Cellular and molecular mechanisms of nicotine's pro-angiogenesis activity and its potential impact on cancer

Nicotine Exerts Cytotoxic Effects in a Panel of Healthy Cell Lines and Strong Irritating Potential on Blood Vessels

The use of tobacco products is a major global public health issue, as it is the leading cause of preventable death worldwide. In addition, nicotine (NIC) is a key component of electronic and conventional cigarettes. Although nicotine's addictive potential is well known, its health effects are not entirely understood. Thus, the main objective of the present study was to evaluate its toxicological profile both in vitro, at the level of three healthy cell lines, and in ovo, at the level of the chorioallantoic membrane. Five different concentrations of nicotine were used in keratinocytes, cardiomyocytes, and hepatocytes for the purpose of evaluating cell viability, cell morphology, and its impact on nuclei. Additionally, the hen's egg test on the chorioallantoic membrane (HET-CAM) method was used to assess the biocompatibility and irritant potential of the chorioallantoic membrane. Across all cell lines studied, nicotine was proven to be significantly damaging to cell viability, with the highest concentration tested resulting in less than 2% viable cells. Moreover, the morphology of cells changed dramatically, with alterations in their shape and confluence. Nicotine-induced cell death appears to be apoptotic, based on its impact on the nucleus. In addition, nicotine was also found to have a very strong irritating effect on the chorioallantoic membrane. In conclusion, nicotine has an extremely strong toxicological profile, as demonstrated by the drastic reduction of cell viability and the induction of morphological changes and nuclear alterations associated with cellular apoptosis. Additionally, the HET-CAM method led to the observation of a strong irritating effect associated with nicotine.

The potential role of nicotine in breast cancer initiation, development, angiogenesis, invasion, metastasis, and resistance to therapy

A large body of research studying the relationship between tobacco and cancer has led to the knowledge that smoking cigarettes adversely affects cancer treatment while contributing to the development of various tobacco-related cancers. Nicotine is the main addictive component of tobacco smoke and promotes angiogenesis, proliferation, and epithelial-mesenchymal transition (EMT) while promoting growth and metastasis of tumors. Nicotine generally acts through the induction of the nicotinic acetylcholine receptors (nAChRs), although the contribution of other receptor subunits has also been reported. Nicotine contributes to the pathogenesis of a wide range of cancers including breast cancer through its carcinogens such as (4-methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N-nitrosonornicotine (NNN). Current study aims to review the mechanistic function of nicotine in the initiation, development, angiogenesis, invasion, metastasis, and apoptosis of breast cancer with the main focus on nicotine acetylcholine receptors (nAChRs) and nAChR-mediated signaling pathways as well as on its potential for the development of an effective treatment against breast cancer. Moreover, we will try to demonstrate how nicotine leads to poor treatment response in breast cancer by enhancing the population, proliferation, and self-renewal of cancer stem cells (CSCs) through the activation of α7-nAChR receptors.

Preclinical assessment of stem of Nicotiana tabacum on excision wound model

Agro-waste material derived from N. tabacum has shown enormous potential antioxidant and antimicrobial activity. Hence in the present study, we investigated the wound healing efficacy of ethanolic extract of stem of Nicotiana tabacum on wistar rat model. Ethanolic extract prepared from defatted stem was to check various phytochemicals using spectrophotometric and chromatographic technique. The antioxidant potential was determined by FRAP and Reducing Power assay in extract. Cytotoxicity of extracts was determined using mouse fibroblast L929 cell lines by MTT assay. In vivo angiogenic activity was observed on chick chorioallantoic membrane (CAM) model by observing blood vessels formation and its branching. In vivo wound healing activity was observed on excision wounds in rat model by quantifying percentage of wound contraction, antioxidant activity and histopathology studies. From the present study, polyphenols, tannins and alkaloids were found to be determined in the ethanolic extract by means of spectrophotometric and chromatographic analysis against standards. Antioxidant assay revealed maximum antioxidant potential in ethanolic extract. Cytotoxic effect of extract has not been shown on L929 cell line. From CAM model, extract has shown growth of blood vessels formation at concentration of 480 µg/ml. Topical application of extracts on excision wounds, revealed wound healing activity i.e. 98.7% ± 0.002 on 14th day as well as enzymatic activity (SOD, CAT, GST) and non enzyme content (GSH and Lipid peroxidation) has been found to be high in granulated tissue. Hisopathological studies confirmed the re-epithelization in skin wounds. It can be concluded that stem of N. tabacum can be used as herbal remedy in wound healing process as a topical application.

Use of Oral Anticoagulation and Diabetes Do Not Inhibit the Angiogenic Potential of Hypoxia Preconditioned Blood-Derived Secretomes

Patients suffering from tissue ischemia, who would greatly benefit from angiogenesis-promoting therapies such as hypoxia preconditioned blood-derived secretomes commonly receive oral anticoagulation (OA) and/or have diabetes mellitus (DM). In this study, we investigated the effect of OA administration on the in vitro angiogenic potential of hypoxia preconditioned plasma (HPP) and serum (HPS), prepared from nondiabetic/diabetic subjects who did not receive OA (n = 5) or were treated with acetylsalicylic acid (ASA, n = 8), ASA + clopidogrel (n = 10), or nonvitamin K antagonist oral anticoagulants (n = 7) for longer than six months. The effect of DM was differentially assessed by comparing HPP/HPS obtained from nondiabetic (n = 8) and diabetic (n = 16) subjects who had not received OA in the past six months. The concentration of key proangiogenic (vascular endothelial growth factor or VEGF) and antiangiogenic (thrombospondin-1 or TSP-1 and platelet factor-4 or PF-4) protein factors in HPP/HPS was analyzed via ELISA, while their ability to induce microvessel formations was examined in endothelial cell cultures. We found that OA use significantly reduced VEGF levels in HPP, but not HPS, compared to non-OA controls. While HPP and HPS TSP-1 levels remained largely unchanged as a result of OA usage, HPS PF-4 levels were significantly reduced in samples obtained from OA-treated subjects. Neither OA administration nor DM appeared to significantly reduce the ability of HPP or HPS to induce microvessel formations in vitro. These findings indicate that OA administration does not limit the angiogenic potential of hypoxia preconditioned blood-derived secretomes, and therefore, it does not prohibit the application of these therapies for supporting tissue vascularization and wound healing in healthy or diabetic subjects.

Disparity in age at lung cancer diagnosis between current and former smokers

PURPOSE

In a previous study of smoking cessation in veterans with lung cancer, we noted as an incidental finding that current smokers were much younger than former smokers at diagnosis. To confirm and extend this observation, we analyzed the association of smoking status with age at diagnosis and survival of lung cancer patients.

METHODS

The Jefferson Cancer Registry collects information on all cancer patients registered at this hospital. Information on smoking status has been recorded since 1995. We determined age at diagnosis and survival of current and former smokers with lung cancer.

RESULTS

5111 lung cancer cases were identified in the registry from 1995 to 2011 inclusive. Smoking status was recorded in 4687 cases (91.7%). Of these, 1859 (39.7%) were current, 2423 (51.7%) were former, and 405 (8.6%) were never smokers. There was a 6-year difference in median age at lung cancer diagnosis between the current (63 years) and former smokers (69 years) (P < 0.0001). The median survival was 12.1 months for current versus 14.5 months for former smokers (P < 0.0001).

