ABCG2 and invasive breast carcinoma: Using the cBioPortal8,9, we found that ABCC1 was among the most frequently altered (amplifications and mRNA-high expression relative to diploid) and highly expressed ABC transporter at the RNA level in the Cancer Genome Atlas (TCGA) invasive breast cancer cohort, and its protein level correlated modestly with transcript expression (r ≈ 0.4) (Supplementary Fig. S3a–c).