Significance of the progesterone receptor in the estrogen-induced and -dependent renal tumor of the Syrian golden hamster

Metabolism of [4-14C]estrone in hamster and rat hepatic and renal microsomes: species-, sex- and age-specific differences

The metabolism of [4-14C]estrone (E1) was examined in liver and kidney microsomes of adult castrated male and ovariectomized female hamsters and rats and in neonatal and immature hamster renal microsomes. In castrated male hamster liver microsomes, E1 was metabolized extensively to six major metabolites; 15 beta-hydroxyestrone, 7 alpha-hydroxyestrone, 6 alpha-hydroxyestrone, 6 beta-hydroxyestrone, 2-hydroxyestrone, and delta(9,11)-dehydroestrone, and a nonpolar fraction. Six minor metabolites of E1 were also detected. In contrast, kidney microsomes derived from castrated male hamsters metabolized E1 to mainly 17 beta-estradiol, 2- and 4-hydroxyestrone, 6 alpha-hydroxyestrone, 6 beta-hydroxyestrone and one monohydroxyestradiol metabolite. However, 16 alpha-hydroxyestrone was not detected. A variable, but low amount of estriol was also found. Interestingly, the quantity of 2-hydroxyestrone found in kidney microsomes of the hamster represented 26% of the total amount of metabolites formed, whereas in liver microsomes, only 9% of the overall metabolism resulted in the formation of 2-hydroxyestrone. The ability of kidney microsomes of female ovariectomized hamsters and two different rat strains to metabolize E1 was 5.9- and 9.4-fold lower, respectively, compared to renal microsomes of male castrated hamsters. The onset of oxidative metabolism in newborn hamster kidneys during development was also assessed. The results indicate that the oxidative metabolism of [14C]E1 in renal microsomes of newborn hamsters was 20-fold less than in kidney microsomes of adult hamsters. While catechol E1 metabolites were essentially negligible in hamster kidneys of these ages, it was evident that the conversion of E1 to estradiol via 17 beta-hydroxysteroid dehydrogenase resembles levels seen in the adult animals. Between the age of one and two months, the male hamster kidney exhibited the capacity to metabolize E1 at levels seen in fully mature adult hamsters.

Experimental induction of renal tumors

Renal tumors have been reported to be induced by natural products, chemical carcinogens, viruses, or radiation. Species or strain specificity and sex also appear to play significant roles in their development. In man, it is also likely that the heredity existence of other diseases, smoking, food habits, and irradiation may be etiological factors. It also appears that hormonal, chemical, and other environmental factors can play a role. Nephrotoxin modifies two-stage chemical carcinogenesis in rat kidney. Some nephrotoxins without carcinogenicity promote the development of renal tumors in rats pretreated with subcarcinogenic doses of chemical carcinogens. The importance of nephrotoxin in development of renal adenocarcinomas needs elucidation. Preneoplastic lesions in the kidneys can be recognized by histochemical methods with specific antibodies. It is hoped that further research will be continued, so that data obtained from experimental work will provide a better understanding of the etiology and induction of renal cancer in man.

Steroid metabolism and binding activity in a murine renal tumor cell line

The purpose of this study was to partially characterize the steroid binding activity of murine renal tumor cells in continuous culture. The steroid receptor content of a cloned renal tumor cell line (RAG) and a subline RAG-2 was examined by sucrose gradient analysis, hydroxylapatite and dextran-coated charcoal methods. The RAG cells lacked estrogen- and progestin-binding activity, whereas specific 5 alpha-dihydrotestosterone (DHT) and dexamethasone (Dx) binding activities were detected as 8S peaks on low salt gradients. The specificity of DHT binding was examined by sucrose gradient analysis: DHT, R1881 and ORG2058 all completely inhibited [3H]DHT binding whereas diethylstilbestrol and Dx were ineffective. The androgen receptor content of the RAG cells was approx. 15 fmol/mg cytosol protein by the hydroxylapatite-filter assay, with an estimated Kd for methyltrienolone (R1881) of 5 nM at 0 degrees C. Scatchard analysis of [3H]Dx binding by RAG cytosol showed a Kd of 6 nM for Dx and 44 nM for corticosterone at 0 degrees C. Glucocorticoid receptor levels were estimated to be 182 fmol/mg cytosol protein by dextran-coated charcoal assay. Metabolism of [3H]testosterone and [3H]DHT by RAG cells was examined 1, 4 and 6 h after exposure to labeled hormone. Radioactive DHT was the primary intracellular metabolite recovered after exposure to [3H]testosterone. There was little conversion of DHT to androstanediol.

Changes in lipid profiles of estrogen-induced and transplanted renal carcinomas in Syrian hamsters

The lipid profiles of estrogen-induced primary renal carcinomas and hormone-dependent and -independent transplanted tumors were compared with those of both normal hamster kidneys and renal tissues of tumor-bearing animals. Autonomous tumors had only one-third the amount of triglycerides present in normal kidneys and hormone-dependent tumors contained intermediate levels. Host kidneys of animals bearing either primary or transplanted tumors contained no more than 50-60% of the triglyceride level found in normal kidneys. In contrast to triglycerides, cholesteryl esters in primary tumors were 200 times higher than in normal kidneys, exhibited a successive decline in hormone-dependent and -independent tumors, but remained 15 times higher in autonomous carcinomas than in normal kidneys. Cholesterol levels were similar in primary tumors, normal kidneys, and host kidneys of animals bearing renal tumors; however, both hormone-dependent and -independent neoplasms had only one-half to two-thirds as much cholesterol as normal kidneys. Total phospholipid levels in primary and transplanted carcinomas were about one-half those in normal kidneys. Host kidneys of animals bearing primary and transplanted, hormone-dependent neoplasms also contained lower phospholipid levels than normal kidneys, but renal tissues from animals with autonomous tumors contained similar levels to those found in kidneys from normal hamsters. The phospholipid composition of primary and transplanted renal tumors was similar, but different from that of normal kidneys, mainly in increased percentages of phosphatidylcholine and decreased percentages of sphingomyelin.

Hormone receptors in renal cell carcinoma. Their utility as predictors of response to endocrine therapy

We have performed 23 estrogen and 24 progesterone receptor assays on tumor specimens from 26 patients with renal cancer, ten of whom subsequently received hormonal therapy for metastatic disease. Only one of these specimens contained measurable estrogen receptor levels, three contained low, but measurable progesterone receptor levels, and the remaining specimens contained no measurable estrogen or progesterone receptors. None of ten patients with metastases showed evidence of an objective response to hormonal therapy. Our data suggest that few, if any, renal cancers have high titers of estrogen or progesterone receptors, and that those patients whose tumors have low receptor titers are unlikely to respond to hormonal therapy.