Regulation of tumor progression via the Snail-RKIP signaling pathway by nicotine exposure in head and neck squamous cell carcinoma

Expression, correlation, and prognostic significance of different nicotinic acetylcholine receptors, programed death ligand 1, and dopamine receptor D2 in lung adenocarcinoma

Objective

The objective of this study is to evaluate the expression of different nicotinic acetylcholine receptors (nAChRs), programmed death ligand-1 (PD-L1), and dopamine receptor D2 (DRD2) as prognostic factors in lung cancer and any correlation among them. Since all of the above genes are typically upregulated in response to smoking, we hypothesized that a correlation might exist between DRD2, PD-L1, and nAChR expression in NSCLC patients with a smoking history and a prediction model may be developed to assess the clinical outcome.

Methods

We retrospectively analyzed samples from 46 patients with primary lung adenocarcinoma who underwent surgical resection at Mayo Clinic Rochester from June 2000 to October 2008. The expression of PD-L1, DRD2, CHRNA5, CHRNA7, and CHRNA9 were analyzed by quantitative PCR and correlated amongst themselves and with age, stage and grade, smoking status, overall survival (OS), and relapse-free survival (RFS).

Results

Only PD-L1 showed a statistically significant increase in expression in patients older than 65. All the above genes showed higher expression in stage IIIB than IIIA, but none reached statistical significance. Interestingly, we did not observe significant differences among never, former, and current smokers, but patients with pack years greater than 30 showed significantly higher expression of CHRNA9. We observed a strong positive correlation between PD-L1/DRD2, PD-L1/CHRNA5, and CHRNA5/CHRNA7 and a weak positive correlation between DRD2/CHRNA5 and DRD2/CHRNA7. Older age was independently associated with poor OS, whereas lower CHRNA7 expression was independently associated with better OS.

Conclusions

We observed strong positive correlations among PD-L1, DRD2, and some of the nAChRs. We investigated their prognostic significance in lung cancer patients and found CHRNA7 to be an independent prognostic factor. Overall, the results obtained from this preliminary study warrant a large cohort-based analysis that may ultimately lead to potential patient-specific stratification biomarkers predicting cancer-treatment outcomes.

Elevated LSD1 and SNAIL Expression Indicate Poor Prognosis in Hypopharynx Carcinoma

Head and neck squamous cell carcinomas (HNSCC) are among the most common cancers worldwide and are associated with a poor prognosis for patients. Among HNSCC, those originating in the hypopharynx have the worst prognosis. The histone demethylase LSD1 has been shown to promote cancer initiation, progression, and relapse through various mechanisms and is upregulated in many cancer tissues. LSD1 physically interacts with SNAIL and is required for SNAIL mediated transcriptional repression. Previous studies of the prognostic value of LSD1 in HNSCC have been limited in their analysis of sub-sites, and a correlation between LSD1 and SNAIL has not been shown in HNSCC patient samples. Here we used a large, representative, and clinically well-characterized cohort of 339 HNSCC patients to investigate the co-expression of LSD1 and SNAIL and their prognostic value in all HNSCC using immunohistochemical staining. Elevated LSD1 expression correlated with advanced tumor stage and poor progression-free survival (PFS) in HNSCC originating in the hypopharynx. Overexpression of the transcription factor SNAIL independently correlated with worse overall survival (OS) and PFS in HNSCC in general and prominently in tumors of the hypopharynx. Furthermore, increased LSD1 expression significantly correlated with elevated SNAIL expression in patient samples. Therefore, the presented data implicates LSD1 and SNAIL as independent prognostic biomarkers.

