Cysteine and serine proteases in gastric cancer.

Background: Cysteine proteases (cathepsin B [CATB] and cathepsin L [CATL]), the serine protease urokinase-type plasminogen activator (UPA), and plasminogen activator inhibitor type-1 (PAI-1) are thought to play an important part in cancer invasion and metastasis. The aims of this study were to measure CATB, CATL, UPA, and PAI-1 in gastric cancer (GC) and normal mucosa distant from the tumor (NORM); to evaluate whether tissue levels are related to tumor stage, grade, or histotype; to assess their prognostic relevance; and to examine UPA and PAI-1 expression immunohistochemically.

Methods: Gastric cancer and NORM samples were obtained from 25 patients with gastric cancer patients undergoing surgery (17 males, 8 females; mean age, 62 years; range, 31-84 years). Antigen concentrations were measured using the enzyme-linked immunosorbent assay method. Immunohistochemistry was performed using monoclonal UPA and PAI-1 antibodies.

Results: Significantly higher antigen levels were found: (1) in GC vs. NORM (CATB, CATL, UPA, PAI-1) tissues; (2) in GC with versus without metastasis (CATB, CATL, UPA); (3) in poorly or moderately versus well differentiated GC; and (4) in diffuse versus intestinal-type GC (CATB, CATL). Urokinase-type plasminogen activator, PAI-1 and CATB levels had a significant prognostic impact. Cancer and stromal cells, showed immunoreactivity to anti-UPA and anti-PAI-1 antibodies.

Conclusions: These results confirm the important role of CATB, CATL, UPA and PAI-1 in gastric cancer progression. Higher levels are detected in GC with metastases, poorer differentiation, and diffuse histotype, thus identifying patients with a worse prognosis.