05 July 2012

Breast cancer: Size matters

As a result of the analysis of data collected using a unique on-line research platform, the specialists of 23andMe – a leading company in the field of genetic research – identified 7 single nucleotide polymorphisms or "snips" (from the English single-nucleotide polymorphisms, SNP) associated with the size of mammary glands. The presence of three of them in the genome also correlates with the risk of developing breast cancer. These data provide the first specific genetic relationship between breast size and cancer risk.

As part of a genome-wide associative study, the authors analyzed data provided by 16,175 women of European descent. Their answers to the questions of a specially compiled questionnaire, including the size of the bra cup and the size of the bra by the circumference of the chest, were compared with genetic data, including millions of "snips". The analysis was carried out taking into account age, geographical origin, a history of surgical interventions in the breast, pregnancies and breastfeeding.

Previously, the direct involvement of morphological factors such as breast tissue density in the development of cancer of this organ has already been revealed, but the dependence of the risk of tumor appearance on breast size was less clear.

Breast size is an inherited trait, and a slightly increased risk of breast cancer in young women with large breasts has been identified in a number of studies, but the genetic variants causing this relationship have been identified for the first time.

The study revealed the following loci associated with breast size: rs7816345 near the ZNF703 gene; rs4849887 and rs17625845 adjacent to the INHBB gene; rs12173570 near the ESR1 gene; rs7089814 in the ZNF365 gene; rs12371778 near the PTHLH gene and rs62314947 near the AREG gene. There is a pronounced correlation between two of these loci (located near the ESR1 and PTHLH genes) and known "snips" associated with breast cancer risk. Another one, located in the ZNF365 gene, is in close proximity to another well-known "snip" associated with the risk of developing this disease. Three more loci (associated with the ZNF703, INHBB and AREG genes) are involved in the regulation of estrogen production and the formation of mammary glands.

According to the head of the study, Dr. Nicholas Eriksson, the results of the work done shed light on the genetic factors that ensure the normal course of the process of breast formation, and also indicate that some of these factors are involved in the development of cancer of this organ. Although the data obtained do not directly confirm the existence of an epidemiological relationship between breast size and the development of cancer, they help to better understand the subtle mechanisms by which the morphology of the mammary glands affects the risk of developing malignant tumors.

Currently, 23andMe, together with Genentech, continues to actively work on the study of breast cancer, in particular the role of genes in the response of metastatic tumors to therapy.

Article by Nicholas Eriksson et al. Genetic variants associated with breast size also influence breast cancer risk is published in the journal BMC Medical Genetics.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on EurekAlert materials:
23andMe discovers surprising genetic connections between breast size and breast cancer.


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