Regulation of activity of cathepsins B, L, and D in murine lymphosarcoma model at a combined treatment with cyclophosphamide and yeast polysaccharide

Changes in the activity of cysteine (cathepsins B and L) and aspartyl (cathepsin D) proteases were investigated at the development of susceptible and resistant variants of murine lymphosarcoma (LS). It has been demonstrated that the variant resistant to the cyclophosphamide treatment is characterized by a lower activity of all three cathepsins in the tumor tissue. Application of a higher dose of cyclophosphamide led to a more pronounced increase of the studied enzymatic activity in mice with a resistant variant of LS, than in those with a susceptible one. Administration of a yeast polysaccharide derivative - sulfoethyl glucan - enhanced therapeutic effect of cyclophosphamide in mice with both variants of LS, while the most efficient dose was found to be that of 10 mg/kg body mass. In the intact mice, usage of both cyclophosphamide and sulfoethyl glucan led to a similar increase of the cathepsins activity in liver and spleen.