Nicotine promotes acquisition of stem cell and epithelial-to-mesenchymal properties in head and neck squamous cell carcinoma

Cell signaling and epigenetic regulation of nicotine-induced carcinogenesis

Nicotine, a naturally occurring tobacco alkaloid responsible for tobacco addiction, has long been considered non-carcinogenic. However, emerging evidence suggests that nicotine may possess carcinogenic properties in mice and could be a potential carcinogen in humans. This review aims to summarize the potential molecular mechanisms underlying nicotine-induced carcinogenesis, with a specific focus on epigenetic regulation and the activation of nicotinic acetylcholine receptors (nAChRs) in addition to genotoxicity and excess reactive oxygen species (ROS). Additionally, we explore a novel hypothesis regarding nicotine's carcinogenicity involving the downregulation of stem-loop binding protein (SLBP), a critical regulator of canonical histone mRNA, and the polyadenylation of canonical histone mRNA. By shedding light on these mechanisms, this review underscores the need for further research to elucidate the carcinogenic potential of nicotine and its implications for human health.

A Critical Interpretive Synthesis of the Role of Arecoline in Oral Carcinogenesis: Is the Local Cholinergic Axis a Missing Link in Disease Pathophysiology?

Arecoline is the primary active carcinogen found in areca nut and has been implicated in the pathogenesis of oral squamous cell carcinoma (OSCC) and oral submucous fibrosis (OSF). For this study, we conducted a stepwise review process by combining iterative scoping reviews with a post hoc search, with the aim of identifying the specific mechanisms by which arecoline initiates and promotes oral carcinogenesis. Our initial search allowed us to define the current trends and patterns in the pathophysiology of arecoline-induced OSF and OSCC, which include the induction of cell proliferation, facilitation of invasion, adhesion, and migration, increased collagen deposition and fibrosis, imbalance in immune and inflammatory mechanisms, and genotoxicity. Key molecular pathways comprise the activation of NOTCH1, MYC, PRDX2, WNT, CYR61, EGFR/Pl3K, DDR1 signaling, and cytokine upregulation. Despite providing a comprehensive overview of potential pathogenic mechanisms of OSF, the involvement of molecules functioning as areca alkaloid receptors, namely, the muscarinic and nicotinic acetylcholine receptors (AChRs), was not elucidated with this approach. Accordingly, our search strategy was refined to reflect these evidence gaps. The results of the second round of reviews with the post hoc search highlighted that arecoline binds preferentially to muscarinic AChRs, which have been implicated in cancer. Consistently, AChRs activate the signaling pathways that partially overlap with those described in the context of arecoline-induced carcinogenesis. In summary, we used a theory-driven interpretive review methodology to inform, extend, and supplement the conventional systematic literature assessment workflow. On the one hand, the results of this critical interpretive synthesis highlighted the prevailing trends and enabled the consolidation of data pertaining to the molecular mechanisms involved in arecoline-induced carcinogenesis, and, on the other, brought up knowledge gaps related to the role of the local cholinergic axis in oral carcinogenesis, thus suggesting areas for further investigation.

Cancer stem cells of head and neck squamous cell carcinoma; distance towards clinical application; a systematic review of literature

Head and neck squamous cell carcinoma (HNSCC) is the major pathological type of head and neck cancer (HNC). The disease ranks sixth among the most common malignancies worldwide, with an increasing incidence rate yearly. Despite the development of therapy, the prognosis of HNSCC remains unsatisfactory, which may be attributed to the resistance to traditional radio-chemotherapy, relapse, and metastasis. To improve the diagnosis and treatment, the targeted therapy for HNSCC may be successful as that for some other tumors. Nanocarriers are the most effective system to deliver the anti-cancerous agent at the site of interest using passive or active targeting approaches. The system enhances the drug concentration in HCN target cells, increases retention, and reduces toxicity to normal cells. Among the different techniques in nanotechnology, quantum dots (QDs) possess multiple fluorescent colors emissions under single-source excitation and size-tunable light emission. Dendrimers are the most attractive nanocarriers, which possess the desired properties of drug retention, release, unaffecting by the immune system, blood circulation time enhancing, and cells or organs specific targeting properties. In this review, we have discussed the up-to-date knowledge of the Cancer Stem Cells of Head and Neck Squamous Cell Carcinoma. Although a lot of data is available, still much more efforts remain to be made to improve the treatment of HNSCC.

Brain nuclei and neural circuits in neuropathic pain and brain modulation mechanisms of acupuncture: a review on animal-based experimental research

Neuropathic pain (NP) is known to be associated with abnormal changes in specific brain regions, but the complex neural network behind it is vast and complex and lacks a systematic summary. With the help of various animal models of NP, a literature search on NP brain regions and circuits revealed that the related brain nuclei included the periaqueductal gray (PAG), lateral habenula (LHb), medial prefrontal cortex (mPFC), and anterior cingulate cortex (ACC); the related brain circuits included the PAG-LHb and mPFC-ACC. Moreover, acupuncture and injurious information can affect different brain regions and influence brain functions via multiple aspects to play an analgesic role and improve synaptic plasticity by regulating the morphology and structure of brain synapses and the expression of synapse-related proteins; maintain the balance of excitatory and inhibitory neurons by regulating the secretion of glutamate, γ-aminobutyric acid, 5-hydroxytryptamine, and other neurotransmitters and receptors in the brain tissues; inhibit the overactivation of glial cells and reduce the release of pro-inflammatory mediators such as interleukins to reduce neuroinflammation in brain regions; maintain homeostasis of glucose metabolism and regulate the metabolic connections in the brain; and play a role in analgesia through the mediation of signaling pathways and signal transduction molecules. These factors help to deepen the understanding of NP brain circuits and the brain mechanisms of acupuncture analgesia.

Alpha synuclein post translational modifications: potential targets for Parkinson's disease therapy?

Parkinson's disease (PD) is the most common neurodegenerative disorder with motor symptoms. The neuropathological alterations characterizing the brain of patients with PD include the loss of dopaminergic neurons of the nigrostriatal system and the presence of Lewy bodies (LB), intraneuronal inclusions that are mainly composed of alpha-synuclein (α-Syn) fibrils. The accumulation of α-Syn in insoluble aggregates is a main neuropathological feature in PD and in other neurodegenerative diseases, including LB dementia (LBD) and multiple system atrophy (MSA), which are therefore defined as synucleinopathies. Compelling evidence supports that α-Syn post translational modifications (PTMs) such as phosphorylation, nitration, acetylation, O-GlcNAcylation, glycation, SUMOylation, ubiquitination and C-terminal cleavage, play important roles in the modulation α-Syn aggregation, solubility, turnover and membrane binding. In particular, PTMs can impact on α-Syn conformational state, thus supporting that their modulation can in turn affect α-Syn aggregation and its ability to seed further soluble α-Syn fibrillation. This review focuses on the importance of α-Syn PTMs in PD pathophysiology but also aims at highlighting their general relevance as possible biomarkers and, more importantly, as innovative therapeutic targets for synucleinopathies. In addition, we call attention to the multiple challenges that we still need to face to enable the development of novel therapeutic approaches modulating α-Syn PTMs.

