Low-Dose Nicotine Activates EGFR Signaling via α5-nAChR and Promotes Lung Adenocarcinoma Progression

Association between smoking status and the prognosis of brain metastasis in patients with non-small cell lung cancer

Objective

This study aimed to explore the relationship between smoking status and the interval to brain metastasis in patients with non-small cell lung cancer (NSCLC) and its impact on survival time after brain metastasis.

Methods

Data were collected from patients with NSCLC with brain metastases who were treated at our centre between January 2005 and December 2017. Clinical indices such as clinicopathological features and smoking status were recorded, and patients were followed up until 1 September 2022. Based on our inclusion and exclusion criteria, 461 patients were analysed and matched using 1:1 propensity score matching. Three balanced groups were formed: non-smoking (n = 113), smoking cessation (n = 113), and smoking (n = 113). The interval to brain metastasis and overall survival were compared between the groups.

Results

There was a statistically significant difference in the interval to brain metastasis between the non-smoking and smoking cessation groups (p = 0.001), as well as between the non-smoking and smoking groups (p < 0.001). However, the difference between the smoking cessation and smoking groups was not statistically significant (p = 0.106). Multivariate and univariate analyses identified smoking status, clinical stage, lung cancer surgery, chemotherapy, and chest radiotherapy as independent predictors of the interval to brain metastasis. Additionally, the multivariate analysis showed that smoking status, driver gene mutations, and chest radiotherapy independently influenced survival after brain metastasis.

Conclusion

Smoking status in patients with NSCLC affects the interval to brain metastasis and survival after brain metastasis.

Spinosad blocks CHRNA5 mediated EGFR signaling pathway activation to inhibit lung adenocarcinoma proliferation

Lung adenocarcinoma (LUAD) is the leading cause of cancer death worldwide, with high incidence and low survival rates. Nicotinic acetylcholine receptors play an important role in the progression of LUAD. In this study, a screening of 17 nicotinic acetylcholine receptor allosteric agents revealed that spinosad effectively suppressed the proliferation of LUAD cells. The experiments demonstrated that spinosad induced cell cycle arrest in the G1 phase and stimulated apoptosis, thereby impeding the growth of LUAD and enhancing the responsiveness to gefitinib in vitro and vivo. Mechanistic insights obtained through transcriptome sequencing, Co-IP, and protein immunoblots indicated that spinosad disrupted the interaction between CHRNA5 and EGFR, thereby inhibiting the formation of downstream complexes and activation of the EGFR signaling pathway. The supplementation of exogenous acetylcholine showed to mitigate the inhibition of LUAD cell proliferation induced by spinosad. This study elucidates the therapeutic effects and mechanisms of spinosad in LUAD, and offers a theoretical and experimental foundation for novel LUAD treatments.

A review on the effect of COX-2-mediated mechanisms on development and progression of gastric cancer induced by nicotine

Smoking is a documented risk factor for cancer, e.g., gastric cancer. Nicotine, the principal tobacco alkaloid, would exert its role of contribution to gastric cancer development and progression through nicotinic acetylcholine receptors (nAChRs) and β-adrenergic receptors (β-ARs), which then promote cancer cell proliferation, migration and invasion. As a key isoenzyme in conversion of arachidonic acid to prostaglandins, cyclooxygenase-2 (COX-2) has been demonstrated to have a wide range of effects in carcinogenesis and tumor development. At present, many studies have reported the effect of nicotine on gastric cancer by binding to nAChR, as well as indirectly stimulating β-AR to mediate COX-2-related pathways. This review summarizes these studies, and also proposes more potential COX-2-mediated mechanisms. These events might contribute to the growth and progression of gastric cancer exposed to nicotine through tobacco smoke or cigarette substitutes. Also, this review article has therefore the potential not only to make a significant contribution to the treatment and prognosis of gastric cancer for smokers but also to the clinical application of COX-2 antagonists. In addition, this work also discusses the considerable challenges of this field with special reference to the future perspective of COX-2-mediated mechanisms in development and progression of gastric cancer induced by nicotine.

