Enhanced levels of cathepsin B mRNA in murine tumors.

Relative amounts of mRNA for cathepsin B were measured in normal murine liver and three murine tumors, an invasive liver tumor (hepatoma, Hepa cl 9) and two melanoma variants (B16-F1 and B16 amelanotic melanoma, B16a). Using a human cDNA to the cathepsin B coding region as a hybridization probe, we detected two species of cathepsin B specific RNA transcripts (2.2 and 4.1 kb) in total RNA preparations of all four tissues. The concentrations of the 2.2 and 4.1 kb species were 3.6 and 2.7-fold greater in the highly metastatic B16a melanoma than in normal liver. The concentration of the 2.2 kb species in the invasive hepatoma was 1.7-fold greater than in normal liver. The increased levels of the 2.2 kb message were reflected in increases in activity of cathepsin B in both Hepa cl 9 and B16a.