Lenore K. Beitel

The Androgen Receptor Gene Mutations Database

The current version of the androgen receptor (AR) gene mutations database is described. The total number of reported mutations has risen from 212 to 272. We have expanded the database: (i) by adding a large amount of new data on somatic mutations in prostatic cancer tissue; (ii) by defining a new constitutional phenotype, mild androgen insensitivity (MAI); (iii) by placing additional relevant information on an internet site (http://www.mcgill.ca/androgendb/ ). The database has allowed us to examine the contribution of CpG sites to the multiplicity of reports of the same mutation in different families. The database is also available from EMBL (ftp.ebi.ac.uk/pub/databases/androgen) or as a Macintosh Filemaker Pro or Word file (MC33@musica,mcgill.ca)

The androgen receptor gene mutations database: 2012 update

The current version of the androgen receptor gene (AR) mutations database is described. A major change to the database is that the nomenclature and numbering scheme now conforms to all Human Genome Variation Society norms. The total number of reported mutations has risen from 605 to 1,029 since 2004. The database now contains a number of mutations that are associated with prostate cancer (CaP) treatment regimens, while the number of AR mutations found in CaP tissues has more than doubled from 76 to 159. In addition, in a number of androgen insensitivity syndrome (AIS) and CaP cases, multiple mutations have been found within the same tissue samples. For the first time, we report on a disconnect within the AIS phenotype–genotype relationship among our own patient database, in that over 40% of our patients with a classic complete AIS or partial AIS phenotypes did not appear to have a mutation in their AR gene. The implications of this phenomenon on future locus‐specific mutation database (LSDB) development are discussed, together with the concept that mutations can be associated with both loss‐ and gain‐of‐function, and the effect of multiple AR mutations within individuals. The database is available on the internet (http://androgendb.mcgill.ca), and a web‐based LSDB with the variants using the Leiden Open Variation Database platform is available at http://www.lovd.nl/AR. Hum Mutat 33:887–894, 2012.

INTERACTIONS BETWEEN ANDROGEN AND ESTROGEN RECEPTORS AND THE EFFECTS ON THEIR TRANSACTIVATIONAL PROPERTIES

The physiological interplay of androgen and estrogen action in endocrine tissues is well recognized. The biochemical processes responsible for this interplay have yet to be fully defined. We have demonstrated that the androgen receptor (AR) and estrogen receptor-alpha (ERalpha) can interact directly using the yeast and mammalian two-hybrid systems. These interactions occurred between the C-terminal ERalpha ligand-binding domain and either the N-terminal AR transactivational domain or the full-length AR. Estrogen receptor-beta (ERbeta) did not interact with the AR. DNA cotransfection studies employing AR, ERalpha and ERbeta expression vectors and AR- or ER-reporter gene constructs were used to identify and measure potential functional effects of AR-ER interaction. Coexpression of ERalpha with AR decreased AR transactivation by 35%; coexpression of AR with ERalpha decreased ERalpha transactivation by 74%. Coexpression of AR and ERbeta did not significantly modulate AR or ERbeta transactivation. In summary, we have shown that specific domains of AR and ERalpha physically interact and have demonstrated the functional consequences of such interaction. These results may help explain the nature of the physiological interplay between androgens and estrogens.

Estrogen and Androgen Protection of Human Neurons against Intracellular Amyloid β1-42 Toxicity through Heat Shock Protein 70

