Lack of association between androgen receptor CAG polymorphism and familial breast/ovarian cancer

Molecular Regulation of Androgen Receptors in Major Female Reproductive System Cancers

There are three main types of cancer in the female reproductive system, specifically ovarian cancer (OVCA), endometrial cancer (EC), and cervical cancer (CC). They are common malignant tumors in women worldwide, with high morbidity and mortality. In recent years, androgen receptors (ARs) have been found to be closely related to the occurrence, progression, prognosis, and drug resistance of these three types of tumors. This paper summarizes current views on the role of AR in female reproductive system cancer, the associations between female reproductive system cancers and AR expression and polymorphisms. AR regulates the downstream target genes transcriptional activity and the expression via interacting with coactivators/corepressors and upstream/downstream regulators and through the gene transcription mechanism of “classical A/AR signaling” or “non-classical AR signaling”, involving a large number of regulatory factors and signaling pathways. ARs take part in the processes of cancer cell proliferation, migration/invasion, cancer cell stemness, and chemotherapeutic drug resistance. These findings suggest that the AR and related regulators could target the treatment of female reproductive system cancer.

The Role of Androgen Receptor Signaling in Ovarian Cancer

Emerging evidence has suggested that androgen receptor signaling plays an important role in ovarian cancer outgrowth. Specifically, androgen receptor activation appears to be associated with increased risks of developing ovarian cancer and inducing tumor progression. However, conflicting findings have also been reported. This review summarizes and discusses the available data indicating the involvement of androgens as well as androgen receptor and related signals in ovarian carcinogenesis and cancer growth. Although the underlying molecular mechanisms for androgen receptor functions in ovarian cancer remain far from being fully understood, current observations may offer effective chemopreventive and therapeutic approaches, via modulation of androgen receptor activity, against ovarian cancer. Indeed, several clinical trials have been conducted to determine the efficacy of androgen deprivation therapy in patients with ovarian cancer.

Androgen receptor gene CAG repeat polymorphism and ovarian cancer risk: A meta-analysis

Ovarian cancer is one of the common gynecological malignancies worldwide. It is usually diagnosed at a later stage, thus missing the best opportunity for treatment. Despite the advancement of ovarian cancer treatment, the prognosis is still poor. Androgen receptor (AR) may play a role in ovarian carcinogenesis. Previous studies regarding the association between AR CAG repeat length and ovarian cancer risk reported inconsistent results. Therefore, we conducted a meta-analysis to evaluate the association between AR CAG repeat length and ovarian cancer risk following the MOOSE guidelines. PubMed, Web of Science, EBSCO and other databases were searched up to September 15^th 2016. Case control studies with clear definition of CAG repeat length and detailed genotype information were included. Two authors independently reviewed and extracted data. Pooled analysis and subgroup analysis stratified by ethnicity were performed for different genetic models. Begg's funnel plot and Egger's test were performed for publication bias estimation. Overall, there was no association between the AR CAG repeat polymorphism and ovarian cancer risk. However, short CAG repeat polymorphism was associated with increased ovarian cancer risk in African Americans and Chinese under the dominant model, whereas a reverse association was observed in Caucasians and Italians under the other three models. Our study results should be interpreted with caution. Further well-designed epidemiological and functional studies are needed to elucidate the role of AR in ovarian carcinogenesis.

The androgen receptor cytosine-adenine-guanine repeat length contributes to the development of epithelial ovarian cancer

Ovarian cancer is the main cause of death among women with gynecological malignancies. Androgen and its receptors play an important role in ovarian cancer pathogenesis. Here, We aim to evaluate the relationship between AR CAG and GGN repeat length polymorphisms and Epithelial Ovarian Cancer (EOC) risk in a two-stage, case-control study among Chinese women. The repeat length was analyzed as a categorical variable for CAG_A and GGN_A (average allele), CAG-S and GGN_S (shorter allele), CAG-L and GGN_L (longer allele), respectively. The median value of the repeat length among the controls was used as the cutoff point. Women with longer AR CAG repeats had a decreased risk of developing EOC. The results was replicated in an independent samples. Compared to those with shorter (<22) CAG_A repeat length, women with longer (≥22) CAG_A repeats length had a 31% decreased EOC risk (OR = 0.69, 95% CI: 0.62–0.77, P = 5.06 × 10⁻¹¹). For CAG_S and CAG_L, the results remain consistent. However, we didn't detected any significant associations for GGN_A, GGN_S, and GGN_L. This should be the first study to examine the association between AR repeat length polymorphisms and ovarian cancer risk in a relatively large group of Asian women.

The role of reproductive hormones in epithelial ovarian carcinogenesis

Epithelial ovarian cancer comprises ∼85% of all ovarian cancer cases. Despite acceptance regarding the influence of reproductive hormones on ovarian cancer risk and considerable advances in the understanding of epithelial ovarian carcinogenesis on a molecular level, complete understanding of the biologic processes underlying malignant transformation of ovarian surface epithelium is lacking. Various hypotheses have been proposed over the past several decades to explain the etiology of the disease. The role of reproductive hormones in epithelial ovarian carcinogenesis remains a key topic of research. Primary questions in the field of ovarian cancer biology center on its developmental cell of origin, the positive and negative effects of each class of hormones on ovarian cancer initiation and progression, and the role of the immune system in the ovarian cancer microenvironment. The development of the female reproductive tract is dictated by the hormonal milieu during embryogenesis. Intensive research efforts have revealed that ovarian cancer is a heterogenous disease that may develop from multiple extra-ovarian tissues, including both Müllerian (fallopian tubes, endometrium) and non-Müllerian structures (gastrointestinal tissue), contributing to its heterogeneity and distinct histologic subtypes. The mechanism underlying ovarian localization, however, remains unclear. Here, we discuss the role of reproductive hormones in influencing the immune system and tipping the balance against or in favor of developing ovarian cancer. We comment on animal models that are critical for experimentally validating existing hypotheses in key areas of endocrine research and useful for preclinical drug development. Finally, we address emerging therapeutic trends directed against ovarian cancer.

Hormone response in ovarian cancer: time to reconsider as a clinical target?