Snail/HDAC1/2 mediate skeletal growth retardation in fetuses caused by prenatal nicotine exposure

Previous findings have confirmed that prenatal nicotine exposure (PNE) leads to retarded cartilage development in the fetal growth plate. It is characterized by insufficient matrix synthesis and decreased expression of matrix phenotype genes aggrecan (ACAN) and Col2A1 in the fetal growth plate chondrocytes; however, the specific molecular mechanism is yet unclear. This study intends to clarify the specific molecular mechanism of fetal osteochondral retardation caused by PNE through animal and cellular experiments. The present study demonstrated that in male offspring of the PNE group (the pregnant rats were subcutaneously administered nicotine 1.0 mg/kg twice per day (2.0 mg/kg.d) at GD11-20), the cartilage matrix of the fetal growth plate was lightly stained, the collagen was reduced, and expression of the matrix phenotype genes, ACAN and Col2A1, was significantly decreased. It was further found that PNE decreased histone acetylation (H3K9/H3K14) levels in the ACAN and Col2A1 promoter regions. Moreover, the expression of Snail and HDAC1/2 was increased in the PNE group. in vitro, the nicotine treatment at different concentrations elevated the expression of Snail/HDAC1/2 while decreasing the H3K9/H3K14 levels in the ACAN and Col2A1 promoter regions. Snail-siRNA transfection partially abolished the nicotine-induced increase in HDAC1/2 expression and decreased the histone acetylation levels in the ACAN and Col2A1 promoter regions. Trichostatin A (TSA) treatment partially reversed the nicotine-induced changes in downstream parameters. In summary, PNE-induced decreased cartilage matrix synthesis in the fetal growth plate of male offspring is effectuated by Snail/HDAC1/2-mediated decreased H3K9/H3K14 levels in the ACAN and Col2A1 promoter regions.

α-Conotoxins and α-Cobratoxin Promote, while Lipoxygenase and Cyclooxygenase Inhibitors Suppress the Proliferation of Glioma C6 Cells

Among the brain tumors, glioma is the most common. In general, different biochemical mechanisms, involving nicotinic acetylcholine receptors (nAChRs) and the arachidonic acid cascade are involved in oncogenesis. Although the engagement of the latter in survival and proliferation of rat C6 glioma has been shown, there are practically no data about the presence and the role of nAChRs in C6 cells. In this work we studied the effects of nAChR antagonists, marine snail α-conotoxins and snake α-cobratoxin, on the survival and proliferation of C6 glioma cells. The effects of the lipoxygenase and cyclooxygenase inhibitors either alone or together with α-conotoxins and α-cobratoxin were studied in parallel. It was found that α-conotoxins and α-cobratoxin promoted the proliferation of C6 glioma cells, while nicotine had practically no effect at concentrations below 1 µL/mL. Nordihydroguaiaretic acid, a nonspecific lipoxygenase inhibitor, and baicalein, a 12-lipoxygenase inhibitor, exerted antiproliferative and cytotoxic effects on C6 cells. nAChR inhibitors weaken this effect after 24 h cultivation but produced no effects at longer times. Quantitative real-time polymerase chain reaction showed that mRNA for α4, α7, β2 and β4 subunits of nAChR were expressed in C6 glioma cells. This is the first indication for involvement of nAChRs in mechanisms of glioma cell proliferation.

Effects of Genetic Polymorphisms of Drug Transporter ABCB1 (MDR1) and Cytochrome P450 Enzymes CYP2A6, CYP2B6 on Nicotine Addiction and Smoking Cessation

Objectives

To determine the effects of genetic polymorphisms of ABCB1 (MDR1), CYP2A6, CYP2B6 on smoking status, and clinical outcomes of smoking cessation therapies in a Turkish population.

Methods

130 smokers and 130 non-smokers were recruited. Individuals who never smoked were described as non-smokers. 130 smokers were treated with nicotine replacement therapy (NRT) (n = 40), bupropion (n = 47), bupropion + NRT (n = 15), and varenicline (n = 28). Smokers were checked by phone after 12 weeks of treatment whether they were able to quit smoking or not. Genotyping and phenotyping were performed.

Results

Cessation rates were as follows; 20.0% for NRT, 29.8% for bupropion, 40.0% for bupropion + NRT, 57.1% for varenicline (p = 0.013). The frequency of ABCB1 1236TT-2677TT-3435TT haplotype was significantly higher in non-smokers as compared to smokers (21.5% vs. 10.8, respectively; p = 0.018). Neither smoking status nor smoking cessation rates were associated with genetic variants of CYP2A6 (p = 0.652, p = 0.328, respectively), or variants of CYP2B6 (p = 0.514, p = 0.779, respectively).

