Anti-tumoral activity of the human-specific duplicated form of α7-nicotinic receptor subunit in tobacco-induced lung cancer progression

Translational implications of CHRFAM7A, an elusive human-restricted fusion gene

Genes restricted to humans may contribute to human-specific traits and provide a different context for diseases. CHRFAM7A is a uniquely human fusion gene and a negative regulator of the α7 nicotinic acetylcholine receptor (α7 nAChR). The α7 nAChR has been a promising target for diseases affecting cognition and higher cortical functions, however, the treatment effect observed in animal models failed to translate into human clinical trials. As CHRFAM7A was not accounted for in preclinical drug screens it may have contributed to the translational gap. Understanding the complex genetic architecture of the locus, deciphering the functional impact of CHRFAM7A on α7 nAChR neurobiology and utilizing human-relevant models may offer novel approaches to explore α7 nAChR as a drug target.

The role of α7-nAChR-mediated PI3K/AKT pathway in lung cancer induced by nicotine

Nicotine enters the environment mainly through human activity, as well as natural sources. This review article examines the increasing evidence implicating nicotine in the initiation and progression of lung cancer. Moreover, it primarily focuses on elucidating the activation mechanism of phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB, also known as AKT) signaling pathway, regulated by α7 subtype nicotinic acetylcholine receptor (α7-nAChR), in relation to the proliferation, invasion, and metastasis of lung cancer cells induced by nicotine, as well as nicotine-mediated anti-apoptotic effects. This process involves PI3K/AKT phosphorylated-B-cell lymphoma-2 (Bcl-2) family proteins, PI3K/AKT/mammalian target of rapamycin (mTOR), PI3K/AKT/nuclear factor-κB (NF-κB), hepatocyte growth factor (HGF)/cellular-mesenchymal epithelial transition factor (c-Met)-induced PI3K/AKT and PI3K/AKT activated-hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) pathways. In addition, we also deliberated on the related challenges and upcoming prospects within this field. These lay the foundation for further study on nicotine, lung tumorigenesis, and PI3K/AKT related molecular mechanisms. This work has the potential to significantly contribute to the treatment and prognosis of gastric cancer in smokers. Besides, the crucial significance of PI3K/AKT signaling pathway in multiple molecular pathways also suggests that its target antagonists may inhibit the development and progression of lung cancer, providing a possible new perspective for solving the problem of nicotine-promoted lung cancer. The emerging knowledge about the carcinogenic mechanisms of nicotine action should be considered during the environmental assessment of tobacco and other nicotine-containing products.

Targeting Alpha7 Nicotinic Acetylcholine Receptors in Lung Cancer: Insights, Challenges, and Therapeutic Strategies

Alpha7 nicotinic acetylcholine receptor (α7 nAChR) is an ion-gated calcium channel that plays a significant role in various aspects of cancer pathogenesis, particularly in lung cancer. Preclinical studies have elucidated the molecular mechanism underlying α7 nAChR-associated lung cancer proliferation, chemotherapy resistance, and metastasis. Understanding and targeting this mechanism are crucial for developing therapeutic interventions aimed at disrupting α7 nAChR-mediated cancer progression and improving treatment outcomes. Drug research and discovery have determined natural compounds and synthesized chemical antagonists that specifically target α7 nAChR. However, approved α7 nAChR antagonists for clinical use are lacking, primarily due to challenges related to achieving the desired selectivity, efficacy, and safety profiles required for effective therapeutic intervention. This comprehensive review provided insights into the molecular mechanisms associated with α7 nAChR and its role in cancer progression, particularly in lung cancer. Furthermore, it presents an update on recent evidence about α7 nAChR antagonists and addresses the challenges encountered in drug research and discovery in this field.

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.

