This suggests that upregulation of ER signaling partly suppresses MEK pathway activity (30/200 genes [15%] in the HALLMARK_ESTROGEN_RESPONSE_EARLY pathway overlap genes in the MEK_UP.V1_DN pathway) but that MEK activation in tumors other than breast tumors might interfere with the activation of the ER-mediated HALLMARK_ESTROGEN_RESPONSE_EARLY pathway by downregulating gene expression in the MEK_UP.V1_DN pathway, thus affecting the EERES enrichment and reducing the correlation of ESR1 expression with EERES. This evidence concerns the gene ESR1 and breast neoplasm.