Conclusion

Genetic variants of the drug transporter ABCB1 and the 1236TT-2677TT-3435TT haplotype was significantly associated with non-smoking status. Neither ABCB1 nor CYP2A6, CYP2B6 genetic variants were associated with smoking cessation rates at the 12th week of drug treatment.

An Integrated Genomic Strategy to Identify CHRNB4 as a Diagnostic/Prognostic Biomarker for Targeted Therapy in Head and Neck Cancer

Although many studies have shown the association between smoking and the increased incidence and adverse prognosis of head and neck squamous cell carcinoma (HNSCC), the mechanisms and pharmaceutical targets involved remain unclear. Here, we integrated gene expression signatures, genetic alterations, and survival analyses to identify prognostic indicators and therapeutic targets for smoking HNSCC patients, and we discovered that the FDA-approved drug varenicline inhibits the target for cancer cell migration/invasion. We first identified 18 smoking-related and prognostic genes for HNSCC by using RNA-Seq and clinical follow-up data. One of these genes, CHRNB4 (neuronal acetylcholine receptor subunit beta-4), increased the risk of death by approximately threefold in CHRNB4-high expression smokers compared to CHRNB4-low expression smokers (log rank, p = 0.00042; hazard ratio, 2.82; 95% CI, 1.55–5.14), former smokers, and non-smokers. Furthermore, we examined the functional enrichment of co-regulated genes of CHRNB4 and its 246 frequently occurring copy number alterations (CNAs). We found that these genes were involved in promoting angiogenesis, resisting cell death, and sustaining proliferation, and contributed to much worse outcomes for CHRNB4-high patients. Finally, we performed CHRNB4 gene editing and drug inhibition assays, and the results validate these observations. In summary, our study suggests that CHRNB4 is a prognostic indicator for smoking HNSCC patients and provides a potential new therapeutic drug to prevent recurrence or distant metastasis.

Ion Channel Dysregulation in Head and Neck Cancers: Perspectives for Clinical Application

Head and neck cancers are a highly complex and heterogeneous group of malignancies that involve very diverse anatomical structures and distinct aetiological factors, treatments and clinical outcomes. Among them, head and neck squamous cell carcinomas (HNSCC) are predominant and the sixth most common cancer worldwide with still low survival rates. Omic technologies have unravelled the intricacies of tumour biology, harbouring a large diversity of genetic and molecular changes to drive the carcinogenesis process. Nonetheless, this remarkable heterogeneity of molecular alterations opens up an immense opportunity to discover novel biomarkers and develop molecular-targeted therapies. Increasing evidence demonstrates that dysregulation of ion channel expression and/or function is frequently and commonly observed in a variety of cancers from different origin. As a consequence, the concept of ion channels as potential membrane therapeutic targets and/or biomarkers for cancer diagnosis and prognosis has attracted growing attention. This chapter intends to comprehensively and critically review the current state-of-art ion channel dysregulation specifically focusing on head and neck cancers and to formulate the major challenges and research needs to translate this knowledge into clinical application. Based on current reported data, various voltage-gated potassium (K_v) channels (i.e. K_v3.4, K_v10.1 and K_v11.1) have been found frequently aberrantly expressed in HNSCC as well as precancerous lesions and are highlighted as clinically and biologically relevant features in both early stages of tumourigenesis and late stages of disease progression. More importantly, they also emerge as promising candidates as cancer risk markers, tumour markers and potential anti-proliferative and anti-metastatic targets for therapeutic interventions; however, the oncogenic properties seem to be independent of their ion-conducting function.

miR-181a Upregulation Promotes Radioresistance of Nasopharyngeal Carcinoma by Targeting RKIP

Background

Radioresistance is the leading cause of treatment failure for nasopharyngeal carcinoma (NPC). Therefore, screening the critical regulators in radioresistance and revealing the underlying mechanisms is imperative for improvement of therapeutical efficacy in NPC.

