The evolutionary impact of androgen levels on prostate cancer in a multi-scale mathematical model

<p>Abstract</p> <p>Background</p> <p>Androgens bind to the androgen receptor (AR) in prostate cells and are essential survival factors for healthy prostate epithelium. Most untreated prostate cancers retain some dependence upon the AR and respond, at least transiently, to androgen ablation therapy. However, the relationship between endogenous androgen levels and cancer etiology is unclear. High levels of androgens have traditionally been viewed as driving abnormal proliferation leading to cancer, but it has also been suggested that low levels of androgen could induce selective pressure for abnormal cells. We formulate a mathematical model of androgen regulated prostate growth to study the effects of abnormal androgen levels on selection for pre-malignant phenotypes in early prostate cancer development.</p> <p>Results</p> <p>We find that cell turnover rate increases with decreasing androgen levels, which may increase the rate of mutation and malignant evolution. We model the evolution of a heterogeneous prostate cell population using a continuous state-transition model. Using this model we study selection for AR expression under different androgen levels and find that low androgen environments, caused either by low serum testosterone or by reduced 5<it>α</it>-reductase activity, select more strongly for elevated AR expression than do normal environments. High androgen actually slightly reduces selective pressure for AR upregulation. Moreover, our results suggest that an aberrant androgen environment may delay progression to a malignant phenotype, but result in a more dangerous cancer should one arise.</p> <p>Conclusions</p> <p>The model represents a useful initial framework for understanding the role of androgens in prostate cancer etiology, and it suggests that low androgen levels can increase selection for phenotypes resistant to hormonal therapy that may also be more aggressive. Moreover, clinical treatment with 5<it>α</it>-reductase inhibitors such as finasteride may increase the incidence of therapy resistant cancers.</p> <p>Reviewers</p> <p>This article was reviewed by Ariosto S. Silva (nominated by Marek Kimmel) and Marek Kimmel.</p

A review of hyperandrogenism state in polycystic ovarian syndrome

Polycystic ovary syndrome is one of the most prevalent endocrinopathy in premenopausal women. The pathophysiology of PCOS is not clear, however disturbance in the hypothalamic-pituitary-ovarian axis and abnormal steroidogenesis along with genetic and environmental factors act as main contributors to this disorder. The steroidogenic pathway is affected by the overexpression of the CYP11A, CYP17, and CYP19 genes in PCOS, which results in a hyperandrogenic condition. The initial effect of too much androgen in PCOS is impaired folliculogenesis. The most frequent clinical manifestations of hyperandrogenism in women with PCOS include hirsutism, acne, and androgenic alopecia. Women with PCOS may have an excess of androgen during foetal life due to the elevated expression of P450c17a during the whole pregnancy. PCOS is believed to be formed in utero by the influence of androgen excess on gene expression in adolescence and adulthood, which offers more solid evidence that real PCOS can be induced by prenatal androgenization. A prenatal androgen excess-induced epigenetic phenomena is suggested by the current theory of PCOS's developmental genesis. It is currently believed that the many tiny follicles seen in polycystic ovaries and the considerable irregularity in the very early stages of folliculogenesis are associated to the formation of anovulation in PCOS

Genes-alvo para os androgénios na gónada da dourada, Sparus auratus

Mestrado em Microbiologia Molecula

Male Genital Tract Development: looking at the protein side of life

__Abstract__ Androgens regulate a large number of developmental processes, starting in fetal life and going on all the way through puberty. The action of androgens is essential for development of the male genital tract in the embryo, and development of secondary male characteristics at puberty. In addition, androgens are important for maintenance of normal male functions in adulthood, such as spermatogenesis, sexual libido, and other aspects of the male phenotype. Lack of androgens or androgen action during embryonic development inevitably results in partial or more complete lack of virilization or feminization of the genital tract. Primary sex determination is strictly chromosomal, while gonadal hormones and their downstream effects are responsible for differentiation of genital tract tissues. This chapter describes the ontogeny of sex determination and differentiation, and the factors involved in androgen-regulated genital tract development. Furthermore, androgen receptor function and mechanism of action is described in more detail, as well as the involvement of the androgen receptor in different pathological conditions. Mouse models are being widely used to study processes and factors involved in genital tract development, and therefore throughout this thesis the situation for the mouse will be outlined and, where applicable, observations in humans will be referred to

Genetic and Epigenetic Profiling of Human Prostate Cancer Cell-Subsets

Perturbation of androgen signalling drives progression of human prostate cancer (CaP) to castration-resistant prostate cancer (CRPC). Additionally, CaP is initiated and maintained by cancer stem cells (CSC)s which are analogous to normal prostate stem cells (SC)s. This study presents a qPCR assay to detect androgen receptor gene amplification (GAAR), which is the most common mechanism of castration resistance (>30%). Also, the epigenetic regulation and function of two SC-silenced genes with tumour-suppressive activity (Latexin (LXN) and Retinoic Acid Receptor Responder 1 (RARRES1)) were interrogated using micro-ChIP, transcriptional profiling and mass spectrometry. Traditionally, GAAR is detected using FISH which is labour-intensive and semi-quantitative, limiting clinical applicability. The mechanism of action of LXN or RARRES1 in CaP is unknown, and epigenetic regulation by DNA methylation has been ruled-out in primary CaP. The qPCR assay can detect GAAR in minor cell populations (~1%) within a heterogeneous sample and also quantifies X chromosome aneuploidy (XCA) - a predictor of poor-prognosis in CaP. GAAR and XCA were detected in near-patient xenografts derived from CRPC-tissue indicating that these abnormalities are present in cells capable of in vivo tumour-reconstitution. Micro-ChIP analysis of fractionated primary CaP cultures identified bivalent chromatin at LXN and RARRES1 promoters. Transcriptomic profiling failed to reveal significant changes in gene expression after transduction with LXN or RARRES1. However, an interactome for LXN and RARRES1 was successfully generated in PC3 cells. Additionally, confocal microscopy of mVenus-tagged LXN revealed a pan-cellular distribution which is reflected in the interactome. Screening for GAAR and XCA, using a high-throughput qPCR assay, could facilitate a targeted-medicine strategy in the treatment of CaP and CRPC. Further investigation of the LXN and RARRES1 interactomes may identify their mechanism(s) of action and the micro-ChIP assay could be used to identify epigenetic-inducers of LXN and RARRES1 which could provide a CSC-targeted strategy for CaP treatment

