Surprisingly, in contrast to previous reports which show Her2-dependent Mcl-1 regulation under normoxic conditions [24, 25, 29], siRNA-mediated knockdown of the HER2 gene (siHER2) in Her2-positive BC cells did not affect Mcl-1 protein levels under hypoxic conditions (Fig. 2b). This evidence concerns the gene ERBB2 and breast cancer.