Materials and methods

Our previous study has proved that miR-181a may serve as a pro-radioresistant miRNA. In this study, we explored the expression of miR-181a in NPC, especially in radioresistant NPC samples, by qPCR. Moreover, the clinical significance of miR-181a level was also analyzed. Furthermore, the functions of miR-181a, both in vitro and in vivo, were detected via a serial of assays such as CCK-8, plate clone survival, apoptosis, and xenograft tumor model. The downstream target of miR-181a was also validated by dual luciferase reporter assay and the roles of miR-181a’s target in the regulation of NPC radioresistance were investigated.

Results

The results revealed that miR-181a was significantly upregulated in NPC, especially in radioresistant NPC. MiR-181a level is positively correlated to lymph node metastasis and advanced TNM stages and negatively associated with overall survival rate in NPC. Ectopic expression of miR-181a in radiosensitive NPC cells, or overexpression of miR-181a inhibitor in radioresistant NPC cells, could enhance or impair the radioresistance of NPC cells supported by the results from both in vitro and in vivo, respectively. Mechanistically, dual luciferase report assay indicated that miR-181a could directly target RKIP. Moreover, both in vitro and in vivo experimental outcomes indicated that RKIP restoration and knockdown could antagonize the effects of miR-181a and miR-181a inhibitor in the regulation of NPC radioresistance.

Conclusion

Collectively, the findings of this study proved that miR-181a is upregulated and promotes radioresistance by targeting RKIP in NPC. Targeting miR-181a/RKIP axis may be a valid path for reinforcing radiosensitivity and eventually improving the outcomes of clinical treatment in NPC.

Involvement of twist in NNK exposure-promoted lung cancer cell migration and invasion

Nicotine-derived nitrosamine ketone (NNK), one of the potent carcinogens in cigarette smoke, has been reported to facilitate lung cancer cell migration and invasion. Twist plays an important role in regulating migration and invasion of lung cancer cells. However, it is unclear whether Twist is implicated in NNK-induced migration and invasion of lung cancer cells. Lung cancer cells were exposed to various doses of NNK for four weeks. The expression levels of protein and mRNA were detected by western blot and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. Small interfering RNA (siRNA) was applied to knock down the expression of Twist. The ability of cell migration and invasion was evaluated by wound-healing assay and Transwell invasion assay. NNK exposure increased the levels of Twist protein and mRNA expression in lung cancer cells compared to solvent control. Lung cancer cells exposed to NNK exhibited higher ability of migration and invasion than those with solvent control did. Twist silencing could block NNK-promoted migration and invasion of lung cancer cells. NNK exposure increased the expression levels of N-cadherin mRNA and decreased the expression levels of E-cadherin mRNA in lung cancer cells, which could be modulated by Twist silencing. In conclusion, Twist was involved in NNK-induced migration and invasion of lung cancer cells.

Cervical Cancer Correlates with the Differential Expression of Nicotinic Acetylcholine Receptors and Reveals Therapeutic Targets

Nicotinic acetylcholine receptors (nAChRs) are associated with various cancers, but the relation between nAChRs and cervical cancer remains unclear. Therefore, this study investigated the differential expression of nAChR subunits in human cervical cancer cell lines (SiHa, HeLa, and CaSki) and in normal ectocervical cell lines (Ect1/E6E7) at mRNA and protein levels. Two specific nAChR subtype blockers, αO-conotoxin GeXIVA and α-conotoxin TxID, were then selected to treat different human cervical cancer cell lines with specific nAChR subtype overexpression. The results showed that α3, α9, α10, and β4 nAChR subunits were overexpressed in SiHa cells compared with that in normal cells. α9 and α10 nAChR subunits were overexpressed in CaSki cells. α*-conotoxins that targeted either α9α10 or α3β4 nAChR were able to significantly inhibit cervical cancer cell proliferation. These findings may provide a basis for new targets for cervical cancer targeted therapy.

