Yuan-Shan Zhu

5α-Reductase Isozymes and Androgen Actions in the Prostate

Androgens acting via the androgen receptor play critical roles in prostate development, growth, and pathogenesis. There are two potent androgens, testosterone and dihydrotestosterone (DHT), in humans and mammals. DHT is converted from testosterone by 5α‐reductase isozymes. Two 5α‐reductase isozymes have been identified. Although both isozymes are expressed, 5α‐reductase‐2 is the predominant isozyme in the human prostate. Mutations in 5α‐reductase‐2 gene cause the 5α‐reductase‐2 deficiency syndrome. Affected 46, XY individuals have a small, nonpalpable, and rudimentary prostate in adulthood. Neither benign prostate hyperplasia (BPH) nor prostate cancer has been reported in these patients. The prostate is small in animals with 5α‐reductase‐2 gene knockout or treated with specific 5α‐reductase inhibitors. 5α‐reductase isozymes are molecular targets for the prevention and treatment of BPH and prostate cancer. Moreover, androgen actions on prostate gene expression and cell growth are directly modulated by estrogen receptor ligands via protein−protein interactions. The studies of 5α‐reductases and androgen actions highlight the importance of 5α‐reductase isozymes in male sexual differentiation and prostate physiology and pathophysiology.

NATURAL POTENT ANDROGENS : LESSONS FROM HUMAN GENETIC MODELS

Male pseudohermaphroditism due to 17 beta-hydroxysteroid dehydrogenase-3 (17 beta-HSD-3) deficiency and 5 alpha-reductase-2 (5 alpha-RD-2) deficiency provides natural human genetic models to elucidate androgen actions. To date, five 17 beta-HSD isozymes have been cloned that catalyse the oxidoreduction of androstenedione and testosterone and dihydrotestosterone (DHT), oestrone and oestradiol. Mutations in the isozyme 17 beta-HSD-3 gene are responsible for male pseudohermaphroditism due to 17 beta-HSD deficiency. The type 3 isozyme preferentially catalyses the reduction of androstenedione to testosterone and is primarily expressed in the testes. Fourteen mutations in the 17 beta-HSD-3 gene have been identified from different ethnic groups. Affected males with the 17 beta-HSD-3 gene defect have normal wolffian structures but ambiguous external genitalia at birth. Many are raised as girls but virilize at the time of puberty and adopt a male gender role. Some develop gynaecomastia at puberty, which appears to be related to the testosterone/oestradiol ratio. Two 5 alpha-reductase (5 alpha-RD) isozymes, types 1 and 2, have been identified, which convert testosterone to the more potent androgen DHT. Mutations in the 5 alpha-RD-2 gene cause male pseudohermaphroditism, and 31 mutations in the 5 alpha-RD-2 gene have been reported from various ethnic groups. Such individuals also have normal wolffian structure but ambiguous external genitalia at birth and are raised as girls. Virilization occurs at puberty, often with a gender role change. The prostate remains infantile and facial hair is decreased. Balding has not been reported.

Mutations in CYP11B1 gene: phenotype-genotype correlations.

11β‐hydroxylase deficiency, an autosomal recessive disorder, is the second most common cause of congenital adrenal hyperplasia. We studied four subjects with classic 11β‐hydroxylase deficiency and severe hypertension: a 46,XX affected subject from a Turkish family with severe ambiguity of the external genitalia and hypertension, and three affected 46,XY subjects from a Dominican kindred with isosexual precocious puberty and severe hypertension. The affected subjects had significantly elevated plasma 11‐desoxycortisol, 11‐desoxycorticosterone, Δ4‐androstenedione, and testosterone. To determine the molecular genetic defects, genomic DNA was isolated from the leukocytes of affected subjects and their family members. The encoding region of the 11β‐hydroxylase gene (CYP11B1) was amplified by PCR with specific primers. Using single‐stranded DNA conformational polymorphism (SSCP) and DNA sequencing, a nonsense mutation in exon 6 of CYP11B1 in the affected 46,XX subject from the Turkish family was identified, where a cytosine was substituted by a thymidine, resulting in the replacement of glutamine (CAG) by a stop codon (TAG) at amino acid position 338 (Q338X). In the three 46,XY Dominican boys, the mutation was also a nonsense mutation in exon 6 of CYP11B1, where a cytosine was substituted by a thymidine, resulting in the replacement of glutamine (CAG) by a stop codon (TAG) at amino acid position 356 (Q356X). Both mutations result in the biosynthesis of a truncated 11β‐hydroxylase protein with loss of enzymatic activity. Heterozygosity was determined in family members of both probands including parents and siblings. These results indicate that mutations of CYP11B1 in these subjects are responsible for their clinical syndromes.