Ovarian cancer is the sixth most common cancer worldwide among women in developed countries and the most lethal of all gynecologic malignancies. There is a critical need for the introduction of targeted therapies to improve outcome. Epidemiological evidence suggests a critical role for steroid hormones in ovarian tumorigenesis. There is also increasing evidence from in vitro studies that estrogen, progestin, and androgen regulate proliferation and invasion of epithelial ovarian cancer cells. Limited clinical trials have shown modest response rates; however, they have consistently identified a small subset of patients that respond very well to endocrine therapy with few side effects. We propose that it is timely to perform additional well-designed trials that should include biomarkers of response.

Hormone response in ovarian cancer: time to reconsider as a clinical target?

Ovarian cancer is the sixth most common cancer worldwide among women in developed countries and the most lethal of all gynecologic malignancies. There is a critical need for the introduction of targeted therapies to improve outcome. Epidemiological evidence suggests a critical role for steroid hormones in ovarian tumorigenesis. There is also increasing evidence from in vitro studies that estrogen, progestin, and androgen regulate proliferation and invasion of epithelial ovarian cancer cells. Limited clinical trials have shown modest response rates; however, they have consistently identified a small subset of patients that respond very well to endocrine therapy with few side effects. We propose that it is timely to perform additional well-designed trials that should include biomarkers of response.

Microsatellites in the estrogen receptor (ESR1, ESR2) and androgen receptor (AR) genes and breast cancer risk in African American and Nigerian women

Genetic variants in hormone receptor genes may be crucial predisposing factors for breast cancer, and microsatellites in the estrogen receptor (ESR1, ESR2) and androgen receptor (AR) genes have been suggested to play a role. We studied 258 African-American (AA) women with breast cancer and 259 hospital-based controls, as well as 349 Nigerian (NG) female breast cancer patients and 296 community controls. Three microsatellites, ESR1_TA, ESR2_CA and AR_CAG, in the ESR1, ESR2 and AR genes, respectively, were genotyped. Their repeat lengths were then analyzed as continuous and dichotomous variables. Analyses of continuous variables showed no association with breast cancer risk in either AA or NG at ESR1_TA; AA cases had shorter repeats in the long allele of ESR2_CA than AA controls (Mann-Whitney P= 0.036; logistic regression P = 0.04, OR= 0.91, 95% CI 0.83-1.00), whereas NG patients had longer repeats in the short allele than NG controls (Mann-Whitney P= 0.0018; logistic regression P= 0.04, OR= 1.06, 95% CI 1.00-1.11); and AA cases carried longer repeats in the short allele of AR_CAG than AA controls (Mann-Whitney P= 0.038; logistic regression P = 0.03, OR= 1.08, 95% CI 1.01-1.15). When allele sizes were categorized as dichotomous variables, we discovered that women with two long alleles of ESR2_CA had increased risk of breast cancer (OR = 1.38, 95% CI 1.10-1.74; P = 0.006). This is the first study to investigate these three microsatellites in hormonal receptor genes in relation to breast cancer risk in an indigenous African population. After adjusting for multiple-testing, our findings suggest that ESR2_CA is associated with breast cancer risk in Nigerian women, whereas ESR1_TA and AR_CAG seem to have no association with the disease among African American or Nigerian women.

Androgens and breast cancer

The role of androgens on breast cancer development and progression has not been fully elucidated. Several in vivo and in vitro studies demonstrate that androgens have an inhibitory effect on the mammary epithelium, whereas the majority of epidemiological studies report a positive association between high androgen levels and risk of breast cancer. Expression of the androgen receptor is a positive prognostic factor. Understanding the role of androgens in breast carcinogenesis is important because many women use testosterone replacement for the alleviation of symptoms brought on by menopause, in particular high-risk women who undergo surgical menopause at an early age. We overview the literature examining a role of androgens in the etiology of breast cancer.

Expression and function of androgen receptor coactivator p44/Mep50/WDR77 in ovarian cancer

Hormones, including estrogen and progesterone, and their receptors play an important role in the development and progression of ovarian carcinoma. Androgen, its receptor and coactivators have also been implicated in these processes. p44/Mep50/WDR77 was identified as a subunit of the methylosome complex and lately characterized as a steroid receptor coactivator that enhances androgen receptor as well as estrogen receptor-mediated transcriptional activity in a ligand-dependent manner. We previously described distinct expression and function of p44 in prostate, testis, and breast cancers. In this report, we examined the expression and function of p44 in ovarian cancer. In contrast to findings in prostate and testicular cancer and similar to breast cancer, p44 shows strong cytoplasmic localization in morphologically normal ovarian surface and fallopian tube epithelia, while nuclear p44 is observed in invasive ovarian carcinoma. We observed that p44 can serve as a coactivator of both androgen receptor (AR) and estrogen receptor (ER) in ovarian cells. Further, overexpression of nuclear-localized p44 stimulates proliferation and invasion in ovarian cancer cells in the presence of estrogen or androgen. These findings strongly suggest that p44 plays a role in mediating the effects of hormones during ovarian tumorigenesis.

Androgen receptor gene CAG repeat polymorphism and breast cancer risk in Iranian women: a case-control study

We investigated the association between polymorphic expansion of trinucleotide CAG repeats in androgen receptor (AR) gene and breast cancer risk among Iranian women in a matched case-control study. There was a strong overall association between per CAG repeat increments in average repeat length and the risk of the malignancy [OR=3.56; 95% CI, 2.80-5.29]. Women carrying one or two alleles with [CAG]n repeat ≥22 units were at increased risk of breast cancer [OR=2.03; 95% CI, 1.56-2.6]. The risk was significantly increased in homozygous longer repeats, versus homozygous alleles <22. We observed reduced risk of developing the tumor in positive familial breast cancer subjects carrying repeats ≥22 and 23. Homozygosity for the longer [CAG]n repeats may be linked to the increased breast cancer risk. In contrast to previous reports, longer AR [CAG]n repeat alleles may decline the risk among women with a familial breast cancer.

Androgen receptor status predicts response to chemotherapy, not risk of breast cancer in Indian women

Background

Considerably little is known about the biological role and clinical significance of androgen receptor expression in breast cancer. The objectives of this study were to characterize AR-CAG repeat genotypes in a cohort of women with breast cancer and to determine the influence of AR on response to neoadjuvant chemotherapy and clinical outcome.