Exposure to nicotine-derived nitrosamine ketone and arecoline synergistically facilitates tumor aggressiveness via overexpression of epidermal growth factor receptor and its downstream signaling in head and neck squamous cell carcinoma

Long-term nicotine-derived nitrosamine ketone (NNK) and arecoline exposure promotes carcinogenesis and head and neck squamous cell carcinoma (HNSCC) progression, although most associated data on the two were analyzed individually. The molecular mechanisms underlying tumor progression associated with the synergistic effects of NNK and arecoline remain unclear. We treated SCC-25 and FaDu cells with NNK and arecoline (separately or in combination) for 3 months. Comparative analysis was performed to investigate the mechanism underlying the acquisition of properties related to tumor promotion, including stemness, anti-apoptosis, and resistance to HNSCC therapeutics. Long-term exposure to NNK and arecoline resulted in an increase in cancer stem cell properties, anti-apoptosis, and the resistance to cisplatin in HNSCC. We detected abundant epidermal growth factor receptor (EGFR) expression in HNSCC cells after combined treatment with NNK and arecoline. EGFR was pivotal in inducing tumor promotion and anti-apoptosis in cancer cells by inducing pAKT and NFκB. Combined treatment with NNK and arecoline synergistically facilitated tumor aggressiveness via EGFR–AKT signaling. Targeting EGFR–AKT signaling may be a feasible strategy for treating HNSCC.

Increased chemoresistance via Snail-Raf kinase inhibitor protein signaling in colorectal cancer in response to a nicotine derivative

A tobacco-specific component, 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK), is a major risk factor for many cancers. Recent reports have demonstrated that NNK exposure may be associated with tumor progression and chemoresistance in certain cancers. However, the underlying NNK-induced mechanism contributing to the aggressiveness of colorectal cancer (CRC) has not been thoroughly studied. In this study, we used HT29 cells treated with NNK to simulate the long-term exposure of cigarette smoke. A comparative analysis was performed to evaluate cell proliferation, migration, and invasion as well as epithelial-mesenchymal transition (EMT) markers and drug-resistance genes expression, cancer stem cell (CSC) properties, and anti-apoptotic activity. Signaling pathways related to chemoresistance were also investigated. As a result, NNK exposure dose-dependently stimulates cell proliferation, enhance abilities of migration and invasion, induce EMT phenomenon, and attenuate apoptosis. Furthermore, NNK exposure also promotes the capabilities of sphere formation, upregulation of Snail, and overexpression of CD133, Nanog, OCT4, and the drug-resistant genes. Knockdown of Snail results in upregulation of Raf kinase inhibitor protein (RKIP), increased apoptosis, reversal of EMT phenomenon, and reducation of expression of CSC markers, all of which contribute to a decrease of chemoresistance. Our study demonstrates a number of related mechanisms that mediate the effect of NNK exposure on increasing CRC therapeutic resistance via the Snail signaling pathway. Targeting Snail may provide a feasible strategy for the treatment of CRC.

Regulation of drug resistance and metastasis of gastric cancer cells via the microRNA647-ANK2 axis

Due to a lack of effective methods for early diagnosis, the majority of patients with gastric cancer (GC) are diagnosed during the late stages of the disease, which are often accompanied by metastasis. For these patients, despite being considered an important therapeutic modality in the treatment of cancer, chemotherapy is usually not effective due to multidrug resistance (MDR). The expression levels of MDR/metastasis-associated genes are regulated by numerous microRNAs (miRNAs/miRs). The expression of miR-647 in GC tissues and SGC7901/VCR cell line (drug resistance to vincristine) was detected by qRT-PCR. The effect of overexpression of miR-647 on drug resistance was evaluated by measuring the half maximal inhibitory concentration (IC₅₀) value of SGC-7901/VCR to vincristine and tumor growth in vivo. Moreover, drug-induced cell apoptosis and cell cycle were evaluated by flow cytometry, as well as the ability of cell migration and invasiveness detected by wound healing and transwell assay. Furthermore, underlying targets of miR-647 were predicted by TargetScan and MicroRNA; meanwhile, the expression of ANK2, FAK, MMP2, MMP12,CD44,SNAIL1 were observed by qRT-PCR and western blot analysis. The present study established that the expression levels of miR-647 were downregulated in GC tissues from patients with metastasis and in the vincristine-resistant SGC7901 (SGC-7901/VCR) GC cell line. The IC₅₀ value for vincristine was significantly decreased, whereas the proportion of cells in G₀/G₁ phase and the drug-induced apoptotic rate were significantly increased following upregulation of miR-647. Furthermore, the results demonstrated that miR-647 overexpression led to decreased migration and invasion of SGC-7901/VCR cells. Overexpression of miR-647 was also demonstrated to sensitize tumors to chemotherapy in vivo. In addition, miR-647 overexpression was able to reduce the expression levels of ankyrin-B, focal adhesion kinase, matrix metalloproteinase (MMP)2, MMP12, cluster of differentiation 44 and snail family transcriptional repressor 1. In conclusion, these findings demonstrated that miR-647 may function as a novel target to ameliorate drug resistance and metastasis of GC cells.

