Isolation and characterization of androgen receptor mutant, AR(M749L), with hypersensitivity to 17-beta estradiol treatment

Preclinical models of prostate cancer - modelling androgen dependency and castration resistance in vitro, ex vivo and in vivo

Prostate cancer is well known to be dependent on the androgen receptor (AR) for growth and survival. Thus, AR is the main pharmacological target to treat this disease. However, after an initially positive response to AR-targeting therapies, prostate cancer will eventually evolve to castration-resistant prostate cancer, which is often lethal. Tumour growth was initially thought to become androgen-independent following treatments; however, results from molecular studies have shown that most resistance mechanisms involve the reactivation of AR. Consequently, tumour cells become resistant to castration - the blockade of testicular androgens - and not independent of AR per se. However, confusion still remains on how to properly define preclinical models of prostate cancer, including cell lines. Most cell lines were isolated from patients for cell culture after evolution of the tumour to castration-resistant prostate cancer, but not all of these cell lines are described as castration resistant. Moreover, castration refers to the blockade of testosterone production by the testes; thus, even the concept of "castration" in vitro is questionable. To ensure maximal transfer of knowledge from scientific research to the clinic, understanding the limitations and advantages of preclinical models, as well as how these models recapitulate cancer cell androgen dependency and can be used to study castration resistance mechanisms, is essential.

Interaction energies between two antiandrogenic and one androgenic agonist receptor in the presence of a T877A mutation in prostate cancer: a quantum chemistry analysis

We provide a detailed picture of the interactions between the androgen receptor T877A mutation and three different compounds used in the treatment of prostate cancer.

Cancer in Transgender People: Evidence and Methodological Considerations

Transgender people comprise a diverse group of individuals whose gender identity or expression differs from that originally assigned to them at birth. Some, but not all, transgender people elect to undergo medical gender affirmation, which may include therapy with cross-sex hormones and/or surgical change of the genitalia and other sex characteristics. As cross-sex hormones administered for the purposes of gender affirmation may be delivered at high doses and over a period of decades, the carcinogenicity of hormonal therapy in transgender people is an area of considerable concern. In addition, concerns about cancer risk in transgender patients have been linked to sexually transmitted infections, increased exposure to well-known risk factors such as smoking and alcohol use, and the lack of adequate access to screening. Several publications have identified cancer as an important priority in transgender health research and called for large-scale studies. The goals of this article are to summarize the evidence on factors that may differentially affect cancer risk in transgender people, assess the relevant cancer surveillance and epidemiologic data available to date, and offer an overview of possible methodological considerations for future studies investigating cancer incidence and mortality in this population.

Puerarin suppresses proliferation of endometriotic stromal cells partly via the MAPK signaling pathway induced by 17ß-estradiol-BSA

BACKGROUND

Puerarin is a major isoflavonoid compound extracted from Radix puerariae. It has a weak estrogenic action by binding to estrogen receptors (ERs). In our early clinical practice to treat endometriosis, a better therapeutic effect was achieved if the formula of traditional Chinese medicine included Radix puerariae. The genomic and non-genomic effects of puerarin were studied in our Lab. This study aims to investigate the ability of puerarin to bind competitively to ERs in human endometriotic stromal cells (ESCs), determine whether and how puerarin may influence phosphorylation of the non-genomic signaling pathway induced by 17ß-estradiol conjugated to BSA (E(2)-BSA).

METHODOLOGY

ESCs were successfully established. Binding of puerarin to ERs was assessed by a radioactive competitive binding assay in ESCs. Activation of the signaling pathway was screened by human phospho-kinase array, and was further confirmed by western blot. Cell proliferation was analyzed according to the protocol of CCK-8. The mRNA and protein levels of cyclin D1, Cox-2 and Cyp19 were determined by real-time PCR and western blotting. Inhibitor of MEK1/2 or ER antagonist was used to confirm the involved signal pathway.

PRINCIPAL FINDINGS

Our data demonstrated that the total binding ability of puerarin to ERs on viable cells is around 1/3 that of 17ß-estradiol (E(2)). E(2)-BSA was able to trigger a rapid, non-genomic, membrane-mediated activation of ERK1/2 in ESCs and this phenomenon was associated with an increased proliferation of ESCs. Treating ESCs with puerarin abrogated the phosphorylation of ERK and significantly decreased cell proliferation, as well as related gene expression levels enhanced by E(2)-BSA.