Materials and methods

Genotyping of the AR CAG repeat region was done on 70 patients and 80 healthy aged- matched female controls. To assess response to NACT, tissue samples from 30 LABC cases were evaluated quantitatively by real time for AR mRNA expression. The clinical response was correlated with both the pre and post chemotherapy AR expression. The CAG alleles did not show differences between cases and controls when the mean of short, long and average length of both CAG alleles was considered. However, analysis when done defining short allele as CAGn < 20 (AR1) and the long as CAGn ≥ 20 (AR2), risk was found associated with AR2 allele with marginal significance (P = 0.09). Stratification by age of onset, FH, stage, grade ER and AR status failed to reveal any association with breast cancer risk. Genotype carriers with ≥20 CAGn showed decrease of AR mRNA expression although significance could not be established (P = 0.47). Tumours in responders had the higher AR mRNA expression levels in pre neo-adjuvant chemotherapy condition (p < 0.02) which got reduced after neoadjuvant chemotherapy and the difference was found to be significant (P = 0.014).

Conclusions

Although, expansion of the CAGn in the AR gene doesn't show any major effect on breast cancer risk, patients with positive AR expression, pre neoadjuvant chemotherapy, were found to be good responders and a decrease in mRNA level of AR gene related to the chemotherapy-induced apoptosis could serve as an important independent predictor of response to NACT.

BRCA1-associated breast and ovarian cancer risks in Poland: no association with commonly studied polymorphisms

Polymorphisms in genes involved in DNA repair, steroid hormone biosynthesis/metabolism/signaling, folate metabolism as well as cell growth are prime candidates for possible associations with breast and ovarian cancer risk in women with an inherited predisposition. We investigated 29 polymorphisms in 20 genes encoding key proteins of the above four biological pathways for their breast and ovarian cancer risk modifying effect in Polish women harboring BRCA1 founder mutations. Of the analyzed genes, ERCC2, XRCC1, XRCC2, XRCC3 and Lig4 participate in DNA repair, TP53 in cell cycle check point control, AIB1, AR, COMT, CYP11A1, CYP17A1, CYP19A1, HSD17 and PGR in steroid hormone biosynthesis/metabolism/signaling, TYMS in folate metabolism and HER2, IL6, LRP1, TGFB and TGFBR1 affect cell growth. Using validated methods, we genotyped 319 breast cancer cases, 146 ovarian cancer cases and 290 unaffected controls, all of whom harbored one of three causative mutations in BRCA1. Our results revealed no association of any of the investigated polymorphisms with BRCA1-associated breast or ovarian cancer risk. Thus, it appears that these polymorphisms do not influence disease risk in Polish women carrying one of the three common BRCA1 founder mutations.

Androgen receptor gene CAG repeats, estrogen exposure status, and breast cancer susceptibility

The length of a polymorphic CAG repeat in exon 1 of the androgen receptor (AR) is inversely correlated with AR transactivation activity. As heightened androgenic stimulation may oppose breast cell proliferation, which is mediated by AR, we examined whether AR-CAG repeat lengths are related to breast cancer susceptibility. A nested case-control study of 88 newly diagnosed cases of breast cancer between 1992 and 2000 and 334 matched controls was carried out in Taiwanese women. Risk factors were obtained through a standardized questionnaire interview and blood samples were collected and used to determine the number of AR-CAG repeats. Women with one or more long AR (CAG)n repeat alleles (>22 repeats) were not at significantly increased risk of breast cancer [odds ratio (OR), 1.52; 95% confidence interval (CI), 0.80-2.90]. Of particular interest was a significantly increased risk associated with the long-allele AR genotype that was present mostly among women with a short duration (<10 years) of early estrogen exposure, as indicated by the interval between age at menarche and age at first full-term pregnancy, as compared with short AR allele genotypes (OR, 2.70; 95% CI, 1.00-7.31), although no such significant association in women with a long duration of early estrogen exposure (OR, 0.70; 95% CI, 0.25-1.59) was detected. These data suggest that longer AR (CAG)n repeat alleles may confer an increased risk of breast cancer among particular subsets of individuals, although these findings need replication in other populations.

Associations between androgen and Vitamin D receptor microsatellites and postmenopausal breast cancer

We investigated the association between polymorphism in the androgen receptor (AR) and vitamin D receptor (VDR) genes and breast cancer risk in a large population-based case-control study of genetically homogenous Swedish women. We successfully determined both AR CAG(n) and VDR A(n) genotype in 1,502 women with invasive breast cancer and in 1,510 control women. We did not find any associations between AR or VDR microsatellite lengths and breast cancer when we used a priori determined cutoffs (</=21 or >/=22 repeats for AR and </=18 or >/=19 for VDR) to define long and short alleles. There was statistically significant interaction between VDR genotype and parity, such that women with two short alleles had a halved risk for breast cancer, irrespective of parity, compared with nulliparous women with two long alleles. Homozygosity for the long VDR allele was associated with a more advanced clinical stage at diagnosis. In exploratory analyses, we determined cutoffs based on visual inspection of distributions of allele lengths among cases and controls and found that women carrying two alleles with <20 AR CAG(n) repeats had an increased risk for breast cancer, odds ratio of 1.67 (95% confidence interval, 1.17-2.38), compared with those with two alleles with >/=20 repeats. Women carrying two VDR alleles with <21 A(n) were also at an increased risk, odds ratio of 1.26 (95% confidence interval, 1.04-1.51). Our data do not support major roles for AR or VDR polymorphism as breast cancer risk factors. However, we did find an interaction between VDR genotype and parity that remains to be corroborated.

