Androgen-binding Capacity Research Articles

Dissecting phenotypic variation among AIS patients

We have created genital skin fibroblast cell lines directly from three patients in a Chinese family affected by androgen insensitivity syndrome (AIS). All patients in the family share an identical AR Arg 840Cys mutant but show different disease phenotypes. By using the cell lines, we find that the mutation has not influenced a normal androgen-binding capacity at 37 °C but has reduced the affinity for androgens and may cause thermolability of the androgen–receptor complex. The impaired nuclear trafficking of the androgen receptor in the cell lines is highly correlated with the severity of donors’ disease phenotype. The transactivity of the mutant is substantially weakened and the extent of the reduced transactivity reflects severity of the donors’ disease symptom. Our data reveal that although etiology of AIS is monogenic and the mutant may alter the major biological functions of its wild allele, the function of the mutant AR can also be influenced by the different genetic backgrounds and thus explains the divergent disease phenotypes.

Modulation of androgen receptor protein by culture conditions of human skin fibroblasts

Cultures of skin fibroblasts show variation of androgen binding with culture conditions; binding variations are usually avoided by using confluent cultures. In this work, we analysed the effect of cell density and mitogenic agents on the level of androgen receptor (AR) of cultured human skin fibroblasts. Results demonstrated that in cultures of human skin fibroblasts, cellular binding of dihydrotestosterone was higher in cells grown at low than at high cell density. The reduction in binding resulted from a decrease in the number of high affinity receptors and not from a change in receptor affinity. Immunocytochemistry for AR showed greater staining intensity in cells grown at low than at high cell density. Additionally, immunoblot analysis demonstrated more AR protein in low cell density cultures. On the other hand, it was observed that cells grown at low cell density showed diminished androgen binding capacity after 24 h of treatment with insulin-like growth factor (IGF-l), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), or granulocyte-colony stimulating factor (G-CSF); this effect of growth factors was not observed in cells grown at high cell density. In conclusion, we found that cell density of cultures and mitogenic agents can regulate AR binding activity in human fibroblasts. While we do not yet know how changes in cell density affect the amount of AR, we conclude that the mechanism could be mediated by activation of the tyrosine kinase pathway, as the effect was reproduced by mitogens.

Disorders of androgen action.

Disorders of androgen action are the main cause of male pseudohermaphroditism and include 5alphaR deficiency and androgen receptor defects. 5alphaR deficiency is characterized by female genitalia with some degree of masculinization, clitoromegaly, and severely bifid scrotum corresponding to the so-called pseudovaginal perineoscrotal hypospadias. At the onset of puberty, increased muscle mass, development of pubic hair, and phallic growth are associated with the acquisition of male gender identity. Normal or increased levels of testosterone and an elevated testosterone-to-dihydrotestosterone ratio after human chorionic gonadotropin stimulation testing suggest 5alphareductase deficiency, and the diagnosis can be ascertained by identifying the mutation in the 5alphaR-2 gene. Whatever the patient's age at diagnosis, psychological evaluation with 5alphaRD is vital. Androgen receptor defects encompass two clinical expressions: the complete and partial androgen insensitivity syndromes. Complete androgen insensitivity syndrome should be suspected at birth in the presence of inguinal hernia in a girl without genital ambiguity. At puberty, the sign of alert is primary amenorrhea with normal female phenotype and harmonious mammary development but no pubic hair growth. Partial androgen insensitivity syndrome covers a wide spectrum of undervirilized phenotypes ranging from clitoromegaly at birth to infertile men. In all cases, complementary investigations should include plasma testosterone and luteinizing hormone as well as androgen-binding capacity in cultured genital skin fibroblasts. Diagnosis is confirmed by identification of the androgen receptor gene mutation. Although patients with complete androgen insensitivity syndrome are raised as females, patients with partial androgen insensitivity syndrome should be managed according to age at diagnosis, response to treatment with exogenous androgens, and the presence of an androgen gene mutation. Gonadectomy in complete androgen insensitivity syndrome should be performed before puberty, and androgen substitution may improve the development of external genitalia in some patients with partial androgen insensitivity syndrome. Psychological follow-up is necessary.

Does obesity diminish the positive effect of oral contraceptive treatment on hyperandrogenism in women with polycystic ovarian syndrome?

