Androgen receptor polymorphisms and testicular cancer risk

Testicular cancer (TC) is currently the most common malignant solid tumour in Caucasian males aged 15-39 years. Epidemiological evidence suggests that its onset may be due to an imbalance in the action of steroidal sex hormones and their receptors. A faulty androgen receptor signalling pathway can, in fact, cause various male reproductive disorders. The androgen receptor (AR) gene has two polymorphic segments consisting of CAG and GGC repeats. The length of CAG repeats has been shown to affect the regulation of AR activity. In our study, we used fragment analysis to evaluate the AR gene repeats of 302 TC patients and 322 controls, to establish if there is any association between repeat number and TC. This study of the largest Italian caseload investigated to date highlighted three particularly significant aspects. First, a CAG repeat number of ≥25 may be considered a risk factor for the onset of TC, given its greater frequency in patients in comparison with controls. This difference became significant for the non-seminoma group. Second, men with CAG repeats below 21 or above 24 were found to have a, respectively, 50 and 76% higher risk of TC than those with CAG 21-24, suggesting that these too can be considered a risk factor for TC. Finally, stage II patients were more likely to have a CAG repeat number 24 than stage I patients. © 2014 American Society of Andrology and European Academy of Andrology

The impact of androgen receptor polymorphism and parental ethnicity on semen quality in young men from Latvia

Recent studies on young men from the general population have demonstrated geographic and ethnic differences in semen quality. The aim of this study was to investigate whether reported ethnic differences in semen quality might be associated with the maternally derived CAG and GGN polymorphisms in the androgen receptor gene or paternal ethnicity. In total 114 military conscripts from Latvia were included in the study. Information on maternal and parental ethnicity was collected by questionnaires. CAG and GGN repeats were analysed by direct sequencing of leukocyte DNA. Men with Latvian mothers (n = 83) had marginally shorter CAG repeat length (21.6 ± 2.9) as compared with those with non-Latvian mothers (22.9 ± 3.2, n = 31), not reaching statistical significance (p = 0.053). Sperm concentration did not differ significantly between these two groups (76 ± 59 and 70 ± 52, p = 0.9 respectively). In contrast, significantly higher sperm concentration and total sperm count were found in men with Latvian fathers (n = 77) as compared with men with non-Latvian fathers (n = 37) (80 ± 61 vs. 62 ± 48, p = 0.035, for sperm concentration and 225.7 ± 209 vs. 158.4 ± 134.4, p = 0.002, for total sperm count respectively). CAG repeat length did not correlate with any semen parameters in the whole population. However, GGN repeat length correlated with semen volume: men with GGN > 23 presented with higher semen volume (3.2 ± 2.1) as compared with men with GGN = 23 (2.6 ± 1.3, p = 0.04) or GGN < 23 (2.0 ± 1.2, p = 0.006). We conclude that GGN repeat length has an impact on semen volume, whereas differences in sperm numbers are associated with the paternal ethnicity.Peer reviewe

Persistent organic pollutants have dose and CAG repeat length dependent effects on androgen receptor activity in vitro.

Recently, the effect of exposure to persistent organic pollutants (POPs) on sperm concentration was only seen in men with a short androgen receptor (AR) gene CAG repeat. In order to investigate whether these effects could be observed also in vitro, we tested the impact of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-bis-(4-chlorophenyl)-2,2-dichloroethene (4,4'-DDE) on 5α-dihydrotestosterone activated ARs containing 16, 22 and 28 CAG repeats, respectively. Single exposure to 4,4'-DDE had the most pronounced effect on the AR activity containing 16 CAG repeats, whereas 28 CAG was the most sensitive variant when a mixture of the two compounds was added. Thus, our in vitro results have confirmed the in vivo data indicating a CAG repeat length dependent effect of endocrine disrupters on the AR activity

Genetic, environmental and life-style effects on androgen receptor function

Androgens regulate male reproductive function and their effects are mediated through the androgen receptor (AR). The AR gene contains a polymorphic CAG repeat, encoding a stretch of glutamines, affecting the transcriptional activity of the AR. Prostate specific antigen (PSA) is a downstream target and is commonly used in the screening of prostate cancer. The relationship between CAG number and male reproductive health has been suggested to be modulated by persistent organic pollutants (POPs). Humans are exposed mainly through food intake, but also from industrial processes and cigarette smoking. The dioxin-like POPs exert their effect through the aryl hydrocarbon receptor (AhR), shown to interact with the AR. The aims were to study the role of the CAG polymorphism on; AR activity and expression in the absence or presence of POPs; PSA concentration in serum and tissue; and reproductive parameters and hormones in men. It was also elucidated whether the CAG number could modify the effect of cigarette smoking on reproductive characteristics in men. The transactivation assay included a reporter gene with a human androgen responsive promoter. Cells were transfected with vectors having CAG numbers of 16, 22 or 28, representative of the human range. To explore the association between CAG number and reproductive outcome, an unprejudiced spline regression model with CAG number as a continuous variable was used, as well as a stratified model and in case of linear pattern, CAG number was investigated in a linear regression model. We found that the CAG variant with the median length had the highest AR activity, shown both in cell lines and prostate tissue, and as highest PSA concentration in younger and older men. The unprejudiced statistical analysis gave a better picture of the relationship between CAG number and reproductive outcomes, demonstrating a CAG-dependent effect on hormone levels. The CAG repeat also had a cell line- and dose-dependent modulating effect of POPs on AR activity and was negatively associated with semen volume in smoking men. To conclude, the median AR CAG number had the highest activity in vivo and in vitro. This pattern consisted even in the presence of POPs, indicating a stronger resistance for the median CAG length to these compounds compared to less common variants. The CAG number was also associated with reproductive hormone regulation and might modify the susceptibility of current cigarette smoking on semen volume in young men