Increased risk of breast cancer in women bearing a combination of large CAG and GGN repeats in the exon 1 of the androgen receptor gene

The exon 1 of the human androgen receptor gene (AR) contains both CAG (polyglutamine) and GGN (polyglycine) repeat length polymorphisms. Large CAG repeats have been related to an increased risk of breast cancer (BC), whereas the influence of the GGN repeats is still unclear. Here, we have studied how the length of CAG and GGN repeats is associated with the risk of BC in a population from Tenerife (Canary Islands, Spain). The study was carried out on 257 woman diagnosed with BC and 393 controls, nesting in the 'CDC of the Canary Islands' cohort study. The AR CAG and GGN genotyping was performed by means of PCR amplification with specific fluorescently labelled primers followed by a capillary electrophoresis. The allelic distribution of CAG and GGN polymorphisms was similar in cases and controls. The mean of short and long CAG and GGN alleles did not show differences between cases and controls and the same was true when the average length of both CAG alleles (CAG(n)) and GGN alleles (GGN(n)) was considered. However, when CAG(n) and GGN(n) were categorised using 22 and 24 repeats as the cut-off point, respectively, significant differences between cases and controls were observed. The CAG(n)>22 repeats were more frequent in cases than in controls, being associated with an increased risk of BC (OR=1.49; CI(95%)=1.06-2.09; p=0.021). No significant differences were found for categorised GGN(n). For CAG(n)/GGN(n) combinations, the highest BC risk was found to be associated with the CAG(n)>22/GGN(n)24 combination (OR=2.47; CI(95%)=1.37-4.46; p=0.003). In conclusion, our results indicate that longer CAG(n)/GGN(n) combinations increase the risk of BC and suggest that CAG and GGN AR polymorphisms should be considered in order to assess the BC risk.

Association of repeat polymorphisms in the estrogen receptors alpha, beta (ESR1, ESR2) and androgen receptor (AR) genes with the occurrence of breast cancer

Genetic variation in genes involved in estrogen biosynthesis, metabolism and signal transduction have been suggested to play a role in breast cancer. To determine the possible contribution of genetic variation in the ESR1 (ER-alpha), ESR2 (ER-beta) and AR genes in breast cancer risk the -1174(TA)(7-27), c. 1092+3607(CA)(10-26) and c. 172(CAG)(6-40) repeat variants were studied in a case-control study of 79 women with sporadic breast cancer and 155 controls. No significant difference was observed in the frequency distribution of -1174(TA)(7-27) in the ESR1 gene between patients and controls, while a significant difference was observed for repeat polymorphisms c. 1092+3607(CA)(10-26) in the ESR2 gene and c. 172(CAG)(6-40) in the AR gene (p0.0001). A significantly decreased odds ratio (OR) for breast cancer risk was observed in individuals having the LL and the SL genotypes for both the ESR2 (OR=0.010, 95% CI 0.003-0.036, p<0.001; OR=0.013, 95% CI 0.004-0.040, p<0.0001, respectively) and the AR gene (OR=0.040, 95% CI 0.011-0.138, p<0.0001; OR=0.189, 95% CI 0.10-0.359, p<0.0001, respectively), compared to SS genotype. The protective effect of these genotypes remained evident even after adjustment for various risk factors (BMI, age, age at menarche and menopause, family history). In conclusion, an association for breast cancer risk between short (SS) alleles for the repeat variants of the ESR2 and AR genes was found in women of Greek descent.

Shorter CAG repeat length in the AR gene is associated with poor outcome in head and neck cancer

OBJECTIVE

Alterations in the size of the [CAG](n) repeats of the AR gene have been described in several types tumors. The purpose of this study was to evaluate if there is an association between the AR [CAG](n) repeat alleles and the relative risk for head and neck cancer and to analyse microsatellite instability (MSI) and loss of heterozygosity (LOH) in these tumors.

DESIGN

Matched samples of blood and head and neck tumors were evaluated using two methodologies, silver-stained gels to perform the analyses of MSI and LOH, and automated analysis to confirm these results and for genotyping of the AR [CAG](n) repeat length. Sixty-nine individuals without cancer were used as a control group for both procedures. The Log-rank test was used to compare overall survival and disease-free survival curves. The Cox proportional hazards regression models were performed to determine the [CAG](n) repeats as an independent prognostic factor.

RESULTS

Patients with alleles <or=20 in the male group showed a correlation with lower disease-free survival (P=0.0325) and with recurrence or metastasis (RR 2.52, CI 95%). In the female group, the allele 2 (longer allele) showed a significant lower mean of [CAG](n) repeat when compared to the control group. Microsatellite instability was detected in nine cases in both procedures. In six out of these nine cases, we observed a reduction of the AR [CAG](n) repeat length. LOH was detected in one out of 17 women informative for oral cancer in both procedures.

CONCLUSION

These results suggest that short [CAG](n) repeat length (<or=20) polymorphism is associated with poor prognosis in a subset of male patients with head and neck cancer and that AR gene microsatellite instability is uncommon in these tumors.

Some Aspects of the Endocrine Profile and Management of Hormone‐Dependent Male Breast Cancer

The management of hormone-dependent male breast cancer is insufficiently understood by practicing oncologists. This article provides a review of the endocrine profile of male breast cancer, and outlines the differences between hormone-dependent female and male breast cancers. A concise review of the past, present, and possible future management of hormone-dependent male breast cancer is presented. For a better understanding of this disease, more information on the natural history and biological behaviors of patients with male breast cancer is needed. This could be accomplished by the development of a specific multi-institutional tumor registry and execution of prospective clinical trials.

Androgens and androgen receptors in breast cancer

Aromatase (CYP19) converts adrenal and ovarian androgens into estrogens, which supports the growth of estrogen-dependent breast cancers. Anti-aromatase agents are displacing antiestrogens as the first-line treatment for estrogen receptor positive breast cancers. Androgens can act as estrogen precursors, but besides this capability they can also directly act on breast cancer cells by binding to androgen receptors, which are present in the majority of breast cancer specimens. Epidemiological and clinical evidences suggest that higher levels of circulating androgen increase the risk of developing breast cancer. Androgen receptor gene polymorphisms which render the more transcriptionally active receptors have been related to a lower risk of breast cancer. It is currently accepted that androgens act as antiproliferative agents in the presence of estrogens in some breast cancer cell lines. However, emerging evidence suggests that direct androgenic activity might also stimulate cell growth in a subset of estrogen-resistant breast tumors. Here we discuss the supporting evidence which proposes that androgens themselves are actively involved in breast carcinogenesis and its clinical behaviour.