Effect of Nicotine on Immune System Function

As a parasympathetic alkaloid and the main substance in cigarette smoke, nicotine modulates the immune system, inhibits innate and acquired immunity and is used in treating many autoimmune diseases. It often stimulates the α7 receptor and causes an anti-inflammatory state in the body. This study is designed to evaluate the role of nicotine treatment on immune system. The results showed that nicotine affects many cells in immune system, alters the downstream intracellular mechanisms and changes lymphocytes polarization. This substance alters TLRs and STATs gene expression and thus changes in the innate immune system. All these events inhibit the secretion of pro-inflammatory cytokines and chemokines which increase angiogenesis and metastasis and exacerbates tumors due to increasing survival and cell growth. Nicotine can aggravate tumors in cancer patients, with many positive effects observed in the treating autoimmune disease, Nicotine treatment function in different conditions depends on factors such as concentration, how it is employed, treatment duration and other conditions such as body conditions affecting the immune system, hence, further studies and review of all conditions are required.

Comparison of effects of tobacco cigarettes, electronic nicotine delivery systems and tobacco heating products on miRNA-mediated gene expression. A systematic review

OBJECTIVES

This work attempts to summarize current knowledge on the effects of cigarettes, electronic nicotine delivery systems and tobacco heating products on miRNA-mediated gene expression regulation and on their possible impact on smoking-related respiratory disease development.

MATERIALS AND METHODS

Literature search by terms combination: 'smoking', 'cigarette' 'THP', 'tobacco heating product', 'ENDS', 'electronic nicotine delivery system', 'e-cigarette', electronic cigarette' and 'miRNA-mediated gene expression' has been performed from October 2021 to February 2022. In this systematic review all relevant literature, including clinical trials, cellular and animal-based studies were included.

RESULTS

Cigarette smoke (CS) significantly altered transcriptome, including miRNAs expression profile. MiRNA-mediated gene expression is mentioned as one of the mechanisms associated with smoking-related respiratory disease development. Differential expression of miRNAs was reduced in aerosol from e-cigarettes (EC) and tobacco heating products (THP) when compared to CS. However, there was a significant alteration of some miRNAs expression when compared to air-controls in both EC and THP.

DISCUSSION

CS negatively affects transcriptome and miRNA-mediated gene expression regulation because of a huge number of hazardous substances which predispose to smoking-related diseases. Despite the reduced effect of ENDS and THP on miRNAs profile compared to CS, differences in expression of miRNAs when compared to air-control were observed, which may be harmful to never-smokers who may perceive such alternative smoking products as non-hazardous. To clearly indicate the role of ENDS and THP in the alteration of miRNA-mediated gene expression and the development of smoking-related respiratory diseases associated with this mechanism, more long-term studies should be performed in the future.

Using ncRNAs as Tools in Cancer Diagnosis and Treatment-The Way towards Personalized Medicine to Improve Patients' Health

Although the first discovery of a non-coding RNA (ncRNA) dates back to 1958, only in recent years has the complexity of the transcriptome started to be elucidated. However, its components are still under investigation and their identification is one of the challenges that scientists are presently facing. In addition, their function is still far from being fully understood. The non-coding portion of the genome is indeed the largest, both quantitatively and qualitatively. A large fraction of these ncRNAs have a regulatory role either in coding mRNAs or in other ncRNAs, creating an intracellular network of crossed interactions (competing endogenous RNA networks, or ceRNET) that fine-tune the gene expression in both health and disease. The alteration of the equilibrium among such interactions can be enough to cause a transition from health to disease, but the opposite is equally true, leading to the possibility of intervening based on these mechanisms to cure human conditions. In this review, we summarize the present knowledge on these mechanisms, illustrating how they can be used for disease treatment, the current challenges and pitfalls, and the roles of environmental and lifestyle-related contributing factors, in addition to the ethical, legal, and social issues arising from their (improper) use.

E-Cigarette Aerosols Promote Oral S. aureus Colonization by Delaying an Immune Response and Bacterial Clearing

E-cigarette (e-cig) vapor has been shown to play a pathological role in oral health and alter the oral microbiota, providing growth advantages for opportunistic pathogens. Enrichment of Staphylococcus aureus, a commensal resident in the oral cavity, correlates with the progression of periodontal disease, suggesting a role as an opportunistic pathogen. Environmental conditions, such as cigarette smoke, are known to increase S. aureus virulence, yet the role of S. aureus in periodontitis and oral preneoplasia is unknown. We exposed oral epithelial cells to e-cig aerosols and showed a dose-dependent cell viability reduction, regardless of nicotine content, in a possible attempt to repair DNA damage, as measured by pH2AX. S. aureus attachment to oral epithelial cells and bacterial biofilm formation were enhanced upon e-cig exposure, indicating an increased capacity for oral colonization. Mechanistically, e-cig aerosol exposure resulted in an immunosuppression, as determined by a reduction in IL8, IL6, and IL1β secretion by oral epithelial cells during co-culture with S. aureus. Consistent with this, e-cig vape reduced the oral epithelial cell clearance of S. aureus. Furthermore, we observed an increased expression of the inflammatory regulator COX2. This work suggests that e-cigs promote S. aureus colonization and modulate the oral inflammatory response, possibly promoting oral periodontitis and preneoplasia.

An APSES Transcription Factor Xbp1 Is Required for Sclerotial Development, Appressoria Formation, and Pathogenicity in Ciboria shiraiana

Sclerotinia diseases are important plant fungal diseases that, causes huge economic worldwide losses every year. Ciboria shiraiana is the main pathogen that results in mulberry sclerotia diseases. Sclerotia and appressoria play important roles in long-term pathogen survival and in host infection during life and disease cycles. However, the molecular mechanisms of sclerotial development and appressoria formation in C. shiraiana have not been well studied. Here, an Asm1p, Phd1p, Sok2p, Efg1p and StuAp (APSES)-type transcription factor in C. shiraiana, CsXbp1, involved in sclerotial development and appressoria formation was functionally characterized. Bioinformatics analyses showed that CsXbp1 contained an APSES-type DNA binding domain. The expression levels of CsXbp1 were higher in sclerotia and during later stages of infection. Compared with wild-type strains, hyphal growth was slower, the number and weight of sclerotia were reduced significantly, and appressoria formation was obviously delayed in CsXbp1 RNA interference (RNAi) strains. Moreover, the CsXbp1 RNAi strains showed weakened pathogenicity owing to compound appressoria defects. Tobacco rattle virus-mediated host-induced gene silencing enabled Nicotiana benthamiana to increase its resistance to C. shiraiana by reducing the CsXbp1 transcripts level. Thus, CsXbp1 plays vital roles in sclerotial formation, appressoria formation, and pathogenicity in C. shiraiana. This study provides new insights into the infection mechanisms of C. shiraiana and plant resistance breeding.

