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The malignant phenotype and cysteine proteinases
B F Sloane1, J Rozhin, E Krepela
1Department of Pharmacology, Wayne State University, Detroit, Michigan 48201.
Biomedica Biochimica Acta
|January 1, 1991
Summary
The study reveals that acidic conditions, common in tumors, promote the secretion of active cathepsin B and cathepsin L. This enhances their role in cancer progression by increasing stability and activity.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Cathepsin B and cathepsin L expression and secretion are linked to the malignant phenotype in B16 melanomas.
- These cysteine proteinases exist in native and latent forms, with distinct localizations in lysosomes and cell membranes.
Purpose of the Study:
- To investigate the forms of cathepsin B and L associated with B16 melanoma cells.
- To determine the effect of acidic pH on the secretion and activity of these enzymes.
Main Methods:
- Analysis of lysosomal and membrane fractions from B16 melanoma cells.
- Exposure of cells to brief acidic pH conditions.
- Assay of enzyme activity and forms (native vs. latent).
Main Results:
- Lysosomal fractions contained only native cathepsin B and L.
- Membrane fractions contained both native and latent forms.
- Acidic pH induced secretion of native cathepsin B and L, reducing membrane-associated activity.
Conclusions:
- Pericellular acidification in tumors favors the release of active cathepsin B and L.
- Acidic conditions enhance enzyme stability and secretion of native forms, promoting tumor proteolysis and malignancy.