Steroid hormone receptors in human malignancy.

Steroid hormones induce responses in target tissues by a mechanism involving the specific initial interaction of hormone with cytoplasmic receptor molecules. These receptors, usually localized in target tissues have high binding affinities and limited binding specificities for biologically active steroids. Examination of human leukemic lymphoblasts has revealed these receptors in some tumor samples. Their presence is well correlated with hormone responsiveness of the tumor $\text{in vitro}$. Similar studies on human breast cancer tumor homogenates has indicated that about $\text{2}\text{3}$ of primary tumors contain estrogen receptor. The absence of receptor predicts a lack of response to hormone therapy almost invariably, while the presence of receptor increases but does not assure that the tumor will be hormone responsive. Recently $\text{in vitro}$ tissue culture systems which mimic the hormone responses observed $\text{in vivo}$ have been developed which should significantly aid in the clarification of the mechanisms whereby steroid hormones stimulate and inhibit growth in target tissues.     

Steroid metabolism in human breast cancer cell lines

The metabolism of 1,2-³H-androstenedione was studied in 2 cell lines, MCF-7 (estrogen responsive) and BT-20 (estrogen nonresponsive) over 48 hrs. Water soluble and unconjugated metabolites were separated by solvent partition and the former was submitted to chromatography on Sephadex LH-20 and enzyme hydrolysis. The resulting unconjugated steroids were separated by paper chromatography and identities were established by reverse isotope dilution. The unconjugated steroids initially obtained were separated by chromatography and identified by reverse isotope dilution. About 70% of the androstenedione was metabolized by both cell lines. However, the respective conversions to conjugates by MCF-7 and BT-20 were 31% and 0.32%. In the former, glucosiduronates predominated (94%) and consisted of androsterone (55%), etiocholanolone (9.4%) and androstanediol (5α-androstane-3α,17β-diol) (9.3%). Androsterone comprised most of the unconjugated metabolites in both cell lines. Androstanediol was found in both cell lines, 2% in MCF-7 and 12% in BT-20. Testosterone, 5α-androstane-3,17-dione and 3β-hydroxy-5α-androstan-17-one were isolated only from MCF-7. The metabolism of ³H-estriol was studied in a similar way. Both cell lines produced about equal amounts of estriol-3-sulfate (9%) and a compound with properties of estriol-3-glucosiduronate (0.15 – 0.5%). The results worthy of emphasis are: 1. The far greater conjugation of androgens exhibited by the MCF-7 cell lines as compared to the BT-20 cell lines; 2. In MCF-7, the high conversion of androstenedione to etiocholanolone (glucosiduronate form), a metabolite reported to form only in liver and sebaceous cysts; 3. The possible formation in both cell lines of estriol-3-glucosiduronate, normally a metabolite of the intestine.     

Steroid receptors and orphan receptors in Drosophila development

Drosophila steroid receptors and related receptor-like proteins show remarkable conservation of structure and function relative to vertebrate homologues. While those proteins are involved in numerous embryonic and post-embryonic developmental processes, a striking number of receptor-like proteins are clustered in regulatory hierarchies under the control of the insect molting hormone ecdysone. This has suggested a number of models based on competitive, cooperative and inter-regulatory interactions between these proteins.     

Steroid metabolism by human breast and rat mammary carcinomata

The metabolism of dehydroepiandrosterone (DHA) and testosterone by both human breast carcinomata and dimethylbenzanthracene (DMBA)-induced rat mammary carcinomata has been investigated.The rat and human carcinomata converted DHA to testosterone and both DHA and testosterone to 5α-dihydrotestosterone, 5α-androstanediol and 16α-hydroxytestosterone. Tentative evidence is also presented to indicate that some rat adenocarcinomata can convert androgen precursors into estradiol-17β.Although quantitative differences between incubations occurred, the spectrum of steroid transformations was similar in both human and rat tumours. The DMBA-induced rat tumour may therefore prove to be a valuable experimental model for human carcinoma tissue with regard to further steroidogenic studies.     

Estrogen receptors in human breast cancer

The present study defines criteria for determining the presence of estrogen-receptors in human breast carcinomas demonstrated by a histochemical assay using 17 beta-estradiol-carboxy-methyl-oxim-bovine serum albumen-FITC. The criteria were: 1) the percentage of cells showing fluorescence; 2) the intensity of the fluorescence observed, and 3) the percentage of epithelial structures in tissue specimens. Using these predefined criteria in 132 human breast carcinomas as 91.6% agreement was found between the results of the histochemical assay and those of the biochemical Charcoal method. The main causes of disagreement (7 of the 11 cases) were sampling errors between the tissue specimens used for the histochemical and biochemical assay, and an insufficient percentage of epithelial structures (less than 15%) to allow biochemical identification of estrogen receptor activity. In the hands of pathologists with experience of the field of histochemistry this histochemical assay may be the method of choice for the assessment of estrogen receptors.     

