GGC and StuI polymorphism on the androgen receptor gene in endometrial cancer patients

Androgens have an anti-proliferative effect on endometrial cells. Human androgen receptor (AR) gene contains two polymorphic short tandem repeats of GGC and CAG, and a single-nucleotide polymorphism on exon 1 that is recognized by the restriction enzyme, StuI. Prior studies have shown that the lengths of the CAG repeat are inversely and linearly related to AR activity and associated with endometrial cancer. However, little is known about the GGC repeat and the StuI polymorphism of the AR gene. Thus, we investigated whether these AR polymorphisms are risk factors for endometrial cancer. To test this hypothesis, the genetic distributions of these polymorphisms were investigated in blood samples from endometrial cancer patients and healthy controls. The allelic and genotyping profiles were analyzed by polymerase chain reaction (PCR), PCR-restriction fragment length polymorphism (PCR-RFLP), and direct DNA sequencing, and analyzed statistically. The GGC repeat was significantly longer in endometrial cancer patients as compared to normal healthy controls. In general, an increased risk of endometrial cancer was found with increasing GGC repeat. The relative risk for the 17 GGC repeat was greater than 4, as compared to controls. However, the StuI polymorphism was not significantly different between patients and controls. The findings suggest that increased numbers of GGC repeat on the AR gene may be a risk factor for endometrial cancer.     

The polyglycine and polyglutamine repeats in the androgen receptor gene in Japanese and Caucasian populations

Human androgen receptor (AR) gene contains two polymorphic trinucleotide repeats of CAG and GGC, which code for polyglutamine and polyglycine tracts in the N-terminal domain in which the receptor activity resides. Longer repeats induce decrease of transactivation function in the AR receptor, weaken an anti-proliferative effect on various steroid-related tissues, and may promote the carcinogenesis of these cancers, such as breast, endometrial, and ovarian cancers. However, the incidences of these steroid-related cancers are remarkably lower in Japanese than in Caucasians. We hypothesize that the GGC and CAG repeats in AR gene correspond to lower incidence of steroid-related cancers in the Japanese population. To test this hypothesis, these two polymorphic trinucleotide repeats in AR gene were genotyped in 221 Japanese and 177 Caucasians. The results of genotyping in these loci clearly show that the distribution of GGC repeat is significantly different between these populations (P<0.001). Japanese (73.7%) had 16 GGC repeats compared to 53.3% for Caucasians. Japanese (3.8%) also had 17 GGC repeats compared to 36.2% for Caucasians. No Japanese had more than 18 GGC repeats compared to 3.4% for Caucasians. The length of CAG repeats in the Japanese population was not significantly different than that of the Caucasian population, although the CAG repeats varied from 14 to 31 and 15 to 29 repeats in Japanese and German populations, respectively. This study demonstrates that the Japanese population has shorter GGC compared to the Caucasian population, which may explain the incidences of estrogen-related cancers in these populations.     

Androgen receptor CAG polymorphism and prostate cancer risk

Recent studies have suggested that polymorphisms of the androgen receptor gene ( AR) may influence the risk of prostate cancer (PC) development and progression. Here, we analyzed the length of the CAG repeat of the AR gene in 1363 individuals, including patients with PC, benign prostate hyperplasia (BPH), and population controls. There was a tendency for short CAG repeats to be associated with PC. The Odds Ratio (OR) for PC was 1.47 ( P=0.05) when individuals with short CAG repeats (18). CAG repeat length was not significantly associated with family history, disease stage, grade, age at diagnosis, prostate-specific antigen (PSA) level at diagnosis, or prognosis of the patients. Unexpectedly, short CAG repeats were significantly less common in patients with BPH compared with controls (OR=0.47, P=0.03). Our results suggest that the CAG polymorphism of the AR gene is unlikely to have a major role in the development or progression of PC in the Finnish population. The association of CAG repeats with the risk of BPH warrants further study.     

