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Thymidine kinase (TK) and thymidylate synthase (TS) play a key role in, respectively, the salvage and the de novo DNA synthesis pathways. TS is a crucial target for 5-fluorouracil(5-FU) and may also influence methotrexate(MTX) efficiency. Tyrosine kinase(TPK) has been associated with the cytoplasmic domain of growth factor receptors as well as oncoproteins. We investigated whether TK, TS and TPK are predictive factors for drug sensitivity evaluated in terms of relapse-free improvement in breast-cancer patients receiving adjuvant chemotherapy. TK, TS and TPK activities were determined in the cytosols of 154 node-positive primary breast cancers. All patients received 5-FU containing adjuvant chemotherapy. Measurements were performed using radioenzymatic methods. The levels of TK were correlated with those of TS and TPK. The levels of TS and TPK were less strongly correlated with each other. High TK levels were more often found in larger tumours, and the levels of both TK and TPK were negatively correlated with those of PgR. Patients whose tumours contained high levels of TK had increased risks of relapse and death. TS was not of prognostic value, while a high level of TPK was associated with early death. In Cox analysis, TK and TPK retained their independent prognostic value. While target enzyme activities on the de novo DNA synthesis pathway could determine response to anti-metabolics mainly inhibiting this pathway, high activities on the alternative salvage pathway could circumvent induced growth inhibition.

The present study describes the independent expression of the type 1 and 2 isoforms of human 5 alpha-reductase in the baculovirus-directed insect cell expression system and the selectivity of their inhibition. The catalytic properties and kinetic parameters of the recombinant isozymes were consistent with published data. The type 1 isoform displayed a neutral (range 6-8) pH optimum and the type 2 isoform an acidic (5-6) pH optimum. The type 2 isoform had higher affinity for testosterone than did the type 1 isoform (Km = 0.5 and 2.9 microM, respectively). Finasteride and turosteride were selective inhibitors of the type 2 isoform (Ki (type 2) = 7.3 and 21.7 nM compared to Ki (type 1) = 108 and 330 nM, respectively). 4-MA and the lipido-sterol extract of Serenoa repens (LSESr) markedly inhibited both isozymes (Ki (type 1) = 8.4 nM and 7.2 micrograms/ml, respectively; Ki (type 2) = 7.4 nM and 4.9 micrograms/ml, respectively). The three azasteroids were competitive inhibitors vs substrate, whereas LSESr displayed non-competitive inhibition of the type 1 isozyme and uncompetitive inhibition of the type 2 isozyme. These observations suggest that the lipid component of LSESr might be responsible for its inhibitory effect by modulating the membrane environment of 5 alpha-reductase. Partially purified recombinant 5 alpha-reductase type 1 activity was preserved by the presence of lipids indicating that lipids can exert either stimulatory or inhibitory effects on human 5 alpha-reductase.

The urokinase type plasminogen activator (u-PA) and the plasminogen activator inhibitor-1 (PAI-1) are among the best second-generation prognostic tissue factors in breast cancer. However, different extraction procedures and assay kits are used in different laboratories. A total of 79 breast tumour tissues stored in liquid nitrogen were analysed in this study. We compared u-PA and PAI-1 levels determined with the American Diagnostics (AD) kit after various extraction procedures. The median cytosolic extraction yield in the presence of 0.4 mol/l KCl, calculated relative to extraction in the presence of 10 ml/l Triton X100 when adapted to standard laboratory working hours (incubation for 2 h instead of 12 h) was 74.4% for u-PA and 85.8% for PAI-1. In addition, the correlations were acceptable. Cytosolic extracts prepared with KCl could permit optimal u-PA and PAI-1 assays while also enabling hormone receptors to be determined with the same specimens. Further studies with clinical data are now necessary to determine the prognostic relevance of this extraction procedure.

In the natural history of post-menopausal patients with primary breast cancer, high estrogen receptor levels (ER) have been associated with a poor recurrence-free survival. The purpose of this study was to investigate whether there are any biological intratumoral characteristics to support this puzzling clinical observation. In a population of 542 post-menopausal, primary-breast-cancer patients, 3 normal distributions fitted into the frequency distribution curve of the logarithmically transformed ER-EIA values. The biological profiles of the low ER group, and of the intermediate and high ER groups identified in the ER-positive population were compared. Parameters correlated with ER functional aspect (progesterone receptors and PS2), receptors of epidermal growth factor (EGFR), protease cathepsin D and tumor proliferation (deduced from thymidine kinase activity) were analyzed. As previously reported, the levels of progesterone receptors and PS2 increased significantly from the low to the high ER groups. The highest levels of cathepsin D and thymidine kinase which have been previously related to a poor prognosis in breast cancer were found in the low ER group, but high levels were, surprisingly, also found in the high ER group. This study indicates that the ER-positive post-menopausal population is biologically heterogeneous. The high levels of thymidine kinase found in the high ER group suggest that overexpression of ER may be associated with proliferation enhancement, partly explaining the poor spontaneous prognosis related to this subset.