Abstract 5817: Exosomal miR-4466 from nicotine-activated neutrophils promotes tumor cell stemness & metabolism in brain metastasis

Abstract Smoking is associated with lung cancer and has a profound impact on tumor immunity. Nicotine, the addictive and non-carcinogenic smoke component, influences various brain cells and the immune system. However, little is known how long-term use of nicotine affects clinical outcomes in patients with brain metastasis. To address this question, we conducted a retrospective analysis of 810 lung cancer patients with smoking history and assessed brain metastasis. We found that lung cancer patients of current smokers have significantly higher brain metastatic incidence compared to the never-smokers. Immune profiling of the brain metastatic lesions among smokers showed predominant infiltration of neutrophils compared to never-smokers. Notably, mice pre-exposed to nicotine showed a significantly increased number of neutrophils in the brains even before implantation of cancer cells (pre-metastatic niche), and their numbers progressively increased during the metastatic stage. Neutrophil depletion during metastatic colonization caused a remarkable decrease in brain metastasis. Furthermore, we found that chronic exposure of nicotine recruited STAT3-activated N2-neutrophils that secreted exosomal miR-4466 in the brain. This pre-metastatic niche promoted stemness and metabolic switching via SKI/SOX2/CPT1A axis in the tumor cells thereby enabling brain metastasis. Importantly, exosomal miR-4466 levels were found to be elevated in serum/urine of cancer-free subjects with a smoking history and promote tumor growth in vivo, suggesting that exosomal miR-4466 may serve as a promising prognostic biomarker for predicting increased risk of metastatic disease among smoker(s). Our findings suggest a novel pro-metastatic role of nicotine-induced N2-neutrophils in the progression of brain metastasis. We also demonstrated that inhibiting nicotine-induced STAT3-mediated neutrophil polarization effectively abrogated brain metastasis in vivo. Our finding for the first time provides compelling evidence related to the mechanism(s) of neutrophil-mediated brain metastasis that arises from nicotine use. Our results also identified a potential prognostic biomarker for the onset of metastasis as a risk-reduction measure in lung cancer patients and implicated the risk of using nicotine gateway for smoking cessation in cancer patients with a smoking history. Citation Format: Abhishek Tyagi, Shih-Ying Wu, Sambad Sharma, Kerui Wu, Dan Zhao, Ravindra Deshpande, Kounosuke Watabe. Exosomal miR-4466 from nicotine-activated neutrophils promotes tumor cell stemness & metabolism in brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5817.