Date of Award


Publication Type

Master Thesis

Degree Name



Biological Sciences


Biology, Cell.


Dufresne, M. J.




The expression of the lysosomal cysteine proteases, cathepsins B, H and L and cysteine protease inhibitors in intracellular and extracellular fractions prepared from the differentiating malignantly transformed human hepatoma cell line HepG2, the differentiating rat myoblast cell line L6, and the L6-D3 non-fusing variant, were examined using synthetic substrates. HepG2 cells were established in serum-free medium for greater than 100 generations and demonstrated biological (e.g., growth characteristics) and biochemical (e.g., the synthesis and secretion of apolipoprotein B and cathepsin B) parameters similar to their serum-grown counterparts. HepG2 cells expressed high constant levels of intracellular cathepsins B and L activity as well as a growth related increase in the secretion of latent activatable cathepsin L. L6 differentiating myoblasts demonstrated high levels of intracellular cathepsins B and L activities, and low levels of intracellular cathepsin H activity. L6 cells also exhibited low levels of latent activatable cathepsin activity. There was a fusion related increase in the intracellular activity of all three cathepsins as well as a fusion related increase in extracellular latent cathepsin L activity. Fusion was not a prerequisite for cathepsin expression as the L6-D3 non-fusing variant demonstrated high constant levels of intracellular cathepsins B and L activities, low levels of cathepsin H activity and high constant levels of extracellular latent cathepsin L activity during phase growth. Since HepG2 and L6-D3 exhibited a similar pattern of cathepsin expression, this suggests that L6-D3 demonstrate malignant transformation rather than differentiation. Although L6-D3 demonstrated levels of cathepsin B significantly higher than L6, the ratio of cathepsin B activity to cathepsin B inhibitory activity as well as the level of cathepsin B inhibitory activity remained constant during growth. In contrast there was a three-fold increase in the ratio of cathepsin B enzyme activity to cathepsin B inhibitor activity during fusion of L6 cells. (Abstract shortened by UMI.)Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1993 .J36. Source: Masters Abstracts International, Volume: 32-06, page: 1582. Adviser: M. Dufresne. Thesis (M.Sc.)--University of Windsor (Canada), 1993.