The relative amounts of the precursor (52 kDa) and processed (31,27 kDa) forms of
cathepsin D have been analyzed by Western blotting in biopsied breast tissue cytosols from 134 lesions from invasive
breast cancer patients, 24 lesions from patients with
ductal carcinoma in situ (
DCIS), 227 lesions from benign
breast disease patients, and 28 lesions from normal control subjects. The mean relative percentage amount of the 31 kDa form was significantly increased (p < 0.001) in the invasive
breast cancer group compared to the other three groups. In addition, the mean relative percentage amount of the 31 kDa form was significantly increased (p < 0.05) in node-positive compared to node-negative
breast cancer patients. In the benign
breast disease group, patients with proliferative-type disease had a significantly increased (p = 0.02) mean relative percentage amount of the 31 kDa form of
cathepsin D compared to patients with nonproliferative-type disease. Invasive
breast cancer patients were followed for up to 75 months to determine if the relative percentage amount of the 31 kDa form of
cathepsin D was predictive of disease-free and overall survival. Although the amount of the 31 kDa form was not predictive of disease-free survival, patients in the 'high' 31 kDa group (> 18%) were significantly (p < 0.05) more likely to die than patients in the 'low' 31 kDa group (< or = 18%). The 12 patients who died were all node-positive and in the high 31 kDa group. It thus appears that the relative amount of the processed, active 31 kDa form of
cathepsin D is a useful prognostic
indicator, at least in node-positive
breast cancer patients.