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We assayed methyl-p-hydroxyphenyllactate esterase (MeHPLAase) activity in 48 cases of primary breast cancer. MeHPLAase activity did not show significant correlation with estrogen receptor and progesterone receptor levels. No significant relationship was found between enzymatic activity and tumor diameter, lymph node status, mitotic activity, degree of nuclear differentiation, and proportion of the S-phase fraction. During the follow-up period (median, 18.8 months; range, 6-69 months), recurrences were observed in 18 of 48 (37%) cases. The Weibull survival regression model using the enzymatic activity as a continuous covariate showed that levels of enzymatic activity were directly associated with the risk of recurrence (P = 0.02). Assuming the mean value of enzymatic activity as the cutoff value, we found a statistically significant relationship between high MeHPLAase activity and shorter recurrence-free survival. On multivariate analysis, MeHPLAase activity proved to be an independent factor for predicting a short period of recurrence-free survival.

Preliminary experiments on thymocyte suspensions derived from human thymus hyperplasia indicated the presence of specific cytoplasmic receptors binding [3H]-dexamethasone with high affinity and specificity. The receptor was rapidly transferred into the nuclei at 28 degrees but not at 2 degrees. With cell-free preparations and ion-exchange cellulose-impregnated paper filters, thymus cytosol bound [3H]dexamethasone with a dissociation constant of 4.3 x 10(-9) M; the concentration of receptor sites was 9.6 x 10(-14) mole/mg cytosol protein. Cytosol contained binding components that sedimented at approximately 7S and 3.6S (low ionic strength) and at 4S (high ionic strength). Competition studies showed high specificity for glucocorticoids since binding of labeled dexamethasone was inhibited in the presence of 10(-6) M beta-methasone, prednisolone acetate, dexamethasone, corticosterone, cortisol, and cortisone. 17beta-Estradiol, testosterone, and dihydrotestosterone at 10(-6) M did not inhibit specific binding of [3H]dexamethasone. Thus, the dexamethasone-binding components of the human thymus hyperplasia had properties similar to those described for steroid hormone receptors present in target tissues.

Parallel determinations of glucocorticoid receptors in the cells of patients with various forms of leukemia were made by two assay methods, one using cell-free cytosolic extracts and the other using whole-cell preparations. Both assays revealed saturable binding of triamcinolone acetonide in all cases. The mean equilibrium dissociation constant for the interaction of triamcinolone acetonide with the cytoplasmic receptor at 2 degrees was 9.45 +/- 6.33 (S.D.) nM while that for the whole-cell binding at 37 degrees was 6.13 +/- 3.25 nM, suggesting an increase in receptor affinity at physiological temperatures. Competition experiments with various unlabeled steroids revealed a higher degree of glucocorticoid specificity at 37 degrees in whole-cell suspensions than at 2 degrees in cytosol. In a comparative analysis of 41 leukemic cell specimens, it was found that determinations carried out by whole-cell assay, calculated as number of sites per cell correlated well with those performed by cytosol assay, calculated as fmol/mg protein, independent of the type of leukemia. However, for cells with low receptor content, the two assay methods were more difficult to compare. In agreement with previous reports, the cytosol assay consistently underestimated the number of receptors with respect to the whole-cell assay, particularly in cases of lymphatic leukemia. Furthermore, the underestimation decreased for increasing levels of total cellular receptor. These results suggest that, in addition to possible defects in the cytoplasm-to-nucleus translocation process, the acceptor-binding capacity of the nucleus may also represent one of the factors which determines the levels of assayable cytoplasmic receptors. Moreover, they indicate that the two assay methods furnish nonequivalent information.