CONCLUSIONS

These results confirm and extend our observation that among patients diagnosed with lung cancer, current smokers are younger than former smokers. The possible explanations include higher competing causes of death and increased risk of lung cancer among current smokers as well as increasing proportions of former smokers in older populations. Ongoing exposure to tobacco carcinogens may accelerate the development of lung cancer in continuing smokers. This provides more incentive for smokers to quit at the earliest age possible.

Promotion of mammalian angiogenesis by neolignans derived from soybean extracellular fluids

Excessive or insufficient angiogenesis is associated with major classes of chronic disease. Although less studied, small molecules which can promote angiogenesis are being sought as potential therapeutics for cardiovascular and peripheral arterial disease and stroke. Here we describe a bioassay-directed discovery approach utilising size exclusion and liquid chromatography to purify components of soybean xylem sap that have pro-angiogenic activity. Using high resolution accurate mass spectrometry and nuclear magnetic resonance spectroscopy, the structure of two pro-angiogenic molecules (FK1 and FK2) were identified as erythro-guaiacylglycerol-8-O-4'-(coniferyl alcohol) ether (eGGCE), and threo-guaiacylglycerol-8-O-4'-(coniferyl alcohol) ether (tGGCE). These two molecules, which are coniferyl neolignan stereoisomers, promoted in vitro angiogenesis in the μM to nM range. Independently sourced samples of eGGCE and tGGCE exhibited comparable pro-angiogenic activity to the soybean derived molecules. The cellular mode of action of these molecules was investigated by studying their effect on endothelial cell proliferation, migration, tube formation and adhesion to the extracellular matrix (ECM) components, fibronectin and vitronectin. They were found to enhance endothelial cell proliferation and endothelial cell tube formation on Matrigel, but did not affect endothelial cell migration or adhesion to fibronectin and vitronectin. Thus, this study has identified two coniferyl neolignan stereoisomers, eGGCE and tGGCE, as pro-angiogenic molecules, with eGGCE being less active than tGGCE.

Active heavy cigarette smoking is associated with poor survival in Japanese patients with advanced renal cell carcinoma: sub-analysis of the multi-institutional national database of the Japanese Urological Association

Objective

The association between cigarette smoking and survival in patients with renal cell carcinoma is not well studied. We examined the impact of cigarette smoking on survival of patients with advanced renal cell carcinoma using the multi-institutional national database of the Japanese Urological Association.

Methods

From 340 Japanese institutions, 963 patients with renal cell carcinoma of clinical Stage 3 or higher were analyzed. Univariate analysis using the Kaplan-Meier method and multivariate Cox regression models with stepwise selection was used to evaluate overall and cause-specific survival.

Results

Median duration of follow-up was 842 days, and overall and cancer death occurred in 392 (40.7%) and 351 (36.4%) patients, respectively. In multivariate analysis, smoking 20 or more cigarettes daily at diagnosis was associated with poorer overall and cancer-specific survival, especially in Stage 3. According to a Cox proportional hazards model, heavy cigarette smoking at diagnosis and the variables of underweight, fever symptoms, serum lactic dehydrogenase value, serum C-reactive protein value, serum creatinine value, Eastern Cooperative Oncology Group performance status, nephrectomy and clinical stage were significant (P < 0.05) for overall and cancer-specific survival.

Conclusions

We could compare the smoking status at diagnosis and the prognosis of renal cell carcinoma at national wide scale. Heavy active smoking was an independent prognostic factor for overall and cancer-specific survival in patients with advanced renal cell carcinoma, especially in Stage 3.

SNP rs16969968 as a Strong Predictor of Nicotine Dependence and Lung Cancer Risk in a North Indian Population

Background:

The 15q24-25 loci contain genes (CHRNA5 and CHRNA3) encoding nicotinic acetylcholine receptor subunits. We here determined for the first time the association of genetic variants rs16969968 and rs3743074 in CHRNA5 and CHRNA3, respectively, on nicotine dependence and lung cancer risk in a North Indian population by a case-control approach.

Methods:

Venous blood samples were obtained from 324 participants (108 lung cancer patients and 216 healthy individuals). DNA was extracted and PCR amplified with primers flanking the SNPs rs16969968 and rs3743074. Amplicons were subjected to sequencing and logistic regression was used to analyze association between variables.

Results:

The risk variant SNP rs16969968 in both heterozygous and homozygous forms appeared to exert a significant effect on nicotine dependence [GA (OR=2.77) and AA (OR=2.53)]. As expected, smoking was strongly associated with lung cancer (OR= 2.62). Risk allele rs16969968 in CHRNA5 also showed a significant association with increased lung cancer risk in our cohort, alone (OR= 4.99) and with smoking as a co-variable (OR= 4.28). Comparison of our analysis with other populations suggested that individuals with rs16969968 risk allele in the Indian population are more susceptible to lung cancer.

Conclusion:

Overall, the results strongly indicated that, in our cohort North Indian population, the genetic variant rs16969968, but not rs3743074, is significantly associated with both nicotine dependence and increased risk of lung cancer. While the results are significant, there is further need to increase the sample size and improve precision of our risk prediction.

Angiogenic activity in vivo of the particulate matter (PM10)

BACKGROUND

Particulate matter (PM) is the most efficient vehicle for the inhalation and absorption of toxic substances into the body.

METHOD

The present study was aimed at testing the hypothesis that PM10 samples collected on quartz filters exert an angiogenic activity in vivo in the chick embryo chorioallantoic membrane (CAM) assay.

RESULTS

When the low, medium, and high PM10 concentrations filters were tested in the CAM assay, an increasing number of microvessels was detectable after 4 days of applications of the filters. Moreover, at histological level, numerous microvessels and a dense inflammatory infiltrate were recognizable in the CAM mesenchyme.

CONCLUSION

Our data show a clear dose-response relationship between the dose variable (PM10 and Bap) and the outcome variable. So far, the PM10 target value is determined on the basis of regulatory agreements and is not health-based. In addition, the mere gravimetric measure of PM10 cannot be considered a fully reliable surrogate of the overall toxicity of the mixture.

Snus use, smoking and survival among prostate cancer patients

Smoking is associated with prostate cancer mortality. The Scandinavian smokeless tobacco product snus is a source of nicotine but not the combustion products of smoke and has not been studied with respect to prostate cancer survival. The study is nested among 9,582 men with incident prostate cancer within a prospective cohort of 336,381 Swedish construction workers. Information on tobacco use was collected at study entry between 1971 and 1992, and categorized into (i) never users of any tobacco, (ii) exclusive snus: ever users of snus only, (iii) exclusive smokers: ever smokers (cigarette, cigar and/or pipe) only and (iv) ever users of both snus and smoking. Hazard ratios for prostate cancer-specific and total mortality for smoking and snus use based on Cox proportional hazards models adjusted for age, calendar period at diagnosis and body mass index at baseline. During 36 years of follow-up, 4,758 patients died-2,489 due to prostate cancer. Compared to never users of tobacco, exclusive smokers were at increased risk of prostate cancer mortality (HR 1.15, 95% CI: 1.05-1.27) and total mortality (HR 1.17, 95% CI: 1.09-1.26). Exclusive snus users also had increased risks for prostate cancer mortality (HR 1.24, 95% CI: 1.03-1.49) and total mortality (HR 1.19, 95% CI: 1.04-1.37). Among men diagnosed with nonmetastatic disease, the HR for prostate cancer death among exclusive snus users was 3.17 (95% CI: 1.66-6.06). The study is limited by a single assessment of tobacco use prior to diagnosis. Snus use was associated with increased risks of prostate cancer and total mortality among prostate cancer patients. This suggests that tobacco-related components such as nicotine or tobacco-specific carcinogens may promote cancer progression independent of tobacco's combustion products.