Polycystic ovarian syndrome (PCOS) is an obvious indication for long-term treatment. Combined oral contraceptives (COC) remain the first choice for the treatment of hyperandrogenism in most patients. However, differences in endocrine and metabolic parameters between obese and lean patients have been postulated. This is the first study evaluating the effect of COC treatment in obese versus non-obese PCOS patients. In total, 28 lean [body mass index (BMI) <25 kg/m(2))] and 15 obese (BMI >30 kg/m(2)) women patients were enrolled in the study. The concentrations of androgens, sex hormone-binding globulin (SHBG) and lipids were measured before and after 6 months of treatment with COC containing low-androgenic progestins. Clinical androgenic symptoms were monitored. There was a lower concentration of SHBG in obese patients, but there were no differences in androgen concentrations between both groups before the study. Highly significant changes in concentrations of testosterone (P < 0.001), androstenedione (P < 0.0001), SHBG (P < 0.001) and LH (P = 0.01) were demonstrated in lean patients, with only less significant changes in SHBG (P < 0.01) and testosterone (P < 0.05) in obese patients during the study. Clinical androgenic symptoms improved significantly (P = 0.05) only in the group of lean women. No reduction in low-density lipoprotein-cholesterol/high-density lipoprotein-cholesterol ratio was observed in either group. In conclusion, the positive effect of COC treatment on androgen production, serum androgen binding capacity, and clinical androgenic symptoms was negatively influenced by an increased BMI.

Could testicular descent in humans be promoted by direct androgen stimulation of the gubernaculum testis?

Gubernaculum testis and androgens play an important role in physiologic testicular descent. A direct androgen stimulation of the gubernaculum is only possible in the presence of specific receptors, which have not yet been demonstrated. We have determined the androgen-binding capacity in 61 samples of gubernaculum testis from 48 patients, 34 samples belonging to patients with maldescended testes. In 43 out of 61 instances we found androgen binding with values up to 72 fmol/mg, with a mean of 13.08 fmol/mg. In 27 samples from patients with a deep scrotal positioned gonad the mean androgen-binding capacity was 18.74 fmol/mg. In 10 samples from patients with a gonad in the proximal scrotum and 19 patients with epifascial ectopy or a low inguinal position the mean androgen-binding capacities decreased progressively to 9 fmol/mg and 5.95 fmol/mg. In the 5 samples from patients with high inguinal or abdominal testes the binding capacity of 17.8 fmol/mg did not significantly differ from the value obtained in the samples of the normal-positioned gonads, suggesting that transabdominal descent is probably not androgen-dependent. We divided the probes into receptor status positive for a binding capacity higher than or equal to 10 fmol/mg, and receptor status negative for a binding capacity under 10 fmol/mg. 63% of the samples from patients with scrotal positioned testes were receptor status positive, 85% of the samples belonging to patients with maldescended testes were receptor status negative. Receptor status was negative in patients with high scrotal, epifascial or low inguinal and high inguinal or abdominal testes in 90%, 95% and 40% of the samples respectively. Immunohistochemical examination of 10 samples showed small cell groups with stained nuclei in 2 out of 5 patients with normal-positioned testes. All other samples were negative. These findings prove that hormone binding was accomplished by specific intranuclear receptors. These findings allow for the first time the hypothesis of a direct androgen stimulation of the human gubernaculum testis. The probable mechanism is an increase in mucopolysaccharides leading to a swelling of the gubernaculum, dilating the inguinal canal and promoting testicular descent. Although certainly a multifactorial process, quality and quantity of androgen receptors would influence the extent of transinguinal testicular descent.

Functional characterisation of mutations in the ligand-binding domain of the androgen receptor gene in patients with androgen insensitivity syndrome.

Five mutations in the ligand-binding domain of the androgen receptor gene were identified in patients with complete (A765T, C784Y, R831X and M895T) or partial (R840G) androgen insensitivity. A765T and R831X have been reported previously whereas the other three mutations are novel. Receptors carrying these mutations were transiently expressed in COS-1 cells, and androgen binding and capacity to transactivate an androgen-responsive reporter gene were assayed. C784Y led to abolished androgen binding and transactivating capacity, R840G and M895T showed reduced specific binding and partial transactivation. The in vitro functions of the R840G and M895T mutants were improved with supraphysiological concentrations of steroid.

