CAG repeat length polymorphism in the androgen receptor gene and breast cancer risk: data on Indian women and survey from the world

Abstract

We analyzed the length of the CAG repeats of the androgen receptor gene in Indian women with breast cancer, and compared the data with that of other populations across the world in an attempt to find a potential pattern of association. The study was undertaken on 1,408 individuals comprising 747 breast cancer patients and 661 control individuals recruited from three southern states of India: Andhra Pradesh, Tamil Nadu, and Karnataka. The comparison revealed no difference in mean length of the repeat between cases and controls in any of the three groups or in the analysis of pooled data. No significant difference between pre- and post-menopausal cases in any of the three groups or in the analysis of pooled data was observed. Most of the studies to date support either positive association (longer repeats--increased disease risk) or no association, and only 2 out of 20 studies reported negative association (inverse correlation between repeat length and disease risk). Comparison of these data with those from other populations revealed several interesting facts. Particularly notable is that repeat length shows association with breast cancer risk in a population-specific manner with most of the studies on American and Canadian women showing positive association, whereas those on Australian and Israeli women showing no association. Only one study had been conducted on other populations including Asians/South Asians; this restricted us from finding any patterns of association in these populations.

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

“…Many authors [15][16][17][18][19][20][21][22][23][24][25][26] have found no relationship between the number of CAG repeats in the androgen Table 4. Association of CAG repeat genotypes and alleles in the AR gene with the clinical-pathological parameters of breast cancer.…”

Trinucleotide repeat expansions in human breast cancer-susceptibility genes: relevant targets for aspirin chemoprevention?

“…In a pooled analysis of nested case control studies from the Breast and Prostate Cancer Cohort Consortium (BPC3), which involved 5603 BC patients and 7480 controls, CAG repeat analysis from peripheral blood DNA was not found to be associated with postmenopausal BC [47]. Peripheral blood DNA study on Dravidian populations of India indicated a similar distribution of the CAG repeats between BC patients and healthy controls [1]. These different results may be due to inadequate capability of peripheral DNA analysis to reflect genetic changes in tumor tissues, since the location of the AR gene on the X chromosome limits identification of the potential role of CAG repeat length due to random X-inactivation.…”

“…Female androgens are produced by ovarian interstitial cells and adrenal glands [1]. The ovaries continue to produce testosterone after menopause, and testosterone levels may either do not change or are slightly reduced at menopause [1].…”

“…The ovaries continue to produce testosterone after menopause, and testosterone levels may either do not change or are slightly reduced at menopause [1]. In certain diseases, the extent of sex ratio difference may reflect causal involvement of sex hormones.…”

Association of sex hormone receptor gene polymorphisms with recurrent pregnancy loss: a systematic review and meta-analysis

“…The expansion of CAG repeats, coding for a polyglutamine (polyQ) tract in the N-terminal domain, leads to an increased transactivation function (21). Several clinical conditions had been shown to be associated with the length of CAG repeats in the AR gene (22)(23)(24)(25)(26).…”