Nicotinic acetylcholine receptors in cancer: Limitations and prospects

Nicotinic acetylcholine receptors (nAChRs) have long been considered to solely mediate neurotransmission. However, their widespread distribution in the human body suggests a more diverse physiological role. Additionally, the expression of nAChRs is increased in certain cancers, such as lung cancer, and has been associated with cell proliferation, epithelial-to-mesenchymal cell transition, angiogenesis and apoptosis prevention. Several compounds that interact with these receptors have been identified as potential therapeutic agents. They have been tested as drugs for treating nicotine addiction, alcoholism, depression, pain and Alzheimer's disease. This review focuses on nAChR-mediated signalling in cancer, presenting opportunities for the development of innovative nAChR-based anticancer drugs. It displays the differences in expression of each nAChR subunit between normal and cancer cells for selected cancer types, highlighting their possible involvement in specific cases. Antagonists of nAChRs that could complement existing cancer therapies are summarised and critically discussed. We hope that this review will stimulate further research on the role of nAChRs in cancer potentially leading to innovative cancer therapies.

Contribution of the α5 nAChR Subunit and α5SNP to Nicotine-Induced Proliferation and Migration of Human Cancer Cells

Nicotine in tobacco is known to induce tumor-promoting effects and cause chemotherapy resistance through the activation of nicotinic acetylcholine receptors (nAChRs). Many studies have associated the α5 nicotinic receptor subunit (α5), and a specific polymorphism in this subunit, with (i) nicotine administration, (ii) nicotine dependence, and (iii) lung cancer. The α5 gene CHRNA5 mRNA is upregulated in several types of cancer, including lung, prostate, colorectal, and stomach cancer, and cancer severity is correlated with smoking. In this study, we investigate the contribution of α5 in the nicotine-induced cancer hallmark functions proliferation and migration, in breast, colon, and prostate cancer cells. Nine human cell lines from different origins were used to determine nAChR subunit expression levels. Then, selected breast (MCF7), colon (SW480), and prostate (DU145) cancer cell lines were used to investigate the nicotine-induced effects mediated by α5. Using pharmacological and siRNA-based experiments, we show that α5 is essential for nicotine-induced proliferation and migration. Additionally, upon downregulation of α5, nicotine-promoted expression of EMT markers and immune regulatory proteins was impaired. Moreover, the α5 polymorphism D398N (α5SNP) caused a basal increase in proliferation and migration in the DU145 cell line, and the effect was mediated through G-protein signaling. Taken together, our results indicate that nicotine-induced cancer cell proliferation and migration are mediated via α5, adding to the characterization of α5 as a putative therapeutical target.

Alpha5 nicotinic acetylcholine receptor mediated immune escape of lung adenocarcinoma via STAT3/Jab1-PD-L1 signalling

Background

Immunotherapy has proven to be an emerging treatment for non-small-cell lung cancer in recent years. Notably, smokers show higher programmed cell death ligand-1 (PD-L1) expression and better responses to PD-1/PD-L1 inhibitors than nonsmokers. Genome-wide association studies show that the CHRNΑ5 encoding α5-nicotinic acetylcholine receptor (α5-nAChR) is especially relevant to lung cancer and nicotine dependence. Jab1 is a key regulatory factor and promotes the stabilization of PD-L1. Our previous study reported that α5-nAChR mediates lung adenocarcinoma (LUAD) epithelial-mesenchymal transition (EMT) and metastasis via STAT3/Jab1. However, the link between α5-nAChR and PD-L1 is unclear in LUAD.

Methods

We used various bioinformatics databases to analyze the expression of related genes and their correlations. Expression and clinicopathologic significance of α5-nAChR and PD-L1 were detected by immunohistochemistry in a tissue microarray. α5-nAChR regulated LUAD cell immune escape by targeting the STAT3/Jab1-PD-L1 signalling by Western-blotting and ChIP in vitro. We used T cell coculture, flow cytometry, ELISA, CCK8 assay and crystal violet staining to detect the expression of regulatory T cell (Tregs), IFN-γ, IL-2 and the ability of T cell-mediated tumour cell killing respectively. IF assays were performed in both cancer cells and tumour xenograft paraffin sections to analyze the protein expression. The in vivo experiments in mouse model were performed to show the α5-nAChR-mediated immune escape via PD-L1 pathway.