Accuracy of Self-reported Smoking Exposure Among Bladder Cancer Patients Undergoing Surveillance at a Tertiary Referral Center

BACKGROUND

Smoking is a risk factor for developing bladder cancer (BCa). Even though continued exposure after diagnosis may adversely affect prognosis, patients may be reluctant to disclose to their physicians that they are currently smoking, leading to inaccurate reporting of exposure and missed opportunities to deliver smoking-cessation advice and treatment in the context of cancer care.

OBJECTIVE

We examined the extent of misclassification of recent smoking exposure among patients undergoing BCa surveillance.

DESIGN SETTING AND PARTICIPANTS

A consecutive sample of 145 patients with a self-reported smoking history and prior initial diagnosis of BCa was recruited from a tertiary referral urology clinic.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Patients were asked if they had smoked a cigarette or used nicotine replacement therapy (NRT) within the past week and whether they lived with a smoker. At the same visit, we collected urine under a biospecimen protocol. We used urinary cotinine, the primary metabolite of nicotine, as an objective biomarker of recent smoking exposure. Nine patients whose urine could not be interpreted for cotinine were excluded. We calculated the smoking status misreporting rate by comparing biochemically verified smoking status (≥31.5 ng/ml vs <31.5 ng/ml) against self-reported current smoking status (yes vs no) while considering recent NRT use.

RESULTS AND LIMITATIONS

Overall, 11% (15 of 136) of patients had cotinine values consistent with current smoking. Of these 15 patients, 7 reported being former smokers, resulting in a 47% misclassification rate. However, three of the seven patients who denied smoking in the past week were currently using NRT. Excluding NRT users, the misclassification rate was 33%.

CONCLUSIONS

Future studies investigating the impact of postdiagnosis nicotine exposure on BCa outcomes should use biochemical verification combined with self-reported smoking exposure to classify patients accurately.

PATIENT SUMMARY

Bladder cancer patients may misreport smoking exposure, thereby missing opportunities for smoking cessation.

Screening of cytotoxic, anti-angiogenic, anti-tumorogenic and antimicrobial activities of Anatolian Vipera ammodytes (Nose-horned viper) venom

Objective:

In the present study, we aimed to screen the cytotoxic, antimicrobial, anti-angiogenic and anti-tumorogenic activities of Anatolian

Material and methods:

The cytotoxicity was screened against PC3, HeLa, CaCo-2, U-87MG, MCF-7 and Vero cells by using MTT assay. The antimicrobial activity on

Results:

The IC

Conclusion:

The results of the present study contributed to the knowledge of the biological activities of Anatolian

[Search of (-)-Cytisine Derivatives as Potential Inhibitors of NF-κB and STAT1]

Design and synthesis ofnew derivatives of (-)-cytisine with a wide spectrum of pharmacological activity, represents the potential therapeutic interest for development of drug candidates for neurodegenerative disorders, inflammatory diseases, and treatment of nicotine addiction. We used HEK293 cell line transiently transfected with N F-κB and STATI luciferase reporter constructs to screen the (-)-cytisine derivatives for their potency to modulate basal and induced NF-κB and STAT1 activity. Currently, NF-κB, STAT1 and components of their signaling pathways are considered as attractive targets for pharmacological intervention, primarily in chronic inflammation, cancer, autoimmune, neurodegenerative and infectious diseases. The library of compounds included the derivatives of (-)-cytisine with amino-, amide-, thio- and carboxamide groups at 3, 5 and 12 position of the starting molecule, as well as some bimolecular derivatives. Our experimental data revealed compounds with moderate activating as well as inhibitory effects for basal NF-κB and STATI activity (IC50 or EC50 values are mainly in the micromolar range). The structure-activity relationship analysis demonstrated that the character of activity (activation or inhibition of NFκ-B and STAT1) is determined by the topology of the substituents at the (-)-cytisine molecule, whereas the nature of the substituents mainly contributes to severity of the effect (introduction of aromatic and adamantyl substituents, as well as thionyl or keto groups are of the principal importance). When evaluating the effect of (-)-cytisine derivatives on activity of NF-κB and STATI, induced by specific agents (TNFα and IFNγ, respectively) we observed that some compounds inhibited basal and stimulated activity of NF-κB and STAT1, another compounds showed the dual effect (an increase of basal- and a decrease of stimulated NF-κB activity) and several compounds increase both basal and induced activity of NF-κB and STAT1. Thus, obtained results suggest that one of the possible mechanisms of biological action of (-)-cytisine derivatives is their ability to influence the components of NF-κB and STAT1-dependent signaling pathways.

Nicotine: Carcinogenicity and Effects on Response to Cancer Treatment - A Review

Tobacco use is considered the single most important man-made cause of cancer that can be avoided. The evidence that nicotine is involved in cancer development is reviewed and discussed in this paper. Both tobacco smoke and tobacco products for oral use contain a number of carcinogenic substances, such as polycyclic hydrocarbons and tobacco-specific N-nitrosamines (TSNA), which undoubtedly contribute to tobacco related cancer. Recent studies have shown that nicotine can affect several important steps in the development of cancer, and suggest that it may cause aggravation and recurrence of the disease. TSNA may be formed from nicotine in the body. The role of nicotine as the major addictive component of tobacco products may have distracted our attention from toxicological effects on cell growth, angiogenesis, and tumor malignancy. Effects on cancer disease are important aspects in the evaluation of possible long-term effects from sources of nicotine, such as e-cigarettes and products for nicotine replacement therapy, which both have a potential for life-long use.

Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: focus on the cancer hallmark of tumor angiogenesis

One of the important 'hallmarks' of cancer is angiogenesis, which is the process of formation of new blood vessels that are necessary for tumor expansion, invasion and metastasis. Under normal physiological conditions, angiogenesis is well balanced and controlled by endogenous proangiogenic factors and antiangiogenic factors. However, factors produced by cancer cells, cancer stem cells and other cell types in the tumor stroma can disrupt the balance so that the tumor microenvironment favors tumor angiogenesis. These factors include vascular endothelial growth factor, endothelial tissue factor and other membrane bound receptors that mediate multiple intracellular signaling pathways that contribute to tumor angiogenesis. Though environmental exposures to certain chemicals have been found to initiate and promote tumor development, the role of these exposures (particularly to low doses of multiple substances), is largely unknown in relation to tumor angiogenesis. This review summarizes the evidence of the role of environmental chemical bioactivity and exposure in tumor angiogenesis and carcinogenesis. We identify a number of ubiquitous (prototypical) chemicals with disruptive potential that may warrant further investigation given their selectivity for high-throughput screening assay targets associated with proangiogenic pathways. We also consider the cross-hallmark relationships of a number of important angiogenic pathway targets with other cancer hallmarks and we make recommendations for future research. Understanding of the role of low-dose exposure of chemicals with disruptive potential could help us refine our approach to cancer risk assessment, and may ultimately aid in preventing cancer by reducing or eliminating exposures to synergistic mixtures of chemicals with carcinogenic potential.

