Li-Qun Cai

Molecular analysis of estrogen induction of preproenkephalin gene expression and its modulation by thyroid hormones.

Estrogen receptors (ER) and thyroid hormone receptors (TR) are ligand-dependent nuclear transcription factors. Estrogen-induced preproenkephalin (PPE) gene expression in the hypothalamus is directly related to estrogen-induced lordosis behavior in the rat. In the present study, we showed that the PPE mRNA level in the ventromedial hypothalamus of female rats was significantly decreased by ovariectomy. This decrease was reversed by estrogen replacement in a dose- and time-dependent manner. Using transient transfection and electrophoretic mobility shift assays (EMSA), functional estrogen response elements (ERE) were identified between -437 and -145 base pairs (bp) of the rat PPE gene promoter region. Two ERE-like elements are present between -405 and -364 of the rat PPE gene promoter, which bind ERalpha as demonstrated by EMSA. Estrogen produced a dose-dependent increase in CAT activity in cotransfection assays with ERalpha expression vector and a 437PPE-CAT reporter construct containing 437 bp of the rat PPE gene promoter and the CAT reporter gene. This estrogen-induced PPE promoter activity was inhibited by liganded-TR in transient cotransfection assays. Analysis of DNA-protein interactions by EMSA revealed that both ERalpha and TR (alpha1 and beta1) could bind to the EREs in the rat PPE gene promoter. Furthermore, estrogen induction of PPE mRNA in the ventromedial hypothalamus of the ovariectomized female rat was significantly attenuated by concomitant administration of triiodothyronine. These results suggest that estrogen regulation of the hypothalamic PPE gene expression is mediated through an estrogen-receptor complex directly interacting with the functional EREs in its promoter region; and that this estrogen effect can be modified by thyroid hormones.

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.

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.

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.

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.

17α-Estradiol and Genistein Inhibit High Fat Diet Induced Prostate Gene Expression and Prostate Growth in the Rat

PURPOSE High dietary fat and low phytoestrogen intake are associated with prostate cancer development and progression. Our previous study showed that exposure to a high fat diet significantly increased prostate 5α-reductase-2 mRNA and prostate growth in the rat. In the current experiments we determined the effects of genistein and 17α-estradiol on the modulation of dietary fat induced prostate 5α-reductase-2 and insulin-like growth factor-1 gene expression, and prostate growth. MATERIALS AND METHODS At weaning male ACI/Seg rats (Harlan® Sprague-Dawley®) were fed a low or a high fat diet, with or without genistein or 17α-estradiol for 2, 4 or 10 weeks. The prostate was dissected and weighed. We determined the levels of prostate 5α-reductase-2 mRNA, insulin-like growth factor-1 mRNA, dihydrotestosterone, and plasma insulin-like growth factor-1, dihydrotestosterone and testosterone. RESULTS Two-week exposure to a high fat diet significantly increased prostate insulin-like growth factor-1 mRNA without significant changes in plasma insulin-like growth factor-1, which was blocked by genistein and 17α-estradiol. Genistein but not 17α-estradiol also inhibited prostate 5α-reductase-2 mRNA and intraprostatic dihydrotestosterone induced by the high fat diet at 2 weeks. Genistein and 17α-estradiol completely blocked high fat diet induced prostate growth at 10 weeks of dietary treatment. However, neither genistein nor 17α-estradiol had any significant effect when co-administered with the low fat diet. CONCLUSIONS Results indicate that genistein and 17α-estradiol can inhibit dietary fat induced changes in prostate 5α-reductase-2 and insulin-like growth factor-1 gene expression, and prostate growth in the rat. This may be beneficial to prevent dietary fat associated prostate diseases such as prostate cancer.

Functional characterisation of a natural androgen receptor missense mutation (N771H) causing human androgen insensitivity syndrome

Androgen insensitivity syndrome (AIS) is an X‐linked disorder due to mutations of androgen receptor (AR) gene. Various AR mutations have been identified, and the characterisation of these mutations greatly facilitates our understanding of AR structure–function. In this study, we have analysed an AR missense mutation (N771H) identified in patients with AIS. Functional analysis of the mutant AR was performed by in vitro mutagenesis–cotransfection assays. Compared to the wild‐type AR, the dose–response curve of dihydrotestosterone‐induced transactivation activity in the mutant AR was greatly shifted to the right and significantly decreased. However, the maximal efficacy of transactivation activity in the mutant AR was similar to that of the wild type. Receptor binding assay indicated that the mutant AR had an approximately 2.5‐fold lower binding affinity to dihydrotestosterone compared to the wild type. Western blot analysis showed that the size and the expression level of mutant AR in transfected cells were comparable to the wild type. These data underscore the importance of asparagine at amino acid position 771 of human AR in normal ligand binding and normal receptor function, and a mutation at this position results in androgen insensitivity in affected subjects.