Abnormal accumulation of copper in LEC rat liver induces expression of p53 and nuclear matrix-bound p21waf 1/cip 1

The LEC rat is an inbred mutant strain which spontaneously develops liver injury and subsequent liver cancer. Liver injury in LEC rats has recently been shown to be closely related to abnormal copper accumulation in the liver. Previously, we reported that LEC rat hepatocytes lose their growth potential, probably allowing selective growth of preneoplastic cells. In this study, to elucidate the effects of copper accumulation on the growth activity of LEC rat hepatocytes, we examined the growth activity and the expression of p53 and p21waf 1/cip 1 in the livers of LEC rats fed on either a control or a low-copper diet. Potential for cell proliferation of hepatocytes obtained from normal diet fed LEC rats was almost comparable to that of the cells from age-matched Sprague-Dawley (SD) rats. Northern blot analysis showed that the expression of p53 and p21waf 1/cip 1 was significantly high in the livers of LEC rats fed a control diet, while the expression of p53 and p21waf 1/cip 1 in the LEC rats fed a low-copper diet was as low as that of SD rat livers. Western blot analysis consistently showed that the amount of p21waf 1/cip 1 bound to the nuclear matrix scaffold of the LEC rat liver was reduced by feeding a low-copper diet. These findings suggest that abnormal accumulation of copper induced the expression of p53 and p21waf 1/cip 1, resulting in the inhibition of cell proliferation of LEC rat hepatocytes.