Precision Medicine Gains Momentum: Novel 3D Models and Stem Cell-Based Approaches in Head and Neck Cancer

Despite the current progress in the development of new concepts of precision medicine for head and neck squamous cell carcinoma (HNSCC), in particular targeted therapies and immune checkpoint inhibition (CPI), overall survival rates have not improved during the last decades. This is, on the one hand, caused by the fact that a significant number of patients presents with late stage disease at the time of diagnosis, on the other hand HNSCC frequently develop therapeutic resistance. Distinct intratumoral and intertumoral heterogeneity is one of the strongest features in HNSCC and has hindered both the identification of specific biomarkers and the establishment of targeted therapies for this disease so far. To date, there is a paucity of reliable preclinical models, particularly those that can predict responses to immune CPI, as these models require an intact tumor microenvironment (TME). The "ideal" preclinical cancer model is supposed to take both the TME as well as tumor heterogeneity into account. Although HNSCC patients are frequently studied in clinical trials, there is a lack of reliable prognostic biomarkers allowing a better stratification of individuals who might benefit from new concepts of targeted or immunotherapeutic strategies. Emerging evidence indicates that cancer stem cells (CSCs) are highly tumorigenic. Through the process of stemness, epithelial cells acquire an invasive phenotype contributing to metastasis and recurrence. Specific markers for CSC such as CD133 and CD44 expression and ALDH activity help to identify CSC in HNSCC. For the majority of patients, allocation of treatment regimens is simply based on histological diagnosis and on tumor location and disease staging (clinical risk assessments) rather than on specific or individual tumor biology. Hence there is an urgent need for tools to stratify HNSCC patients and pave the way for personalized therapeutic options. This work reviews the current literature on novel approaches in implementing three-dimensional (3D) HNSCC in vitro and in vivo tumor models in the clinical daily routine. Stem-cell based assays will be particularly discussed. Those models are highly anticipated to serve as a preclinical prediction platform for the evaluation of stable biomarkers and for therapeutic efficacy testing.

MicroRNA and circRNA Expression Analysis in a Zbtb1 Gene Knockout Monoclonal EL4 Cell Line

Zinc finger and BTB domain containing 1(Zbtb1) is a transcriptional suppressor protein, and a member of the mammalian Zbtb gene family. Previous studies have shown that Zbtb1 is essential for T-cell development. However, the role of Zbtb1 in T-cell lymphoma is undetermined. In this study, an EL4 cell line with Zbtb1 deletion was constructed using the CRISPR-Cas9 technique. The expression profiles of microRNA and circRNA produced by the control and gene deletion groups were determined by RNA-seq. In general, 24 differentially expressed microRNA and 16 differentially expressed circRNA were found between normal group and gene deletion group. Through further analysis of differentially expressed genes, GO term histogram and KEGG scatter plot were drawn, and three pairs of miRNA and circRNA regulatory relationships were found. This study describes the differentially expressed microRNA and circRNA in normal and Zbtb1-deficient EL4 cell lines, thus providing potential targets for drug development and clinical treatment of T-cell lymphoma.

Epimutational effects of electronic cigarettes

Electronic cigarettes (e-cigarettes), since they do not require tobacco combustion, have traditionally been considered less harmful than conventional cigarettes (c-cigarettes). In recent years, however, researchers have found many toxic compounds in the aerosols of e-cigarettes, and numerous studies have shown that e-cigarettes can adversely affect the human epigenome. In this review, we provide an update on recent findings regarding epigenetic outcomes of e-cigarette aerosols. Moreover, we discussed the effects of several typical e-cigarette ingredients (nicotine, tobacco-specific nitrosamines, volatile organic compounds, carbonyl compounds, and toxic metals) on DNA methylation, histone modifications, and noncoding RNA expression. These epigenetic effects could explain some of the diseases caused by e-cigarettes. It also reminds the public that like c-cigarettes, inhaling e-cigarette aerosols could also be accompanied with potential epigenotoxicity on the human body.

Circulating tumor cell analysis in locally advanced and metastatic squamous cell carcinoma of the head and neck

BACKGROUND

Circulating tumors cells (CTCs) are considered an early step towards metastasis and have been linked to poor prognosis in several types of cancer. CTCs in squamous cell carcinoma of the head and neck (SCCHN) have an unclear role.

METHODS

In this prospective study, patients with locally advanced or metastatic SCCHN had CTC counts assessed before starting systemic treatment using the CellSearch System. Select cases also had sequential CTC evaluation. Presence of CTCs was correlated with patient characteristics and outcomes.

RESULTS

Forty-eight patients enrolled, and 36 had evaluable clinical data and baseline CTC counts. Twenty-five patients had locally advanced disease (LAD) and 11 had metastatic disease. ≥1 CTCs were detected in six patients with LAD (24%) and four with metastatic disease (36%). On univariate analysis, smoking was associated with CTCs.

CONCLUSION

CTCs are not associated with prognosis in patients with LAD and metastatic disease; however, they are present in this patient population, and ≥1 CTCs is associated with a history of smoking.

LEVEL OF EVIDENCE

1b; individual prospective cohort study.

Environmental chemicals, breast cancer progression and drug resistance

Breast cancer (BC) is one of the most common causes of cancer in the world and the second leading cause of cancer deaths among women. Mortality is associated mainly with the development of metastases. Identification of the mechanisms involved in metastasis formation is, therefore, a major public health issue. Among the proposed risk factors, chemical environment and pollution are increasingly suggested to have an effect on the signaling pathways involved in metastatic tumor cells emergence and progression. The purpose of this article is to summarize current knowledge about the role of environmental chemicals in breast cancer progression, metastasis formation and resistance to chemotherapy. Through a scoping review, we highlight the effects of a wide variety of environmental toxicants, including persistent organic pollutants and endocrine disruptors, on invasion mechanisms and metastatic processes in BC. We identified the epithelial-to-mesenchymal transition and cancer-stemness (the stem cell-like phenotype in tumors), two mechanisms suspected of playing key roles in the development of metastases and linked to chemoresistance, as potential targets of contaminants. We discuss then the recently described pro-migratory and pro-invasive Ah receptor signaling pathway and conclude that his role in BC progression is still controversial. In conclusion, although several pertinent pathways for the effects of xenobiotics have been identified, the mechanisms of actions for multiple other molecules remain to be established. The integral role of xenobiotics in the exposome in BC needs to be further explored through additional relevant epidemiological studies that can be extended to molecular mechanisms.

Nicotine inhibits MAPK signaling and spheroid invasion in ovarian cancer cells

Nicotine is the major addictive component of cigarette smoke and although it is not considered carcinogenic, it can enhance or inhibit cancer cell proliferation depending on the type of cancer. Nicotine mediates its effects through nicotinic acetylcholine receptors (nAChRs), which are expressed in many different neuronal and non-neuronal cell types. We observed that the nAChR α4, α5, α7 subunits were expressed in ovarian cancer (OC) cells. Nicotine inhibited the proliferation of SKOV3 and TOV112D OC cells, which have TP53 mutation and wild-type KRAS, but did not inhibit the proliferation of TOV21G or HEY OC cells, which have KRAS mutation and wild-type TP53. Exposure to nicotine for 96 h led to a significant reduction in the amounts of activated extracellular signal-regulated kinase (ERK) and activated p38 mitogen-activated protein kinases (MAPKs) in SKOV3 cells, and in activated ERK in TOV112D cells. In addition, SKOV3 and TOV112D invasion and spheroid formation were substantially inhibited by siRNA knockdown of mixed lineage kinase 3 (MLK3), or MEK inhibition. Nicotine treatment reduced SKOV3 and TOV112D spheroid invasion and compaction but did not significantly affect spheroid formation. Furthermore, SKOV3 spheroid invasion was blocked by p38 inhibition with SB202190, but not by MEK inhibition with U0126; whereas TOV112D spheroid invasion was reduced by MEK inhibition, but not by p38 inhibition. These results indicate that nicotine can suppress spheroid invasion and compaction as well as proliferation in SKOV3 and TOV112D OC cells; and p38 and ERK MAPK signaling pathways are important mediators of these responses.