Unanswered questions in the regulation and function of the duplicated α7 nicotinic receptor gene CHRFAM7A

The α7 nicotinic receptor (α7 nAChR) is an important entry point for Ca²⁺ into the cell, which has broad and important effects on gene expression and function. The gene (CHRNA7), mapping to chromosome (15q14), has been genetically linked to a large number of diseases, many of which involve defects in cognition. While numerous mutations in CHRNA7 are associated with mental illness and inflammation, an important control point may be the function of a recently discovered partial duplication CHRNA7, CHRFAM7A, that negatively regulates the function of the α7 receptor, through the formation of heteropentamers; other functions cannot be excluded. The deregulation of this human specific gene (CHRFAM7A) has been linked to neurodevelopmental, neurodegenerative, and inflammatory disorders and has important copy number variations. Much effort is being made to understand its function and regulation both in healthy and pathological conditions. However, many questions remain to be answered regarding its functional role, its regulation, and its role in the etiogenesis of neurological and inflammatory disorders. Missing knowledge on the pharmacology of the heteroreceptor has limited the discovery of new molecules capable of modulating its activity. Here we review the state of the art on the role of CHRFAM7A, highlighting unanswered questions to be addressed. A possible therapeutic approach based on genome editing protocols is also discussed.

Effect of smoking habits on the efficacy of EGFR-TKI plus anti-angiogenic agent in advanced EGFR-mutant NSCLC

BACKGROUND

The types of epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancer (NSCLC) patients who could obtain significant clinical benefit from the dual inhibition of EGFR/vascular EGFR (VEGFR) pathways remain unclear. No consensus has been reached on the significance of smoking habits in clinical benefit obtained from EGFR-TKI plus anti-angiogenic agents.

METHODS

PubMed, EMBASE, and Cochrane databases for all phase II/III randomized clinical trials (RCTs) investigating the efficacy of EGFR-TKI combined with anti-angiogenic agents stratified by smoking habits (updated October 2021) were searched systematically. The primary outcomes were the pooled HRs for PFS/OS in smokers and non-smokers, and differences in efficacy of EGFR-TKI plus anti-angiogenic treatment between smokers and non-smokers, measured by difference in PFS and OS.

RESULTS

Seven phase II/III RCTs involving 1452 patients were identified. The pooled analysis demonstrated that EGFR-TKI plus anti-angiogenic agent could decrease the risk of progression by 40% (HR, 0.60; 95%CI 0.48-0.75) in smokers when compared with EGFR-TKI alone, but not in non-smokers (HR, 0.92; 95%CI 0.68-1.25). The comparison analysis further demonstrated that EGFR-mutated NSCLC patients who smoked obtained greater progression-free survival (PFS) benefit from treatment with EGFR-TKI plus anti-angiogenic agents (HR, 0.68; 95%CI 0.51-0.91). Consistent with the results for PFS, smokers receiving EGFR-TKI plus anti-angiogenic agents appeared to exhibit better overall survival (OS) than non-smokers but not to a statistically significant degree (HR, 0.60; 95%CI 0.23-1.52). Meta-regression analysis revealed no significant effect of the line of treatment (P = 0.52), trial phase (P = 0.52), EGFR-TKI type (P = 0.13), or anti-angiogenic agent type (P = 0.50) on PFS effect sizes under multivariate models.

CONCLUSION

Comprehensive analysis suggested that EGFR-TKI plus anti-angiogenic agents led to favorable PFS among smoking EGFR-mutant patients, comparable to nonsmokers, which might provide a useful guide for clinicians.

The Human-Restricted Isoform of the α7 nAChR, CHRFAM7A: A Double-Edged Sword in Neurological and Inflammatory Disorders