Mechanisms of tumor-promoting activities of nicotine in lung cancer: synergistic effects of cell membrane and mitochondrial nicotinic acetylcholine receptors

Background

One of the major controversies of contemporary medicine is created by an increased consumption of nicotine and growing evidence of its connection to cancer, which urges elucidation of the molecular mechanisms of oncogenic effects of inhaled nicotine. Current research indicates that nicotinergic regulation of cell survival and death is more complex than originally thought, because it involves signals emanating from both cell membrane (cm)- and mitochondrial (mt)-nicotinic acetylcholine receptors (nAChRs). In this study, we elaborated on the novel concept linking cm-nAChRs to growth promotion of lung cancer cells through cooperation with the growth factor signaling, and mt-nAChRs — to inhibition of intrinsic apoptosis through prevention of opening of mitochondrial permeability transition pore (mPTP).

Methods

Experiments were performed with normal human lobar bronchial epithelial cells, the lung squamous cell carcinoma line SW900, and intact and NNK-transformed immortalized human bronchial cell line BEP2D.

Results

We demonstrated that the growth-promoting effect of nicotine mediated by activation of α7 cm-nAChR synergizes mainly with that of epidermal growth factor (EGF), α3 — vascular endothelial growth factor (VEGF), α4 — insulin-like growth factor I (IGF-I) and VEGF, whereas α9 with EGF, IGF-I and VEGF. We also established the ligand-binding abilities of mt-nAChRs and demonstrated that quantity of the mt-nAChRs coupled to inhibition of mPTP opening increases upon malignant transformation.

Conclusions

These results indicated that the biological sum of simultaneous activation of cm- and mt-nAChRs produces a combination of growth-promoting and anti-apoptotic signals that implement the tumor-promoting action of nicotine on lung cells. Therefore, nAChRs may be a promising molecular target to arrest lung cancer progression and re-open mitochondrial apoptotic pathways.

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.

Functional properties of ion channels and transporters in tumour vascularization

Vascularization is crucial for solid tumour growth and invasion, providing metabolic support and sustaining metastatic dissemination. It is now accepted that ion channels and transporters play a significant role in driving the cancer growth at all stages. They may represent novel therapeutic, diagnostic and prognostic targets for anti-cancer therapies. On the other hand, although the expression and role of ion channels and transporters in the vascular endothelium is well recognized and subject of recent reviews, only recently has their involvement in tumour vascularization been recognized. Here, we review the current literature on ion channels and transporters directly involved in the angiogenic process. Particular interest will be focused on tumour angiogenesis in vivo as well as in the different steps that drive this process in vitro, such as endothelial cell proliferation, migration, adhesion and tubulogenesis. Moreover, we compare the 'transportome' system of tumour vascular network with the physiological one.

The impact of smoking on pathologic response to neoadjuvant cisplatin-based chemotherapy in patients with muscle-invasive bladder cancer

PURPOSE

Smoking is the primary etiologic risk factor for bladder cancer and has been implicated in mechanisms of chemoresistance. We investigated smoking as a potential predictor for pathologic outcomes after neoadjuvant chemotherapy (NC) and radical cystectomy (RC) for muscle-invasive bladder cancer.

METHODS

We identified 139 patients treated with neoadjuvant cisplatin-based chemotherapy followed by RC for T2-4aN0M0 bladder cancer. Logistic regression was used to evaluate associations between smoking characteristics and pathologic outcomes (pT0, complete response; pT0/pTis/pT1, any response). In a secondary analysis, multivariate Cox regression was used to assess associations between smoking and recurrence-free and cancer-specific survival.

RESULTS

Our cohort consisted of 99 (71 %) males, with a median age of 65 (interquartile range 56, 71). Prevalence of never, former, and current smokers was 25, 45, and 29 %, respectively. In total, 63 patients experienced disease recurrence, 39 died of disease, and 11 died of other causes. There were no statistically significant associations between smoking characteristics and complete (p = 0.5) or any (p = 0.2) pathologic response to NC. Similarly, we did not find any association between smoking characteristics and recurrence (p = 0.6) or cancer-specific survival (p = 0.9).

CONCLUSIONS

In this series, smoking characteristics were not found to be predictive of pathologic response after NC and RC, although this analysis was limited by the small study sample size. However, the harmful effects of smoking warrants continued emphasis on smoking cessation counseling in bladder cancer patients.

The pathobiological impact of cigarette smoke on pancreatic cancer development (review)

Despite extensive efforts, pancreatic cancer remains incurable. Most risk factors, such as genetic disposition, metabolic diseases or chronic pancreatitis cannot be influenced. By contrast, cigarette smoking, an important risk factor for pancreatic cancer, can be controlled. Despite the epidemiological evidence of the detrimental effects of cigarette smoking with regard to pancreatic cancer development and its unique property of being influenceable, our understanding of cigarette smoke-induced pancreatic carcinogenesis is limited. Current data on cigarette smoke-induced pancreatic carcinogenesis indicate multifactorial events that are triggered by nicotine, which is the major pharmacologically active constituent of tobacco smoke. In addition to nicotine, a vast number of carcinogens have the potential to reach the pancreatic gland, where they are metabolized, in some instances to even more toxic compounds. These metabolic events are not restricted to pancreatic ductal cells. Several studies show that acinar cells are also greatly affected. Furthermore, pancreatic cancer progenitor cells do not only derive from the ductal epithelial lineage, but also from acinar cells. This sheds new light on cigarette smoke-induced acinar cell damage. On this background, our objective is to outline a multifactorial model of tobacco smoke-induced pancreatic carcinogenesis.

Impact of smoking status at diagnosis on disease recurrence and death in upper tract urothelial carcinoma

Cigarette smoking is the leading cause of urothelial carcinoma; however, the impact of smoking on outcomes after surgery for upper tract urothelial carcinoma is unknown. One study suggests that patients with a smoking history have an increased risk of recurrence in the bladder compared with never smokers but these patients did not differ with respect to time to pelvic recurrence or distant metastasis. We subdivided smokers into current and former smokers and performed multivariate analyses that showed that smoking status was not an independent predictor of recurrence when traditional prognostic factors were taken into account. In addition, competing risks analyses showed that although current smoking did not increase the risk of recurrence, it imparted a significant risk of dying compared with former and never smoking.

OBJECTIVE

To evaluate the impact of smoking exposure on oncological outcomes in patients with upper tract urothelial carcinoma (UTUC) treated with radical nephroureterectomy (RNU).

MATERIALS AND METHODS

Patient and disease characteristics from 288 patients with UTUC treated with RNU between 1995 and 2008 were collected from a prospectively maintained database at the Memorial Sloan-Kettering Cancer Center. Disease recurrence was defined as distant metastases, or local failure in the operative site or regional nodes. Factors associated with recurrence and death were determined.

RESULTS

The prevalence of current, former and never smoking at diagnosis was 19.1%, 55.2%, and 25.7%, respectively. 71.0% of patients reported a ≥20 pack-year smoking history. With a median follow-up of 4.02 years, disease recurrence occurred in 27% (n = 79) of patients and 41% (n = 117) died during follow-up. While age at diagnosis, American Society of Anesthesiologists score, advanced stage, nodal involvement and high grade adversely affected recurrence-free survival, smoking status was not associated with risk of recurrence or death in multivariate analysis (P = 0.60). Multivariate competing risks regression showed that current smokers faced a significantly higher risk of death than never smokers (hazard ratio 3.64, 95% confidence interval 1.59-8.34).

