Accordingly, not only we noticed that ERα-positive LumA IDC cell lines, which are the more sensitive to the antiproliferative activity of Tam are also those cell lines in which the LMX-induced ERα degradation is higher, but also we report that the GART mRNA expression is high in ERα IDCs of high grade and stage and that women with LumA BC treated with both chemotherapy and ET have a higher survival rate when the tumor contains low GART mRNA levels. This evidence concerns the gene ESR1 and breast cancer.