CONCLUSIONS/SIGNIFICANCE

Puerarin suppresses proliferation of ESCs induced by E(2)-BSA partly via impeding a rapid, non-genomic, membrane-initiated ERK pathway, and down-regulation of Cyclin D1, Cox-2 and Cyp19 are involved in the process. Our data further show that puerarin may be a new candidate to treat endometriosis.

Stearoyl CoA desaturase (SCD) facilitates proliferation of prostate cancer cells through enhancement of androgen receptor transactivation

Stearoyl-CoA desaturase (SCD), the rate-limiting enzyme in the biosynthesis of monounsaturated fatty acids, is highly expressed in prostate cancer although the SCD protein has been known to be rapidly turned over by proteolytic cleavage. The present data demonstrate that SCD can promote proliferation of androgen receptor (AR)-positive LNCaP prostate cancer cells and enhance dihydrotestosterone (DHT)-induced AR transcriptional activity, resulting in increased expression of prostate-specific antigen (PSA) and kallikrein-related peptidase 2 (KLK2). Interestingly, among the previously reported SCD-derived peptides produced by proteolytic cleavage of SCD, a peptide spanning amino acids 130-162 of SCD (SCD-CoRNR) contained the CoRNR box motif (LFLII) and enhanced AR transcriptional activity. In contrast, a mutant SCD-CoRNR in which Leu136 was replaced by Ala had no effect on AR transcriptional activity. Moreover, SCD-CoRNR directly interacted with AR and inhibited RIP140 suppression of AR transactivation. Knockdown of the SCD gene by SCD microRNA suppressed AR transactivation with decreased cell proliferation, suggesting that SCD may regulate the proliferation of LNCaP cells via modulation of AR transcriptional activity. Moreover, ectopic expression of SCD in LNCaP cells facilitated LNCaP tumor formation and growth in nude mice. Together, the data indicate that SCD plays a key role in the regulation of AR transcriptional activity in prostate cancer cells.

Broadening of transgenic adenocarcinoma of the mouse prostate (TRAMP) model to represent late stage androgen depletion independent cancer

BACKGROUND

The transgenic adenocarcinoma of the mouse prostate (TRAMP) model closely mimics PC-progression as it occurs in humans. However, the timing of disease incidence and progression (especially late stage) makes it logistically difficult to conduct experiments synchronously and economically. The development and characterization of androgen depletion independent (ADI) TRAMP sublines are reported.

METHODS

Sublines were derived from androgen-sensitive TRAMP-C1 and TRAMP-C2 cell lines by androgen deprivation in vitro and in vivo. Epithelial origin (cytokeratin) and expression of late stage biomarkers (E-cadherin and KAI-1) were evaluated using immunohistochemistry. Androgen receptor (AR) status was assessed through quantitative real time PCR, Western blotting, and immunohistochemistry. Coexpression of AR and E-cadherin was also evaluated. Clonogenicity and invasive potential were measured by soft agar and matrigel invasion assays. Proliferation/survival of sublines in response to androgen was assessed by WST-1 assay. In vivo growth of subcutaneous tumors was assessed in castrated and sham-castrated C57BL/6 mice.

RESULTS

The sublines were epithelial and displayed ADI in vitro and in vivo. Compared to the parental lines, these showed (1) significantly faster growth rates in vitro and in vivo independent of androgen depletion, (2) greater tumorigenic, and invasive potential in vitro. All showed substantial downregulation in expression levels of tumor suppressor, E-cadherin, and metastatis suppressor, KAI-1. Interestingly, the percentage of cells expressing AR with downregulated E-cadherin was higher in ADI cells, suggesting a possible interaction between the two pathways.

CONCLUSIONS

The TRAMP model now encompasses ADI sublines potentially representing different phenotypes with increased tumorigenicity and invasiveness.