The first detection of complete androgen insensitivity with no mutation in the coding sequence of the androgen receptor gene

We have analyzed the entire nucleotide sequences of complementary DNAs of the androgen receptor gene in two siblings (patients 8044 and 8047) with complete androgen insensitivity. Plasma testosterone was in the normal male range, however, androgen binding capacity was undetectable as measured in skin fibroblasts in both patients. 5alpha-reductase activity was normal in both cases confirming that this enzyme is not involved in the mechanism of androgen insensitivity. Northern blot analysis indicated that mRNA of the AR was normal in size. In addition, no mutation was found in the entire nucleotide sequences of complementary DNAs of the androgen receptor gene. Together, our results reveal an unusual insight into the molecular basis of androgen resistance, and the molecular heterogeneity in this clinical spectrum.

Hepatic expression of sex hormone-binding globulin associated with the postnatal surge of serum androgen-binding activity in the Djungarian hamster

Serum androgen-binding capacity in Djungarian hamsters, as in many other mammals, increases within days after birth and remains elevated until puberty. This increased activity has been attributed to a hepatic glycoprotein, sex hormone-binding globulin (SHBG), but expression of SHBG by the postnatal liver has not been demonstrated. Therefore, a full-length SHBG cDNA was cloned from the liver of neonatal hamsters and the expression of SHBG during development was examined. Hepatic SHBG RNA levels, as measured by both competitive RT-PCR and Northern analysis, were very low in fetal animals but increased significantly within 24 h of birth. Maximal values were maintained for 1 week after parturition, and then declined to basal adult levels. The developmental pattern in hepatic SHBG immunoactivity, as determined by Western analysis, mirrored that of hepatic SHBG mRNA. However, changes in serum SHBG immunoactivity and steroid-binding activity occurred approximately 1 week later. There were no sex differences in the levels of hepatic SHBG mRNA or protein during development, but serum immunoactivity tended to be higher in females at puberty. Sex- and age-related differences in the relative abundance of SHBG isoforms were also noted. Results of these studies demonstrate that Djungarian hamsters express an authentic SHBG and indicate that the postnatal surge in serum androgen-binding activity is due to perinatal up-regulation of SHBG expression.

Androgen Receptor Binding Studies on Heterozygotes in a Family with Androgen Insensitivity Syndrome

A large family with androgen insensitivity syndrome (AIS) has been investigated, in order to detect carrier individuals and to investigate their AR binding. We have previously reported that different affected members of this family have different AR gene deletions, and, testing normal female relatives of the affected individuals, we have identified three heterozygote females all of whom carry a deletion of exon E of the AR gene. Androgen binding capacity was measured in cultured genital skin fibroblasts from normal male and female controls, the affected, and the heterozygote individuals in this family. A significant difference was found between the binding ranges for normal male foreskin and suprapubic skin fibroblasts ( P < 0.005), and the three individuals with AIS had very low androgen binding capacity in their genital skin fibroblasts (2.6, 5.0, and 3.4 fmol 3HR1881/mg protein) compared to the normal range. The heterozygote females all had binding within the normal female suprapubic skin fibroblast range (12.5, 6.1, and 6.4 fmol 3HR1881/mg protein, respectively, for the three heterozygotes). Thus, we conclude that the absence of one functional AR gene in heterozygote females has no effect on AR binding capacity in cultured genital skin fibroblasts. In addition, bone mineral density was measured in the affected aunt and found to be significantly lowered at the lumbar spine ( Z = −2.81) and hip ( Z = −1.54); however, the role of the AR in determination of bone mineral density remains to be elucidated.

Specificity of ligand-dependent androgen receptor stabilization: receptor domain interactions influence ligand dissociation and receptor stability.

The molecular basis for the different physiological effects of testosterone (T) and dihydrotestosterone (DHT) was investigated using recombinantly expressed wild-type and mutant androgen receptor (AR). Rates of androgen dissociation from nuclear and cytoplasmic AR were compared with hormone- and concentration-dependent receptor degradation rates. T dissociates from AR 3 times faster than DHT or methyltrienolone (R1881) and is less effective in stabilizing the receptor. Analysis of AR deletion mutants and AR/glucocorticoid receptor chimeras indicates that the AR NH2-terminal domain has a specific role in stabilizing the receptor by slowing the rate of ligand dissociation and AR degradation. Amino acid mutations that abolish receptor dimerization, nuclear localization, or DNA-binding activity have no significant effect on androgen dissociation or AR degradation. A naturally occurring steroid-binding domain mutation (Val889 to Met) that causes androgen insensitivity, but does not alter equilibrium androgen binding affinity, lowered the androgen-binding capacity as a result of increased rates of androgen dissociation and AR degradation. Thus, AR stabilization and function require prolonged receptor occupancy with androgen, with a similar extent of stabilization observed at higher concentrations of faster dissociating androgens and lower concentrations of slower dissociating androgens. Retention of receptor-bound androgen is enhanced by an interaction between the AR NH2-terminal and steroid-binding domains. The ligand specificity and concentration dependence of receptor stabilization provide an explanation for physiological differences in the actions of T and DHT.

