MCL1 and breast cancer: Moreover, Mcl-1 protein levels of BC exposed to hypoxia were transiently increased 2.41-fold (standard deviation (SD) ±0.44), 2.57-fold (SD ±0.34), and 3.31-fold (SD ±0.31) in Her2-positive BT474, SKBR3, and HCC-1954 BC cells, respectively.