Sphingolipid and ether lipid expression patterns are altered in breast cancer cells in an estrogen-receptor-dependent manner, being strongly upregulated in SKBr3 (ER-negative and G-protein coupled estrogen receptor 1, GPER1, positive) in comparison to T47D (ER + and GPER1-) and MCF-7 (ER + and GPER1+) cells [135]. Here, ESR1 is linked to breast cancer.