Premature termination mutation (772Glu-->stop) in the hormone-binding domain of the androgen receptor in a patient with the receptor-negative form of complete androgen insensitivity syndrome.

We have characterized the androgen receptor in a Japanese infant with complete androgen insensitivity syndrome (or androgen resistance), and have investigated the molecular basis. Androgen binding was undetectable in cultured genital skin fibroblasts from this patient by whole-cell androgen receptor binding assay. Sequence analysis of the entire coding region of the androgen receptor gene from this patient revealed a single nucleotide substitution (G-->T) at nucleotide position 2676 in exon E (or 5), resulting in conversion of glutamine codon (GAG) to amber stop codon (TAG) at amino acid position 772 within the hormone-binding domain of the androgen receptor. This premature termination mutation (or nonsense mutation), introducing a truncated androgen receptor that lacks most of its androgen binding capacity, is though to cause the receptor-negative form of complete androgen insensitivity syndrome in this patient.

Characterization of alternative amino acid substitutions at arginine 830 of the androgen receptor that cause complete androgen insensitivity in three families.

We have studied two different missense mutations at arginine-830 in exon 7 of the human androgen receptor (hAR) gene that cause complete androgen insensitivity (CAIS) in three families. These substitutions result from point mutations at nucleotide 2489: a G-->T transversion causes Arg830Leu and a G-->A transition causes Arg830Gln. Genital skin fibroblasts of the patients have negligible androgen-binding capacity. The mutations were recreated in an hAR cDNA expression vector that was transiently transfected into COS-1 cells. Both mutant androgen receptors have increased dissociation rate constants and apparent equilibrium rate constants when measured with 5 alpha-dihydrotestosterone or the synthetic, nonmetabolizable androgens, mibolerone or methyltrienolone. The mutant androgen-binding activities share a distinctive thermal misbehavior. At 37 degrees C R830Q and R830L are about 40% and 10% of normal, respectively. At 22 degrees C both mutants gain androgen binding while the normal decreases by 20%; for R830Q the augmented value approaches 60% of the normal. During prolonged 18 h incubation at 37 degrees C, androgen binding of the normal AR is stable while that of both mutants decreases by at least 85%. Both mutants have a very reduced ability to transactivate a cotransfected androgen-responsive reporter gene, but R830Q is better than R830L. We conclude that arginine-830 is important for A-R complex stability, and that its replacement by glutamine or leucine yields distinctive functional aberrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Endurance and resistance exercise induce muscle fiber type specific responses in androgen binding capacity

This study examined the effects of different exercise training programs on androgen receptor content and receptor affinity to dihydrotestosterone in fast glycolytic (FG) and slow oxidative (SO) skeletal muscle fibers in rats. Twenty-four male Sprague-Dawley rats were equally divided into three groups: control, endurance exercise trained and resistance exercise trained. After the exercise programs were completed, the extensor digitorum longus (EDL), predominantly a FG muscle, and the soleus, predominantly a SO muscle, were isolated, weighed and both androgen receptor content and affinity to dihydrotestosterone were determined. Resistance training evoked a significant ( P < 0.05) hypertrophic response in the soleus but not the EDL. Endurance training was not associated with any significant hypertrophy in either the soleus or the EDL. Neither the endurance nor the resistance training program resulted in changes in androgen receptor affinity to dihydrotestosterone. However, alterations in androgen receptor content were noted. The endurance training program resulted in a significant increase in androgen receptor content in the soleus, but no significant difference in the EDL. The resistance training program elicited a significant decrease in androgen receptor content in the soleus, and a significant increase in the EDL. These results indicate that different exercise stimuli induce changes in androgen receptor content that are specific to skeletal muscle fiber type.

