RB1 and neoplasm: Furthermore, a regulatory feedback loop between AHR (aryl hydrocarbon receptor) and CYP1 genes is known, thus AhR interacts with nuclear factor κb (NFκB), estrogen receptor 1 (ESR1) and retinoblastoma 1 (RB1), which triggers the transcription of genes involved in growth, cell cycle and apoptosis, leading to abnormal growth and tumor promotion [29].