Gamma synuclein is a novel nicotine responsive protein in oral cancer malignancy

Background

The mechanisms of neuronal protein γ-synuclein (SNCG) in the malignancy of oral squamous cell carcinoma (OSCC) are not clear. This study tested the hypothesis that SNCG is involved in nicotine-induced malignant behaviors of OSCC. The effect of nicotine on SNCG expression and epithelial-to-mesenchymal transition (EMT) markers were examined.

Methods

Short hairpin RNA (shRNA) and an antagonist specific for α7-nicotine acetylcholine receptors (α7-nAChRs) were used to examine the role of α7-nAChRs in mediating the effects of nicotine. Knockdown of SNCG in nicotine-treated cells was performed to investigate the role of SNCG in cancer malignancy. The in vivo effect of nicotine was examined using a nude mouse xenotransplantation model.

Results

Nicotine increased SNCG expression in a time- and dose-dependent manner. Nicotine treatment also increased E-cadherin and ZO-1 and decreased fibronectin and vimentin expression. After specific knockdown of α7-nAChRs and inhibition of the PI3/AKT signal, the effect of nicotine on SNCG expression was attenuated. Silencing of SNCG abolished nicotine-induced invasion and migration of OSCC cells. The xenotransplantation model revealed that nicotine augmented tumor growth and SNCG expression.

Conclusion

Nicotine upregulated SNCG expression by activating the α7-nAChRs/PI3/AKT signaling that are participated in nicotine-induced oral cancer malignancy.

Prognostic Significance of the Pluripotency Factors NANOG, SOX2, and OCT4 in Head and Neck Squamous Cell Carcinomas

Cancer stem cells (CSCs) play major roles in tumor initiation, progression, and resistance to cancer therapy. Several CSC markers have been studied in head and neck squamous cell carcinomas (HNSCC), including the pluripotency factors NANOG, SOX2, and OCT4; however, their clinical significance is still unclear. NANOG, SOX2, and OCT4 expression was evaluated by immunochemistry in 348 surgically-treated HNSCC, and correlated with clinicopathological parameters and patient outcomes. mRNA expression was further analyzed in 530 The Cancer Genome Atlas (TCGA) HNSCC. NANOG protein expression was detected in 250 (72%) cases, more frequently in patients with lymph node metastasis (p = 0.003), and was an independent predictor of better survival in multivariate analysis. While OCT4 expression was undetectable, SOX2 expression was observed in 105 (30%) cases, and strongly correlated with NANOG expression. Combined expression of both proteins showed the highest survival rates, and double-negative cases the worst survival. Strikingly, the impact of NANOG and SOX2 on outcome varied depending on tumor site and lymph node infiltration, specifically showing prognostic significance in pharyngeal tumors. Correlation between NANOG and SOX2 at mRNA and protein was specifically observed in node positive (N+) patients, and consistently correlated with better survival rates. According to our findings, NANOG protein expression is frequent in HNSCC, thereby emerging as an independent predictor of better prognosis in pharyngeal tumors. Moreover, this study uncovers a differential impact of NANOG and SOX2 expression on HNSCC prognosis, depending on tumor site and lymph node infiltration, which could facilitate high-risk patient stratification.

Comparative Gene Expression Profiling of Tobacco-Associated HPV-Positive versus Negative Oral Squamous Carcinoma Cell Lines

Background: HPV-positive oral squamous cell carcinomas (OSCCs) are specific biological and clinical entities, characterized by a more favorable prognosis compared to HPV-negative OSCCs and occurring generally in non-smoking and non-drinking younger individuals. However, poor information is available on the molecular and the clinical behavior of HPV-positive oral cancers occurring in smoking/drinking subjects. Thus, this study was designed to compare, at molecular level, two OSCC cell lines, both derived from drinking and smoking individuals and differing for presence/absence of HPV infection. Methods: HPV-negative UPCI-SCC-131 and HPV16-positive UPCI-SCC-154 cell lines were compared by whole genome gene expression profiling and subsequently studied for activation of Wnt/βCatenin signaling pathway by the expression of several Wnt-target genes, βCatenin intracellular localization, stem cell features and miRNA let-7e. Gene expression data were validated in head and neck squamous cell carcinoma (HNSCC) public datasets. Results: Gene expression analysis identified Wnt/βCatenin pathway as the unique signaling pathway more active in HPV-negative compared to HPV-positive OSCC cells and this observation was confirmed upon evaluation of several Wnt-target genes (i.e., Cyclin D1, Cdh1, Cdkn2a, Cd44, Axin2, c-Myc and Tcf1). Interestingly, HPV-negative OSCC cells showed higher levels of total βCatenin and its active form, increase of its nuclear accumulation and more prominent stem cell traits. Furthermore, miRNA let-7e was identified as potential upstream regulator responsible for the downregulation of Wnt/βCatenin signaling cascade since its silencing in UPCI-SCC-154 cell resulted in upregulation of Wnt-target genes. Finally, the analysis of two independent gene expression public datasets of human HNSCC cell lines and tumors confirmed that Wnt/βCatenin pathway is more active in HPV-negative compared to HPV-positive tumors derived from individuals with smoking habit. Conclusions: These data suggest that lack of HPV infection is associated with more prominent activation of Wnt/βCatenin signaling pathway and gain of stem-like traits in tobacco-related OSCCs.

Prognostic Significance of ALDH1, Bmi1, and OCT4 Expression in Oral Epithelial Dysplasia and Oral Squamous Cell Carcinoma

BACKGROUND

Increasing evidence suggests the involvement of cancer stem cells (CSCs) in both oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC). Among the various CSC markers, aldehyde dehydrogenase (ALDH) 1, B cell-specific Moloney murine leukaemia virus integration site 1 (Bmi1), and octamer-binding protein 4 (OCT4) have been noted to increase in OSCC. The aim of the study was to analyze ALDH1, Bmi1, and OCT4 expression in OED and OSCC with clinicopathologic correlation and survival analysis.

METHODS

A total of 40 cases each of OED and OSCC were retrieved from departmental archives. Expression of ALDH1, Bmi1, and OCT4 was analyzed using immunohistochemistry and was correlated with clinicopathological parameters. A follow-up ranging from 6 to 52 months was considered for Kaplan-Meier survival analysis. The log-rank test was performed to analyze significant difference in survival rates.

RESULTS

The expression levels of ALDH1, Bmi1, and OCT4 increased significantly from OED through OSCC (P < .05). The expression of ALDH1 and OCT4 showed a significant correlation with lymph node metastasis. Positive cases of ALDH1 showed a significantly reduced survival rate compared to cases showing negative expression. Kaplan-Meier survival analysis showed a significant reduction of survival rate (P = .00) in patients showing a positive expression for all the 3 markers.

