The Tobacco Metabolite NNK Enhances Pancreatic Cancer Cell Stemness and Chemoresistance by Activating the β2AR-Akt Autophagy Axis
Abstract Background: Low responsiveness to chemotherapy is an important cause of poor prognosis in pancreatic cancer. Smoking is a high-risk factor for pancreatic cancer and its resistance to gemcitabine; however, the underlying mechanisms remain unclear. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is the main metabolite of tobacco burning and has been shown to be associated with cancer development and chemoresistance, but in pancreatic cancer, its mechanism remains poorly understood.Methods: The effect of NNK on pancreatic cancer cell viability was confirmed by using Cell Counting Kit-8 and colony formation assays. Stem cell sphere formation assays and western blotting/qPCR measurements of stemness-related molecules were used to detect pancreatic cancer cell stemness. The pancreatic cancer autophagy status was evaluated by immunofluorescence staining of LC3 and western blotting/qPCR analysis of autophagy-related molecules.Results: NNK promoted stemness and gemcitabine resistance in pancreatic cancer cell lines. Furthermore, NNK intervention increased autophagy and changed the expression levels of autophagy-related markers, which preliminarily confirmed the activation of autophagy by NNK. Finally, the results showed that NNK-promoted stemness, and gemcitabine resistance was activated by the autophagy pathway, which was mediated by the β2AR-Akt signalling pathway.Conclusions: Autophagy induced by activating the NNK-induced β2AR-Akt signalling pathway promoted stemness and gemcitabine resistance in pancreatic cancer cells.