The effect of 5α-reductase-2 deficiency on human fertility.

A most interesting and intriguing male disorder of sexual differentiation is due to 5α-reductase-2 isoenzyme deficiency. These male infants are born with ambiguous external genitalia due to a deficiency in their ability to catalyze the conversion of T to dihydrotestosterone. Dihydrotestosterone is a potent androgen responsible for differentiation of the urogenital sinus and genital tubercle into the external genitalia, urethra, and prostate. Affected males are born with a clitoral-like phallus, bifid scrotum, hypospadias, blind shallow vaginal pouch from incomplete closure of the urogenital sinus, and a rudimentary prostate. At puberty, the surge in mainly T production prompts virilization, causing most boys to choose gender reassignment to male. Fertility is a challenge for affected men for several reasons. Uncorrected cryptorchidism is associated with low sperm production, and there is evidence of defective transformation of spermatogonia into spermatocytes. The underdeveloped prostate and consequent low semen volumes affect sperm transport. In addition, semen may not liquefy due to a lack of prostate-specific antigen. In the present review, we discuss the 5α-reductase-2 deficiency syndrome and its impact on human fertility.

NSC606985, a novel camptothecin analog, induces apoptosis and growth arrest in prostate tumor cells

PurposeProstate cancer is a major cause of cancer mortality in American males. Once prostate cancer has metastasized, there is currently no curative therapy available. The development of effective agents is therefore a continuing effort to combat this disease. In the present study, the effects and potential mechanisms of NSC606985 (NSC), a water-soluble camptothecin analog, in prostate cancer cells were investigated.MethodsProstatic tumor cells, DU-145, LNCaP and PC-3, were used for the study. Cell proliferation, cell cycle, cell apoptosis and caspase 3/7 activity were determined in the presence or absence of NSC. The levels of Bax and Bak, and the release of cytochrome c from mitochondria were analyzed by Western blot.ResultsTreatment with NSC at nanomolar concentrations produced a time- and dose-dependent decrease in viable cell numbers of multiple prostate cancer cells. In DU-145 cells, NSC produced a time-and dose-dependent induction of cell apoptosis and cell cycle arrest as evidenced by cell morphological changes, increases in S-phase and sub-G1 cell fractions, an elevation of caspase 3/7 activity, DNA fragmentation and apoptotic cells. NSC increased the levels of apoptotic proteins, Bax and Bak, and induced a release of cytochrome c from mitochondria to cytosol in DU-145 cells. Co-administration of Z-VAD-FMK, a pan-caspase inhibitor, blocked NSC-induced caspase 3/7 activity and cell apoptosis without affecting NSC-induced cell cycle arrest. In contrast, co-administration of a PKCδ inhibitor, rottlerin, had no significant effect on NSC induction of caspase activity, and slightly potentiated NSC-induced cell death. Furthermore, like camptothecin, a mutation of topoisomerase 1 that prevents the binding of camptothecin to the enzyme completely abolished the NSC effect in DU-145 cells.ConclusionThe data obtained suggest that NSC is able to decrease cell growth, induce cell apoptosis and cause growth arrest in prostatic tumor cells, which may involve an interaction with topoisomerase 1 and an activation of mitochondrial apoptotic pathway.

Sex Specificity of Ventral Anterior Cingulate Cortex Suppression During a Cognitive Task

Ventral anterior cingulate cortex (vACC) is a highly interconnected brain region considered to reflect the sometimes competing demands of cognition and emotion. A reciprocal relationship between vACC and dorsal ACC (dACC) may play a role in maintaining this balance between cognitive and emotional processing. Using functional MRI in association with a cognitively‐demanding visuospatial task (mental rotation), we found that only women demonstrated vACC suppression and inverse functional connectivity with dACC. Sex differences in vACC functioning—previously described under conditions of negative emotion—are extended here to cognition. Consideration of participant sex is essential to understanding the role of vACC in cognitive and emotional processing. Hum Brain Mapp, 2007.

