Proteolytic enzymes as new tumor markers in rats with benzopyrene sarcoma

Proteolytic enzymes may facilitate tumor invasion by histolysis of the surrounding tissue and inhibit tumor growth in the course of host defense reactions. Using chromogenic peptide substrates, we looked for proteolytic activities related to carcinogenesis in serum and tumor extracts of rats with benzopyrene sarcomas. The enzymatic hydrolysis of two substrates (Boc-(Ala)2-p-nitroanilide and Bz-Lys-p-nitroanilide) was significantly decreased in the sera of tumor-bearing animals (P less than 0.01). This loss of proteolytic activity was highly correlated to tumor growth, so these enzymes might become useful as new tumor markers. In the tumor extracts, we found the Boc-(Ala)2-p-nitroanilide cleaving activity increased with tumor weight, whereas the Bz-Lys-p-nitroanilide cleaving activity did not exhibit any correlation to tumor growth. Studies on the potential use of these results for cancer patients are indicated.