proliferation, such as transforming growth factor (TGF)-β1 (Braun et al, 1988; Kusaka et al, 2006), are strongly expressed in the ligated lobe (Uemura et al, 2000; Kusaka et al, 2006) and these may contribute to increased cancer-cell proliferation. Here, TGFB1 is linked to cancer.