11-Cl-BBQ, a Select Modulator of AhR-regulated Transcription, Suppresses Lung Cancer Cell Growth via activation of p53 and p27 Kip1 .

Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor and functions as a tumor suppressor in different cancer models. In this study, we report detailed characterization of 11-chloro-7H-benzimidazo[2,1-a]benzo[de]iso-quinolin-7-one (11-Cl-BBQ) as a Select Modulator of AhR-regulated Transcription (SMAhRT) with anti-cancer actions. Treatment of lung cancer cells with 11-Cl-BBQ induced potent and sustained AhR-dependent anti-proliferative effects by promoting G1-phase cell cycle arrest. Investigation of 11-Cl-BBQ-induced transcription in H460 cells with or without the AhR expression by RNA-seq revealed activation of p53 signaling. In addition, 11-Cl-BBQ suppressed multiple pathways involved in DNA replication and increased expression of cyclin-dependent kinase inhibitors, including p27 Kip1 , in an AhR-dependent manner. CRIPSR-cas9 knockout of individual genes revealed the requirement for both p53 and p27 Kip1 for the AhR-mediated anti-proliferative effects. Our results identify 11-Cl-BBQ as a potential lung cancer therapeutic, highlight the feasibility of targeting AhR and provide important mechanistic insights into AhR-mediated-anticancer actions.