Substitution of arginine-839 by cysteine or histidine in the androgen receptor causes different receptor phenotypes in cultured cells and coordinate degrees of clinical androgen resistance.

We aim to correlate point mutations in the androgen receptor gene with receptor phenotypes and with clinical phenotypes of androgen resistance. In two families, the external genitalia were predominantly female at birth, and sex-of-rearing has been female. Their androgen receptor mutation changed arginine-839 to histidine. In a third family, the external genitalia were predominantly male at birth, and sex-of-rearing has been male: their codon 839 has mutated to cysteine. In genital skin fibroblasts, both mutant receptors have a normal androgen-binding capacity, but they differ in selected indices of decreased affinity for 5 alpha-dihydrotestosterone or two synthetic androgens. In transiently cotransfected androgen-treated COS-1 cells, both mutant receptors transactivate a reporter gene subnormally. The His-839 mutant is less active than its partner, primarily because its androgen-binding activity is more unstable during prolonged exposure to androgen. Adoption of a nonbinding state explains a part of this instability. In four other steroid receptors, another dibasic amino acid, lysine, occupies the position of arginine-839 in the androgen receptor. Androgen receptors with histidine or cysteine at position 839 are distinctively dysfunctional and appear to cause different clinical degrees of androgen resistance.

Threonine on Amino Acid Position 868 in the Human Androgen Receptor Is Essential for Androgen Binding Specificity and Functional Activity

The human androgen receptor gene in the androgen sensitive prostate tumor cell line (LNCaP) contains a point mutation in codon 868 resulting in the substitution of threonine by alanine. This amino acid change is responsible for the increased affinity of the mutant receptor protein for progestagens and estrogens. To further elucidate the role of threonine 868 on androgen binding capacity, specificity and functional activity, threonine 868 was substituted by six different amino acid residues. Substitution by aspartic acid, lysine or tyrosine totally eliminated androgen binding and the mutated androgen receptors did not have any transcriptional activating potential with either R1881, R5020 or estradiol. Introduction of a serine or an alanine broadened the steroid specificity, as did the introduction of a cysteine to a lesser degree. It is concluded that threonine on position 868 of the human androgen receptor limits the ligand specificity of the receptor to androgens.

A point mutation in the second zinc finger of the DNA-binding domain of the androgen receptor gene causes complete androgen insensitivity in two siblings with receptor-positive androgen resistance.

We have analyzed the nucleotide sequence of complementary and genomic DNAs of the human androgen receptor (AR) gene in two siblings (patients 9006 and 9030) with receptor-positive complete androgen insensitivity (Rec(+)-CAI). Northern analysis indicated that mRNA of the AR was normal in size. However, its expression was relatively reduced in both patients. Consistent with the normal androgen-binding capacity (496 and 552 fmol/mg DNA for patients 9006 and 9030, respectively) but decreased DNA-binding ability (168 fmol/mg DNA) measured in genital skin fibroblasts, no mutation was found in both N-terminal and ligand-binding domains of the AR. However, a single base substitution (G-->A) was found in the second zinc finger of the DNA-binding domain at nucleotide 2372 of the AR cDNA in both cases. This resulted in the replacement of a highly conserved arginine residue (amino acid 614) by a histidine. When the mutated receptor plasmid was cotransfected into PC-3 cells together with the reporter chloramphenicol acetyltransferase gene, chloramphenicol acetyltransferase activity was not induced by 5 alpha-dihydrotestosterone treatment, confirming that the mutation renders the AR nonfunctional and can, therefore, be held responsible for the clinical features in these patients. These results highlight the importance of Arginine-614 in the second zinc finger of the DNA-binding domain of the AR in the protein-DNA interaction.

Up-regulation of the levels of androgen receptor and its mRNA by androgens in smooth-muscle cells from rat penis

