Inhibitory effect of dihydrotestosterone on human thyroid cell growth

Glucose Metabolism Derangements and Thyroid Nodules: Does Sex Matter?

(1) Background: Glucose metabolism derangements (GMD) and thyroid nodules (TNs) are the most frequent endocrine disorders, and their relationship is still controversial; little evidence is reported regarding sex differences. We aim to evaluate the association between GMDs and TNs according to sex and the sex differences in glucose metabolism and insulin sensitivity (IS). (2) Methods: We evaluated 342 patients (268 females and 74 males) at high GMD risk undergoing an oral glucose tolerance test and a thyroid ultrasound. (3) Results: The TN prevalence was 61% (n = 210), with no significant differences according to sex and GMD classes. The TN presence is significantly associated with age and impaired fasting glucose (IFG) in females. Males and females with normal fasting glucose (NFG) had a significantly lower OR of having TNs than females with IFG. IFG females had a significantly higher predicted probability of having TNs than NFG males and females but not IFG males. Impaired glucose tolerance/Type 2 diabetes mellitus (IGT/T2DM) is significantly associated with age and male sex, while IFG is associated with age. Females had significantly lower HOMA-index values than males. (4) Conclusions: No significant association between IGT/T2DM and TNs according to sex was found. IFG seems to play a role in TN development independently of sex. Further studies are needed to explore the relationship between TNs and GMD to identify subgroups with a higher TN risk.

Androgen receptor activation decreases proliferation in thyroid cancer cells

The American Cancer Society predicted more than 52 000 new cases of thyroid cancer in 2020, making it the most prevalent endocrine malignancy. Due to the approximately threefold higher incidence of thyroid cancer in women, we hypothesize that androgens and/or androgen receptors play a protective role and that thyroid cancer in men represents an escape from androgen-mediated cell regulation. The analysis of androgen receptor (AR) expression in patient tissue samples identified a 2.7-fold reduction in AR expression (p < 0.005) in papillary thyroid cancer compared with matched, normal tissue. An in vitro cell model was developed by stably transfecting AR into 8505C undifferentiated thyroid cancer cells (resulting in clone 84E7). The addition of DHT to the clone 84E7 resulted in AR translocation into the nucleus and a 70% reduction in proliferation, with a shift in the cell cycle toward G1 arrest. RNASeq analysis revealed significant changes in mRNA levels associated with proliferation, cell cycle, and cell cycle regulation. Furthermore, androgen significantly decreased the levels of the G1-associated cell cycle progression proteins cdc25a CDK6 CDK4 and CDK2 as well as increased the levels of the cell cycle inhibitors, p27 and p21. The data strongly suggest that DHT induces a G1 arrest in androgen-responsive thyroid cancer cells. Together, these data support our hypothesis that AR/androgen may play a protective, antiproliferative role and are consistent with younger men having a lower incidence of thyroid cancer than women.

The role of the androgen receptor in prostate development and benign prostatic hyperplasia: A review

Benign prostatic hyperplasia (BPH) is a benign enlargement of the prostate in which incidence increases linearly with age, beginning at about 50 years old. BPH is a significant source of morbidity in aging men by causing lower urinary tract symptoms and acute urinary retention. Unfortunately, the etiology of BPH incidence and progression is not clear. This review highlights the role of the androgen receptor (AR) in prostate development and the evidence for its involvement in BPH. The AR is essential for normal prostate development, and individuals with defective AR signaling, such as after castration, do not experience prostate enlargement with age. Furthermore, decreasing dihydrotestosterone availability through therapeutic targeting with 5α-reductase inhibitors diminishes AR activity and results in reduced prostate size and symptoms in some BPH patients. While there is some evidence that AR expression is elevated in certain cellular compartments, how exactly AR is involved in BPH progression has yet to be elucidated. It is possible that AR signaling within stromal cells alters intercellular signaling and a "reawakening" of the embryonic mesenchyme, loss of epithelial AR leads to changes in paracrine signaling interactions, and/or chronic inflammation aids in stromal or epithelial proliferation evident in BPH. Unfortunately, a subset of patients fails to respond to current medical approaches, forcing surgical treatment even though age or associated co-morbidities make surgery less attractive. Fundamentally, new therapeutic approaches to treat BPH are not currently forthcoming, so a more complete molecular understanding of BPH etiology is necessary to identify new treatment options.