Functional characterisation of the CAG polymorphism in the androgen receptor- in vitro and in vivo

The androgen receptor (AR) is the mediator of androgen actions. In the AR coding region there is a polymorphic CAG repeat encoding a stretch of the amino acid glutamine (Q). The repeat length modulates receptor activity and is normally distributed between 10-30 CAG with a median length of 22 repeats in white men. At the start of this work, a negative linear association between AR function and the CAG repeat number was generally assumed. This assumption was supported by clinical findings in patients with Kennedy’s disease, which is a neuromuscular disorder caused by an abnormally expanded CAG repeat (>40 CAG). However, in vivo data concerning the association between CAG numbers within normal length and androgenic effects were conflicting. As understanding the impact of CAG number on the AR activity is important for proper interpretation of this polymorphism and risk of pathological conditions other than Kennedy’s disease, the purpose of this study was to examine the influence of CAG length, if any, on AR activity. Firstly an in vitro study was performed. A reporter gene with a human androgen responsive promoter was used in a transactivation assay. The repeat lengths included were 16, 22 and 28 CAG, which represent a short, the median, and a long repeat within the normal human range. The study showed that the AR with median repeat length had the highest activity in vitro. Secondly, the effect of the CAG repeat in relation to two androgen dependent conditions, infertility and PCa, was analysed in two separate meta-analyses. When stratifying the CAG repeats into three groups, shorter than median, median and longer than the median CAG length, the meta-analysis on infertile men showed 20% increased risk of infertility in men harbouring other repeat lengths than the most common. On the other hand, CAG number did not have any effect on PCa risk. The AR regulates the expression of prostate specific antigen (PSA). Thus the expression of PSA can be used as a marker of AR activity in tissue. We measured the AR protein and PSA amount in human prostate tissue from 19 men with known CAG length. Those who were carriers of 22 CAG had lower AR amount and higher PSA than counterparts with other CAG lengths, but this was not statistically significant, probably due to the small study size. Taken together, these studies indicate that the median length of the androgen receptor CAG repeat is associated with optimal activity, in vitro and in vivo

Testicular cancer; gonadal, sexual and psychological aspects of the disease and its treatment.

The survival rates among testicular germ cell cancer (TGCC) patients have dramatically increased and more than 95 % are cured. The question of quality of life of the survivors is, therefore, important. The TGCC treatment, and thereby its side-effects may vary. A contributing factor to this variation is also genetically determined inter-subject difference in the sensitivity to the adverse effects of cancer therapy. The aim of this thesis has been, in order to improve the management and counselling of TGCC patients, to increase the level of knowledge regarding impairment of reproductive functions as well as the risks of emotional disorders (EMD) related to TGCC and its treatment. In article I, impact of therapy and androgen receptor (AR) polymorphisms on sperm concentration was investigated. Radiotherapy (RT) or 3 to 4 cycles of chemotherapy (SCT) caused initial decline in sperm concentration, which returned to pre-treatment levels 2 to 5 years after therapy. In the SCT group, sperm concentration 1 to 2 years post-treatment was inversely correlated to the androgen receptor (AR) CAG repeat length, indicating a genetic variation in the recovery of sperm concentration. In article II, risk factors for developing hypogonadism were studied. SCT and RT treated were at higher risk of hypogonadism, 6 and 12 months post-treatment as compared to those who received 1 to 2 cycles of chemotherapy. Microlithiasis and hormone deficiency prior to treatment predicted increased risk of hypogonadism after cancer therapy. In article III, TGCC patients, 3 to 5 years after treatment, were compared to the general population concerning prevalence of sexual dysfunctions. A higher proportion of TGCC patients had low sexual desire and erectile dysfunction. Neither hypogonadism nor treatment modality had any obvious impact on the risk of these sexual problems. In article IV, the presence of EMD was investigated, 3 to 5 years after TGCC therapy and related to hypogonadism, AR polymorphisms and treatment modality. Neither anxiety nor depression was overrepresented in hypogonadal TGCC patients and no association between AR polymorphisms and EMD was found. Patients treated with than four cycles of cisplatinum based chemotherapy due to refractory or relapsed disease were more prone to experiencing symptoms of anxiety