ESR1 and cancer: Nonetheless, it has been postulated that intronic polymorphisms such as the rs9340799 polymorphism of ESR1 may influence the cancer susceptibility by (i) being in linkage disequilibrium with another functional polymorphism in the same locus; (ii) influencing the expression of other genes through alterations to their transcriptional activity or mRNA stability; (iii) containing regulatory sequences which can impact gene expression via transcriptional regulation47,69.