Evaluation of the effects of androgen receptor gene trinucleotide repeats and prostate-specific antigen gene polymorphisms on prostate cancer

The number of trinucleotide repeats [CAG (coding for polyglutamine), GGC (coding for polyglycine)] in the first exon of the androgen receptor (AR) gene and prostate-specific antigen (PSA) gene androgen response element I A/G polymorphism are both related to prostate cancer prognosis. We investigated whether these genomic changes occur in the AR and PSA genes, which are usually found in individuals with prostate cancer, of Turkish patients and to find out their distribution in the population. We used PCR and PCR-RFLP assays for AR and PSA genes, respectively, to detect molecular changes in 44 prostate cancer patients. Our findings indicate that individuals with prostate cancer tend to have around 18 CAG trinucleotide repeats. We observed significant differences between 22 controls, 33 benign prostate hyperplasia (BPH) patients and 44 adenocarcinoma patients for long CAG repeats. However, we did not find any significant differences in GGC repeats between controls, BPH and adenocarcinoma patients (P = 0.408). We also did not observe significant differences in the PSA A/G polymorphism frequency between controls, BPH and adenocarcinoma patients (P = 0.483). In conclusion, CAG and GGC repeats in the AR and PSA gene polymorphisms may be associated with prostate cancer risk and BPH in the Turkish population.     

The CAG repeat polymorphism of the androgen receptor gene and breast cancer

Background

Genetic variants in hormone receptor genes may be crucial predisposing factors for breast cancer, and microsatellites in the androgen receptor gene (AR) have been suggested to play a role. The aim of the study was to determine the association between the length of the CAG repeats in the AR gene and the development of breast cancer. Methodology: In total, 75 breast cancer cases and 50 healthy controls were analyzed for CAG repeats in the AR gene by polymerase chain reaction and the GeneScan/Genotyping technique.

Results

CAG repeat genotypes and alleles distribution were found to be significantly different between breast cancer patients and controls (P < 0.05). While the presence of CAG repeats shorter than 22 (classified as short, S) increases the risk of breast cancer, the risk is reduced by the presence of CAG repeats longer than 22. In the group of patients with breast cancer, a high tumor stage was found to have a significant association with genotype S/S of CAG repeats in the AR gene.

Conclusion

Our results suggest that the length of CAG repeats in the androgen receptor gene is associated with the risk of developing breast cancer.     

Polymorphisme du gène du récepteur des androgènes: recherche de mosaïques tissulaires et relation avec l'infertilité masculine

Androgens are male steroid hormones necessary for initiation and maintenance of spermatogenesis. They act via a specific receptor which belongs to the nuclear receptor superfamily. The transactivation N-terminal domain of this receptor is characterized by a CAG repeat polymorphism in the first exon of the gene coding for polyglutamines. An increased CAG repeat length is involved in Kennedy's disease, a neurodegenerative disease associated with infertility and impaired virilization. Some recent studies have shown a correlation between the number of CAG repeats and male fertility. The aim of this study was to define this correlation and to determine whether or not infertile men presented a tissue mosaicism between blood and sperm, as described in several diseases involving CAG repeats. The length of CAG repeats of blood and testicular cells was measured in 36 oligospermic or azoospermic patients and 15 controls. An inverse correlation was found between CAG repeat length and total number of ejaculated spermatozoa. However, no tissue mosaicism between blood and sperm was observed in our population.     

Long CAG Repeat Sequence and Protein Expression of Androgen Receptor Considered as Prognostic Indicators in Male Breast Carcinoma

Background

The androgen receptor (AR) expression and the CAG repeat length within the AR gene appear to be involved in the carcinogenesis of male breast carcinoma (MBC). Although phenotypic differences have been observed between MBC and normal control group in AR gene, there is lack of correlation analysis between AR expression and CAG repeat length in MBC. The purpose of the study was to investigate the prognostic value of CAG repeat lengths and AR protein expression.

Methods

81 tumor tissues were used for immunostaining for AR expression and CAG repeat length determination and 80 normal controls were analyzed with CAG repeat length in AR gene. The CAG repeat length and AR expression were analyzed in relation to clinicopathological factors and prognostic indicators.