The first successful paternity through in vitro fertilization–intracytoplasmic sperm injection with a man homozygous for the 5α-reductase-2 gene mutation

OBJECTIVE To report a case of successful paternity from a male homozygous for 5α-reductase-2 deficiency. DESIGN Case report. SETTING Academic center, division of reproductive endocrinology. PATIENT(S) A 45-year-old Dominican man and his 32-year-old wife. INTERVENTION(S) In vitro fertilization and intracytoplasmic sperm injection. MAIN OUTCOME MEASURE(S) Pregnancy. RESULT(S) Viable twin gestation. CONCLUSION(S) Men homozygous for 5α-reductase-2 deficiency can achieve biologic paternity through in vitro fertilization with intracytoplasmic sperm injection despite severely abnormal semen parameters.

Gender and Behavior in Subjects with Genetic Defects in Male Sexual Differentiation

Publisher Summary This chapter reviews male sexual differentiation in humans and enzyme defects in testosterone (T) biosynthesis, and action resulting in disorders of male sexual differentiation is also discussed. The syndrome of complete androgen insensitivity due to defects in the androgen receptor is addressed. The influence of sex steroids extends beyond their roles in sexual differentiation and development. In many animal species, hormones have been shown to be essential for sexual differentiation of the brain during development and for maintaining sexually dimorphic behavior throughout life. The principals of sex determination, genetic and hormonal, in humans have proven to be similar to other mammals. However, the hormonal influence on sexual dimorphic differences in the nervous system in humans and sex differences in behavior, and its correlation with those of other mammals is still an emerging field.

Suppression of DHT-induced paracrine stimulation of endothelial cell growth by estrogens via prostate cancer cells.

Androgen modulation of angiogenesis in prostate cancer may be not directly mediated by androgen receptor (AR) as AR is not detected in the prostatic endothelial cells.

Inhibition of Aberrant Androgen Receptor Induction of Prostate Specific Antigen Gene Expression, Cell Proliferation and Tumor Growth by 17α-Estradiol in Prostate Cancer

PURPOSE Androgen independent prostate cancer growth and metastasis are a major cause of prostate cancer death. Aberrant androgen receptor activation due to androgen receptor mutation is an important mechanism of androgen independence. We determined the effectiveness and mechanism of 17α-estradiol (Sigma®) in blocking aberrant androgen receptor activation due to androgen receptor mutation. MATERIALS AND METHODS We used LNCaP and MDA Pca-2b prostatic tumor cells (ATCC®) containing a mutated androgen receptor and WT estrogen receptor β to test 17α-estradiol inhibition of aberrant androgen receptor activation of prostate specific antigen gene expression and cell growth. Cotransfection analysis was used to further elucidate the mechanism of 17α-estradiol action. Xenograft animals with an LNCaP prostate tumor were prepared to study the in vivo effect of 17α-estradiol on tumor growth inhibition. RESULTS In LNCaP cells 17α-estradiol produced a dose dependent inhibition of cyproterone acetate (Sigma) or dihydrotestosterone induced prostate specific antigen gene expression. In MDA Pca-2b cells 17α-estradiol inhibited cortisol (Sigma) induced prostate specific antigen expression and blocked dihydrotestosterone and cortisol induced cell proliferation in LNCaP and MDA Pca-2b cells, respectively. Cotransfection analysis showed that 17α-estradiol inhibition of aberrant androgen receptor activation of prostate specific antigen gene expression was medicated via estrogen receptors. In xenograft mice with LNCaP prostate cancer 17α-estradiol but not 17β-estradiol (Sigma) significantly inhibited tumor growth, although each estrogen tended to decrease tumor growth. CONCLUSIONS Results suggest that 17α-estradiol with less classic estrogenic activity is a potential therapeutic agent for androgen independent prostate cancer due to androgen receptor mutation.