Aberrant Expression of Androgen Receptor Associated with High Cancer Risk and Extrathyroidal Extension in Papillary Thyroid Carcinoma

Male gender is a risk factor for mortality in patients with papillary thyroid carcinoma (PTC). This study investigated the impact of androgen receptor (AR) gene expression on the clinical features and progression of PTC. The levels of AR mRNA and protein in frozen, formalin-fixed, paraffin-embedded tissue samples from PTC and adjacent normal thyroid tissue were assessed by quantitative real-time polymerase chain reaction and immunohistochemical staining, respectively, and the relationships between AR expression and clinical features were analyzed. The thyroid cancer cell lines, BCPAP and TPC-1, were used to evaluate the effects of AR on the regulation of cell migration, and key epithelial-mesenchymal transition (EMT) markers. AR mRNA expression was significantly higher in normal thyroid tissue from men than women. The sex difference in AR mRNA expression diminished during PTC tumorigenesis, as AR mRNA expression levels were lower in PTC than normal thyroid tissues from both men and women. AR mRNA expression was significantly decreased in PTC patients with higher risk and in those with extrathyroidal extension. Overexpression of AR in BCPAP cells decreased cell migration and repressed the EMT process by down-regulating mRNA expression of N-cadherin, Snail1, Snail2, Vimentin, and TWIST1 and up-regulating E-cadherin gene expression. These results suggest that suppression of the androgen-AR axis may lead to aggressive tumor behavior in patients with PTC.

Androgen Signaling in Esophageal Adenocarcinoma Cell Lines In Vitro

BACKGROUND

We showed previously that nuclear localization of the androgen receptor (AR) and expression of the androgen-responsive gene FK506-binding protein 5 (FKBP5) in esophageal adenocarcinoma (EAC) tissues were associated with decreased patient survival, suggesting a role for androgens in this cancer.

AIM

To investigate the effect of the AR ligand 5α-dihydrotestosterone (DHT) on AR-expressing EAC cell lines in vitro.

METHODS AND RESULTS

In tissue resection specimens from EAC patients, FKBP5 expression was positively associated with proliferation as measured by Ki-67 expression. We stably transduced AR into three AR-negative EAC cell lines, OE33, JH-EsoAd1, and OE19, to investigate androgen signaling in vitro. In the AR-expressing cell lines, 10 nM DHT, the concentration typically used to study AR signaling, induced changes in the expression of androgen-responsive genes and inhibited proliferation by inducing cell cycle arrest and senescence. At lower DHT concentrations near the half maximal inhibitory concentration (IC50), the AR-expressing cell lines proliferated and there were changes in the expression of androgen-responsive genes. In direct co-culture with cancer-associated fibroblast-like PShTert myofibroblasts, 10 nM DHT induced changes in the expression of androgen-responsive genes but did not inhibit proliferation.

CONCLUSIONS

This is the first study to show that EAC cell lines respond to androgen in vitro. Proliferation together with the expression of androgen-responsive genes was dependent on the concentration of DHT, or the presence of a permissive microenvironment, consistent with observations in the tissues. These findings are consistent with a role for androgen signaling in EAC.

Correlation between Insulin Resistance and Thyroid Nodule in Type 2 Diabetes Mellitus

OBJECTIVE

The present study explored the association between insulin resistance (IR) and the clinical characteristics of thyroid nodules in patients with type 2 diabetes mellitus (T2DM).