Identification of mesenchymal genes involved in prostate organogenesis by LongSAGE analysis

Growth and development of the prostate are regulated by androgens and mesenchymalepithelial interactions. Prostate growth starts in the embryo, continues throughout neonatal life, and is completed at puberty. The male and female embryonic urogenital sinus (UGS) both contain a prostate precursor, but due to the action of testosterone only the male will develop a prostate. Testosterone acts in concert with paracrine signalling from inductive mesenchyme to regulate epithelial growth and branching of the prostate. The ventral mesenchymal pad (VMP) is an area of inductive mesenchyme that is rich in regulatory growth factors of which few have been identified at present. Recently, the role of mesenchyme/stroma in cancer has been established and developmental factors may be involved in mediating the effects of cancer stroma. The aim of this thesis was to identify mesenchymal factors and characterise their expression and function in the developing prostate, and to investigate their expression in prostate cancer stroma.The LongSAGE technique was used to generate a comprehensive transcriptional profile of the neonatal rat prostate rudiment. LongSAGE is an open-ended and unbiased geneprofiling method. Two libraries were made from tissues in the female UGS; one library was prepared from the whole female prostate rudiment and the other library was prepared from the inductive mesenchyme (VMP) isolated from within the rudiment. Several essential factors known to be involved in prostate development were identified in the libraries, including low abundance cDNAs such as AR and FgflO. This suggested that the approach had sufficient sensitivity to identify key mesenchymal factors. The two libraries were compared, and the comparison was statistically analysed, highlighting genes that were VMP-enriched (P<0.05). Candidate mesenchymal transcripts were selected from the VSU and VMP Libraries by two different approaches, either because of their status as VMP -enriched (P<0.05) transcripts, or by an 'intuitive' approach, because the transcripts were associated with genes that are known members of developmental pathways and/or have been associated with prostate cancer. The expression and abundance of candidate transcripts were quantified by qRT-PCR in the male and female neonatal UGS. Subsequently, candidate transcripts were verified as VMP-enriched and were quantified during prostate development by Northern blot analysis. The protein distribution of selected candidates were localised within the neonatal rat UGS by immunocytochemistry, and the effect of testosterone treatment on the protein distribution was studied. To test the function of one of the candidates on prostate growth and development, recombinant protein was added to prostate rudiments grown in vitro. Finally, candidate transcripts were investigated in human prostate cancer associated fibroblast cells (CAFs) and normal prostate fibroblast cells (NPFs) by RT-PCR and Northern blot analysis.SAGE analysis, qRT-PCR and Northen blot analysis identified six candidate transcripts as VMP-enriched; Dlkl, Notch2, Ptn Nell2, MMP2 and MMP14. The transcript expression of each candidate was most abundant in the developing rat prostate during the perinatal period. Proteins for Dlkl, Ptn and Notch2 were localised to mesenchymal cells of the neonatal VMP and ventral prostate (VP). Ptn expression was also associated with the basement membrane and cell-surface of the epithelial duct cells of the VP. Treatment of VP organs with recombinant DLK1 in vitro increased the organ size and epithelial branching. Also, PTN, NOTCH2, MMP2 and MMP14 transcript expression was observed in CAFs and NPFs. PTN and NOTCH2 showed a decrease in CAFs compared to NPFs suggesting a tumour-suppressive role.In summary, a comprehensive gene profiling technique was used to identify mesenchyme specific/enriched transcripts in the developing prostate. The expression, distribution and function of candidate transcripts and proteins were investigated in the developing prostate and in prostate cancer stroma

Molecular mechanisms of androgen receptor functions

The androgens testosterone (T) and dihydrotestosterone (DHT) are steroid hormones, which are necessary for development and maintenance of the functions of the male sex organs, including the prostate. Androgens also play an important role in benign abnormalities of the prostate and in the growth of prostate cancer. Prostate tumors, which are not yet metastatic, are treated with radiotherapy or by surgical removal of the complete prostate. Therapy of metastasized prostate cancer aims on inhibition of androgen action, by inhibtion of the production of T in the testis (chemical castration) and by administration of anti-androgens. T and DHT exert their function by specific binding as a ligand to the androgen receptor (AR). The AR is a member of the family of nuclear receptors. It is expressed in androgen target cells, and functions as a ligand induced transcription factor. In this thesis described research project focusses on several molecular mechanisms of AR functions. Chapter 1 gives an overview of the current knowledge on nuclear receptors in general and different aspects of AR functions in particular. Among the latter are: receptor structure, interaction with other proteins involved in transcription, the ligand-dependent interaction between the N-terminal domain (NTD) and the ligand binding C-terminal domain (LBD) of the AR (N/C interaction), expression of androgen-specific regulated genes, and the role of AR mutations in prostate cancer