KISS1 and breast cancer: Previous work has shown that KISS1 and KISS1R levels are upregulated in invasive ERα-negative breast cancer cells (e.g., MDA-MB-231, Hs578T, SKBR3FLAG-KISS1R) in contrast to weakly invasive, ERα-positive luminal breast cancer cells (T47D, MCF7) or ERα-negative luminal SKBR3 cells25.