ESR1 and breast cancer: On the other hand all cell lines showed elevated transcript levels for RRM1, AKT1, and AKT2. Rare similarities between experimental and clinical cell samples included elevated VIM expression in CTCs and ER-negative cell lines (MDA231 and SKBR3), as well as high S100A9 expression in CTCs and ER-positive primary breast cancer cell lines (CCdl054, CCdl672, CCdl675).