Peroxiredoxin 1 promotes invasion and migration by regulating epithelial-to-mesenchymal transition during oral carcinogenesis

Tobacco smoking is the major risk factor for oral squamous cell carcinoma (OSCC). Previously, we found that nicotine up-regulates peroxiredoxin 1 (Prx1), an important antioxidant enzyme, and nuclear factor kappa B (NFκB) in OSCC cells. However, the molecular mechanism of Prx1 in oral carcinogenesis remains obscure. To improve our understanding of the functional role of Prx1 during the cascade of tobacco-associated oral carcinogenesis, we characterized Prx1, NFκB, and epithelial-to-mesenchymal transition (EMT) markers including E-cadherin, vimentin and Snail in 30 primary oral tumors (15 from smokers with OSCC and 15 from non-smokers with OSCC) and 10 normal oral mucosa specimens from healthy individuals. The expression levels of Prx1, nuclear NFκB, vimentin and Snail were higher in the tumors from smokers with OSCC than in those from non-smokers with OSCC or the healthy controls. The expression levels of E-cadherin showed an opposite trend. Prx1 silencing suppressed the nicotine-induced EMT, cell invasion and migration in SCC15 cells in vitro. Furthermore, Prx1 activated the NFκB pathway in SCC15 cells. Prx1 might therefore play an oncogenic role in tobacco-related OSCC and thus serve as a target for chemopreventive and therapeutic interventions.

Augmenter of liver regeneration potentiates doxorubicin anticancer efficacy by reducing the expression of ABCB1 and ABCG2 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is highly chemoresistant and therefore challenges both physicians and patients. Augmenter of liver regeneration (ALR), previously also known as 'hepatic stimulator substance', is reported to inhibit the epithelial-mesenchymal transition (EMT) in HCC, one of the frequent events that occur in cancer metastasis, suggesting that ALR is involved in HCC. In this study, we report for the first time that the transfection of ALR enhances the antitumor effect of chemotherapy with doxorubicin, a typical anticancer drug, on HCC in vitro and in vivo. The efflux of doxorubicin from ALR-transfected HCC cells is efficiently suppressed. This implies the intracellular retention of doxorubicin in tumor cells, which is at least partly attributable to the effective inhibition of ABCB1 and ABCG2 transporter expression in ALR-expressing cells. The downregulation of ALR expression by short hairpin RNA diminishes the antitumor effect of ALR. We further demonstrate that ALR inhibits the AKT/Snail signaling pathway, resulting in the downregulation of ABCB1 and ABCG2 expression. In conclusion, our results suggest that ALR is a potential chemotherapeutic agent against HCC.

α7 nicotinic acetylcholine receptor in tumor-associated macrophages inhibits colorectal cancer metastasis through the JAK2/STAT3 signaling pathway

