[Prognostic effect of PyNPase (pyrimidine nucleoside phosphorylase) activity in breast cancer]

To clarify the clinical significance of PyNPase (Pyrimidine Nucleoside Phosphorylase)/ PD-ECGF activity in breast cancer, we examined the possible correlation of PyNPase activity to clinicopathological features and prognosis in 195 patients with primary breast cancer between January 1992 through December 1993. The mean PyNPase activity of primary breast cancer, assayed by ELISA method, was 140.6 U/ml, which was between that of benign breast disease (18.2) and recurrent tumors (270.9). In histological type of breast cancer, tumors with solid-tubular carcinoma had significantly higher levels of PyNPase activity. The activity of ER negative or aneuploid tumors was higher than that of ER positive or diploid tumors, respectively. And there was a significant relationship between PyNPase activity and proliferative activity determined by S-phase fraction (SPF) or DNA polymerase alpha. These findings suggested that PyNPase activity was associated with the degree of malignancy. As regards prognosis, in lower SPF (< 16%) group, patients with higher PyNPase activity had significantly lower disease--free survival rates, whereas those with higher activity had a favorable prognosis in the higher SPF (> or = 16%) group. The contradiction might be explained by the possibility that 5-FU derivatives were effective only in patients with high SPF and PyNPase activity, as all patients were treated by a regimen containing 5-FU derivatives. We suggest that PyNPase activity is associated with progression and proliferation of breast cancer, and that it may be useful for prediction of prognosis and therapeutic efficacy of 5-FU derivatives.