Effect of abiraterone acetate on fatigue in patients with metastatic castration-resistant prostate cancer after docetaxel chemotherapy.

BACKGROUND: Fatigue is a common, debilitating side-effect of prostate cancer and its treatment. Patient-reported fatigue was evaluated as part of COU-AA-301, a randomized, placebo-controlled, phase III trial of abiraterone acetate and prednisone versus placebo and prednisone in metastatic castration-resistant prostate cancer (mCRPC) patients after docetaxel chemotherapy. This is the first phase III study in advanced prostate cancer to evaluate fatigue outcomes using a validated fatigue-specific instrument. PATIENTS AND METHODS: The Brief Fatigue Inventory (BFI) questionnaire was used to measure patient-reported fatigue intensity and fatigue interference with activities of daily life. All analyses were conducted using prespecified responder definitions of clinically meaningful changes. RESULTS: A total of 797 patients were randomized to abiraterone acetate and prednisone, and 398 were randomized to placebo and prednisone. Compared with prednisone alone, in patients with clinically significant fatigue at baseline, abiraterone acetate and prednisone significantly increased the proportion of patients reporting improvement in fatigue intensity (58.1% versus 40.3%, P = 0.0001), improved fatigue interference (55.0% versus 38.0%, P = 0.0075), and accelerated improvement in fatigue intensity (median 59 days versus 194 days, P = 0.0155). CONCLUSIONS: In patients with mCRPC progressing after docetaxel chemotherapy, abiraterone acetate and prednisone yielded clinically meaningful improvements in patient-reported fatigue compared with prednisone alone.

Molecular basis of mammalian sexual determination: activation of Müllerian inhibiting substance gene expression by SRY.

The pathway of male sexual development in mammals is initiated by SRY, a gene on the short arm of the Y chromosome. Its expression in the differentiating gonadal ridge directs testicular morphogenesis, characterized by elaboration of Müllerian inhibiting substance (MIS) and testosterone. SRY and MIS each belong to conserved gene families that function in the control of growth and differentiation. Structural and biochemical studies of the DNA binding domain of SRY (the HMG box) revealed a protein-DNA interaction consisting of partial side chain intercalation into a widened minor groove. Functional studies of SRY in a cell line from embryonic gonadal ridge demonstrated activation of a gene-regulatory pathway leading to expression of MIS. SRY molecules containing mutations associated with human sex reversal have altered structural interactions with DNA and failed to induce transcription of MIS.

SRYand architectural gene regulation: the kinetic stability of a bent protein-DNA complex can regulate its transcriptional potency.

Protein-directed DNA bending is proposed to regulate assembly of higher-order DNA-multiprotein complexes (enhanceosomes and repressosomes). Because transcriptional initiation is a nonequilibrium process, gene expression may be modulated by the lifetime of such complexes. The human testis-determining factor SRY contains a specific DNA-bending motif, the high-mobility group (HMG) box, and is thus proposed to function as an architectural factor. Here, we test the hypothesis that the kinetic stability of a bent HMG box-DNA complex can in itself modulate transcriptional potency. Our studies employ a cotransfection assay in a mammalian gonadal cell line as a model for SRY-dependent transcriptional activation. Whereas sex-reversal mutations impair SRY-dependent gene expression, an activating substitution is identified that enhances SRY's potency by 4-fold. The substitution (I13F in the HMG box; fortuitously occurring in chimpanzees) affects the motif's cantilever side chain, which inserts between base pairs to disrupt base pairing. An aromatic F13 cantilever prolongs the lifetime of the DNA complex to an extent similar to its enhanced function. By contrast, equilibrium properties (specific DNA affinity, specificity, and bending; thermodynamic stability and cellular expression) are essentially unchanged. This correlation between potency and lifetime suggests a mechanism of kinetic control. We propose that a locked DNA bend enables multiple additional rounds of transcriptional initiation per promoter. This model predicts the occurrence of a novel class of clinical variants: bent but unlocked HMG box-DNA complexes with native affinity and decreased lifetime. Aromatic DNA-intercalating agents exhibit analogous kinetic control of transcriptional elongation whereby chemotherapeutic potencies correlate with drug-DNA dissociation rates.

Mullerian inhibiting substance ontogeny and its modulation by follicle-stimulating hormone in the rat testes.

Mullerian Inhibiting Substance (MIS) production in rat testes from the late fetal to the adult period and its modulation by gonadotropins in neonatal testes were studied using immunohistochemistry, northern analysis, and a graded organ culture bioassay for MIS. The intense immunohistochemical staining for MIS seen in fetal and newborn testes began to decrease gradually after the third postnatal day, then decreased dramatically on the fifth postnatal day. MIS immunohistochemical activity was then present at a low level until about the 20th postnatal day, after which it was barely detectable. The testes from rats treated with FSH at birth showed a considerable drop in MIS immunohistochemical activity on the third postnatal day to 29% of control testes, and a less profound decrease on the second and fourth postnatal days to 46% and 61% of control, respectively; thereafter MIS levels were the same in treated and untreated animals. With shorter courses of FSH treatment, immunohistochemical staining showed less depression of MIS on the third day, and no difference by the fourth postnatal day, indicating that the inhibitory effect on testicular MIS production may require continued FSH exposure. Three-day testes that had been treated with FSH for 2-1/2 days had less MIS messenger RNA compared to control testes of the same age, suggesting that the inhibitory effect of FSH on MIS production could be transcriptionally mediated. In contrast LH treatment produced no difference in either messenger RNA expression or immunohistochemical staining for MIS. These findings suggested that FSH may be a modulator of MIS production in neonatal testes.