METHODS

All the patients were newly diagnosed with T2DM. 201 patients with thyroid nodule disease and 308 patients without the nodular thyroid disease. The participants were evaluated by relevant examination. Correlation analyses and regression analyses were performed to examine the relationships between the two groups.

RESULTS

HOMA-IR values, serum FT4 (free thyroxine) levels, and age were higher in the thyroid nodule group than in the control group. The proportion of women in the thyroid nodule group is greater than the proportion of women in the control group. Logistic regression analysis showed that age, sex, FT4, and HOMA-IR were positive factors for thyroid nodule. The volume and size of the thyroid nodule were positively correlated with HOMA-IR, irrespective of gender. The thyroid nodule volume and size and the TSH (thyroid stimulating hormone) were greater in females than in males, whereas FT3 (free triiodothyronine) was lower in females.

CONCLUSION

IR might be a risk factor for thyroid nodule. Whether alleviating the IR might slow the growth, or diminish the volume and size of the thyroid nodules, is yet to be elucidated.

Metabolic and immunologic aspects of fetoplacental insufficiency

PROBLEM

The chronic placental insufficiency is the most common cause of intrauterine hypoxia, retardation of fetal growth, and other threatening conditions. Immune disturbances may occur in the system "mother-placenta-fetus."

METHOD OF STUDY

Biochemical blood indicators were studied on an automated biochemical analyzer. Pattern of lymphocyte subpopulations was detected by direct membrane immunofluorescence.

RESULTS

Study revealed imbalance of immune parameters, caused by placental insufficiency (increase natural killers (CD16(+) , CD56(+) ), B lymphocytes (CD19(+) CD3(-) ), T and B lymphocytes with HLA-DR(+) antigen, and early activation of immune cells (by CD25(+) ), as well as disorders in apoptotic mechanisms (by CD95(+) )).

CONCLUSION

Placental insufficiency leads to abnormalities of the immune system in pregnant, parturient women and maternity patients which were evaluated by localization of activation markers CD25(+) CD95(+) on the CD3(+) , CD4(+) , CD8(+) , CD16(+) , CD56(+) lymphocytes. This is reflected in the change of lymphocyte functions in newborns.

Androgen receptor (AR) suppresses normal human prostate epithelial cell proliferation via AR/β-catenin/TCF-4 complex inhibition of c-MYC transcription

INTRODUCTION

Physiologic testosterone continuously stimulates prostate stromal cell secretion of paracrine growth factors (PGFs), which if unopposed would induce hyperplastic overgrowth of normal prostate epithelial cells (PrECs).

METHODS

Lentiviral shRNA stable knock down of c-MYC, β-catenin, or TCF-4 completely inhibits normal (i.e., non-transformed) human PrECs growth. c-MYC enhancer driven reporter expression and growth is inhibited by two chemically distinct molecules, which prevent β-catenin signaling either by blocking TCF-4 binding (i.e., toxoflavin) or by stimulating degradation (i.e., AVX939). Recombinant DKK1 protein at a dose, which inhibits activation of canonical Wnt signaling does not inhibit PrEC growth. Nuclear β-catenin translocation and PrEC growth is prevented by both lack of PGFs or Akt inhibitor-I. Growth inhibition induced by lack of PGFs, toxoflavin, or Akt inhibitor-I is overcome by constitutive c-MYC transcription.

RESULTS

In the presence of continuous PGF signaling, PrEC hyperplasia is prevented by androgen binding to AR suppressing c-MYC transcription, resulting in G0 arrest/terminal differentiation independent of Rb, p21, p27, FoxP3, or down regulation of growth factors receptors and instead involves androgen-induced formation of AR/β-catenin/TCF-4 complexes, which suppress c-MYC transcription. Such suppression does not occur when AR is mutated in its zinc-finger binding domain.