Smooth-muscle cells cultured from the penis of sexually immature (I-PSMC) and adult (A-PSMC) rats express similar high levels of the androgen receptor (AR) mRNA. This contrasts with the marked in vivo decline of both AR mRNA and androgen binding in the penile smooth muscle of adult rats, which appears to be responsible for the cessation of androgen-dependent penile growth upon sexual maturation. PSMC is therefore a good model to study down-regulators of AR expression as a function of cell proliferation in the smooth muscle of androgen-reputative sponsive vascular tissue. In order to determine whether AR protein levels in PSMC correlate with AR mRNA levels, the immunocytochemical detection of ARs and their androgen binding capacity were compared between I- and A-PSMC. The number of ARs and their protein half-lives suggested similar levels of translation of the AR mRNA in both cell lines. The effect of the synthetic analog methyltrienolone (R-1881) on androgen binding was studied in contact-inhibited androgen-deprived PSMC. In contrast to the postulated role of androgens as down-regulators of AR expression in rat penis, ARs were up-regulated in A-PSMC by R-1881. Contact inhibition of A-PSMC combined with serum depletion and androgen deprivation down-regulated AR mRNA levels, and dihydrotestosterone (DHT) counteracted this effect. These results suggest that the loss in A-PSMC of the age-dependent down-regulation of ARs observed in vivo in adult corpora cavernosa smooth muscle is related to the in vitro resumption of cell proliferation and that DHT acts directly on the penile smooth muscle as a positive modulator of AR levels.

Androgen receptor gene mutation in male breast cancer.

We screened thirteen male breast cancers for the presence of germline mutations in exons 2 and 3 encoding the DNA-binding domain of the androgen receptor. These two exons were amplified from genomic DNA extracted from patients' white blood cells. In one of these thirteen patients, single strand conformation polymorphism and direct sequencing detected a guanine-adenine point mutation at nucleotide 2185 that changes Arg608 into Lys in a highly conserved region of the second zinc finger of the androgen receptor. This mutation occurred in a 38 year old man with partial androgen insensitivity syndrome and normal androgen-binding capacity in cultured genital skin fibroblasts. To our knowledge, only one germline Arg to Gln androgen receptor gene mutation has been previously reported at position 607 in male breast cancer. This androgen receptor mutation along with the Arg608 into Lys mutation we describe, suggests that this genetic abnormality is not fortuitous: a decrease in androgen action within the breast cells could account for the development of male breast cancer by the loss of a protective effect of androgens on these cells. Activation of estrogen regulated genes by the change of DNA-binding characteristics of the mutant androgen receptor cannot, however, be ruled out.

Immunoreactive androgen receptor expression in subjects with androgen resistance.

Individuals with androgen resistance encompass a spectrum of phenotypic abnormalities ranging from complete testicular feminization to undervirilized men. Such subjects have been classified according to the hormone-binding characteristics in genital skin fibroblasts and on the basis of the mutation in the androgen receptor (AR) gene. Antibodies to the amino-terminal region of the human AR were used to develop an immunoblot assay for the comparison of androgen binding with the amount of AR expressed in genital skin fibroblasts. In controls and 4 androgen-resistant subjects with DNA-binding domain mutations, levels of immunoreactive AR correlated closely with androgen-binding capacity. In 15 androgen-resistant subjects with qualitatively abnormal AR, immunoreactive AR levels tended to be higher than predicted from the ligand-binding capacity. Discordance between immunoreactivity and androgen binding also occurred in fibroblasts from 3 other subjects. One carries a stop codon in the AR gene and produces a truncated AR that is immunoreactive but does not bind androgen. Two carry single point mutations in the hormone-binding domain and produce immunoreactive AR that is normal in size but does not bind androgen.

Endocrine mediation of psychosocial stressor effects on mouse mammary tumor growth

We have demonstrated that differential housing alters the growth rate of the androgenresponsive Shionogi mouse mammary carcinoma (SC115). In the present study we wished to determine if changes in plasma levels of hormones or a shift in the responsiveness of the tumor cells to hormones was responsible for the differential tumor growth rates observed. Plasma testosterone and corticosterone levels were assayed 24 h, 3 days and 1 week post tumor cell/vehicle injection. Also 3 weeks post injection androgen and glucocorticoid receptor binding capacity (B max ) and binding affinity (K d ) and the in vitro responsiveness of tumor cells to dihydrotestosterone and hydrocortisone were measured. At 24 h post injection, plasma testosterone levels were significantly increased in mice with large tumors, but remained low in mice with small tumors. Plasma corticosterone levels were significantly elevated in mice with small tumors compared to those of mice with large tumors at all time points measured. Androgen and glucocorticoid receptor binding capacity and binding affinity of tumor cells did not differ among groups. Further, all groups tested had the ability to respond to dihydrotestosterone and hydrocortisone in vitro. These data indicate that an effect of housing condition on plasma levels of steroid hormones may, in part, mediate the differential tumor growth rates observed in this model.