Lysosomal Proteases Cathepsins D, B, H, L and Their Inhibitors Stefins A and B in Head and Neck Cancer

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Abstract
In cytosols of tumour and normal tissue of 53 patients suffering from head and neck carcinoma cathepsins D, B, H and L were measured using quantitative immunoreactive assays (ELISA). The values of cathepsins D, B and L were significantly higher in tumour tissue, whereas cathepsin H concentration was lower in tumour than in normal tissue. Median cathepsin D values were 27 pmol (tumour tissue) vs. 12 pmol (normal tissue) per mg of total protein, median cathepsin B values were 1.25 micrograms/mg (tumour tissue) vs. 0.23 micrograms/mg (normal tissue) and median cathepsin L values were 39.8 ng/mg (tumour tissue) vs. 20.0 ng/mg (normal tissue). Median cathepsin H values were 1.05 micrograms/mg and 2.20 micrograms/mg for tumour and normal tissue, respectively. Additionally, stefin A and stefin B were measured in tumour and normal tissue samples. In contrast to the cathepsins, the concentrations of these inhibitors of cysteine proteinases was not significantly different between tumour and normal samples. The concentrations of cathepsins D, B, H and L and stefins A and B measured in head and neck tumours, were independent of standard clinical and histological prognostic factors. Significant correlation of tumour tissue values was observed between cathepsins B and L and between both stefins.