Mechanism of action of the sex steroid hormones (first of three parts)

Dexamethasone-resistant cystic fibrosis fibroblasts show cross-resistance to sex steroids

Diploid skin fibroblasts derived from individuals with the autosomal recessive disease, cystic fibrosis (CF), were shown previously to be significantly more resistant to the cytotoxicity of dexamethasone, a glucocorticoid hormone, than were normal human fibroblasts. Here cystic fibrosis fibroblasts are also shown to be more resistant than normal human fibroblasts to the cytotoxic effects of the sex hormones, 17 beta-estradiol, dihydrotestosterone and progesterone. Since cells are believed to contain different receptors for each of the steroid hormones, it is not probable than the resistance of CF cells to these hormones results from a receptor deficiency. This was shown by the fact that CF cells were found to exhibit the same receptor activity as normal cells for 3-H-dexamethasone. Furthermore, neither normal human nor CF fibroblasts could be demonstrated to contain detectable receptor activity for 3H-17 beta-estradiol. In addition, the studies of fibroblast killing by hormones led to the further interesting observation that normal human diploid fibroblasts, regardless of the sex of the tissue donor, are sensitive to killing by each of the sex hormones. These findings suggest that the cytotoxic effects of the steroid hormones may be observed independently of the specific hormone receptors. The studies reported here thus suggest that the resistance of CF cells to the different steroid hormones is probably the result of a defect in a pathway in cellular steroid hormone metabolism other than that involving receptors.

Low incidence of estrogen receptor in breast carcinomas with rapid rates of cellular replication

The results of assay for estrogen receptor (ER) in the tumor cytosol and thymidine labeling indices (TLI) of 63 primary invasive carcinomas of the breast were analyzed. The ER assay was performed by using dextran-charcoal to adsorb unbound tritiated estradiol-17beta (E2) in cytosol. The TLI was measured as the number per hundred of neoplastic cell nuclei labeled by tritiated thymidine. A significant association between low TLI and presence of ER was found. Wereas all 19 tumors with TLI less than 2.5 contained ER in the primary lesion or in axillary metastases and ER was found in 25 of 30 tumors with TLI between 2.5 and 10, only 4 of 14 tumors with TLI greater 10 contained ER (p less than 0.001). TLI and saturable binding of E2 were significantly negatively correlated (r=-0.436,P. less than 0.001). It is concluded that dedifferentiation in breast carcinomas is associated with both high TLI and absence of ER, and suggested that the carcinomas with the most rapid proliferative rates will include the highest proportion of tumors unresponsive to hormonal therapy.

Partial androgen insensitivity: the Reifenstein syndrome revisited

We investigated eight patients with the Reifenstein syndrome to define the hormonal basis for this condition. The patients had normal or elevated concentrations of plasma androgens, normal production rates of testosterone and dihydrotestosterone, elevated serum levels of luteinizing hormone and normal 5alpha-reductase activity in skin fibroblasts. These findings indicate that the syndrome results from defective androgen action rather than from decreased androgen synthesis. The term "partial androgen insensitivity syndrome" describes this condition more accurately than a term based on clinical phenotype. Dihydrotestosterone binding studies in skin fibroblasts demonstrated two genetic variants similar to those reported in complete androgen insensitivity syndrome. One patient had a partial deficiency of cytoplasmic dihydrotestosterone binding, and four others had normal binding activity. The cause of the androgen insensitivity in the last four cases is unknown. Treatment with testosterone suppressed serum luteinizing hormone levels and promoted mild virilizing effects.