Results

AR gene in many MBCs has long CAG repeat sequence compared with that in control group (P = 0.001) and controls are more likely to exhibit short CAG repeat sequence than MBCs. There was statistically significant difference in long CAG repeat sequence between AR status for MBC patients (P = 0.004). The presence of long CAG repeat sequence and AR-positive expression were associated with shorter survival of MBC patients (CAG repeat: P = 0.050 for 5y-OS; P = 0.035 for 5y-DFS AR status: P = 0.048 for 5y-OS; P = 0.029 for 5y-DFS, respectively).

Conclusion

The CAG repeat length within the AR gene might be one useful molecular biomarker to identify males at increased risk of breast cancer development. The presence of long CAG repeat sequence and AR protein expression were in relation to survival of MBC patients. The CAG repeat length and AR expression were two independent prognostic indicators in MBC patients.     

Expression of size-polymorphic androgen receptor (AR) gene in ovarian endometriosis according to the number of cytosine, adenine, and guanine (CAG) repeats in AR alleles.

An increase in androgen receptor (AR) caused by estrogen is recognized as one of the biological phenomena related to estrogen-induced growth in uterine endometrium. The A/B region of AR gene in X chromosome involves the cytosine, adenine, and guanine (CAG) repeats. Random X chromosome inactivation with AR alleles in individual cells occurs in females. Therefore, approximately either paternal or maternal single dominant polymorphic AR mRNA must be expressed in neoplastic tissue originated from monoclone. This prompted us to determine deviated number of CAG repeats in AR mRNA to understand clonality in ovarian endometriosis. In all cases of heterozygous AR alleles, although paternal and maternal AR mRNAs from normal eutopic uterine endometrium were consistently expressed as AR alleles, either paternal or maternal single dominant AR mRNA expression was found in an individual ovarian endometrioma. Therefore, an individual ovarian endometrioma might be formed from an independent monoclonal ovarian endometriotic endometrial cell after inactivation of either AR allele in X chromosome.     

An investigation into CAG repeat length variation and N/C terminal interactions in the T877A mutant androgen receptor found in prostate cancer

Prostate cancer may progress by circumventing ablation therapy due to mutations in the androgen receptor (AR) gene. The most intensively studied is the T877A mutation in the ligand binding domain (LBD), which causes the AR to become promiscuous, i.e., respond to a number of different ligands. Our investigations have shown that the T877A mutation alters the inverse relationship between CAG repeat length and transactivation in a noticeable albeit minor manner, while increasing N/C terminal interactions. In the presence of beta-catenin, a coactivator over-expressed in prostate cancer, the inverse relationship between CAG repeat length and transactivation is reversed for the wild type (wt) AR as well. We have also used molecular modeling with the AR and FXXLF and LXXLL peptides to investigate N/C terminal and coactivator interactions. In T877A, this approach revealed an increase in the flexibility of amino acid residues in the activation function 2 (AF-2) domain in the LBD, and a larger solvent accessible surface in T877A compared to the wt AR AF-2 domain. Thus, the improved induced fit of the AR N-terminal domain FXXLF-containing peptide into the T877A LBD could be due to the increased flexibility and solvent accessibility of the AF-2 domain. These new observations suggest that the AR CAG effect can be overridden by prostate cancer mutations, and also further our understanding of hormone-refractory prostate cancer by helping to explain the promiscuity of the T877A mutation.     