Intracellular amyloidβ peptide (iAβ1-42) accumulates in the Alzheimers disease brain before plaque and tangle formation (Gouras et al., 2000) and is extremely toxic to human neurons (Zhang et al., 2002). Here, we investigated whether androgen and estrogen could prevent iAβ1-42 toxicity, because both these hormones have a wide range of neuroprotective actions. At physiological concentrations, 17-β-estradiol, testosterone, and methyl testosterone reduce iAβ1-42-induced cell death by 50% in neurons treated after the injection and by 80-90% in neurons treated 1 hr before the injection. The neuroprotective action of the hormones is mediated by receptors, because the estrogen receptor (ER) antagonist tamoxifen and the androgen receptor (AR) antagonist flutamide completely block the estrogen- and androgen-mediated neuroprotection, respectively. Transcriptional activity is required for the neuroprotective action, because dominant negative forms of the receptors that block the transcriptional activity of the ER and AR prevent estrogen- and androgen-mediated neuroprotection. Proteomics followed by Western blot analyses identified increased levels of heat shock protein 70 (Hsp70) in testosterone- and estrogen-treated human neurons. Comicroinjection of Hsp70 with the iAβ1-42 blocks the toxicity of iAβ1-42. We conclude that estrogen and androgens protect human neurons against iAβ1-42 toxicity by increasing the levels of Hsp70 in the neurons.

Update of the androgen receptor gene mutations database.

The current version of the androgen receptor (AR) gene mutations database is described. The total number of reported mutations has risen from 309 to 374 during the past year. We have expanded the database by adding information on AR‐interacting proteins; and we have improved the database by identifying those mutation entries that have been updated. Mutations of unknown significance have now been reported in both the 5′ and 3′ untranslated regions of the AR gene, and in individuals who are somatic mosaics constitutionally. In addition, single nucleotide polymorphisms, including silent mutations, have been discovered in normal individuals and in individuals with male infertility. A mutation hotspot associated with prostatic cancer has been identified in exon 5. The database is available on the internet (http://www.mcgill.ca/androgendb/), from EMBL‐European Bioinformatics Institute (ftp.ebi.ac.uk/pub/databases/androgen), or as a Macintosh FilemakerPro or Word file (MC33@musica.mcgill.ca). Hum Mutat 14:103–114, 1999.

Cancer systems biology in the genome sequencing era: Part 1, dissecting and modeling of tumor clones and their networks

Recent tumor genome sequencing confirmed that one tumor often consists of multiple cell subpopulations (clones) which bear different, but related, genetic profiles such as mutation and copy number variation profiles. Thus far, one tumor has been viewed as a whole entity in cancer functional studies. With the advances of genome sequencing and computational analysis, we are able to quantify and computationally dissect clones from tumors, and then conduct clone-based analysis. Emerging technologies such as single-cell genome sequencing and RNA-Seq could profile tumor clones. Thus, we should reconsider how to conduct cancer systems biology studies in the genome sequencing era. We will outline new directions for conducting cancer systems biology by considering that genome sequencing technology can be used for dissecting, quantifying and genetically characterizing clones from tumors. Topics discussed in Part 1 of this review include computationally quantifying of tumor subpopulations; clone-based network modeling, cancer hallmark-based networks and their high-order rewiring principles and the principles of cell survival networks of fast-growing clones.

Somatic Mosaicism and Cancer: A Micro-Genetic Examination into the Role of the Androgen Receptor Gene in Prostate Cancer

Recent evidence has shown that the androgen receptor (AR) plays a major role in all prostate cancer stages, including both androgen-dependent and -independent tumors. A large number of studies have examined the possible effects of a functional polymorphism in the AR gene, a variable-length CAG repeat, on the development of prostate cancer, but the results to date have been inconclusive. We have considered the fact that the tissue heterogeneity present in almost all prostate cancer tumors has rarely been regarded as an indicator of AR genetic heterogeneity. To determine if genetic heterogeneity exists and is a significant event in prostate cancer development, we have examined prostate cancer tumors for somatic shortening of the AR gene CAG repeat. All 72 laser capture microdissected samples from archival prostate cancer tissues, as well as samples from freshly prepared prostate cancer tissues, showed some genetic heterogeneity (somatic mosaicism) for AR CAG repeat length. Cancerous tissues showed a much greater degree of genetic heterogeneity than adjacent benign tissues, as well as a very significant shortening of their CAG repeat lengths. However, CAG repeat length heterogeneity was not observed in normal prostate tissues. It is hypothesized that somatic mosaicism of the AR CAG repeat in prostate cancer tumors may be found to be an important genetic event in precancerous tissue, which may subsequently lead to the development of prostate cancer.