CONCLUSION

ALDH1 and OCT4 could be used as individual prognostic markers for assessing prognosis. ALDH1, Bmi1, and OCT4 could be used as a collective panel of markers to enable surgeons in predicting the prognosis of patients and thereby carry out prompt follow-up for such cases.

Environmental exposures, stem cells, and cancer

An estimated 70-90% of all cancers are linked to exposure to environmental risk factors. In parallel, the number of stem cells in a tissue has been shown to be a strong predictor of risk of developing cancer in that tissue. Tumors themselves are characterized by an acquisition of "stem cell" characteristics, and a growing body of evidence points to tumors themselves being sustained and propagated by a stem cell-like population. Here, we review our understanding of the interplay between environmental exposures, stem cell biology, and cancer. We provide an overview of the role of stem cells in development, tissue homeostasis, and wound repair. We discuss the pathways and mechanisms governing stem cell plasticity and regulation of the stem cell state, and describe experimental methods for assessment of stem cells. We then review the current understanding of how environmental exposures impact stem cell function relevant to carcinogenesis and cancer prevention, with a focus on environmental and occupational exposures to chemical, physical, and biological hazards. We also highlight key areas for future research in this area, including defining whether the biological basis for cancer disparities is related to effects of complex exposure mixtures on stem cell biology.

Nicotinic Acetylcholine Receptor Subunit Alpha-5 Promotes Radioresistance via Recruiting E2F Activity in Oral Squamous Cell Carcinoma

Radiotherapy is commonly used to treat patients with oral squamous cell carcinoma (OSCC), but a subpopulation of OSCC patients shows a poor response to irradiation treatment. Therefore, identifying a biomarker to predict the effectiveness of radiotherapy in OSCC patients is urgently needed. In silico analysis of public databases revealed that upregulation of CHRNA5, the gene encoding nicotinic acetylcholine receptor subunit alpha-5, is extensively detected in primary tumors compared to normal tissues and predicts poor prognosis in OSCC patients. Moreover, CHRNA5 transcript level was causally associated with the effective dose of irradiation in a panel of OSCC cell lines. Artificial silencing of CHRNA5 expression enhanced, but nicotine reduced, the radiosensitivity of OSCC cells. Gene set enrichment analysis demonstrated that the E2F signaling pathway is highly activated in OSCC tissues with high levels of CHRNA5 and in those derived from patients with cancer recurrence after radiotherapy. CHRNA5 knockdown predominantly suppressed E2F activity and decreased the phosphorylation of the Rb protein; however, nicotine treatment dramatically promoted E2F activity and increased Rb phosphorylation, which was mitigated after CHRNA5 knockdown in OSCC cells. Notably, the signature combining increased mRNA levels of CHRNA5 and the E2F signaling gene set was associated with worse recurrence-free survival probability in OSCC patients recorded to be receiving radiotherapy. Our findings suggest that CHRNA5 is not only a useful biomarker for predicting the effectiveness of radiotherapy but also a druggable target to enhance the cancericidal effect of irradiation on OSCC.

The Emerging Role of NANOG as an Early Cancer Risk Biomarker in Patients with Oral Potentially Malignant Disorders

NANOG, a key regulator of pluripotency and self-renewal in embryonic and adult stem cells, is frequently overexpressed in multiple cancers, including oral squamous cell carcinoma (OSCC). It has been frequently associated with poor outcomes in epithelial cancers, and recently implicated in laryngeal tumorigenesis. On this basis, we investigated the role of NANOG protein expression as an early cancer risk biomarker in oral potentially malignant disorders (OPMD), and the impact on prognosis and disease outcomes in OSCC patients. NANOG expression was evaluated by immunohistochemistry in 55 patients with oral epithelial dysplasia, and 125 OSCC patients. Correlations with clinical and follow-up data were assessed. Nuclear NANOG expression was detected in 2 (3.6%) and cytoplasmic NANOG expression in 9 (16.4%) oral dysplasias. NANOG expression increased with the grade of dysplasia. Cytoplasmic NANOG expression and the histopathological grading were significantly correlated with oral cancer risk, although dysplasia grading was the only significant independent predictor of oral cancer development in multivariate analyses. Cytoplasmic NANOG expression was also detected in 39 (31%) OSCC samples. Positive NANOG expression was significantly associated with tobacco and alcohol consumption, and was more frequent in pN0 tumors, early I-II stages. These data unveil the clinical relevance of NANOG in early stages of OSCC tumorigenesis rather than in advanced neoplastic disease. NANOG expression emerges as an early predictor of oral cancer risk in patients with OPMD.

Nicotine promotes cervical metastasis of oral cancer by regulating peroxiredoxin 1 and epithelial-mesenchymal transition in mice

Background

Tobacco is a major risk factor for oral squamous cell carcinoma (OSCC). However, the role of nicotine in OSCC is not completely understood.

Materials and methods

To analyze the mechanisms of nicotine-induced cervical metastasis, we investigated whether nicotine induced invasion, migration, and epithelial–mesenchymal transition (EMT) via regulating peroxiredoxin 1 (Prx1) in CAL 27 cells. In addition, we established a mouse model to confirm the roles of nicotine in regulating Ets1/Prx1/EMT signaling in OSCC metastasis.

Results

We showed that nicotine induced CAL 27 cell invasion, migration, EMT, and Prx1 and Ets1 expression. Prx1 knockdown inhibited cell invasion, migration, and EMT. Ets1 silencing downregulated Prx1 expression and EMT. Prx1 and Ets1 were shown to interact in CAL 27 cells treated with nicotine, and nicotine could significantly upregulate the binding of the transcription factor Ets1 to the Prx1 gene promoter region. Additionally, an in vivo study showed that nicotine induced tumor metastasis and EMT. Prx1 knockdown inhibited cervical metastasis rates and EMT progression. No significant differences in metastasis rates and EMT-related marker expression levels were observed between vehicle- and nicotine-treated mice.

Conclusion

The results indicate that nicotine promotes cervical lymph node metastasis through regulating Ets1/Prx1/EMT signaling during OSCC pathogenesis; consequently, Prx1 may represent a potential target for the prevention and treatment of OSCC.

Nicotine-induced oxidative stress contributes to EMT and stemness during neoplastic transformation through epigenetic modifications in human kidney epithelial cells

Nicotine is a component of cigarette smoke and mounting evidence suggests toxicity and carcinogenicity of tobacco smoke in kidney. Carcinogenicity of nicotine itself in kidney and the underlying molecular mechanisms are not well-understood. Hence, the objective of this study was to determine the carcinogenic effects of chronic nicotine exposure in Hk-2 human kidney epithelial cells. The effects of nicotine exposure on the expression of genes for cellular reprogramming, redox status, and growth signaling pathways were also evaluated to understand the molecular mechanisms. Results revealed that chronic exposure to nicotine induced growth and neoplastic transformation in HK-2 cells. Increased levels of intracellular reactive oxygen species (ROS), acquired stem cell-like sphere formation, and epithelial-mesenchymal-transition (EMT) changes were observed in nicotine exposed cells. Treatment with antioxidant N-acetyl cysteine (NAC) resulted in abrogation of EMT and stemness in HK-2 cells, indicating the role of nicotine-induced ROS in these morphological changes. The result also suggests that ROS controls the stemness through regulation of AKT pathway during early stages of carcinogenesis. Additionally, the expression of epigenetic regulatory genes was altered in nicotine-exposed cells and the changes were reversed by NAC. The epigenetic therapeutics 5-aza-2'-deoxycytidine and Trichostatin A also abrogated the stemness. This suggests the nicotine-induced oxidative stress caused epigenetic alterations contributing to stemness during neoplastic transformation. To our knowledge, this is the first report showing the ROS-mediated epigenetic modifications as the underlying mechanism for carcinogenicity of nicotine in human kidney epithelial cells. This study further suggests the potential of epigenetic therapeutics for pharmacological intervention in nicotine-induced kidney cancer.