CHRFAM7A is a relatively recent and exclusively human gene arising from the partial duplication of exons 5 to 10 of the α7 neuronal nicotinic acetylcholine receptor subunit (α7 nAChR) encoding gene, CHRNA7. CHRNA7 is related to several disorders that involve cognitive deficits, including neuropsychiatric, neurodegenerative, and inflammatory disorders. In extra-neuronal tissues, α7nAChR plays an important role in proliferation, differentiation, migration, adhesion, cell contact, apoptosis, angiogenesis, and tumor progression, as well as in the modulation of the inflammatory response through the “cholinergic anti-inflammatory pathway”. CHRFAM7A translates the dupα7 protein in a multitude of cell lines and heterologous systems, while maintaining processing and trafficking that are very similar to the full-length form. It does not form functional ion channel receptors alone. In the presence of CHRNA7 gene products, dupα7 can assemble and form heteromeric receptors that, in order to be functional, should include at least two α7 subunits to form the agonist binding site. When incorporated into the receptor, in vitro and in vivo data showed that dupα7 negatively modulated α7 activity, probably due to a reduction in the number of ACh binding sites. Very recent data in the literature report that the presence of the duplicated gene may be responsible for the translational gap in several human diseases. Here, we will review the studies that have been conducted on CHRFAM7A in different pathologies, with the intent of providing evidence regarding when and how the expression of this duplicated gene may be beneficial or detrimental in the pathogenesis, and eventually in the therapeutic response, to CHRNA7-related neurological and non-neurological diseases.

The human-specific duplicated α7 gene inhibits the ancestral α7, negatively regulating nicotinic acetylcholine receptor-mediated transmitter release

Gene duplication generates new functions and traits, enabling evolution. Human-specific duplicated genes in particular are primary sources of innovation during our evolution although they have very few known functions. Here we examine the brain function of one of these genes (CHRFAM7A) and its product (dupα7 subunit). This gene results from a partial duplication of the ancestral CHRNA7 gene encoding the α7 subunit that forms the homopentameric α7 nicotinic acetylcholine receptor (α7-nAChR). The functions of α7-nAChR in the brain are well defined, including the modulation of synaptic transmission and plasticity underlying normal attention, cognition, learning, and memory processes. However, the role of the dupα7 subunit remains unexplored at the neuronal level. Here, we characterize that role by combining immunoblotting, quantitative RT-PCR and FRET techniques with functional assays of α7-nAChR activity using human neuroblastoma SH-SY5Y cell variants with different dupα7 expression levels. Our findings reveal a physical interaction between dupα7 and α7 subunits in fluorescent protein-tagged dupα7/α7 transfected cells that negatively affects normal α7-nAChR activity. Specifically, in both single cells and cell populations, the [Ca²⁺]_i signal and the exocytotic response induced by selective stimulation of α7-nAChR were either significantly inhibited by stable dupα7 overexpression or augmented after silencing dupα7 gene expression with specific siRNAs. These findings identify a new role for the dupα7 subunit as a negative regulator of α7-nAChR-mediated control of exocytotic neurotransmitter release. If this effect is excessive, it would result in an impaired synaptic transmission that could underlie the neurocognitive and neuropsychiatric disorders associated with α7-nAChR dysfunction.

Cardioprotective role of GTS-21 by attenuating the TLR4/NF-κB pathway in streptozotocin-induced diabetic cardiomyopathy in rats