Cytochrome c oxidase subunit Vb interacts with human androgen receptor: a potential mechanism for neurotoxicity in spinobulbar muscular atrophy

Spinobulbar muscular atrophy (SBMA) is a neurodegenerative disease caused by the expansion of the polyglutamine (polyGln) tract in the human androgen receptor (hAR). One mechanism by which polyGln-expanded proteins are believed to cause neuronotoxicity is through aberrant interaction(s) with, and possible sequestration of, critical cellular protein(s). Our goal was to confirm and further characterize the interaction between hAR and cytochrome c oxidase subunit Vb (COXVb), a nuclear-encoded mitochondrial protein. We initially isolated COXVb as an AR-interacting protein in a yeast two-hybrid screen to identify candidate proteins that interacted with normal and polyGln-expanded AR. Using the mammalian two-hybrid system, we confirm that COXVb interacts with normal and mutant AR and demonstrated that the COXVb-normal AR interaction is stimulated by heat shock protein 70. In addition, blue fluorescent protein-tagged AR specifically co-localized with cytoplasmic aggregates formed by green fluorescent protein-labeled polyGln-expanded AR in androgen-treated cells. Mitochondrial dysfunction may precede neuropathological findings in polyGln-expanded disorders and may thus represent an early event in neuronotoxicity. Interaction of COXVb and hAR, with subsequent sequestration of COXVb, may provide a mechanism for putative mitochondrial dysfunction in SBMA.

Analysis of exon 1 mutations in the androgen receptor gene.

Eleven mutations in exon 1 of the androgen receptor gene (AR) have been identified in 15 individuals with Androgen Insensitivity syndrome (AIS). Nine of the mutations yield a stop codon directly, or due to a frameshift, in individuals with complete AIS (CAIS). One individual with CAIS had three different mutations in exon 1: one is nominally silent (Glu 211; GAG 995 GAA); two are missense (Pro 390 Arg and Glu 443 Arg). Five unrelated individuals with either CAIS, partial AIS (PAIS) or mild AIS (MAIS) had GAG 995 GAA as their only alteration. This report almost doubles the number of exon 1 mutations stored in the AR Mutation Database, reinforces their highly predominant nonsense character, and identifies Pro 390 and/or Gln 443 as residues that are probably necessary for one or more specific functions of the ARs N‐terminal transactivation domain. Hum Mutat 14:527–539, 1999.

The polymorphic CAG repeat of the androgen receptor gene: a potential role in breast cancer in women over 40

Previous investigations into the relationship of CAG-repeat lengths in the androgen receptor (AR) gene to female breast cancer (BC) have yielded somewhat confusing results. Decreased AR transactivational activity lowers androgen:estrogen balance, and may thereby effect functional hyperestrogenicity. This may promote the pathogenesis of BC. To elucidate whether longer CAG repeats of the AR gene (AR), which correlate with lower transactivational activity of the AR, are associated with BC in women over 40, we examined the distribution of CAG-repeat lengths in BC tissue from this population. The BC tissue was histologically graded as: Grade 1, well differentiated (WD); Grade 2, moderately differentiated (MD); and Grade 3, poorly-differentiated (PD). Analysis showed significant differences as compared to controls when CAG lengths greater than 21 were examined, and that alleles with ≥26 repeats were 2.4-fold more frequent in BC samples than in constitutional samples from a normal population. A significant shift to greater CAG-repeat lengths, appeared in WD and MD tumors only. Our results give some indication as to the progression of BC by suggesting that hypotransactive ARs with long polyglutamine (polyGln) tracts may have a role in the initiation and/or progression of BC. PD tumors tended to have shorter than normal CAG-repeat lengths. In this case it is hypothesized that the ARs have now become hypertransactive, possibly coinciding with the estrogen resistance that is associated with PD tumors. Whether this shift is of germline or somatic origin was not clear, though the appearance in 14% of the BC samples of a third CAG-repeat length indicates that it may be somatic.