TATA Box-Binding Protein gene is associated with risk for schizophrenia, age at onset and prefrontal function

Schizophrenia is a common polygenic disease in distinct populations, while spinocerebellar ataxia type 17 (SCA17) is a rare autosomal dominant neurodegenerative disorder. Both diseases involve psychotic symptoms. SCA17 is caused by an expanded polyglutamine tract in the TATA box-binding protein ( TBP ) gene. In the present study, we investigated the association between schizophrenia and CAG repeat length in common TBP alleles with fewer than 42 CAG repeats in a Japanese population (326 patients with schizophrenia and 116 healthy controls). We found that higher frequency of alleles with greater than 35 CAG repeats in patients with schizophrenia compared with that in controls ( p = 0.042). We also examined the correlation between CAG repeats length and age at onset of schizophrenia. We observed a negative correlation between the number of CAG repeats in the chromosome with longer CAG repeats out of two chromosomes and age at onset of schizophrenia ( p = 0.020). We further provided evidence that TBP genotypes with greater than 35 CAG repeats, which were enriched in patients with schizophrenia, were significantly associated with hypoactivation of the prefrontal cortex measured by near-infrared spectroscopy during the tower of Hanoi, a task of executive function (right PFC; p = 0.015, left PFC; p = 0.010). These findings suggest possible associations of the genetic variations of the TBP gene with risk for schizophrenia, age at onset and prefrontal function.     

Androgen receptor gene methylation and exon one CAG repeat length in ovarian cancer: differences from breast cancer

More than one neoplastic founder clone can exist in benign epithelial tumours. Although theories of clonal selection make pluriclonality appear unlikely in carcinomas, published data do not exclude this possibility. This study looked for evidence of multiclonal X inactivation in ovarian carcinoma using AR methylation as a marker. Fifteen unifocal ovarian carcinomas and 14 multifocal carcinomas all in Scottish patients were studied. One representative formalin-fixed paraffin-embedded tumour block was chosen for each of the former and two for the latter. From each of these 43 tumour blocks three samples each of approximately 10(4) carcinoma cells were obtained by microdissection (129 in all). DNA released by proteinase K digestion was subjected to PCR amplification of the androgen receptor gene AR exon I CAG repeat polymorphism with and without prior digestion with methylation-sensitive restriction enzymes HpaII and HhaI. Complex amplification patterns were consistent with mosaic X inactivation in some ovarian carcinomas but acquired anomalies of AR methylation cannot be excluded. Parallel analysis of other X-linked polymorphic loci would strengthen the inference of clonality status from DNA methylation data in tumour X studies. Strikingly, the number of CAG repeats in the 29 ovarian tumour patients (median 16, range 11 - 20) was substantially fewer than in 34 previously studied breast cancer patients from the same scottish population (median 21, range 14 - 26; P < 0.0001), and women homozygous for the AR CAG repeat were over-represented in the ovarian cancer patients but not in the breast cancer series. These findings reinforce recent suggestions that AR may have a role in ovarian carcinogenesis.     

Polymorphic GGC repeats in the androgen receptor gene are associated with hereditary and sporadic prostate cancer risk

Androgen receptor (AR) has long been hypothesized to play an important role in prostate cancer etiology. Two trinucleotide repeat polymorphisms (CAG and GGC repeats in exon 1 of the AR gene) have been investigated as risk factors for prostate cancer in several studies. However, the results are inconclusive, probably because of the variations of study designs, characteristics of study samples, and choices of analytical methods. In this study, we evaluated evidence for linkage and association between the two AR repeats and prostate cancer by using the following comprehensive approaches: (1) a combination of linkage and association studies, (2) a test for linkage by parametric analysis and the male-limited X-linked transmission/disequilibrium test (XLRC-TDT), (3) a test for association by using both population-based and family-based tests, and (4) a study of both hereditary and sporadic cases. A positive but weak linkage score (HLOD=0.49, P=0.12) was identified in the AR region by parametric analysis; however, stronger evidence for linkage in the region, especially at the GGC locus, was observed in the subset of families whose proband had < or = 16 GGC repeats (HLOD=0.70, P=0.07) or by using XLRC-TDT ( z'=2.65, P=0.008). Significantly increased frequencies of the < or = 16 GGC repeat alleles in 159 independent hereditary cases (71%) and 245 sporadic cases (68%) cases compared with 211 controls (59%) suggested that GGC repeats were associated with prostate cancer ( P=0.02). Evidence for the association between the < or = 16 GGC repeats and prostate cancer risk was stronger with XLRC-TDT ( z'=2.66, P=0.007). No evidence for association between the CAG repeats and prostate cancer risk was observed. The consistent results from both linkage and association studies strongly implicate the GGC repeats in the AR as a prostate cancer susceptibility gene. Further studies on this polymorphism in other independent data sets and functional analysis of the GGC repeat length on AR activity are warranted.     