CONCLUSIONS

While smoking status at diagnosis and cumulative smoking exposure were not associated with UTUC recurrence, our findings highlight the substantial risk of death in patients with UTUC who are active smokers. Treatment plans to promote smoking cessation are recommended for these patients.

Knock-down of endothelial connexins impairs angiogenesis

Connexins (Cx) are suggested to play important roles in growth and differentiation. Aim of our study was to investigate the role of endothelial Cx in the angiogenic process. Several parameters of angiogenesis were assessed in 18 h Matrigel in vitro angiogenesis assays with human umbilical vein endothelial cells (HUVEC). Prior to culture on Matrigel cells were treated with nicotine or the gap junction inhibitor palmitoleic acid (PA), or siRNA-knock-down of either Cx37, Cx40 or Cx43 was performed. Changes in Cx expression and their effects on gap-junctional communication were investigated using immunofluorescence microscopy, Western blot and Lucifer Yellow dye transfer. Knock-down of each Cx-isoform significantly reduced the amount of specific Cx protein in HUVEC. Cx-knock-down as well as treatment with PA impaired intercellular communication via gap junctions and diminished significantly the number of capillary branches. Knock-down of Cx43 and Cx40 or treatment with PA reduced complexity pattern in the angiogenesis assay. Nicotine significantly reduced expression of Cx43 and Cx37 as well as average length of capillary branches, number of branches and pattern in the Matrigel assay. We can conclude that connexins are involved in angiogenesis, in particular in branch formation. This can partly explain the changes in angiogenesis seen under nicotine treatment.

Nicotine: specific role in angiogenesis, proliferation and apoptosis

Nowadays, tobacco smoking is the cause of ~5-6 million deaths per year, counting 31% and 6% of all cancer deaths (affecting 18 different organs) in middle-aged men and women, respectively. Nicotine is the addictive component of tobacco acting on neuronal nicotinic receptors (nAChR). Functional nAChR, are also present on endothelial, haematological and epithelial cells. Although nicotine itself is regularly not referred to as a carcinogen, there is an ongoing debate whether nicotine functions as a 'tumour promoter'. Nicotine, with its specific binding to nAChR, deregulates essential biological processes like regulation of cell proliferation, apoptosis, migration, invasion, angiogenesis, inflammation and cell-mediated immunity in a wide variety of cells including foetal (regulation of development), embryonic and adult stem cells, adult tissues as well as cancer cells. Nicotine seems involved in fundamental aspects of the biology of malignant diseases, as well as of neurodegeneration. Investigating the biological effects of nicotine may provide new tools for therapeutic interventions and for the understanding of neurodegenerative diseases and tumour biology.

The use of in vitro systems to assess cancer mechanisms and the carcinogenic potential of chemicals

Carcinogenesis is a highly complex, multi-stage process that can occur over a relatively long period before its clinical manifestation. While the sequence in which a cancer cell acquires the necessary traits for tumour formation can vary, there are a number of mechanisms that are common to most, if not all, cancers across the spectrum of possible causes. Many aspects of carcinogenesis can be modelled in vitro. This has led to the development of a number of mechanistically driven, cell-based assays to assess the pro-carcinogenic and anti-carcinogenic potential of chemicals. A review is presented of the current in vitro models that can be used to study carcinogenesis, with examples of cigarette smoke testing in some of these models, in order to illustrate their potential applications. We present an overview of the assays used in regulatory genotoxicity testing, as well as those designed to model other aspects that are considered to be hallmarks of cancer. The latter assays are described with a view to demonstrating the recent advances in these areas, to a point where they should now be considered for inclusion in an overall testing strategy for chemical carcinogens.

Spontaneous smoking cessation before lung cancer diagnosis

INTRODUCTION

We have observed that many patients with lung cancer stop smoking before diagnosis, usually before clinical symptoms, and often without difficulty. This led us to speculate that spontaneous smoking cessation may be a presenting symptom of lung cancer.

METHODS

Patients from the Philadelphia Veterans Affairs Medical Center with lung cancer and for comparison, prostate cancer and myocardial infarction underwent a structured interview about their smoking habits preceding diagnosis. Severity of nicotine addiction was graded using the Fagerström Test for Nicotine Dependence. Among former smokers, dates of cessation, onset of symptoms, and diagnosis were recorded. Difficulty quitting was rated on a scale of 0 to 10. Distributions of intervals from cessation to diagnosis were compared between groups.

RESULTS

All 115 patients with lung cancer had been smokers. Fifty-five (48%) quit before diagnosis, and only six of these (11%) were symptomatic at quitting. Patients with lung cancer who quit were as dependent on nicotine, when smoking the most, as those who continued to smoke, unlike the other groups. Despite this, 31% quit with no difficulty. The median interval from cessation to diagnosis was 2.7 years for lung cancer, 24.3 years for prostate cancer, and 10.0 years for patients with myocardial infarction.

CONCLUSIONS

These results challenge the notion that patients with lung cancer usually quit smoking because of disease symptoms. The hypothesis that spontaneous smoking cessation may be a presenting symptom of lung cancer warrants further investigation.

Acute effects of ethanol on the transfer of nicotine and two dietary carcinogens in human placental perfusion

Many mothers use, against instructions, alcohol during pregnancy. Simultaneously mothers are exposed to a wide range of other environmental chemicals. These chemicals may also harm the developing fetus, because almost all toxic compounds can go through human placenta. Toxicokinetic effects of ethanol on the transfer of other environmental compounds through human placenta have not been studied before. It is known that ethanol has lytic properties and increases the permeability and fluidity of cell membranes. We studied the effects of ethanol on the transfer of three different environmental toxins: nicotine, PhIP (2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine) and NDMA (N-nitrosodimethylamine) in placental perfusion. We tested in human breast cancer adenocarcinoma cell line MCF-7 whether ethanol affects ABCG2/BCRP, which is also the major transporter in human placenta. We found that the transfer of ethanol is comparable to that of antipyrine, which points to passive diffusion as the transfer mechanism. Unexpectedly, ethanol had no statistically significant effect on the transfer of the other studied compounds. Neither did ethanol inhibit the function of ABCG2/BCRP. These experiments represent only the effects of acute exposure to ethanol and chronic exposure remains to be studied.

Cigarette Smoking Is Associated With Advanced Renal Cell Carcinoma

Purpose

Cigarette smoking is a recognized risk factor for renal cell carcinoma (RCC), but little data are available on the association between smoking and RCC biology. We investigated the association between cigarette smoking and RCC stage in a large contemporary multiethnic surgical cohort.

Patients and Methods

We retrospectively reviewed the demographic, clinical, and pathologic data of patients undergoing surgery for RCC between 2000 and 2009. Advanced RCC was defined as metastatic disease, pathologic stage ≥ T3, and/or lymph node involvement. Self-reported smoking history included smoking status, duration, intensity, cumulative exposure, and cessation. Patient and tumor characteristics were compared between the groups in univariate and multivariate analyses.

