Whether the gene expression of hepatic Ca(2+)-
binding protein regucalcin is altered in
hepatomas was investigated. The change in regucalcin
mRNA levels was analyzed by Northern blotting using liver regucalcin
complementary DNA (0.9 kb). Rat
hepatoma was induced by continuous feeding of basal diet containing 0.06%
3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB). After 35 weeks feeding, rats were sacrificed, and the non-tumorous and tumorous tissues of the livers were removed. In individual rats, the regucalcin
mRNA levels in the tumorous tissues were generally decreased in comparison with that of the non-tumorous tissues of the chemical-fed rats, although the chemical administration might decrease the
mRNA expression in normal rat liver, suggesting that the chemical administration causes a suppressive effect on the
mRNA expression. When the genomic
DNA extracted from the liver tumorous tissues was digested with restriction
enzymes (EcoRI, BamHI and HindIII) and analyzed by Southern blotting, no rear-ranged band was found in the regucalcin gene from the
hepatoma. Interestingly, in the transplantable
Morris hepatoma cells, the regucalcin
mRNA was markedly expressed, while the
albumin mRNA was expressed only slightly. The present study demonstrates that regucalcin
mRNA is clearly expressed in the transformed cells (
Morris hepatoma cells).