A naturally occurring mutation in the human androgen receptor of a subject with complete androgen insensitivity confers binding and transactivation by estradiol

The clinical phenotype of complete androgen insensitivity (CAIS) was associated with a mutation in the human androgen receptor (hAR) gene encoding the amino acid substitution, M745I, in the hAR protein. Transcriptional activation of hAR(M745I) by the synthetic androgen, methyltrienolone (R1881), was reduced compared to wild-type (wt) hAR. The transcriptional co-activator, androgen receptor associated protein 70 (ARA70), failed to enhance transactivation of hAR(M745I) at lower concentrations of R1881 (0.01-0.1 nM), whereas the p160 co-activators, SRC-1 and TIF2, stimulated activity. Transcriptional activity of hAR(M745I) was stimulated by 1 or 10 nM R1881 and activity was further enhanced by co-expression of ARA70 similar to that of the hAR(wt). Transcriptional activity of hAR(wt) was minimally stimulated by estradiol (E2) without or with co-expression of ARA70, whereas 10 or 100 nM E2 increased transactivation by hAR(M745I) of the androgen-responsive MMTV-luciferase reporter gene by 10-fold and activity was further enhanced by ARA70. Increasing concentrations of E2 competed more effectively for binding of R1881 to hAR(M745I) than to hAR(wt), indicative of the preferential binding of E2 to the mutant hAR. Partial tryptic digestion of hAR wt and M745I revealed that activation of the mutant protein was reduced in the presence of R1881. By contrast, tryptic digestion showed that the mutant hAR was activated by the binding of E2. In conclusion, the clinical phenotype of CAIS resulted from a hAR gene mutation encoding hAR(M745I) with reduced binding and transactivation by androgens, but the novel properties of enhanced affinity for and increased transactivation by estradiol.

PC-3 cells with enhanced androgen receptor signaling: a model for clonal selection in prostate cancer

BACKGROUND

Two sublines of the human prostate cancer cell line, PC-3, which is widely used as a model of prostate cancer progression, have been reported: PC-3(AR-) that do not express androgen receptor (AR), and PC-3AR+ that have measurable AR RNA but little protein.

METHODS

We assayed the geneotype, karyotype, AR expression, and physical characteristics of the two PC-3 sublines, and compared their ability to elicit a transactivation response from ectopic AR in the presence and absence of specific AR coregulators.

RESULTS

PC-3(AR-) and PC-3AR+ cells are genotypically and karyotypically similar, but exhibit salient differences in their morphology, growth rate, and expression of AR RNA. Whereas endogenous AR expression in PC-3AR+ cells does not result in sufficient protein to confer androgen responsiveness in culture, ectopic AR consistently elicited a much greater transactivation response in PC-3AR+ than in PC-3(AR-) cells, without altered sensitivity to activation by native ligand or AR coregulators including GRIP1, BRCA1, and Zac1. Moreover, phenotypic differences of AR variants implicated in prostate cancer susceptibility and progression were only observed in PC-3AR+ cells. Higher levels of known AR coregulator proteins detected in PC-3AR+ compared with PC-3(AR-) cells likely contribute to these differences.

CONCLUSIONS

These studies provide new evidence that the androgen-signaling axis can be sensitized in prostate cancer cells, and have important implications for the analysis and interpretation of AR structure and function in in vitro cell systems.

Human checkpoint protein hRad9 functions as a negative coregulator to repress androgen receptor transactivation in prostate cancer cells

Positive responses to combined androgen elimination therapy and radiation therapy have been well documented in the treatment of prostate cancer patients. The detailed mechanisms how androgen-androgen receptor (AR) cross talks to the radiation-related signal pathways, however, remain largely unknown. Here we report the identification of hRad9, a key member of the checkpoint Rad protein family, as a coregulator to suppress androgen-AR transactivation in prostate cancer cells. In vivo and in vitro interaction assays using Saccharomyces cerevisiae two-hybrid, mammalian two-hybrid, glutathione S-transferase pull-down, and coimmunoprecipitation methods prove that AR can interact with the C terminus of hRad9 via its ligand binding domain. The FXXLF motif within the C terminus of hRad9 interrupts the androgen-induced interaction between the N terminus and C terminus of AR. This interaction between AR and hRad9 may result in the suppression of AR transactivation, demonstrated by the repressed AR transactivation in androgen-induced luciferase reporter assay and the reduced endogenous prostate-specific antigen expression in Western blot assay. Addition of small interfering RNA of hRad9 can reverse hRad9 suppression effects, which suggests that hRad9 functions as a repressor of AR transactivation in vivo. Together, our data provide the first linkage between androgen-AR signals and radiation-induced responses. Further studies of the influence of hRad9 on prostate cancer growth may provide potential new therapeutic approaches.