Breast cancer risk associated with genotypic polymorphism of the mitosis‐regulating gene Aurora‐A/STK15/BTAK

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Abstract
Aneuploidy, an abnormal number of chromosomes, is relatively common and occurs early in breast cancer development. This observation supports a breast tumorigenic contribution of mechanisms responsible for maintaining chromosome number stability in which centrosomes play an essential role. We therefore speculated that the Aurora-A/STK15/BTAK gene, implicated in the regulation of centrosome duplication, may be associated with breast tumorigenesis. To test this hypothesis, we conducted a case-control study of 709 primary breast cancer patients and 1,972 healthy controls, examining single-nucleotide polymorphisms (SNPs), including a suggested functional Phe31Ile SNP, in Aurora-A. We were also interested in knowing whether any association between Aurora-A and breast cancer was modified by reproductive risk factors reflecting susceptibility to estrogen exposure. Our hypothesis is that, since estrogen is known to promote breast cancer development via its mitogenic effect leading to malignant proliferation on breast epithelium and since Aurora-A is involved in regulating mitosis, the discovery of a joint effect between the Aurora-A genotype and reproductive risk factors on cancer risk might yield valuable clues to the association of breast tumorigenesis with estrogen. Support for this hypothesis came from the following observations. (i) Two SNPs in Aurora-A were significantly associated with breast cancer risk (p < 0.05). (ii) Haplotype analyses, based on different combinations of multiple SNPs in Aurora-A, revealed a strong association with breast cancer risk; interestingly, the genotypic distribution of the suggested functional Phe31Ile SNP was not significantly different between breast cancer patients and controls, but the specific haplotype containing the putative at-risk Ile allele was more common in patients. (iii) This association between risk and putative high-risk genotypes was stronger and more significant in women thought to be more susceptible to estrogen, i.e., those with a longer interval between menarche and first full-term pregnancy. (iv) The protective effect conferred by a history of full-term pregnancy was significant only in women with a putative low-risk genotype of Aurora-A. Our study provides new findings supporting the mutator role of Aurora-A in breast cancer development, suggesting that breast cancer could be driven by genomic instability associated with variant Aurora-A, the tumorigenic contribution of which could be enhanced as a result of increased mitosis due to estrogen exposure.