Epithelial-mesenchymal transition and microRNAs: Challenges and future perspectives in oral cancer

BACKGROUND

Head and neck cancer is the sixth most common cancer worldwide, with oral squamous cell carcinoma (OSCC) being the most representative type. OSCC is a public health problem with high morbidity and poor survival rate. Epithelial-mesenchymal transition is emerging as a hallmark in OSCC.

METHODS

In this study, we described the role of microRNAs in epithelial-mesenchymal transition regulation in OSCC based on a PubMed search using articles published in English between January 1, 2010, and January 31, 2018.

RESULTS

MicroRNA's regulatory networks seem to be a hallmark of epithelial-mesenchymal transition in OSCC pathophysiology becoming a growing challenge to design new studies and strategies from biology to clinical applications.

CONCLUSION

Therefore, we propose that targeting therapies to epithelial-mesenchymal transition-type cells, namely, coordinating microRNAs and/or hydrophobic drugs, such as conventional therapy, could be a promising strategy to improve the outcomes of patients with OSCC.

Nicotine associated breast cancer in smokers is mediated through high level of EZH2 expression which can be reversed by methyltransferase inhibitor DZNepA

Recent studies show substantial growth-promoting properties of nicotine (NIC) in cancer, which is a combined outcome of genetic and epigenetic alterations. However, the role of epigenetic modifiers in response to NIC in breast cancer is less studied. In the present study, for the first time we have shown NIC-induced enhanced EZH2 expression. Six pairs of smoking-associated breast cancer patient tissues were analyzed. Samples from smoking breast cancer patients showed distinguished enhanced EZH2 expression in comparison to non-smoking ones. The upregulation in EZH2, which is due to NIC, was further confirmed in breast carcinoma cell lines using 10 µM NIC, 1 µM DZNepA, and EZH2si. The upregulation of EZH2 was concomitant with upregulation in Myc and α9-nAChR. The xenograft of breast cancer cells in BALB/c nude mice in the presence or absence of NIC showed significantly higher tumor uptake in the NIC injected group, which clearly demonstrates the effect of NIC in breast cancer progression. Interestingly, DZNepA considerably suppressed the NIC-mediated tumor growth. CHIP-qPCR assay confirmed the increased Myc enrichment on EZH2 promoter upon NIC treatment, thereby strengthening our findings that there exists an association between NIC, Myc, and EZH2. Overall, the present study identifies a strong association between NIC and EZH2 particularly in the progression of breast cancer in smokers through a novel axis involving nAChR and Myc. Moreover, the findings provide preliminary evidence suggesting potential of high level of EZH2 expression as a prognostic marker in smoking-associated breast cancer.

USP21 promotes cell proliferation and metastasis through suppressing EZH2 ubiquitination in bladder carcinoma

Bladder cancer (BC) is the second most common malignant tumor of the urinary tract in the world. In this study, we found that ubiquitin-specific protease (USP21) was upregulated in BC and the ectopic expression of USP21 was closely associated with tumor size and metastasis. Moreover, patients with higher levels of USP21 had poorer survival rate. Multiple function analysis such as CCK-8, colony formation, wound healing, and transwell analysis indicated that USP21 regulated cell proliferation and metastasis in bladder carcinoma cell lines. We also found that USP21 could facilitate epithelial–mesenchymal transition. As EZH2 has been reported to promote cell metastasis in BC, our work identified that USP21 deubiquitinated EZH2 and stabilized it. Our data demonstrated that USP21 might play a crucial role in regulating BC progression and could provide a potential therapeutic strategy for BC.

Epithelial to mesenchymal transition and HPV infection in squamous cell oropharyngeal carcinomas: the papillophar study

Background:

Human Papillomavirus (HPV) infection is recognised as aetiological factor of carcinogenesis in oropharyngeal squamous cell carcinomas (OPC). HPV-related OPC respond better to treatments and have a significantly favourable outcome. Epithelial to mesenchymal transition (EMT) implicated in tumour invasion, is a hallmark of a poor prognosis in carcinomas.

Methods:

We have studied the relationship of EMT markers (E-cadherin, β-catenin and vimentin) with HPV infection (DNA and E6/E7 mRNA detection), p16^INK4a expression and survival outcomes in a cohort of 296 patients with OPC.

Results:

Among the 296 OPSSC, 26% were HPV positive, 20.3% had overt EMT (>25% of vimentin positive tumour cells). Lower E-cadherin expression was associated with a higher risk of distant metastasis in univariate (P=0.0110) and multivariate analyses (hazard ratios (HR)=6.86 (1.98; 23.84)). Vimentin expression tends towards worse metastasis-free survival (MFS; HR=2.53 (1.00; 6.41)) and was an independent prognostic factor of progression-free survival (HR=1.55 (1.03; 2.34)).

Conclusions:

There was a non significant association of EMT with HPV status. This may be explained by a mixed subpopulation of patients HPV positive with associated risk factors (HPV, tobacco and alcohol). Thus, the detection of EMT in OPC represents another reliable approach in the prognosis and the management of OPC whatever their HPV status.

Valproic acid inhibits irradiation-induced epithelial-mesenchymal transition and stem cell-like characteristics in esophageal squamous cell carcinoma

Esophageal carcinoma is one of the most aggressive malignancies, and is characterized by poor response to current therapy and a dismal survival rate. In this study we investigated whether irradiation induces epithelial-mesenchymal transition (EMT) in esophageal squamous cell carcinoma (ESCC) TE9 cells and whether the classic histone deacetylase (HDAC) inhibitor valproic acid (VPA) suppresses these changes. First, we showed that 2 Gy irradiation induced spindle cell-like morphologic changes, decreased expression of membranous E-cadherin, upregulated vimentin expression, and altered the localization of β-catenin from its usual membrane-bound location to cytoplasm in TE9 cells. Irradiation induced upregulation of transcription factors including Slug, Snail, and Twist, which regulate EMT. Stimulation by irradiation resulted in increased TGF-β1 and HIF-1α expression and induced Smad2 and Smad3 phosphorylation. Furthermore, irradiation enhanced CD44 expression, indicating acquisition of cancer stem-like cell properties. In addition, irradiation enhanced invasion and migration ability with upregulation of matrix metalloproteinases. These findings indicate that single-dose irradiation can induce EMT in ESCC cells. Second, we found that treatment with 1 mM VPA induced reversal of EMT caused by irradiation in TE9 cells, resulting in attenuated cell invasion and migration abilities. These results suggest that VPA might have clinical value to suppress irradiation-induced EMT. The reversal of EMT by HDAC inhibitors may be a new therapeutic strategy to improve the effectiveness of radiotherapy in ESCC by inhibiting the enhancement of invasion and metastasis.