Phenotypic heterogeneity of mutations in androgen receptor gene

Androgen receptor (AR) gene has been extensively studied in diverse clinical conditions. In addition to the point mutations, trinucleotide repeat (CAG and GGN) length polymorphisms have been an additional subject of interest and controversy among geneticists. The polymorphic variations in triplet repeats have been associated with a number of disorders, but at the same time contradictory findings have also been reported. Further, studies on the same disorder in different populations have generated different results. Therefore, combined analysis or review of the published studies has been of much value to extract information on the significance of variations in the gene in various clinical conditions. AR genetics has been reviewed extensively but until now review articles have focused on individual clinical categories such as androgen insensitivity, male infertility, prostate cancer, and so on. We have made the first effort to review most the aspects of AR genetics. The impact of androgens in various disorders and polymorphic variations in the AR gene is the main focus of this review. Additionally, the correlations observed in various studies have been discussed in the light of in vitro evidences available for the effect of AR gene variations on the action of androgens.

Trinucleotide repeat polymorphisms in the androgen receptor gene and risk of ovarian cancer

INTRODUCTION

Androgens may play a role in the development of ovarian cancers. Two trinucleotide repeat polymorphisms have been described in exon 1 of the androgen receptor (AR) gene that may affect its function. Previous studies of ovarian cancer and AR repeat polymorphisms have been inconsistent.

METHODS

We analyzed CAG and GGC repeat length polymorphisms in the AR gene using data from a population-based case-control study of ovarian cancer that included 594 cases and 681 controls. Repeat lengths were determined by fluorescent DNA fragment analysis using ABI GeneScan software. Change point models were used to determine appropriate repeat length cutoff points by race (African American versus Caucasian) for both the shorter and longer CAG and GGC repeats.

RESULTS

No relationship was observed between CAG repeat length and ovarian cancer among Caucasians. Among African Americans, having a short repeat length on either allele was associated with a 2-fold increase in ovarian cancer risk (age-adjusted odds ratio, 2.2; 95% confidence interval, 1.1-4.1). Having short CAG repeat lengths for both alleles was associated with a 5-fold increased risk for developing ovarian cancer (age-adjusted odds ratio, 5.4; 95% confidence interval, 1.4-1.7). No relationship with the GGC repeat length polymorphisms was observed.

CONCLUSION

These results suggest that having a short CAG repeat length in AR increases ovarian cancer risk in African Americans. The failure to observe this relationship in Caucasians may be due to the rarity of such short CAG alleles in this population or could reflect racial differences in disease etiology.

Disruption of androgen receptor signaling by synthetic progestins may increase risk of developing breast cancer

There is now considerable evidence that using a combination of synthetic progestins and estrogens in hormone replacement therapy (HRT) increases the risk of breast cancer compared with estrogen alone. Furthermore, the World Health Organization has recently cited combination contraceptives, which contain synthetic progestins, as potentially carcinogenic to humans, particularly for increased breast cancer risk. Given the above observations and the current trend toward progestin-only contraception, it is important that we have a comprehensive understanding of how progestins act in the millions of women worldwide who regularly take these medications. While synthetic progestins, such as medroxyprogesterone acetate (MPA), which are currently used in both HRT and oral contraceptives were designed to act exclusively through the progesterone receptor, it is clear from both clinical and experimental settings that their effects may be mediated, in part, by binding to the androgen receptor (AR). Disruption of androgen action by synthetic progestins may have serious deleterious side effects in the breast, where the balance between estrogen signaling and androgen signaling plays a critical role in breast homeostasis. Here, we review the role of androgen signaling in the normal breast and in breast cancer and present new data demonstrating that androgen receptor function can be perturbed by low doses of MPA, similar to doses achieved in serum of women taking HRT. We propose that the observed excess of breast malignancies associated with combined HRT may be explained, in part, by synthetic progestins such as MPA acting as endocrine disruptors to negate the protective effects of androgen signaling in the breast. Understanding the role of androgen signaling in the breast and how this is modulated by synthetic progestins is necessary to determine how combined HRT alters breast cancer risk, and to inform the development of optimal preventive and treatment strategies for this disease.

Steroid hormones polymorphisms and cholelithiasis in Greek population

BACKGROUND

Genetic variation in genes involved in steroid biosynthesis, metabolism and signal transduction have been suggested to play a role in gallstone disease.

METHODS

To elucidate the possible role of genetic variation in the estrogen receptors alpha and beta (ER-alpha, ER-beta) and androgen receptor (AR) genes in breast cancer risk, the -1174(TA)n, c.1092+3607(CA)(n) and c.172(CAG)n repeat polymorphisms of the three genes were studied. A case-control cohort of 99 patients with cholelithiasis and 179 controls were used.

RESULTS

No significant difference was observed in the frequency distribution of -1174(TA)(0-26) in the ER-alpha gene between patients and controls, while a significant difference was observed in the frequency distribution of repeat polymorphism c.1092+3607(CA)5-27 and c.172(CAG)5-32 in the ER-beta gene and AR gene, respectively (P< or =0.001 and P=0.05, respectively). A significant difference was observed in the repeat genotype distribution (SS, SL, LL) in the (CA)n of the ER-beta gene (P<0.0001) and in the (CAG)n of the AR gene (P< or =0.0001). A significantly decreased odds ratio for cholelithiasis risk was observed in individuals having the SL and LL genotype for ER-beta gene compared with SS genotype (OR=0.212; 95% CI 0.105-0.426; P<0.0001 and OR=0.042; 95% CI 0.018-0.097, respectively) and LL genotype for AR gene (OR=0.622; 95% CI 0.345-1.121; P=0.114 and OR=0.287; 95% CI 0.151-0.543, P<0.0001, respectively). This protective effect of SL and LL genotypes for ER-beta and LL for AR gene remained evident (P<0.0001 for all of them) even after adjustment for various risk factors.

CONCLUSIONS

In conclusion an association for cholelithiasis risk between short alleles for both c.1092+3607(CA)5-27 and c.172(CAG)5-32 repeat polymorphisms of the ER-beta and AR was found in individuals of Greek descent.

