AHR and neoplasm: AHR activation plays important distinct roles in cancer biology even in the absence of environmental toxins.371–375 Depending on the context, AHR can exert either tumor-promoting or tumor-suppressive effects.371,376 The opposing effects of AHR in cancer likely stem from the complexity of its activation and biological functions, which are cell type-, ligand-, and context-specific.377 Moreover, the timing of AHR activation during tumorigenesis and its interactions with cellular signaling pathways may contribute to the complex biology of AHR in cancer.