DISCUSSION

Proliferation of non-transformed human PrECs is dependent upon c-MYC transcription via formation/binding of β-catenin/TCF-4 complexes at both 5' and 3' c-MYC enhancers stimulated by Wnt-independent, PGF induced Akt signaling. In the presence of continuous PGF signaling, PrEC hyperplasia is prevented by androgen-induced formation of AR/β-catenin/TCF-4 complexes, which retains binding to 3' c-MYC enhancer, but now suppresses c-MYC transcription.

Androgen receptor expression in human thyroid cancer tissues: a potential mechanism underlying the gender bias in the incidence of thyroid cancers

Gender bias in the incidence of thyroid cancer is well known, however, the underlying mechanism is largely unknown. The current study determines variations in the molecular characteristics of thyroid cancers between men and women. Normal and cancerous thyroid tissues were collected from a total of 125 men and women who underwent surgical thyroidectomy. Testosterone levels in serum and thyroid cancer tissues were elevated in women while it decreased in men compared to respective control groups; whereas, ligand binding activity increased in men and decreased in women. Androgen receptor (AR) mRNA expression increased in a majority of men while it decreased in a majority of women except those with follicular thyroid carcinoma (FTC). In thyroid cancers of women, Pearson's correlation analysis showed a positive correlation of AR mRNA with AR protein, CBP and Sp1, whereas AR mRNA showed a negative correlation with p53. In case of men, AR mRNA showed a positive correlation with AR and cyclin D1 proteins in papillary thyroid carcinoma (PTC); and CBP and Sp1 in follicular thyroid adenoma (FTA), whereas AR mRNA showed a positive correlation with p53. Our study identified for the first time that AR is posttranscriptionally regulated by miR-124a in thyroid cancer tissues. Further, our in vitro studies with a PTC cell line (NPA-87-1) showed miR-124a as the potent inhibitor of AR that impairs cell proliferation even in the presence of testosterone. Thus, the current study suggests that: (i) the varying pattern of testosterone level and AR status in thyroid tissues of men and women may predispose to the gender specific incidence of thyroid tumors and (ii) miR-124a plays a significant role in determining the AR gene expression pattern and thus, androgen mediated thyroid tumor growth.

An intronic polymorphism of IRF4 gene influences gene transcription in vitro and shows a risk association with childhood acute lymphoblastic leukemia in males

The interferon regulatory factor (IRF) family of DNA-binding proteins regulates expression of interferon-inducible genes with roles in the immune response and carcinogenesis. IRF4 is involved in the differentiation of B and T cells and is overexpressed in B-cell malignancies as a result of c-REL (NF-kappaB) hyperactivation. IRF4 polymorphisms are associated with susceptibility to chronic lymphoid leukemia (CLL) and non-Hodgkin lymphoma (NHL). We examined 13 IRF4 SNPs in 114 cases of childhood acute lymphoblastic leukemia (ALL) and 388 newborn controls from Wales (U.K.) using TaqMan assays. IRF4 intron 4 SNP rs12203592 showed a male-specific risk association (OR=4.4, 95% CI=1.5 to 12.6, P=0.007). Functional consequences of the C>T substitution at this SNP were assessed by cell-based reporter assays using three different cell lines. We found a repressive effect of the rs12203592 wildtype allele C on IRF4 promoter activity (P<0.001) but no repression by the variant allele in any cell line tested. Thus, homozygosity for the rs12203592 variant allele would result in increased IRF4 expression. This increase would be compounded by high levels of NF-kappaB activity in males due to the absence of estrogen. IRF4 differs from other IRFs in its anti-interferon activity which interferes with immune surveillance. We propose that a detailed study of IRF4 can provide information on the mechanism of the sex effect and the role of immune surveillance in childhood ALL development.

