Smoking-Induced M2-TAMs, via circEML4 in EVs, Promote the Progression of NSCLC through ALKBH5-Regulated m6A Modification of SOCS2 in NSCLC Cells

Abstract

Lung cancer is a commonly diagnosed disease worldwide, with non-small cell lung cancers (NSCLCs) accounting for ≈ 85% of cases. Cigarette smoke is an environmental exposure promoting progression of NSCLC, but its role is poorly understood. This study reports that smoking-induced accumulation of M2-type tumor-associated macrophages (M2-TAMs) surrounding NSCLC tissues promotes malignancy. Specifically, extracellular vesicles (EVs) from cigarette smoke extract (CSE)-induced M2 macrophages promoted malignancy of NSCLC cells in vitro and in vivo. circEML4 in EVs from CSE-induced M2 macrophages is transported to NSCLC cells, where it reduced the distribution of ALKBH5 in the nucleus by interacting with Human AlkB homolog H5 (ALKBH5), resulting in elevated N6-methyladenosine (m6A) modifications. m6A-seq and RNA-seq revealed suppressor of cytokine signaling 2 (SOCS2)-mediated activation of the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway by regulating m6A modification of SOCS2 via ALKBH5. Down-regulation of circEML4 in EVs from CSE-induced M2 macrophages reversed EVs-enhanced tumorigenicity and metastasis in NSCLC cells. Furthermore, this study found that smoking patients showed an increase in circEML4-positive M2-TAMs. These results indicate that smoking-induced M2-TAMs via circEML4 in EVs promote the NSCLC progression through ALKBH5-regulated m6A modification of SOCS2. This study also reveals that circEML4 in EVs from TAMs acts as a diagnostic biomarker for NSCLC, especially for patients with smoking history.

Keywords: N6-methyladenosine; circRNAs; non-small cell lung cancer; smoking; tumor-associated macrophages.