Role of miRNA dynamics and cytokine profile in governing CD44v6/Nanog/PTEN axis in oral cancer: modulating the master regulators

Late diagnosis, low therapeutic response, and metastasis are accountable for poor 5-year survival rate of OSCC. These failures are attributed to the existence of "cancer stem cell (CSC)" subpopulation. Hence, it is necessary to identify and understand the mechanism of CSCs in tumor development, metastasis, and chemotherapeutic response. Propelling evidences suggest that microRNA (miRNA)-mediated regulation and cytokines of tumor microenvironment have the ability to modulate CSC signalling pathway; however, their exact mechanism needs to be elucidated. Thus, in this study, we characterized CSC markers and highlighted the miRNA dynamics and cytokine profile regulating these CSCs in a pathway-dependent manner. Our results demonstrated CD44+ subpopulation as tumor-initiating cells with self-renewal capability, tumorigenic growth potential and intrinsic chemoresistance. These tumors exhibited increased expression of CSC markers (CD44v3, CD44v6, Nanog, and Bmi1) and significantly reduced expression of PTEN and ATM in OSCC patients. Pathway analysis of these CSC markers demonstrated a prospective pathway regulated by miRNA and cytokine network. On analyzing these modulators, we observed decreased expression of miRNA542-3p, miRNA34a and miRNA9, and significant upregulation of miRNA21, thus forming an unexplored axis. Cytokine profiling revealed significantly increased levels of IL-6 and IL-8 compared to normals and demonstrated their strong association with CD44v6. Collectively, this study indicates that miR5423p and miR34a targets the CD44v6-Nanog-PTEN axis, thus playing a vital role in regulating the CSC properties. Furthermore, we speculate an impinging role of cytokines IL-6 and IL-8 in regulating this CSC-mediated pathway which can have prognostic and therapeutic implications.

Comprehensive review of epidemiological and animal studies on the potential carcinogenic effects of nicotine per se

The effects of long-term use of nicotine per se on cancer risk, in the absence of tobacco extract or smoke, are not clearly understood. This review evaluates the strength of published scientific evidence, in both epidemiological and animal studies, for the potential carcinogenic effects of nicotine per se; that is to act as a complete carcinogen or as a modulator of carcinogenesis. For human studies, there appears to be inadequate evidence for an association between nicotine exposure and the presence of or lack of a carcinogenic effect due to the limited information available. In animal studies, limited evidence suggests an association between long-term nicotine exposure and a lack of a complete carcinogenic effect. Conclusive studies using current bioassay guidelines, however, are missing. In studies using chemical/physical carcinogens or transgenic models, there appears to be inadequate evidence for an association between nicotine exposure and the presence of or lack of a modulating (stimulating) effect on carcinogenesis. This is primarily due to the large number of conflicting studies. In contrast, a majority of studies provides sufficient evidence for an association between nicotine exposure and enhanced carcinogenesis of cancer cells inoculated in mice. This modulating effect was especially prominent in immunocompromized mice. Overall, taking the human and animal studies into consideration, there appears to be inadequate evidence to conclude that nicotine per se does or does not cause or modulate carcinogenesis in humans. This conclusion is in agreement with the recent US Surgeon General's 2014 report on the health consequences of nicotine exposure.

Nicotine enhances invasion and metastasis of human colorectal cancer cells through the nicotinic acetylcholine receptor downstream p38 MAPK signaling pathway

Nicotine as a cigarette component is an established risk factor for colorectal cancer tumorigenesis. The downstream signaling pathways of nicotinic acetylcholine receptors (nAchRs) are believed to be responsible for the cellular effects. In the present study, we evaluated the effects and novel mechanisms for nicotine on the capacity for colorectal cancer cell invasion and metastasis. LOVO and SW620 colorectal cancer cells were stimulated with nicotine in vitro. A Transwell chamber model was applied to detect the capacity for tumor cell invasion. Assays for gelatin zymography and western blotting were applied to detect the activity and expression of metastasis-related matrix metalloproteinases (MMPs), respectively. Signal transduction was assessed by immunoblotting for the phosphorylation of relevant signal molecules and the application of pharmaceutical inhibitors. We showed that nicotine increased LOVO and SW620 colorectal cancer cell invasion along with enhanced activity and expression of MMP-1, -2 and -9. Nicotine increased phosphorylation of p38, ERK, Akt and PI3K p85 but had no effect on phosphorylation of JNK, or NF-κB. Of the pharmaceutical inhibitors of U0126 (ERK1/2 inhibitor), LY294002 (Akt activation inhibitor), SB239063 (p38 MAPK activation inhibitor) and hexamethonium (Hex) (nAchRs inhibitor), the cellular and molecular effects were reduced by the applications of SB239063 and Hex. We concluded that nicotine stimulates the invasion and metastasis of colon cancer cells in vitro via activation of the nAchRs and the p38 MAPK downstream signaling pathway. Therefore, p38 MAPK may have potential as a therapeutic target for smoking-related human colorectal cancer metastasis.

Alcohol-dysregulated miR-30a and miR-934 in head and neck squamous cell carcinoma

BACKGROUND

Alcohol consumption is a well-established risk factor for head and neck squamous cell carcinoma (HNSCC); however, the molecular mechanisms by which alcohol promotes HNSCC pathogenesis and progression remain poorly understood. Our study sought to identify microRNAs that are dysregulated in alcohol-associated HNSCC and investigate their contribution to the malignant phenotype.

METHOD

Using RNA-sequencing data from 136 HNSCC patients, we compared the expression levels of 1,046 microRNAs between drinking and non-drinking cohorts. Dysregulated microRNAs were verified by qRT-PCR in normal oral keratinocytes treated with biologically relevant doses of ethanol and acetaldehyde. The most promising microRNA candidates were investigated for their effects on cellular proliferation and invasion, sensitivity to cisplatin, and expression of cancer stem cell genes. Finally, putative target genes were identified and evaluated in vitro to further establish roles for these miRNAs in alcohol-associated HNSCC.

RESULTS

From RNA-sequencing analysis we identified 8 miRNAs to be significantly upregulated in alcohol-associated HNSCCs. qRT-PCR experiments determined that among these candidates, miR-30a and miR-934 were the most highly upregulated in vitro by alcohol and acetaldehyde. Overexpression of miR-30a and miR-934 in normal and HNSCC cell lines produced up to a 2-fold increase in cellular proliferation, as well as induction of the anti-apoptotic gene BCL-2. Upon inhibition of these miRNAs, HNSCC cell lines exhibited increased sensitivity to cisplatin and reduced matrigel invasion. miRNA knockdown also indicated direct targeting of several tumor suppressor genes by miR-30a and miR-934.

CONCLUSIONS

Alcohol induces the dysregulation of miR-30a and miR-934, which may play crucial roles in HNSCC pathogenesis and progression. Future investigation of the alcohol-mediated pathways effecting these transformations will prove valuable for furthering the understanding and treatment of alcohol-associated HNSCC.