MCM7 interacts with androgen receptor

MCM7 is a critical component of the DNA replication licensing complex that controls DNA replication in both yeast and Xenopus. Our previous studies have indicated that MCM7 is both amplified and overexpressed in metastatic prostate cancer. In this study, we found that MCM7 interacts with the androgen receptor (AR) with high affinity both in vitro and in vivo. We identified the AR-binding motif for MCM7, comprised of amino acids 221 to 248, and the MCM7-binding motif for the AR, comprised of amino acids 426 to 475. AR stimulation with high doses of the synthetic androgen R1881 led to a decrease in MCM7 binding to genomic DNA, a reduction of DNA synthesis, decreases in the number of cells progressing through S phase and cell proliferation, whereas low doses produced an increase in the DNA licensing activity of MCM7 and higher levels of cell proliferation. In addition, the MCM7/AR interaction down-regulated MCM7 expression. The gene transcription or repressor activity of AR is dependent on its interaction with MCM7 because either a mutant AR defective in its interaction with MCM7 or a MCM7 knockdown primarily eliminated AR effects on gene expression. Thus, this study reveals a novel mechanism by which AR and MCM7 facilitate each other's function, suggesting that AR-independent activation of MCM7 may be a mechanism by which prostate cancers bypass therapeutically induced AR blockade.

PC3, but not DU145, human prostate cancer cells retain the coregulators required for tumor suppressor ability of androgen receptor

BACKGROUND

Androgen receptor (AR) functions in normal prostate epithelium as a tumor suppressor to inhibit continuous proliferation of these cells. Such tumor suppressor function of AR is lost in androgen depletion independent (ADI) prostate cancers. In type-I ADI cancers AR is not expressed, while in type-II ADI cancers AR is recaptured as an oncogene. The PC3 and DU145 human prostate cancer cell lines are representative of the earlier type-I ADI prostate cancers. While these cells do not express AR, it is unclear whether they retained the coactivators necessary for AR-dependent tumor suppression. To answer this question the response to AR protein expression by PC3 and DU145 cells was evaluated.

METHODS

To do this, a lentiviral AR (Lenti-AR) expression system was engineered to encode an AR transcript which includes appropriate 5' and 3' untranslated regions (UTRs) containing all previously identified post-transcriptional regulatory sequences. AR expression and transcriptional activity were evaluated in Lenti-AR transduced cells by Western blot and luciferase assay, respectively. Cell growth in culture and in mouse xenografts was evaluated in correlation to expression changes in p21, p27, and p45(SKP2) proteins.

RESULTS

Lenti-AR transduced PC3 and DU145 lines expressed transcriptionally functional AR protein at appropriate physiological levels. Expression and engagement of AR protein in PC3-Lenti-AR cells resulted in transactivation of p21 and subsequent growth inhibition of these cells in culture and in mouse xenografts. Such inhibition was due to induced G1 arrest of these cells as documented by expression changes in p27 and p45(SKP2) proteins. Such growth inhibition was not observed in DU145-Lenti-AR cells.

CONCLUSIONS

These results document that PC3, but not DU145 cells retain the coregulators needed for AR tumor suppressor ability.

Role of complex cyclin d1/cdk4 in somatostatin subtype 2 receptor-mediated inhibition of cell proliferation of a medullary thyroid carcinoma cell line in vitro

Somatostatin (SRIH) inhibits cell proliferation by interacting with five distinct SRIH receptor subtypes (SSTRs) activating several pathways in many tissues. We previously demonstrated that SRIH, by activating Src homology-2-containing protein, inhibits cell proliferation of the human medullary thyroid carcinoma cell line, TT, which expresses all SSTRs. However, the effects of SRIH on cell cycle proteins have not been investigated so far. We therefore evaluated the effects of SRIH and a selective SSTR2 agonist on cell cycle protein expression, mainly focusing on cyclin D1 and its associated kinases. Our data show that SRIH and the selective SSTR2 agonist, BIM-23120, reduce cell proliferation and DNA synthesis as well as induce a delay of the cell cycle in G(2)/M phase. Moreover, treatment with both SRIH and BIM-23120 decreases cyclin D1 levels, with a parallel increase in phosphocyclin D1 levels, suggesting protein degradation. Moreover, our data show an increase in glycogen synthase kinase-3beta activity, which triggers phosphorylation-dependent cyclin D1 degradation. Indeed, we observed a reduction in cyclin D1 protein half-life under treatment with SRIH or the SSTR2 selective agonist. A reduction in cdk4 protein levels is also observed with a parallel reduction in Rb phosphorylation levels at Ser-780. Our data indicate that the subtype 2 receptor-mediated antiproliferative effect of SRIH on TT cell proliferation may be exerted through a decrease in cyclin D1 levels.

