In addition to being hyper-expressed in some malignant cells, the AHR was shown, as early as 2000 [85], to be “constitutively active” in adult T cell leukemias [83] and cancers of the stomach [101,102], liver [103,104], prostate [105], head and neck [86,87,106], breast [100,107,108,109], brain [88,90], and skin [110,111]. Here, AHR is linked to gastric cancer.