An exception to this relationship is that hyperactivation of MAPK does not lead to re-expression of ERα in SUM-102 and SUM-159, two ER-negative basal type breast cancer cell lines that are found to exhibit hypermethylation of the ESR1 promoter suggesting that additional mechanisms may operate to repress ERα expression in these cell lines [44]. The gene discussed is ESR1; the disease is breast carcinoma.