Alteration of urinary profiles of endogenous steroids and polyunsaturated fatty acids in thyroid cancer

To explore the possible involvement of a relationship between steroids and polyunsaturated fatty acids (PUFAs) in thyroid cancer, we studied the concentration levels of 21 endogenous urinary androgens and glucocorticoids, and 6 urinary PUFAs in female patients with thyroid cancer (n=29, 49.4+/-12.6 years) and in normal female subjects (n=20, 48.3+/-11.9 years). Using gas chromatography-mass spectrometry in selected ion-monitoring mode, we performed quantification of androgens, glucocorticoids, and PUFAs. In the case of the urinary androgens and the glucocorticoids, the concentration of androgens was not altered between patients with thyroid cancer and normal controls. However, the concentration of glucocorticoid significantly decreased in patients with thyroid cancer compared to that of the normal controls. Also, in case of urinary PUFAs, the precursor of cholesterol, the concentration of linoleic acid, arachidonic acid, and docosahexaenoic acid (DHA) were decreased in patient with thyroid cancer (P<0.05). In this results, it can be concluded that the glucocorticoids milieu induced from the decreasing urinary concentration of DHA may exert an important influence upon thyroid cancer. Consequently, the change of urinary glucocorticoids concentration may play an important role in thyroid cancer.

Modulatory effect of estradiol and testosterone on the development of N-nitrosodiisopropanolamine induced thyroid tumors in female rats

Both experimental and clinical research support the conclusion that thyroid tumors are sex dependent. Also, several studies have pointed out that the use of oral contraceptives is associated with a higher risk of thyroid tumor. Most of the existing reports suggest indirect effects of sex steroids on thyroid tumor growth in women. In this work, we present data to support the direct promoting effect of estradiol and testosterone on carcinogen-induced thyroid tumorigenesis. Thyroid tumors were induced in rats by a combination of N-nitrosodiisopropanolamine (DHPN) and phenobarbital (PB) treatment. Serum thyroid hormones, thyroid stimulating hormone (TSH), steroid hormones, thyroidal steroid concentration, androgen and estrogen receptors were quantified. Serum thyroid hormones and TSH suggested euthyroid status of the all experimental animals. Ovariectomy decreased the incidence of DHPN + PB induced thyroid tumor when compared with ovary intact rats and estradiol/testosterone supplementation increased the same. Thyroidal estradiol level and its nuclear receptors increased in the tumor tissue specifically. Testosterone supplementation to DHPN-treated ovariectomized rats specifically induced the development of malignant thyroid tumors. Addition of estradiol in vitro to thyrocytes induced a higher proliferation rate. Our data proves a direct promoting role of estrogen on carcinogen-induced thyroid tumor development.