Steroid hormones and their receptors in the brain

Steroid hormones regulate several important functions of the brain by altering the expression of particular genes through their receptors. First in this paper the localization of glucocorticoid receptor immunoreactivity and mRNA in the brain was examined. Second biphasic effects of glucocorticoid on the hippocampus was described and particular emphasis was given on the apoptosis. Third the significance of estrogen receptor in the sexually dimorphic areas was discussed. These results suggest that steroids modulate the gene expression along with the alteration of cell structures in a different manner in a tissue-specific pattern.     

Steroid sulfatase and estrogen sulfotransferase in normal human tissue and breast carcinoma

Steroid sulfatase (STS) hydrolyzes inactive estrone sulfate (E1-S) to estrone (E1), while estrogen sulfotransferase (EST; SULT 1E1 or STE gene) sulfonates estrogens to estrogen sulfates. They are considered to play important roles in the regulation of local estrogenic actions in various human tissues, however, their biological significance remains largely unknown. Therefore, we examined the expression of STS and EST in non-pathologic human tissues and breast carcinomas. STS expression was very weak except for the placenta, while EST expression was markedly detected in various tissues examined. In breast carcinoma tissues, STS and EST immunoreactivity was detected in carcinoma cells in 74 and 44% of cases, respectively, and was significantly associated with their mRNA levels and enzymatic activities. STS immunoreactivity was significantly correlated with the tumor size, and an increased risk of recurrence. EST immunoreactivity was inversely correlated with the tumor size or lymph node status. Moreover, EST immunoreactivity was significantly associated with a decreased risk of recurrence or improved prognosis. Our results suggest that EST is involved in protecting various peripheral tissues from excessive estrogenic effects. In the breast carcinoma, STS and EST are suggested to play important roles in the regulation of in situ estrogen production in the breast carcinomas.     

Steroid receptors analysis in human mammary tumors by isoelectric focusing in agarose

A high resolution and quantitative method for isoelectric focusing has been developed to separate the isoforms of estrogen and progesterone receptors in human mammary tumor cytosols stabilized by sodium molybdate. Agarose gels (0.5%) were used. Six samples can be analyzed on one gel in about 2 h, and 35-microliters samples are sufficient to determine the estrogen receptor isoform pattern. The constant yields and the reproducibility of data allow a quantitative analysis of these receptors. Four estrogen receptor isoforms have been observed (pI 4.7, 5.5, 6, and 6.5), isoforms with pI 4.7 and 6.5 being present in all tumors. After incubation at 28 degrees C in high ionic strength, the comparison of isoelectric focusing and high-performance size exclusion chromatography patterns of estrogen receptor confirms the oligomeric structure of the pI 4.7 isoform and suggests a monomeric structure for the pI 6.5 isoform. Under the same conditions of analysis, only one progesterone receptor isoform has been detected with pI 4.7.     

Steroid modulation of aromatase activity in human cultured breast carcinoma cells

Cortisol and steroids with progestational or androgenic activity were studied to determine the effects of these steroids on the conversion of androstenedione (A) to estrone (E1) in human cultured breast carcinoma cells. Cortisol (10(-6) M) stimulated aromatase activity in two estrogen unresponsive cell lines (MD, DM) and in an estrogen responsive cell line (MCF7) with the maximum stimulation occurring during confluence. Cortisol inhibited the replication of MCF7 cells but not MD and DM. Dihydrotestosterone, androsterone and 5 alpha-androstanedione (10(-6) M) inhibited the conversion of A to E1 by greater than 90% under basal and cortisol stimulated conditions. Progesterone (10(-6) M) had no effect on aromatase activity while the progestational agent R5020 (10(-6) M) produced a 30% inhibition. The anabolic steroids 19-nortestosterone and 19-norandrostenedione which also have progestational activity inhibited the conversion of A to E1 in a dose dependent manner with 90% inhibition at 10(-6) M. Danazol (10(-6) M) a drug with both androgenic and progestational activity inhibited E1 formation by 30%. Under the same conditions, the known inhibitor of aromatase, 4-hydroxyandrostenedione (10(-6) M) decreased E1 formation by more than 90% and aminoglutethimide (10(-6) M) caused only 25% inhibition. These studies demonstrate that endogenous and exogenous steroids may have significant effects in modulating the local formation of estrogens from androgen precursors in cultured breast carcinoma cells. This effect on estrogen formation may be a factor in the biological response of breast tissue.