ABCG2 and glioblastoma: Several genes associated with drug resistance, particularly those involved in drug efflux, such as members of the ATP binding cassette (ABC) transporter family, including ABCC1, ABBC2, ABBC3, ABCC5, ABCB1, and ABCG2, displayed a general trend of significant negative associations with PEBP1/STK11 co-expression across the majority of cancer types, with a few exceptions observed mainly in LIHC and GBM (Figure 9A).