Results

Of the 845 eligible patients, 19.4% and 29.1% were current and former smokers, respectively, and 207 patients (24.5%) had advanced disease. In both univariate and multivariate analyses, smoking was consistently associated with advanced RCC, and cessation reversed the risk. Current and former smokers had 1.5- and 1.6-fold increased odds of advanced disease, respectively. Heavier smoking (longer duration and exposure) was associated with increased risk of advanced RCC, whereas durable cessation reduced the odds of advanced disease.

Conclusion

Cigarette smoking is an independent risk factor for advanced RCC. Heavier smoking increases the likelihood of advanced disease. Durable smoking cessation attenuated the risk of advanced disease. Given that cigarette smoking is among the few modifiable risk factors for RCC, our results reinforce the importance of smoking cessation and encourage further investigation of the association between smoking and RCC biology.

Nicotinic acetylcholine receptor-based blockade: applications of molecular targets for cancer therapy

The nicotinic acetylcholine receptor (nAChR) was first characterized in 1970 as a membrane receptor of a neurotransmitter and an ion channel. nAChRs have been shown to be involved in smoking-induced cancer formation in multiple types of human cancer cells. In vitro and in vivo animal studies have shown that homopentameric nAChR inhibitors, such as methyllycaconitine and α-Bgtx, can attenuate nicotine-induced proliferative, angiogenic, and metastatic effects in lung, colon, and bladder cancer cells. Recent publications have shown that α9-nAChR is important for breast cancer formation, and in many in vivo studies, α9-nAChR-specific antagonists (e.g., α-ImI, α-ImI, Vc1.1, RgIA, and It14a) produced an analgesic effect. Vc1.1 functions in a variety of animal pain models and currently has entered phase II clinical trials. For cancer therapy, natural compounds such as garcinol and EGCG have been found to block nicotine- and estrogen-induced breast cancer cell proliferation through inhibition of the α9-nAChR signaling pathway. A detailed investigation of the carcinogenic effects of nAChRs and their specific antagonists would enhance our understanding of their value as targets for clinical translation.

Tetraiodothyroacetic acid (tetrac) and nanoparticulate tetrac arrest growth of medullary carcinoma of the thyroid

CONTEXT

Tetraiodothyroacetic acid (tetrac) blocks angiogenic and tumor cell proliferation actions of thyroid hormone initiated at the cell surface hormone receptor on integrin alphavbeta3. Tetrac also inhibits angiogenesis initiated by vascular endothelial growth factor and basic fibroblast growth factor.

OBJECTIVE

We tested antiangiogenic and antiproliferative efficacy of tetrac and tetrac nanoparticles (tetrac NP) against human medullary thyroid carcinoma (h-MTC) implants in the chick chorioallantoic membrane (CAM) and h-MTC xenografts in the nude mouse.

DESIGN

h-MTC cells were implanted in the CAM model (n = 8 per group); effects of tetrac and tetrac NP at 1 microg/CAM were determined on tumor angiogenesis and tumor growth after 8 d. h-MTC cells were also implanted sc in nude mice (n = 6 animals per group), and actions on established tumor growth of unmodified tetrac and tetrac NP ip were determined.

RESULTS

In the CAM, tetrac and tetrac NP inhibited tumor growth and tumor-associated angiogenesis. In the nude mouse xenograft model, established 450-500 mm(3) h-MTC tumors were reduced in size over 21 d by both tetrac formulations to less than the initial cell mass (100 mm(3)). Tumor tissue hemoglobin content of xenografts decreased by 66% over the course of administration of each drug. RNA microarray and quantitative real-time PCR of tumor cell mRNAs revealed that both tetrac formulations significantly induced antiangiogenic thrombospondin 1 and apoptosis activator gene expression.

CONCLUSIONS

Acting via a cell surface receptor, tetrac and tetrac NP inhibit growth of h-MTC cells and associated angiogenesis in CAM and mouse xenograft models.

Tetraiodothyroacetic acid and tetraiodothyroacetic acid nanoparticle effectively inhibit the growth of human follicular thyroid cell carcinoma

BACKGROUND

Tetraiodothyroacetic acid (tetrac) is a deaminated analogue of L-thyroxine that blocks the actions of L-thyroxine and 3,5,3'-triiodo-L-thyronine at the cell surface receptor for thyroid hormone on integrin alpha v beta 3. Tetrac blocks the proliferative effects of thyroid hormone on tumor cells and the proangiogenesis actions of the hormone. In the absence of thyroid hormone, tetrac also blocks angiogenesis induced by various growth factors. Covalently linked to poly(lactide-co-glycolide), tetrac nanoparticles (tetrac NP) do not gain access to the cell interior and act exclusively at the integrin receptor. Here, the activity of tetrac and tetrac NP against follicular thyroid carcinoma (FTC)-236 cells was studied in two models: (1) tumor cell implants in the chick chorioallantoic membrane (CAM) system and (2) xenografts in the nude mouse.

METHODS

FTC-236 cells (10(6)) were implanted in the CAM (n = 8 each for control, and for tetrac and tetrac NP, both at 1 microg/CAM) and the actions of tetrac and tetrac NP were determined after 8 days on tumor-related angiogenesis and tumor growth. Xenografts of 10(7) FTC-236 cells were implanted in nude mice (n = 8 per group). Tetrac or tetrac NP was administered intraperitoneal (1 mg/kg and 1 mg tetrac equivalent/kg, respectively) every other day for 32 days beginning on day 10, when tumor volume was 200-250 mm(3). Animals were monitored after discontinuation of treatment up to day 40.

RESULTS

In the CAM paradigm, tetrac and tetrac NP arrested tumor-related angiogenesis and tumor growth. In the xenograft model, tetrac and tetrac NP promptly and progressively reduced tumor volume (p < 0.01) over 32 days. There was some regrowth of tumor after interruption of tetrac treatment, but at day 40, tumor volume and tumor weight at sacrifice were 45-55% below those of controls (p < 0.01). Animal weight gain was comparable in the control and treatment groups of animals.

CONCLUSIONS

Tetrac and tetrac NP effectively arrest FTC-236 cell tumor growth in the CAM and xenograft models, suggesting its potential utility against FTC.

Long-term nicotine exposure-induced chemoresistance is mediated by activation of Stat3 and downregulation of ERK1/2 via nAChR and beta-adrenoceptors in human bladder cancer cells

Previous reports suggested that bladder cancer patients who continue to smoke while receiving chemotherapy have poorer outcomes than their nonsmoking counterparts. Nicotine, the major addictive compound in cigarette smoke, is known to induce chemoresistance in some cancer cells. Chemoresistance has been linked to the activation of Stat3 (signal transducer and activator of transcription). The objective of this study was to identify the role of Stat3 in chemoresistance induced by nicotine in human bladder cancer cell line, T24 cells. Chemoresistant T24 cells were established by persistent nicotine treatment. Apoptosis and cell cycle parameters were analyzed by Annexin V staining, poly(ADP-ribose) polymerase degradation, caspase activity, and propidium iodide staining. Signal transduction mediating the chemoresistance was detected by Western blotting and small interfering RNA (siRNA) transfection. We provide evidence for the first time that nicotine strongly activated Stat3, leading to Cyclin D1 overexpression, cell cycle perturbations, and chemoresistance. Furthermore, nicotine mobilized Stat3 signaling, resulting in the loss of extracellular signal-regulated protein kinase 1/2 (ERK 1/2) activation and reduced chemosensitivity via nicotinic acetylcholine receptors and beta-adrenoceptors. Inhibition of Stat3 by siRNA or a specific inhibitor restored chemosensitivity in T24 cells. Stat3 could be the major target for increasing chemosensitivity in patients who develop chemoresistance during chemotherapy, and avoidance of cigarette smoking or nicotine-based treatments may increase the efficacy of chemotherapy.

