ABCG2 and head and neck squamous cell carcinoma: The largest numbers of significant ABC transporter associations were identified for ccRCC (n = 12), HCC (n = 5) and BRCA (n = 4 for chemotherapy and n = 3 for endocrine cohort), whereas only a single significant correlation was found for lung adenocarcinoma, PRCC, HNSCC, bladder carcinoma and ovarian cancer (Fig. 1c).