AHR and lung carcinoma: In MCA-7 cells grown under CoCl2-induced hypoxia, 2,3,7,8-tetrachlorodibenzo-p-dioxin induction of CYP1A1 activity, a marker of AhR sensitivity, is significantly suppressed [53], and in human lung carcinoma A549 cells, HIF-1 induction weakens B[a]P-induced CYP1A1 and CYP1B1 mRNA expressions, and B[a]P attenuates the induction of a HIF-1 target: CA-IX [54].