Faster and stronger vascular "Biotube" graft fabrication in vivo using a novel nicotine-containing mold

To accelerate the fabrication of in vivo-tissue engineered autologous vascular prosthetic tissues, the "Biotube," a novel drug-coating mold was designed. The mold was prepared by impregnating nicotine as a model drug into a gelatinous matrix coated on acrylate rods (diameter, 2 mm; length, 20 mm). Upon embedding the molds into dorsal subcutaneous pouches of rats, completely encapsulated Biotubes with significant tissue migration accompanied by rich angiogenesis and having 3.8 times as many neovessels as the uncoated controls, were formed at only 2 weeks. The wall thickness and burst strength of the Biotubes were 399.9 +/- 135.2 microm and 2682.6 +/- 722.6 mmHg, respectively. These values were, respectively, more than 9.6 and 3.2 times greater than the corresponding controls. Therefore, it is confidently expected that the mechanical properties of Biotubes obtained by nicotine coating make them suitable for application as vascular grafts.

Prognostic factors for limited-stage small cell lung cancer: a study of 284 patients

Combined modality therapy is the standard care for limited stage-small cell lung cancer (LS-SCLC) and has led to a significant improvement in patients' survival. This study sought to investigate and define the importance of prognostic effects of known and controversial factors especially the impact of smoking status and treatment strategies. A total of 284 patients with LS-SCLC were diagnosed and prospectively followed from 1997 to 2008 at Mayo Clinic; their characteristics and survival outcome were assessed on the basis of age, gender, smoking history, performance status (PS), tumor recurrence or progression, and treatment using Cox proportional hazards models. Our main results are as follows: (1) Although neither smoking status (former or current smokers) nor intensity (pack-years smoked) at the time of SCLC diagnosis were significant survival predictors, compared to continued smokers (who never quit smoking), patients who quit at or after diagnosis cut the risk of death by 45% (HR=0.55, 95% CI 0.38-0.79); patients who quit before lung cancer diagnosis also experienced survival benefit (HR=0.72, 95% CI 0.52-1.00). (2) Thoracic radiotherapy and platinum-based chemotherapy could significantly improve survival but the timing (within or after one month of diagnosis) of starting chemotherapy or radiation therapy did not. (3) After adjusting for other known factors, a lower PS did not predict poorer survival, suggesting that PS should not be the only factor for making treatment decisions. In conclusion, this study demonstrated the negative impact of continued cigarette smoking on survival; therefore, clinicians and all care providers should strongly encourage smoking cessation at diagnosis of LS-SCLC.

Inhibition of non-neuronal alpha7-nicotinic receptor reduces tumorigenicity in A549 NSCLC xenografts

Nicotinic acetylcholine receptors (nAChR) are expressed on bronchial epithelial and non-small cell lung cancer cells and are involved in cell growth regulation. Nicotine (classical nAChR agonist) induced cell proliferation, whereas nAChR antagonists, d- tubocurarine or alpha-cobratoxin (alpha-CbT), induced cell death. In the current study, we further explored the antitumor potential mechanisms and activities of alpha-CbT. NOD/SCID mice were grafted intraperitoneally or orthotopically and treated with alpha-CbT. alpha-CbT treatment [0.04 ng/kg or 0.12 ng/kg] induced a strong reduction in tumor size ( approximately 90%) in comparison with mice treated with the vehicle alone. Tumor inhibition was related to severe induction of apoptosis. Moreover, neoangiogenesis was strongly inhibited (reduction of cells positive to vascular endothelial growth factor and CD31). Biochemical analyses of the cells, isolated by the primary lung tumor in alpha-CbT-treated mice, showed apoptosis features characterized by: (i) inhibition of BAD phosphorylation at Ser(112) and Ser(136); (ii) BAD dissociation from 14-3-3; (iii) BAD association with BCL-XL; and (iv) cleavage of caspase-9. Moreover, these cells were unable to grow in soft agar and develop tumor, when reinjected into mice. The small interfering RNA-mediated silencing of the alpha7-nAChR gene confirmed that alpha-CbT specifically inhibited the alpha7-nAChR-mediated survival pathway in A549 cells. Furthermore, the specificity of alpha-CbT is reinforced by the lack of effect of short chain toxin (Erabutoxin-a). Once more, the no effect of the low-affinity R33E-modified alpha-CbT strengthened the specificity of this inhibition. Although alpha7-nAChR antagonists, such as alpha-CbT, are unlikely to be a primary therapy, it may provide lead compounds for the design of clinically useful drugs.

Endothelial nicotinic acetylcholine receptors and angiogenesis

Nicotinic acetylcholine receptors (nAChRs) were first described in non-excitable cells just more than a decade ago. The nAChRs on endothelial cells modulate key angiogenic processes, including endothelial cell survival, proliferation, and migration. The receptors may be stimulated by endogenous agonists such as acetylcholine, or exogenous chemicals such as nicotine, to activate physiologic angiogenesis (such as in wound healing) or pathologic angiogenesis (such as retinal neovascularization or tumor angiogenesis). The endothelial nAChRs may represent a target for therapeutic modulation of disorders characterized by insufficient or pathologic angiogenesis.

Nicotine: a pro-angiogenic factor

Angiogenesis, the formation of new blood vessels from pre-existing ones, is regulated by the balance between angiogenic activating and inhibiting factors. Recent evidence indicates that nicotine, an alkaloid compound, presents pro-angiogenic effects in certain concentrations. Nicotine-induced angiogenesis results from the stimulation of non-neuronal nicotinic acetylcholinergic receptors (particularly alpha 7-NAChR subtype) and involves growth factor secretion and activation of intracellular signalling pathways. Although nicotine is a constituent of tobacco smoke, its contribution towards pathophysiology of several tobacco-associated pathologies is controversial. Nowadays, nicotine is used in tobacco smoke cessation programs, but, again, its use is still a matter of discordance regarding cardiovascular morbidity. Nevertheless, given the established effects of nicotine-induced angiogenesis, this alkaloid might be of therapeutic value in situations of inefficient angiogenesis, such as peripheral vascular impairment and tissue ischemia. Conversely, blockade of nicotine pathway can be helpful in complications exhibiting excessive angiogenesis, namely in diabetic retinopathy and nephropathy or neoplasia. Knowing that nicotine is involved in many angiogenic-associated disorders with a high prevalence in the western world, and that this alkaloid widely used in smoke cessation programs, elucidation of the action of nicotine on the vascularization process is of utmost importance. The current paper provides an overview of the effects of nicotine in angiogenesis.