Considerable evidence has implied that α7 nicotinic receptor subtypes play an important role in chronic inflammatory and neuropathic pain signaling. The aim of the present study was to determine the role of endogenous α7nAChR signaling in tumor-associated macrophages (TAMs) in human colorectal cancer (CRC) metastasis and prognosis. α7nAChR expression in primary tumor cells and adjacent stroma cells especially in TAMs in 51 CRC patients was observed. Using a human monocyte THP-derived macrophages (TMs) with α7nAChR-siRNA knockdown (TMα7-/-) and a CRC cell Transwell co-culture model, the migration and invasion of two CRC cells, LoVo and SW620, were determined. Western blotting was carried out to investigate the expression of multiple molecules involved in the NF-κB, STAT3, PI3K signaling pathways in mimic TAMs, i.e., TMs exposed to in-direct LoVo cell stimulation. A nicotinic α7 receptor antagonist [α-bungarotoxin (α-Btx)] and three pharmaceutical inhibitors: AG490 (JAK2/STAT3 inhibitor), LY294002 (PI3K inhibitor) and Bay 11-7082 (NF-κB inhibitor) were applied to evaluate whether these signaling pathways were associated with the enhanced migration of CRC cells when co-cultured with α7nAChR knockdown TMs. The results revealed that the expression of α7nAChR in TAMs differed in patients. However, CRC patients who had a high incidence of hepatic metastasis showed no or low expression of α7nAChR in TAMs. TMs with α7nAChR-siRNA knockdown (TMα7-/-) significantly enhanced the migration and invasion of the two CRC cell lines LoVo and SW620. α7nAChR knockdown in TMs significantly downregulated phosphorylation of STAT3, PI3K p85 and NF-κB p65 after co-culturing with LoVo cells. Inhibition of JAK2/STAT3 prevented the TMα7-/--enhanced migration of LoVo cells. α7nAChR expressed in TAMs in human CRC patients plays an important role in preventing metastasis and could be a prognostic marker in CRCs, which may be regulated by the JAK2/STAT3 signaling pathway.

Nicotine suppresses apoptosis by regulating α7nAChR/Prx1 axis in oral precancerous lesions

Nicotine, a tumor promoter in tobacco, can increase Peroxiredoxin (Prx1) and nicotinic acetylcholine receptors (nAChRs) in oral squamous cell carcinoma (OSCC). In the present study, we investigate the effects of nicotine in oral precancerous lesions focusing on apoptosis and nAChR/Prx1 signaling. We detected expression of Prx1, α3nAChR, α7nAChR, phosphorylation of mitogen-activated protein kinases (MAPK) and apoptosis in dysplastic oral keratinocyte (DOK) cells as well as in 4-nitroquinoline 1-oxide (4NQO) or 4NQO + nicotine – induced oral precancerous lesions in Prx1 wild-type (Prx1^+/+) and Prx1 knockdown (Prx1^+/-) mice. In DOK cells, Prx1 knockdown and blocking α7nAChR activated apoptosis, and nicotine increased the expression of Prx1, α3nAChR and α7nAChR, and inhibited MAPK activation. Moreover, nicotine suppressed apoptosis depending on Prx1 and α7nAChR in DOK cells. In animal bioassay, nicotine and Prx1 promoted growth of 4NQO-induced precancerous lesions in mouse tongue. 4NQO plus nicotine suppressed MAPK activation in Prx1 wild-type mice but not in Prx1 knockdown mice. Our data demonstrate that nicotine inhibits cell apoptosis and promotes the growth of oral precancerous lesions via regulating α7nAChR/Prx1 during carcinogenesis of OSCC.

Alpha5 Nicotinic Acetylcholine Receptor Contributes to Nicotine-Induced Lung Cancer Development and Progression

Nicotine and nicotinic acetylcholine receptors (nAChRs) are considered to be involved in lung cancer risk, onset and progression, but their precise physiological roles in these contexts remain unclear. Our previous studies suggested that α5-nAChR mediates nicotine-induced lung cancer cell proliferation, migration, and invasion in vitro. In this study, we aimed to determine the role of α5-nAChR in the development and progression of non-small cell lung cancer (NSCLC). Our microarray results reveal that knockdown of the CHRNA5 gene encoding α5-nAChR significantly modulates key pathways including the cell cycle, DNA replication, pathway in cancer. α5-nAChR knockdown in cultured A549 cells affected cell cycle distribution, apoptosis, and cyclin expression. In vivo, α5-nAChR silencing inhibited the growth of lung tumors, especially in the context of nicotine exposure. Importantly, α5-nAChR expression in patient tumors correlated with the primary T stage, N stage, and reduced survival time. These results reveal that α5-nAChR silencing inhibits the progression of nicotine-related NSCLC, making this receptor a potential pharmacological target for the treatment of nicotine-related lung carcinogenesis.

