Lung cancer is globally the most common cancer, and most cases are associated with smoking. Smoking exposes respiratory epithelial tissues to various carcinogens. Evaluating the effects of these carcinogens administered intratracheally in mouse models would allow us to study lung carcinogenesis in a relevant manner and determine therapeutically targetable pathways.

Cigarette smoking exposure was mimicked in vivo using a smoke machine and the condensate was subjected to chemical analysis. In addition to nicotine, cigarette smoking condensate included significant levels of the carcinogens, Nicotine-derived nitrosamine ketone (NNK) and Benzo(α)pyrene (BP). Next, a mouse model of cigarette smoking-induced carcinogenesis was developed by exposing ICR mice to intratracheal exposure to NNK and BP three times a week for 18 months.

Mice chronically exposed to NNK and BP developed epithelial dysplasia at 4 months of exposure and lung cancers at 8-12 mo. of exposure at significantly increased rates relative to controls. Histology revealed myeloid inflammation in murine lung tissues. Exposure of lung epithelial cells to cigarette smoking condensate led to increased production of pro-inflammatory IL-1β. Downstream mediator of IL-1β signaling, Interleukin 1 receptor associated kinase-4 (IRAK4), was overexpressed in murine lung tissues exposed to carcinogens in vivo. Two-thirds of human tissue sections obtained from archived lung cancers also exhibited overactivated IRAK4 expression.

In lung cancer cell lines, IRAK4 immunofluorescence revealed a microtubule like pattern of expression in lung cancer cells. Immunoblotting confirmed IRAK4 colocalization within purified microtubules. Using mass spectrometry on isolated microtubules, we observed that phosphorylation decreased in various tubular proteins after IRAK4 inhibition. Inhibition of IRAK4 using small molecule specific inhibitors resulted in decreased invasion in lung cancer cell lines.

These data show that chronic intratracheal exposure of smoking associated carcinogens leads to dysplasia and malignancies in mouse models. This exposure also leads to myeloid inflammation and activation of IRAK4 in lung tissues. Therapeutic targeting of IRAK4 can have potentially beneficial effects in lung cancer models.

Citation Format: Ritesh K. Aggarwal, Simone Sidoli, Srabani Sahu, Srinivas Aluri, Charan Vegivinti, Divij Verma, Shanisha Gordon-Mitchell, Beamon Agarwal, Tanya Verma, Daniel T. Starczynowski, Ulrich G. Steidl, Balazs Halmos, Lindsay M. LaFave, Haiying Cheng, Amit Verma, Yiyu Zou. Smoking carcinogen-induced inflammation promotes lung carcinogenesis via IRAK4 activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1464.