Angiogenic activity of nicotinic acetylcholine receptors: implications in tobacco-related vascular diseases

Cigarette smoking bears a strong etiological association with many neovascularization-related diseases like cancer, cardiovascular disease and macular degeneration. Although cigarette smoke is a complex mixture of many compounds, nicotine is the major active and addictive component of tobacco. Recent studies have shown that nicotine can enhance angiogenesis and arteriogenesis in several experimental systems and animal models. The pro-angiogenic activity of nicotine is mediated by nicotinic acetylcholine receptors, which have been found to be expressed on several types of cells in the vasculature like endothelial cells, smooth muscle cells and immune cells. The present review summarizes the pro-angiogenic activity of nicotine in neoplastic and non-neoplastic disease. The present article focuses on the role of nAChRs, particularly alpha7-nAChR in mediating the pro-angiogenic effects of nicotine. The expression patterns of nAChRs on various components of the vasculature are discussed. The complex signaling pathways underlying the angiogenic effect of nAChRs are described. The review also takes a look at the therapeutic potential of nAChR agonists and antagonists in angiogenesis-related diseases. More basic research as well as patient-oriented clinical studies is needed to firmly establish the clinical potential of nAChR ligands in angiogenesis-based therapies. Also the side effects of targeting nAChRs remain to be established in patients. The development of selective nAChR agonists and antagonists with improved specificity may represent novel therapeutic regimens in the treatment of angiogenesis-related diseases.

Role of non-neuronal nicotinic acetylcholine receptors in angiogenesis

Angiogenesis is a critical physiological process for cell survival and development. Endothelial cells, necessary for the course of angiogenesis, express several non-neuronal nicotinic acetylcholine receptors (AChRs). The most important functional non-neuronal AChRs are homomeric alpha7 AChRs and several heteromeric AChRs formed by a combination of alpha3, alpha5, beta2, and beta4 subunits, including alpha3beta4-containing AChRs. In endothelial cells, alpha7 AChR stimulation indirectly triggers the activation of the integrin alphavbeta3 receptor and an intracellular MAP kinase (ERK) pathway that mediates angiogenesis. Non-selective cholinergic agonists such as nicotine have been shown to induce angiogenesis, enhancing tumor progression. Moreover, alpha7 AChR selective antagonists such as alpha-bungarotoxin and methyllycaconitine as well as the non-specific antagonist mecamylamine have been shown to inhibit endothelial cell proliferation and ultimately blood vessel formation. Exploitation of such pharmacologic properties can lead to the discovery of new specific cholinergic antagonists as anti-cancer therapies. Conversely, the pro-angiogenic effect elicited by specific agonists can be used to treat diseases that respond to revascularization such as diabetic ischemia and atherosclerosis, as well as to accelerate wound healing. In this mini-review we discuss the pharmacological evidence supporting the importance of non-neuronal AChRs in angiogenesis. We also explore potential intracellular mechanisms by which alpha7 AChR activation mediates this vital cellular process.

Nicotine induces hypoxia-inducible factor-1alpha expression in human lung cancer cells via nicotinic acetylcholine receptor-mediated signaling pathways

PURPOSE

Nicotine, the major component in cigarette smoke, can promote tumor growth and angiogenesis in various cancers, including lung cancer. Hypoxia-inducible factor-1alpha (HIF-1alpha) is overexpressed in human lung cancers, particularly in non-small cell lung cancers (NSCLC), and is closely associated with an advanced tumor grade, increased angiogenesis, and resistance to chemotherapy and radiotherapy. The purpose of this study was to investigate the effects of nicotine on the expression of HIF-1alpha and its downstream target gene, vascular endothelial growth factor (VEGF), in human lung cancer cells.

EXPERIMENTAL DESIGN

Human NSCLC cell lines A549 and H157 were treated with nicotine and examined for expression of HIF-1alpha and VEGF using Western blot or ELISA. Loss of HIF-1alpha function using specific small interfering RNA was used to determine whether HIF-1alpha is directly involved in nicotine-induced tumor angiogenic activities, including VEGF expression, cancer cell migration, and invasion.

RESULTS

Nicotine increased HIF-1alpha and VEGF expression in NSCLC cells. Pharmacologically blocking nicotinic acetylcholine receptor-mediated signaling cascades, including the Ca2+/calmodulin, c-Src, protein kinase C, phosphatidylinositol 3-kinase, mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2, and the mammalian target of rapamycin pathways, significantly attenuated nicotine-induced up-regulation of HIF-1alpha protein. Functionally, nicotine potently stimulated in vitro tumor angiogenesis by promoting tumor cell migration and invasion. These proangiogenic and invasive effects were partially abrogated by treatment with small interfering RNA specific for HIF-1alpha.

CONCLUSION

These findings identify novel mechanisms by which nicotine promotes tumor angiogenesis and metastasis and provide further evidences that HIF-1alpha is a potential anticancer target in nicotine-associated lung cancer.

Nicotine inhibits apoptosis induced by cisplatin in human oral cancer cells

Oral cancer demonstrates a strong epidemiological association with smoking, but little is known about the effect of nicotine on oral cancer cell apoptosis. Nicotine, a major component of cigarette smoke, can regulate cell proliferation and angiogenesis and suppress apoptosis induced by chemotherapeutic drugs. The main aim of this study was to investigate the effects of nicotine on apoptosis induced by cisplatin, which is commonly used to treat advanced oral cancers, in the human oral cancer cell line Tca8113. The cells were stimulated with nicotine in the presence or absence of cisplatin, and apoptosis was assayed. The results showed that nicotine inhibited apoptosis induced by cisplatin. It was also observed that survivin played a role in the inhibitory effect of nicotine on apoptosis. Depletion of survivin reduced the protective effect of nicotine against cisplatin-induced apoptosis. Akt, a physiological survivin kinase, is activated by nicotine. Treatment of Tca8113 cells with the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 blocked nicotine-induced survivin expression and enhanced cell apoptosis. These studies suggest that exposure to nicotine might negatively impact on the apoptotic potential of chemotherapeutic drugs, and that survivin plays a key role in the anti-apoptotic effect of nicotine. The Akt pathway may be required for nicotine function.

Nicotine promotes cell proliferation via α7-nicotinic acetylcholine receptor and catecholamine-synthesizing enzymes-mediated pathway in human colon adenocarcinoma HT-29 cells

Cigarette smoking has been implicated in colon cancer. Nicotine is a major alkaloid in cigarette smoke. In the present study, we showed that nicotine stimulated HT-29 cell proliferation and adrenaline production in a dose-dependent manner. The stimulatory action of nicotine was reversed by atenolol and ICI 118,551, a beta(1)- and beta(2)-selective antagonist, respectively, suggesting the role of beta-adrenoceptors in mediating the action. Nicotine also significantly upregulated the expression of the catecholamine-synthesizing enzymes [tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DbetaH) and phenylethanolamine N-methyltransferase]. Inhibitor of TH, a rate-limiting enzyme in the catecholamine-biosynthesis pathway, reduced the actions of nicotine on cell proliferation and adrenaline production. Expression of alpha7-nicotinic acetylcholine receptor (alpha7-nAChR) was demonstrated in HT-29 cells. Methyllycaconitine, an alpha7-nAChR antagonist, reversed the stimulatory actions of nicotine on cell proliferation, TH and DbetaH expression as well as adrenaline production. Taken together, through the action on alpha7-nAChR nicotine stimulates HT-29 cell proliferation via the upregulation of the catecholamine-synthesis pathway and ultimately adrenaline production and beta-adrenergic activation. These data reveal the contributory role alpha7-nAChR and beta-adrenoceptors in the tumorigenesis of colon cancer cells and partly elucidate the carcinogenic action of cigarette smoke on colon cancer.