Androgen dynamics and serum PSA in patients treated with abiraterone acetate.

BACKGROUND: We analyzed the potential of abiraterone acetate (henceforth abiraterone) to reduce androgen levels below lower limits of quantification (LLOQ) and explored the association with changes in PSA decline in metastatic castration-resistant prostate cancer (mCRPC) patients. METHODS: COU-AA-301 is a 2:1 randomized, double-blind, placebo-controlled study comparing abiraterone (1000 mg q.d.) plus low-dose prednisone (5 mg b.i.d.) with placebo plus prednisone in mCRPC patients post docetaxel. Serum testosterone, androstenedione and dehydroepiandrosterone sulfate from baseline to week 12 were measured by novel ultrasensitive two-dimensional liquid chromatography coupled to tandem mass spectrometry assays in a subset of subjects in each arm (abiraterone plus prednisone, n=80; prednisone, n=38). The association between PSA response (< or =50% baseline) and undetectable androgens (week 12 androgen level below LLOQ) was analyzed using logistic regression. RESULTS: A significantly greater reduction in serum androgens was observed with abiraterone plus prednisone versus prednisone (all P < or = 0.0003), reaching undetectable levels for testosterone (47.2% versus 0%, respectively). A positive association was observed between achieving undetectable serum androgens and PSA decline (testosterone: odds ratio=1.54; 95% confidence interval: 0.546-4.347). Reduction of androgens to undetectable levels did not occur in all patients achieving a PSA response, and a PSA response did not occur in all patients achieving undetectable androgen levels. CONCLUSIONS: Abiraterone plus prednisone significantly reduced serum androgens, as measured by ultrasensitive assays and was generally associated with PSA response. However, androgen decline did not uniformly predict PSA decline suggesting ligand-independent or other mechanisms for mCRPC progression.

Regulation of sexual dimorphism in mammals.

Sexual dimorphism in humans has been the subject of wonder for centuries. In 355 BC, Aristotle postulated that sexual dimorphism arose from differences in the heat of semen at the time of copulation. In his scheme, hot semen generated males, whereas cold semen made females (Jacquart, D., and C. Thomasset. Sexuality and Medicine in the Middle Ages, 1988). In medieval times, there was great controversy about the existence of a female pope, who may have in fact had an intersex phenotype (New, M. I., and E. S. Kitzinger. J. Clin. Endocrinol. Metab. 76: 3-13, 1993.). Recent years have seen a resurgence of interest in mechanisms controlling sexual differentiation in mammals. Sex differentiation relies on establishment of chromosomal sex at fertilization, followed by the differentiation of gonads, and ultimately the establishment of phenotypic sex in its final form at puberty. Each event in sex determination depends on the preceding event, and normally, chromosomal, gonadal, and somatic sex all agree. There are, however, instances where chromosomal, gonadal, or somatic sex do not agree, and sexual differentiation is ambiguous, with male and female characteristics combined in a single individual. In humans, well-characterized patients are 46, XY women who have the syndrome of pure gonadal dysgenesis, and a subset of true hermaphrodites are phenotypic men with a 46, XX karyotype. Analysis of such individuals has permitted identification of some of the molecules involved in sex determination, including SRY (sex-determining region Y gene), which is a Y chromosomal gene fulfilling the genetic and conceptual requirements of a testis-determining factor. The purpose of this review is to summarize the molecular basis for syndromes of sexual ambiguity seen in human patients and to identify areas where further research is needed. Understanding how sex-specific gene activity is orchestrated may provide insight into the molecular basis of other cell fate decisions during development which, in turn, may lead to an understanding of aberrant cell fate decisions made in patients with birth defects and during neoplastic change.

SRY recognizes conserved DNA sites in sex-specific promoters.

Formation of male-specific structures and regression of female primordia are regulated in early male embryogenesis by SRY, a single-copy gene on the Y chromosome. Assignment of SRY as the testis-determining factor in eutherian mammals is supported by molecular analysis of cytogenetic sex reversal (i.e., XX males and XY females) and by complementary studies of transgenic murine models. Here we characterize the putative DNA-binding domain of SRY, which contains a conserved sequence motif shared by high-mobility group nuclear proteins and a newly recognized class of transcription factors. The SRY DNA-binding domain specifically recognizes with nanomolar affinity proximal upstream elements (designated SRYe) in the promoters of the sex-specific genes encoding P450 aromatase and Mullerian inhibiting substance (MIS). P450 aromatase catalyzes the conversion of testosterone to estradiol, and in the male embryo its expression is down-regulated. Conversely, MIS is expressed in the male embryo to induce testicular differentiation and regression of female reproductive ducts. SRYe-binding activity is observed in nuclear extracts obtained from embryonic urogenital ridge immediately preceding morphologic testicular differentiation. Our results support the hypothesis that SRY directly controls male development through sequence-specific regulation of target genes.