Modification of BRCA1-associated breast cancer risk by the polymorphic androgen-receptor CAG repeat

Compared with the general population, women who have inherited a germline mutation in the BRCA1 gene have a greatly increased risk of developing breast cancer. However, there is also substantial interindividual variability in the occurrence of breast cancer among BRCA1 mutation carriers. We hypothesize that other genes, particularly those involved in endocrine signaling, may modify the BRCA1-associated age-specific breast cancer risk. We studied the effect of the CAG repeat-length polymorphism found in exon 1 of the androgen-receptor (AR) gene (AR-CAG). AR alleles containing longer CAG repeat lengths are associated with a decreased ability to activate androgen-responsive genes. Using a sample of women who inherited germline BRCA1 mutations, we compared AR-CAG repeat length in 165 women with and 139 women without breast cancer. We found that women were at significantly increased risk of breast cancer if they carried at least one AR allele with >/=28 CAG repeats. Women who carried an AR-CAG allele of >/=28, >/=29, or >/=30 repeats were given a diagnosis 0.8, 1.8, or 6.3 years earlier than women who did not carry at least one such allele. All 11 women in our sample who carried at least one AR-CAG allele with >/=29 repeats had breast cancer. Our results support the hypothesis that age at breast cancer diagnosis is earlier among BRCA1 mutation carriers who carry very long AR-CAG repeats. These results suggest that pathways involving androgen signaling may affect the risk of BRCA1-associated breast cancer.     

Androgen receptor gene CAG repeats length in fertile and infertile Tunisian men

Several reports implicated a relation between the trinucleotide (CAG) repeat length in the androgen receptor (AR) gene and male infertility. But such result was not reproduced in others. To test this hypothesis, we investigated the number of (CAG) repeats in the AR gene among two groups of infertile (n = 129) and fertile Tunisian men (n = 98), using polymerase chain reaction (PCR) targeting the AR CAG repeat tract, followed by electrophoresis on polyacrylamide gel (6%). For statistical analysis we used Student, Kolmogorov-Smirnov (KS) and chi(2)-tests. Significance was reached when P < 0.05. No statistically significant difference in the mean length of the CAG repeat was found between infertile and control groups (P = 0.47). Moreover, using KS test, we have not found a difference in the distribution of allele frequencies between infertile and controls (D(obs) = 0.046 < D(crit) = 0.180). We also did not found a statistically significant relationship between the size of the CAG repeat and impaired sperm production in Tunisian population. Our results may be attributed to the high probability that infertile males may represent a heterogeneous group with respect to the causes of defective spermatogenesis.     

CAG repeat length in an infertile male population of Irish origin

The androgen receptor (AR) gene, located on the X chromosome, is an important regulator of human spermatogenesis. In the past decade, the link between the CAG polyglutamine tract, situated on exon one of the AR gene, and reduced spermatogenesis has become a controversial one. Alterations in the length of the CAG polyglutamine tract have been associated with prostate cancer at a reduced intrinsic length and neuromuscular diseases at a CAG repeat length of 40. Minimal intermediate increases have been linked with depressed spermatogenesis in infertile males. Asian and Australian groups have published an association between increased CAG repeat length and reduced spermatogenesis while many European studies have found no such association. The aim of this study was to document the association between increased CAG repeat length and reduced spermatogenesis in a group of Irish infertile males and controls known to have fathered at least one child. The study employed the ABI 377 DNA sequencer to size the CAG repeat region of exon one of the AR gene in each group. Statistical analysis revealed no actual link between the length of the CAG tract and a reduction of spermatogenesis in a cohort of infertile patients (n = 66) of Irish ethnic origin when compared to a fertile control group (n = 77) (p = 0.599).