Male breast cancer: a gender issue

The incidence of male breast cancer (MBC) is rising; however, mortality due to MBC has not changed, unlike female breast cancer. This lack of change is mostly attributable to a lack of major progress in the understanding and treatment of the disease. The treatment of MBC has been extrapolated from the knowledge of female breast cancer, despite the multiple differences in the pathogenesis, biology and genetics of these two disease entities, especially the differences with regard to the role of male hormones as well as estrogens in MBC compared with female disease. Although major advances in hormonal manipulation for the treatment of breast cancer are being developed, an improved understanding of the potential differences between male and female breast cancer is essential, as this would provide new opportunities for therapeutic intervention and probable improved outcome for MBC. This review aims at highlighting the major differences between male and female breast cancer with an emphasis on hormonal therapy, and discusses some of the recent advances in MBC.

Combined profile of the tandem repeats CAG, TA and CA of the androgen and estrogen receptor genes in breast cancer

PURPOSE

Case-control studies have reported inconsistent results concerning the association between polymorphisms in the androgen and estrogen receptor (ER) genes and breast cancer. While several studies investigated the association between the androgen receptor (AR) gene, CAG repeat and breast cancer, for the CA and TA repeats in the ER genes there are considerably fewer studies (one for CA and none for TA).

METHODS

We have investigated the potential link between three tandem repeats (CAG, TA, and CA) in the AR, ERs alpha and beta genes, respectively, and breast cancer. DNA was isolated from 153 invasive breast tumors and 318 controls, and the three tandem repeats were sized by polyacrylamide electrophoresis. Number of repeats in each allele and the total repeats of both alleles were taken as variables for classification into dichotomous groups using the median of each variable in the control group as cut-off point. Relationship between polymorphic tandem repeats and breast cancer was assessed by multivariate logistic regression models.

RESULTS

Three variables combined, longer CAGsum (> or =28), shorter TA (<23) and CA (<23) repeats could constitute a possible genetic profile associated with breast cancer.

CONCLUSIONS

Our results confirm previous reports regarding an association between longer CAG repeats and breast cancer. In addition to that, we found that the combination of long CAG, short TA and CA repeats are strongly associated with breast cancer.

Hormonal therapy for male breast cancer: A different approach for a different disease

Male breast cancer (MBC) is on the rise in the United States [Surveillance, Epidemiology, and End Results (SEER) Program () SEER Stat Database: Incidence-SEER 9 Regs Public-Use; November 2004 submission (1973-2002), National Cancer Institute, DCPPS, Surveillance Research Program, Cancer Statistics Branch, released April 2005, based on the November 2004 submission]; however mortality due to MBC has not changed unlike in its female counterpart [American Cancer Society: Cancer facts and figures 2005. Atlanta (GA): American Cancer Society; 2005]. The rarity of MBC has precluded major progress in the understanding and treatment of this disease. Treatment has often been extrapolated from female breast cancer (FBC) despite distinct clinicopathologic features between the two entities, especially with regards to the role of male hormones and estrogens in this disease. Also, it is uncertain if hormone receptor positive tumors carry the same prognostic implication in MBC as in the female disease. Hormonal therapy has been the mainstay of treatment in MBC with tamoxifen the front-line drug. The role of the newer generation aromatase inhibitors has not been well defined but they are being used in clinical practice for the treatment of MBC, based on accepted data for women with the disease. This commentary focuses on the major hormonal differences between male and female breast cancer that would suggest the need to explore different treatment strategies if significant advances are to be made in the understanding and treatment of this distinct disease.

Androgen Receptor and Prostate-Specific Antigen Gene Polymorphisms and Breast Cancer in African-American Women

Several previous studies have found the CAG repeat polymorphism in exon 1 of the androgen receptor (AR) gene to be associated with breast cancer risk among some groups of Caucasian and Asian women. In a population-based case-control study of 488 African-American women (239 cases and 249 controls), we examined this polymorphism along with a polymorphism (-158 G/A) in an androgen-regulated gene (PSA) whose expression has been correlated with breast cancer prognosis. Overall, we did not observe any significant association between the CAG repeat polymorphism and breast cancer risk. However, among women with a first-degree family history of breast cancer, longer CAG repeats were associated with a significantly increased risk. Women carrying at least one longer allele [(CAG)n > or = 22] had a 3-fold increased risk compared to those with two shorter alleles (odds ratio, 3.18; 95% confidence interval, 1.08-9.36). There was no significant association between the PSA gene polymorphism and breast cancer risk, nor was there significant gene-gene interaction. In summary, our results further support that shorter CAG repeats (stronger AR transactivation activity) may reduce the risk of breast cancer, at least among some groups of women. Our data, however, are unable to provide evidence that PSA is the pathway through which the protective effect of androgens operates.

Microsatellite profile in hormonal receptor genes associated with breast cancer

Given that breast cancer is depending on multiple hormonal influences, the nuclear receptors, estrogen receptor alpha, estrogen receptor beta and androgen receptor, are candidates for cancer susceptibility markers. We conducted an association study in a case-control population (139 cases and 145 controls) by genotyping three potentially functional microsatellites (TA)n, (CA)n and (CAG)n in the ERa, ERb and AR genes respectively. For (CAG)n polymorphism, a significant difference was observed using a cut-off 15 repeats CAG between genotypes short-short/short-long/long-long in cases and control subjects (p = 0.009) and also between the distribution of short/long allele in the two groups of individuals (p = 0.001). Genotypes comprising one or two short (CAG)n sequences had higher risk of breast cancer compared to genotypes with two long allele (odds ratio = 1,93; confidence interval = 1.05-3.55; p = 0.03). No significant difference was observed in allele frequency or in short/long allele percentage for (CA)n or (TA)n polymorphism (cut-off 22 CA and 19 TA repeats), neither in genotype frequencies (short-short, short-long or long-long). When the three microsatellite genotype were taken in analysis, the profile short CA-long TA-short CAG could clearly discriminate between cases and controls (p = 0.006). Also, this combined genotype profile has greater predictive values for breast cancer than (CAG)n genotype alone (predictive positive value 57,1% versus 53,7% and predictive negative value 53% versus 23% respectively). Our results sustain a polygenic model of breast cancer with gene-gene interactions; combined effects of three low-risk polymorphisms conferred significant genetic predisposition. Genotyping hormonal receptor genes ERa, ERb and AR could be a useful genetic marker for defining disease risk.

