In breast cancer cells, Skp2 expression is associated with lack of estrogen receptor (ER) and HER-2 [22], which is reflected by the elevated expression levels of Skp2 in the triple-negative breast cancer cell lines MDA-MB-468, and, to a lesser extent, MDA-MB-231, relative to ER-positive MCF-7 cells. The gene discussed is ESR1; the disease is breast cancer.