The impact of low-dose carcinogens and environmental disruptors on tissue invasion and metastasis

The purpose of this review is to stimulate new ideas regarding low-dose environmental mixtures and carcinogens and their potential to promote invasion and metastasis. Whereas a number of chapters in this review are devoted to the role of low-dose environmental mixtures and carcinogens in the promotion of invasion and metastasis in specific tumors such as breast and prostate, the overarching theme is the role of low-dose carcinogens in the progression of cancer stem cells. It is becoming clearer that cancer stem cells in a tumor are the ones that assume invasive properties and colonize distant organs. Therefore, low-dose contaminants that trigger epithelial-mesenchymal transition, for example, in these cells are of particular interest in this review. This we hope will lead to the collaboration between scientists who have dedicated their professional life to the study of carcinogens and those whose interests are exclusively in the arena of tissue invasion and metastasis.

Revisiting Chaos Theorem to Understand the Nature of miRNAs in Response to Drugs of Abuse

Just like Matryoshka dolls, biological systems follow a hierarchical order that is based on dynamic bidirectional communication among its components. In addition to the convoluted inter-relationships, the complexity of each component spans several folds. Therefore, it becomes rather challenging to investigate phenotypes resulting from these networks as it requires the integration of reductionistic and holistic approaches. One dynamic system is the transcriptome which comprises a variety of RNA species. Some, like microRNAs, have recently received a lot of attention. miRNAs are very pleiotropic and have been considered as therapeutic and diagnostic candidates in the biomedical fields. In this review, we survey miRNA profiles in response to drugs of abuse (DA) using 118 studies. After providing a summary of miRNAs related to substance use disorders (SUD), general patterns of miRNA signatures are compared among studies for single or multiple drugs of abuse. Then, current challenges and drawbacks in the field are discussed. Finally, we provide support for considering miRNAs as a chaotic system in normal versus disrupted states particularly in SUD and propose an integrative approach for studying and analyzing miRNA data.

The translational significance of epithelial-mesenchymal transition in head and neck cancer

Positive markers of epithelial-mesenchymal transition (EMT) in head and neck cancers complicate clinical management and are associated with reduced survival. We discuss recent translational discoveries in EMT and suggest additional actionable molecular pathways, biomarkers, and clinical agents.

Connections of nicotine to cancer

This Opinion article discusses emerging evidence of direct contributions of nicotine to cancer onset and growth. The list of cancers reportedly connected to nicotine is expanding and presently includes small-cell and non-small-cell lung carcinomas, as well as head and neck, gastric, pancreatic, gallbladder, liver, colon, breast, cervical, urinary bladder and kidney cancers. The mutagenic and tumour-promoting activities of nicotine may result from its ability to damage the genome, disrupt cellular metabolic processes, and facilitate growth and spreading of transformed cells. The nicotinic acetylcholine receptors (nAChRs), which are activated by nicotine, can activate several signalling pathways that can have tumorigenic effects, and these receptors might be able to be targeted for cancer therapy or prevention. There is also growing evidence that the unique genetic makeup of an individual, such as polymorphisms in genes encoding nAChR subunits, might influence the susceptibility of that individual to the pathobiological effects of nicotine. The emerging knowledge about the carcinogenic mechanisms of nicotine action should be considered during the evaluation of regulations on nicotine product manufacturing, distribution and marketing.

Nicotine activates YAP1 through nAChRs mediated signaling in esophageal squamous cell cancer (ESCC)

Cigarette smoking is an established risk factor for esophageal cancers. Yes-associated protein 1 (YAP1), the key transcription factor of the mammalian Hippo pathway, has been reported to be an oncogenic factor for many cancers. In this study, we find nicotine administration can induce nuclear translocation and activation of YAP1 in ESCC. Consistently, we observed nuclear translocation and activation of YAP1 by knockdown of CHRNA3, which is a negative regulator of nicotine signaling in bronchial and esophageal cancer cells. Nicotine administration or CHRNA3 depletion substantially increased proliferation and migration in esophageal cancer cells. Interestingly, we find that YAP1 physically interacts with nAChRs, and nAChRs-signaling dissociates YAP1 from its negative regulatory complex composed with α-catenin, β-catenin and 14-3-3 in the cytoplasm, leading to upregulation and nuclear translocation of YAP1. This process likely requires PKC activation, as PKC specific inhibitor Enzastaurin can block nicotine induced YAP1 activation. In addition, we find nicotine signaling also inhibits the interaction of YAP1 with P63, which contributes to the inhibitory effect of nicotine on apoptosis. Using immunohistochemistry analysis we observed upregulation of YAP1 in a significant portion of esophageal cancer samples. Consistently, we have found a significant association between YAP1 upregulation and cigarette smoking in the clinical esophageal cancer samples. Together, these findings suggest that the nicotine activated nAChRs signaling pathway which further activates YAP1 plays an important role in the development of esophageal cancer, and this mechanism may be of a general significance for the carcinogenesis of smoking related cancers.

Nicotine-mediated cell proliferation and tumor progression in smoking-related cancers

Tobacco smoke contains multiple classes of established carcinogens including benzo(a)pyrenes, polycyclic aromatic hydrocarbons, and tobacco-specific nitrosamines. Most of these compounds exert their genotoxic effects by forming DNA adducts and generation of reactive oxygen species, causing mutations in vital genes such as K-Ras and p53. In addition, tobacco-specific nitrosamines can activate nicotinic acetylcholine receptors (nAChR) and to a certain extent β-adrenergic receptors (β-AR), promoting cell proliferation. Furthermore, it has been demonstrated that nicotine, the major addictive component of tobacco smoke, can induce cell-cycle progression, angiogenesis, and metastasis of lung and pancreatic cancers. These effects occur mainly through the α7-nAChRs, with possible contribution from the β-ARs and/or epidermal growth factor receptors. This review article will discuss the molecular mechanisms by which nicotine and its oncogenic derivatives such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N-nitrosonornicotine induce cell-cycle progression and promote tumor growth. A variety of signaling cascades are induced by nicotine through nAChRs, including the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway, phosphoinositide 3-kinase/AKT pathway, and janus-activated kinase/STAT signaling. In addition, studies have shown that nAChR activation induces Src kinase in a β-arrestin-1-dependent manner, leading to the inactivation of Rb protein and resulting in the expression of E2F1-regulated proliferative genes. Such nAChR-mediated signaling events enhance the proliferation of cells and render them resistant to apoptosis induced by various agents. These observations highlight the role of nAChRs in promoting the growth and metastasis of tumors and raise the possibility of targeting them for cancer therapy.

The cancer stem cell hypothesis applied to oral carcinoma

It has been proposed that the development of tumors is based exclusively on the activity of cancer stem cells (CSCs) leading to a new model of carcinogenesis, the CSC hypothesis, in opposition to the conventional model of clonal evolution. The new model may help to explain the high mortality of oral cancer, unchanged over the past decades, the low response to treatment and the tendency of oral squamous cell carcinoma (OSCC) patients to develop multiple tumors. However, a more profound understanding of the molecular pathways involved in maintaining the stem cell (SC) state and of their alterations is required to elucidate the mechanisms underlying the development of tumors and metastatic spread, but research into SC biopathology is hampered by the lack of specific markers for identifying SCs and CSCs in tissues and for establishing topographic relationships with their lineage. We review current knowledge on stem cells in relation to oral cancer, including their possible origins, focusing on the CSC hypothesis of oral tumorigenesis and attempts being made to identify oral stem cells.