Androgen receptor polymorphisms and endometrial cancer risk

The androgen receptor (AR) gene is a transcription factor responsible for mediating the physiological effects of androgens. Evidence suggests that androgens and the androgen receptor are involved in uterine cell proliferation. A polymorphic CAG repeat in exon 1 of the AR gene encodes a polyglutamine tract that is inversely correlated with the transcriptional activity of this gene. We assessed the association between the functional CAG repeat polymorphism and AR haplotypes and the risk of endometrial cancer in two nested case-control studies within the Nurses' Health Study (n = 222 cases, 666 controls) and the Women's Health Study (n = 137 cases, 411 controls) using conditional and unconditional logistic regression. Associations between AR CAG repeat polymorphism and endometrial cancer risk were similar in the 2 case-control studies. In the pooled analysis, women with an average repeat allele > or =22 repeats compared to <22 repeats were at a statistically significant decreased risk of endometrial cancer (odds ratio (OR) = 0.76; 95% confidence interval (CI), 0.59-0.98). Women with one or two long alleles (> or =27 repeats) compared to both alleles <22 repeats were also at a statistically significant decreased risk (OR = 0.60; 95% CI, 0.36-0.99). We observed a modest yet statistically significant association for each one unit increase in the average repeat length and endometrial cancer risk (OR = 0.94; 95% CI, 0.88-1.00). Associations for the AR CAG average repeat length and endometrial cancer risk differed by menopausal status (p = 0.02). No significant associations between the AR haplotypes and endometrial cancer risk were observed. Our findings suggest that an increasing number of functional CAG repeats may be associated with endometrial carcinogenesis because of AR's reduced ability to recruit coregulators and other transcriptional components. (supplementary material for this article can be found on the International Journal of Cancer website at http://www.interscience.wiley.com/jpages/0020-7136/suppmat/index.html).

Androgen receptor cytosine, adenine, guanine repeats, and haplotypes in relation to ovarian cancer risk

Biological and epidemiologic evidence suggest that androgen or its receptor may play a role in ovarian cancer pathogenesis. The most notable genetic factor influencing androgen receptor (AR) activity is the functional cytosine, adenine, guanine (CAG) repeat in which length is inversely proportional to its transactivational activity. Additional genetic variation due to single nucleotide polymorphisms in the AR gene may be captured through haplotypes. We genotyped the CAG microsatellite and six haplotype-tagging single nucleotide polymorphisms (rs962458, rs6152, rs1204038, rs2361634, rs1337080, rs1337082) of the androgen receptor gene in 987 ovarian cancer cases and 1,034 controls from a study conducted in New Hampshire and eastern Massachusetts between May 1992 and July 2003. We estimated haplotype frequencies and calculated odds ratios with 95% confidence intervals to evaluate the association between the haplotypes and the AR CAG microsatellite with ovarian cancer risk. We observed that carriage of two alleles with > or = 22 CAG repeats was associated with an increased risk of ovarian cancer compared with carriage of two alleles with <22 CAG repeats (covariate-adjusted odds ratios, 1.31; 95% confidence intervals, 1.01-1.69). Five common haplotypes in the AR gene were identified, but no association between these and ovarian cancer risk was observed. Our results suggest that possession of two long AR alleles (> or = 22 CAG repeats) may be associated with increased risk of ovarian cancer compared with women with two short AR alleles (<22 CAG repeats).

Androgen receptor trinucleotide polymorphism in leiomyoma

OBJECTIVE

Androgen receptor (AR) was detected in leiomyoma. AR gene has a polymorphic microsatellite encoding cytosine, adenine, and guanine (CAG) repeats. We aimed to investigate the association between the AR gene CAG repeats and leiomyoma.

METHODS

Women were divided into two groups: (1) leiomyoma (n = 159); (2) non- leiomyoma groups (n = 129). Their CAG repeats were detected by polymerase chain reaction. The CAG repeats ranged in length from 168 bp (9 CAG repeats, genotype A) to 234 bp (31 CAG repeats, genotype W). Distributions of CAG repeats in both groups were compared.

RESULTS

Genotype proportions of different CAG repeats for AR gene in both groups were significantly different. The genotype S (27 CAG repeats) is associated with higher susceptibility of leiomyoma. Distribution of CAG repeats in both groups appeared mono-peak distributions. Percentages of genotypes K-S (19-27 CAG repeats) in leiomyoma and non-leiomyoma groups were: (1) 5,11,19.5, 10.4, 12.9, 8.8, 7.5, 5.7, 4.4%; (2) 5.4, 14.3,16.7, 12.8, 12.4, 5.8, 9.3, 7,1.2%.

CONCLUSIONS

AR trinucleotide polymorphism is associated with leiomyoma susceptibility. The 27 CAG repeats is related with higher risk of leiomyoma.

Increased frequency of long androgen receptor CAG repeats in male breast cancers

We have investigated the possible link between androgen hyposensitivity caused by long androgen receptor (AR) CAG repeats, and breast carcinogenesis, in men. AR gene mutations have been described in men with androgen insensitivity syndrome and breast carcinoma, and some studies have shown long CAG repeats are associated with increased risk of breast cancer in women. DNA was isolated from male breast cancer biopsies, and the AR CAG repeat sized. Forty one male breast cancer samples were studied, including one sample from a man with spinal and bulbar muscular atrophy (SBMA), which is caused by an AR CAG repeat expansion. The man with breast cancer and SBMA had 49 CAG repeats (normal range 6-35), but all other breast cancer samples had repeats within the normal range. The frequency of CAG repeats > or =24 was significantly higher in the breast cancer group (excluding the SBMA subject) than in the normal population (p<0.05), and was more marked in grade I and II tumors (p=0.001). There was no correlation between AR CAG repeat length and age at diagnosis. In conclusion, longer AR CAG repeats are more common in men with breast cancer than in the control male population. Androgen hyposensitivity, caused by long AR CAG repeats, may increase the risk of breast cancer in men.

Endometriosis and ovarian cancer: thoughts on shared pathophysiology

BACKGROUND

Endometriosis appears to predispose to ovarian cancer. How this may occur has been little discussed.