Notch signaling plays a crucial role in cancer stem-like cells maintaining stemness and mediating chemotaxis in renal cell carcinoma

Background

Cancer stem cells (CSCs) are correlated with the initiation, chemoresistance and relapse of tumors. Notch pathway has been reported to function in CSCs maintenance, but whether it is involved in renal cell carcinoma (RCC) CSCs maintaining stemness remain unclear. This study aims to explore the effect of Notch pathway on stemness of CSCs in RCC and the underlying mechanisms.

Methods

The CD133⁺/CD24⁺ cells were isolated from RCC ACHN and Caki-1 cell line using Magnetic-activated cell sorting and identified by Flow cytometry analysis. RT-PCR and immunoblot analyses were used for determining the stemness maker expression. The effect of Notch pathway on function of CSCs was assessed by self-renewal ability, chemosensitivity, invasive and migratory ability tumorigenicity in vivo using soft agar colony formation assay, sphere-forming assay, MTT assay, Transwell assay.

Results

Here, we found that the sorted CD133⁺/CD24⁺cells possessed elevated stemness maker CTR2, BCL-2, MDR1, OCT-4, KLF4, compared with parental cells, as well as enhanced self-renewal ability, stronger resistance to cisplatin and sorafenib, increased invasion and migration, and higher tumorigenesis in vivo, suggesting the CD133⁺/CD24⁺ cells have the stem-like characteristics of CSCs and thus identified as RCC CSCs. Then the enhanced notch1, notch2, Jagged1, Jagged2, DLL1 and DLL4 expression were detected in RCC CSCs and blockage of Notch1 or notch2 using pharmacological inhibitor MRK-003 or its endogenous inhibitor Numb resulted in loss of its stemness features: self-renewal, chemoresistance, invasive and migratory potential, and tumorigenesis in vivo. Moreover, it is confirmed that overexpression of notch1 up-regulated CXCR4 inRCC CSCs and augmented SDF-1-induced chemotaxis in RCC CSCs in vitro, which could be rescued when treatment of CXCR4 inhibitor, suggesting that notch signaling promotes the chemotaxis of RCC CSCs by SDF-1/CXCR4 axis.

Conclusions

Our results provide a new mechanism of RCC CSCs maintaining stemness via notch pathway as well as a potential therapeutic target in human RCC.

Nicotine-Mediated Regulation of Nicotinic Acetylcholine Receptors in Non-Small Cell Lung Adenocarcinoma by E2F1 and STAT1 Transcription Factors

Cigarette smoking is the major risk factor for non-small cell lung cancer (NSCLC), which accounts for 80% of all lung cancers. Nicotine, the addictive component of tobacco smoke, can induce proliferation, migration, invasion, epithelial-mesenchymal transition (EMT), angiogenesis, and survival in NSCLC cell lines, as well as growth and metastasis of NSCLC in mice. This nicotine-mediated tumor progression is facilitated through activation of nicotinic acetylcholine receptors (nAChRs), specifically the α7 subunit; however, how the α7 nAChR gene is regulated in lung adenocarcinoma is not fully clear. Here we demonstrate that the α7 nAChR gene promoter is differentially regulated by E2F and STAT transcription factors through a competitive interplay; E2F1 induces the promoter, while STAT transcription factors repress it by binding to an overlapping site at a region -294 through -463bp upstream of the transcription start site. Treatment of cells with nicotine induced the mRNA and protein levels of α7 nAChR; this could be abrogated by treatment with inhibitors targeting Src, PI3K, MEK, α7 nAChR, CDK4/6 or a disruptor of the Rb-Raf-1 interaction. Further, nicotine–mediated induction of α7 nAChR was reduced when E2F1 was depleted and in contrast elevated when STAT1 was depleted by siRNAs. Interestingly, extracts from e-cigarettes, which have recently emerged as healthier alternatives to traditional cigarette smoking, can also induce α7 nAChR expression in a manner similar to nicotine. These results suggest an autoregulatory feed-forward loop that induces the levels of α7 nAChR upon exposure to nicotine, which enhances the strength of the signal. It can be imagined that such an induction of α7 nAChR contributes to the tumor-promoting functions of nicotine.