Risk factors for goiter and thyroid nodules

The occurrence of thyroid diseases is determined by interplay between genetic and environmental factors. The major environmental factor that determines goiter prevalence is iodine status, but other environmental factors influencing entire populations have been identified such as goitrogens in food and drinking water. Less focus has been on individual environmental factors and the interplay between factors. The goiter prevalence is higher in certain groups in the population. The variation in goiter prevalence between the genders is well known with a higher occurrence among women. The association with age is probably dependent on iodine status, because it seems that the zenith of goiter prevalence appears earlier in life the more severe iodine deficiency the population is exposed to. The association with individual risk factors has been investigated in some studies, especially the association with tobacco smoking. In iodine-deficient areas, a strong association between tobacco smoking and goiter prevalence is found, whereas the association is less pronounced in iodine-replete areas. This was predictable from experimental studies showing thiocyanate to be the mediator of the goitrogenic effect of tobacco smoke acting as a competitive inhibitor of iodine uptake. The association with alcohol intake has only been investigated in few studies, but a low occurrence of goiter among alcohol consumers has been found. The mechanism of this association is not known. Increased goiter prevalence during pregnancy has been reported, and recently a long-term goitrogenic effect of pregnancies has also been shown. As demonstrated for tobacco smoking, this association is dependent on iodine status, because the association has only been found in areas with a suboptimal iodine intake. This indicates pregnancy-induced goiter to be the result of exacerbation of existing iodine deficiency. Recently, the use of oral contraceptives has been shown to be associated with a markedly reduced prevalence of goiter, although experimental studies have previously shown proliferative effects of estrogens on thyrocytes. Some implications for prevention of thyroid disease could be suggested. Discussion of smoking habits should be included in a consultation for goiter with a motivation to quit smoking. Iodine deficiency has particularly strong goitrogenic effects during pregnancy and for the sake of the mother as well as the fetus, sufficient iodine supply should be ensured to all pregnant women. The difference in age maximum in goiter prevalence suggests that monitoring of iodine deficiency disorders should ideally include a spectrum of age groups.

K562 erythroid and HL60 macrophage differentiation downregulates polycystin, a large membrane-associated protein

Polycystin, the PKD1 gene product mutated in autosomal dominant polycystic kidney disease, is a large membrane protein which is important in the differentiation of epithelial tubular structure. Furthermore, PKD1 mRNA is expressed in various tissues and in neoplastic cell lines particularly, suggesting that polycystin might be involved in differentiation and/or proliferation of other cell types. Therefore, in order to investigate such a possible role, polyclonal antibodies against a recombinant polycystin peptide were raised and used to study polycystin expression in human leukemia cell lines committed to differentiation. Using Western blot and laser scanning confocal microscopy analyses, we demonstrated expression of polycystin in erythroleukemia K562 cells as a membrane-associated polypeptide of approximately 450 kDa, mainly localized in cell-cell contacts. Protein size and subcellular distribution were similar to those found in the kidney epithelial KJ29 cell line. In addition, K562 cell erythroid differentiation induced by hemin was characterized by a reduction in polycystin expression, as measured by Western blot and Northern blot analyses. Cytofluorimetric analysis indicated that upon hemin treatment there was a progressive reduction in the number of polycystin-expressing cells as well as in proliferation rate. Furthermore, reduction in proliferating and polycystin-expressing cells was also observed in K562 cells after serum starvation. When serum was added to the serum-deprived cells an increase in cell number as well as in number of polycystin-positive cells was observed. In addition, polycystin, also expressed in promyelocytic leukemia HL60 cells, was downregulated when macrophage differentiation in HL60 was induced by TPA. Therefore, in these leukemic cells downregulation of polycystin appeared to be closely related to reduction in cell proliferation and to induction of differentiation. This suggests that polycystin may play a relevant role in these cell processes.

The role of androgens in female vertebrates

The role of androgens in vertebrate females has been overlooked until recently. We examine the functional significance of androgens in females by reviewing studies that document relatively high levels of circulating plasma androgens, androgen receptors, or androgen-metabolizing enzymes in females. Among the mechanisms of androgenic action identified are enhanced neuron survival, stimulation of muscle satellite cell proliferation, alteration of ion current kinetics, and release of somatostatin. These mechanisms are not sex specific and thus we hypothesize that androgens play a significant role in normal female development. We encourage study in this nontraditional research area.