The individual breast cancer molecular subtypes also showed systematic differences in expression of proliferative markers (MKI67 mRNA; Figure 9—figure supplement 1D) and lactate dehydrogenase involved in fermentative glycolysis (LDHA mRNA; Figure 9—figure supplement 1E), consistent with the notion that malignancy gradually increases from normal-like and luminal A across luminal B and HER2-enriched to basal-like breast cancer (Dai et al., 2015). This evidence concerns the gene ERBB2 and breast cancer.