The cholinergic anti-inflammatory pathway (CAP) was investigated in a variety of inflammatory conditions and constitutes a valuable line in their treatment. In the current study, we investigated the anti-inflammatory effect of GTS-21 (GTS) as a partial selective α7 nicotinic acetylcholine receptor (α7-nAchR) agonist in diabetic cardiomyopathy model in rats. This mechanism was elaborated to study whether it could alleviate the electrocardiographic, histopathological, and molecular levels of Toll-like receptor 4 (TLR4)/nuclear factor κB (NF-κB) pathway proteins. Diabetes was induced by the injection of streptozotocin (STZ) (50 mg/kg). Diabetic rats were treated with GTS (1 or 2 mg/kg/day), methyllycaconitine (MLA), a selective α7-nAchR antagonist (2 mg/kg/day) plus GTS (2 mg/kg/day), or the vehicle. All treatments were given by the intraperitoneal route. Ventricular rate and different electrocardiograph (ECG) anomalies were detected. Plasma levels of cardiac troponin T (cTnT) and creatine kinase MB (CK-MB) were measured by ELISA. Additionally, we elucidated the levels of several proteins involved in the TLR4/NF-κB pathway. Cardiac levels of TLR4 and phosphorylated protein kinase B (p-Akt) were detected by ELISA. The cardiac expression of myeloid differentiation primary response 88 (Myd88), tumor necrosis factor receptor-associated factor 6 (TRAF6), NF-κB, interleukin 1β (IL-1β), and active caspase-1 were evaluated by immunohistochemical staining. Finally, the cardiac levels of interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α) were determined by ELISA. Diabetic rats showed (i) ECG signs of cardiomyopathy such as significant ST segment elevations, prolonged QRS, QT intervals, and ventricular tachycardia; (ii) increased plasma levels of cTnT and CK-MB; (iii) increased expression of cardiac TLR4; (iv) elevated immunohistochemical expression of cardiac, Myd88, TRAF6, and NF-κB; (v) diminution in the cardiac expression of p-Akt; and (vi) adaptive increases in cardiac expression of TNF-α and IL-6. These effects were ameliorated in diabetic rats treated with both doses of GTS. Pretreatment with MLA did not completely reverse the ameliorative effect of GTS on cTnT, TRAF6, TNF-α, and IL-6, thereby reinforcing the presence of possible α7-nAchR-independent mechanisms. The activation of α7-nAchR with GTS offers a promising prophylactic strategy for diabetic cardiomyopathy by attenuating the TLR4/NF-κB pathway.

Ion Channels in Lung Cancer

Ion channels are a major class of membrane proteins that play central roles in signaling within and among cells, as well as in the coupling of extracellular events with cellular responses. Dysregulated ion channel activity plays a causative role in many diseases including cancer. Here, we will review their role in lung cancer. Lung cancer is one of the most frequently diagnosed cancers, and it causes the highest number of deaths of all cancer types. The overall 5-year survival rate of lung cancer patients is only 19% and decreases to 5% when patients are diagnosed with stage IV. Thus, new therapeutical strategies are urgently needed. The important contribution of ion channels to the progression of various types of cancer has been firmly established so that ion channel-based therapeutic concepts are currently developed. Thus far, the knowledge on ion channel function in lung cancer is still relatively limited. However, the published studies clearly show the impact of ion channel inhibitors on a number of cellular mechanisms underlying lung cancer cell aggressiveness such as proliferation, migration, invasion, cell cycle progression, or adhesion. Additionally, in vivo experiments reveal that ion channel inhibitors diminish tumor growth in mice. Furthermore, some studies give evidence that ion channel inhibitors can have an influence on the resistance or sensitivity of lung cancer cells to common chemotherapeutics such as paclitaxel or cisplatin.

The impact of smoking and the influence of other factors on lung cancer

Introduction: Smoking is the main preventable cause of lung cancer. This review summarizes preclinical and clinical data on the mechanisms of smoking-associated cancer development of the major histological lung cancer types small cell lung carcinoma squamous cell carcinoma and pulmonary adenocarcinoma (PAC) and the impact of several factors other than smoking on this process. Areas covered: The role of intracellular signaling induced by nicotinic receptors and beta-adrenergic receptors, the resulting increase in intracellular cyclic adenosine monophosphate (cAMP) as a key driver of PAC and the promoting effects of respiratory tract diseases and their therapeutics, psychological stress and global warming. Expert opinion: Smoking has deleterious effects on the regulation of lung epithelia by neurotransmitter receptors that are further enhanced by gene mutations. Sensitization of the alpha-7 nicotinic receptor (α7nAChR) by COPD enhances the carcinogenic effects of smoking and turns nicotine into a carcinogen. Nicotine vaping may, therefore, cause cancer in individuals with chronic obstructive pulmonary disease. The opposing effects of cAMP on the major lung cancer types indicate that patients with PAC of Clara cell phenotype (PAC-Cl) will benefit from treatment with cAMP reducers and suggest that global warming-induced respiratory tract diseases and their therapeutics cause the global increase in the incidence of PAC.