STUDY DESIGN

This article reviews the English language literature for in vitro, animal, clinical, and epidemiologic studies linking the two conditions.

RESULTS

Pathology case series consistently report endometrioid and clear cell types of ovarian cancer arising from endometriotic foci. Epidemiologic studies have been consistent with this association. There are also marked similarities between the proposed etiology of ovarian cancer and the observed pathophysiology of endometriosis. Specifically, both are characterized by immune alterations. Both conditions are promoted by estrogen excess and by progesterone deficit. Finally, steroid hormones interacting with the immune system may stimulate both endometriosis and ovarian cancer. I propose that the biology common to endometriosis and ovarian cancer represents not just a parallelism, but instead a causal pathway: aberrant immune function, fed by and feeding on estrogens, unbalanced by progesterone, may create a positive feed-forward loop that enhances the growth and invasiveness of endometriosis and promotes its malignant transformation.

CONCLUSIONS

The same pathophysiology may orchestrate the progression of endometriosis and its transformation to endometroid and clear cell ovarian neoplasias. This notion of a unifying biology suggests a directed approach to future research and identifies possible chemoprevention strategies for women with endometriosis.

A physiologic role for testosterone in limiting estrogenic stimulation of the breast

OBJECTIVE

The normal ovary produces abundant testosterone in addition to estradiol (E(2)) and progesterone, but usually only the latter two hormones are "replaced" in the treatment of ovarian failure and menopause. Some clinical and genetic evidence suggests, however, that endogenous androgens normally inhibit estrogen-induced mammary epithelial proliferation (MEP) and thereby may protect against breast cancer.

DESIGN

To investigate the role of endogenous androgen in regulating mammary epithelial proliferation, normal-cycling rhesus monkeys were treated with flutamide, an androgen receptor antagonist. To evaluate the effect of physiological testosterone (T) supplementation of estrogen replacement therapy, ovariectomized monkeys were treated with E(2), E(2) plus progesterone, E(2) plus T, or vehicle.

RESULTS

We show that androgen receptor blockade in normal female monkeys results in a more than twofold increase in MEP, indicating that endogenous androgens normally inhibit MEP. Moreover, we show that addition of a small, physiological dose of T to standard estrogen therapy almost completely attenuates estrogen-induced increases in MEP in the ovariectomized monkey, suggesting that the increased breast cancer risk associated with estrogen treatment could be reduced by T supplementation. Testosterone reduces mammary epithelial estrogen receptor (ER) alpha and increases ERbeta expression, resulting in a marked reversal of the ERalpha/beta ratio found in the estrogen-treated monkey. Moreover, T treatment is associated with a significant reduction in mammary epithelial MYC expression, suggesting that T's antiestrogenic effects at the mammary gland involve alterations in ER signaling to MYC.

CONCLUSIONS

These findings suggest that treatment with a balanced formulation including all ovarian hormones may prevent or reduce estrogenic cancer risk in the treatment of girls and women with ovarian failure.

Early events in ovarian epithelial carcinogenesis: progress and problems in experimental approaches

The etiology and early events in the progression of epithelial ovarian carcinomas are among the least understood of all major human malignancies. There are no adequate means for early detection of these neoplasms and, as a result, they are usually diagnosed in late stages. The purpose of this review is to point out some of the peculiar problems and limitations that have hampered progress in ovarian carcinogenesis research and to summarize new approaches and recent advances in our understanding of this process. The review first presents an overview of the properties of the ovarian surface epithelium (OSE) which is thought to be the source of epithelial ovarian carcinomas, followed by a discussion of recent research based on human OSE. This includes sections on methodology for the attainment and study of OSE, investigations of OSE from women with predisposing mutations, and attempts to convert normal OSE to malignancy. This overview is followed by a discussion of the contributions, potential, and limitations of animal models. The knowledge gained by these approaches will likely lead to improvements in our ability to prevent, diagnose, and treat ovarian cancer.

Androgens and mammary growth and neoplasia

OBJECTIVE

Evaluation of current clinical, experimental, genetic, and epidemiological data pertaining to the role of androgens in mammary growth and neoplasia.

DESIGN

Literature review.

SETTING

National Institutes of Health.

SUBJECT(S)

Recent, basic, clinical, and epidemiological studies.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Effects of androgens on mammary epithelial proliferation and/or breast cancer incidence.

RESULT(S)

Experimental data derived from rodents and cell lines provide conflicting results that appear be strain- and cell line-dependent. Epidemiologic studies have significant methodological limitations and provide inconclusive results. The study of molecular defects involving androgenic pathways in breast cancer is in its infancy. Clinical and nonhuman primate studies, however, suggest that androgens inhibit mammary epithelial proliferation and breast growth and that conventional estrogen treatment suppresses endogenous androgens.

CONCLUSION(S)

Abundant clinical evidence suggests that androgens normally inhibit mammary epithelial proliferation and breast growth. Suppression of androgens by conventional estrogen treatment may thus enhance estrogenic breast stimulation and possibly breast cancer risk. Clinical trials to evaluate the impact of combined estrogen and androgen hormone replacement regimens on mammary gland homeostasis are needed to address this issue.

Inherited predisposition and breast cancer: modifiers of BRCA1/2-associated breast cancer risk

Germline mutations in the BRCA1 and BRCA2 (BRCA1/2) genes explain a substantial proportion of hereditary breast and ovarian cancer. Women who have inherited a mutation in one of these genes are at increased risk to develop breast and/or ovarian cancer, although there is variability in the manifestation of tumors by age and site. This variability may be explained, in part, by the BRCA1/2 mutation type or location. However, it is also possible that risk-modifying factors exist that explain interindividual variability in cancer risk. These factors include genes at other loci and endogenous or exogenous exposures. A more complete understanding of factors that modify cancer risk in BRCA1 and BRCA2 mutation carriers may help to refine estimates of cancer risk. A number of exposures, including reproductive history and exogenous hormone use, have been implicated as BRCA1/2-associated cancer risk modifiers. Similarly, genes involved in hormone metabolism, including the AIB1 and AR genes, have been linked with altered breast cancer risk. Therefore, although germline BRCA1/2 mutations raise a woman's breast and ovarian cancer risk, other factors may interact with BRCA1/2 mutations to modulate this risk.