Results

The expression of α5-nAChR was correlated with PD-L1 expression, smoking status and lower survival of LUAD in vivo. In vitro, the expression of α5-nAChR mediated phosphorylated STAT3 (pSTAT3), Jab1 and PD-L1 expression. STAT3 bound to the Jab1 or PD-L1 promoter and mediated PD-L1 expression. Jab1 stabilized PD-L1 expression in LUAD cells. Furthermore, in primary T cell cocultured system, downregulation of α5-nAChR suppressed the function of CD4⁺CD25⁺FOXP3⁺ Tregs, enhanced IFN-γ secretion, and increased T cell-mediated killing of LUAD cells. In the Jurkat T cells and LUAD cells coculture assay, inhibition of α5-nAChR increased IL-2 secretion. In tumour xenograft tissues, α5-nAChR expression was related to PD-L1, Jab1, pSTAT3, CD4 and granzyme B expression (GB).

Conclusions

Our results suggest that the novel α5-nAChR/STAT3-Jab1-PD-L1 axis is involved in LUAD immune escape, which could lead to potential therapeutic strategies for cancer immunotherapy.

α5-nAChR associated with Ly6E modulates cell migration via TGF-β1/Smad signaling in non-small cell lung cancer

The α5-nicotinic acetylcholine receptor (α5-nAChR) is closely associated with nicotine-related lung cancer, offering a novel perspective for investigating the molecular pathogenesis of this disease. However, the mechanism by which α5-nAChR functions in lung carcinogenesis remains to be elucidated. Lymphocyte antigen 6 (Ly6) proteins, like snake three-finger alpha toxins such as α-bungarotoxin, can modulate nAChR signaling. Ly6E, a member of the Ly6 family, is a biomarker of poor prognosis in smoking-induced lung carcinogenesis and is involved in the regulation of TGF-β1/Smad signaling. Here, we explored the underlying mechanisms linking α5-nAChR and Ly6E in non-small cell lung cancer (NSCLC). The expression of α5-nAChR was correlated with Ly6 expression, smoking status and lower survival in NSCLC tissues. In vitro, α5-nAChR mediated Ly6E, the phosphorylation of the TGF-β1 downstream molecule Smad3 (pSmad3, a key mediator of TGF-β1 signaling), the epithelial-mesenchymal transition (EMT) markers Zeb1, N-cadherin and vimentin expression in NSCLC cells. The downregulation of Ly6E reduced α5-nAChR, pSmad3, Zeb1, N-cadherin and vimentin expression. Functionally, silencing both α5-nAChR and Ly6E significantly inhibited cell migration compared to silencing α5-nAChR or Ly6E alone. Furthermore, the functional effects of α5-nAchR and Ly6E were confirmed in chicken embryo chorioallantoic membrane (CAM) and mouse xenograft models. Therefore, our findings uncover a new interaction between α5-nAChR and Ly6E that inhibits cancer cell migration by modulating the TGF-β1/Smad signaling pathway in NSCLC, which may serve as a novel target for therapeutic intervention.

The effects of thirdhand smoke on reproductive health

Tobacco smoke is an environmental pollutant that can cause follicle destruction and oocyte dysfunction. Thirdhand smoke (THS) is residual tobacco smoke existing in the environment long after cigarettes have been extinguished, which can react with other environmental compounds to produce secondary pollutants. THS contains a variety of toxic and harmful chemicals, such as nicotine and 1-(N-methyl-N-nitrosamino)-1-(3-pyridinyl)-4-butanal (NNA), a logical biomarker of THS exposure. The health hazards of THS exposure and its components have been researched in recent years. In this review, we have summarized research progress on the effects of THS exposure on organs in mice and humans especially on the reproductive system. This review may help evaluate the health risks of THS, in particular reproduction and offspring health. We hope this review will guide public health education on the dangers of THS exposure and promotion of healthy living habits.