Ethanol and the tobacco-specific carcinogen, NNK, contribute to signaling in immortalized human pancreatic duct epithelial cells

Major Stressful Life Events and the Risk of Pancreatic, Head and Neck Cancers: A Case-Control Study

BACKGROUND

Major stressful life events have been shown to be associated with an increased risk of lung cancer, breast cancer and the development of various chronic illnesses. The stress response generated by our body results in a variety of physiological and metabolic changes which can affect the immune system and have been shown to be associated with tumor progression. In this study, we aim to determine if major stressful life events are associated with the incidence of head and neck or pancreatic cancer (HNPC).

METHODS

This is a matched case-control study. Cases (CAs) were HNPC patients diagnosed within the previous 12 months. Controls (COs) were patients without a prior history of malignancy. Basic demographic data information on major stressful life events was collected using the modified Holmes-Rahe stress scale. A total sample of 280 was needed (79 cases, 201 controls) to achieve at least 80% power to detect odds ratios (ORs) of 2.00 or higher at the 5% level of significance.

RESULTS

From 1 January 2018 to 31 August 2021, 280 patients were enrolled (CA = 79, CO = 201) in this study. In a multivariable logistic regression analysis after controlling for potential confounding variables (including sex, age, race, education, marital status, smoking history), there was no difference between the lifetime prevalence of major stressful event in cases and controls. However, patients with HNPC were significantly more likely to report a major stressful life event within the preceding 5 years when compared to COs (p = 0.01, OR = 2.32, 95% CI, 1.18-4.54).

CONCLUSIONS

Patients with head, neck and pancreatic cancers are significantly associated with having a major stressful life event within 5 years of their diagnosis. This study highlights the potential need to recognize stressful life events as risk factors for developing malignancies.

Clinical and Biological Data in Patients with Pancreatic Cancer vs. Chronic Pancreatitis-A Single Center Comparative Analysis

INTRODUCTION

In some patients with chronic pancreatitis, the diagnosis of pancreatic cancer can be missed. The objective of the study was to identify clinical and paraclinical data with statistical significance in the differential diagnosis between chronic pancreatitis and pancreatic cancer.

MATERIALS AND METHODS

We conducted a retrospective, observational study on a cohort of 120 patients hospitalized over 3 years. The patients were equally distributed in two groups: group A, with 60 patients with pancreatic cancer, and group B, with 60 patients with chronic pancreatitis. The statistical analysis was carried out by using the R program.

RESULTS

The comparative analysis of pancreatic cancer vs. chronic pancreatitis revealed a stronger link between pancreatic cancer, female gender (p = 0.001) and age over 60 years (p < 0.001). Patients with pancreatic cancer had higher serum values of aspartate aminotransferase (p 0.005), alanine aminotransferase (p 0.006), total bilirubin (p < 0.001), direct bilirubin (p < 0.001), alkaline phosphatase (p 0.030), C-reactive protein (p = 0.049) and uric acid (p 0.001), while patients with chronic pancreatitis presented slightly higher values of amylase (p 0.020) and lipase (p 0.029).

CONCLUSIONS

Female gender, advanced age, elevated aminotransferases, cholestasis markers and uric acid were associated with a higher probability of pancreatic cancer.

The Diverse Involvement of Cigarette Smoking in Pancreatic Cancer Development and Prognosis

Despite extensive research in the pathogenesis, early detection, and therapeutic approaches of pancreatic ductal adenocarcinoma (PDAC), it remains a devastating and incurable disease. As the global incidence and prevalence of PDAC continue to rise, there is a pressing need to place strong emphasis on its prevention. Although it is widely recognized that cigarette smoking, a potentially modifiable risk factor, has been linked to PDAC development, its contribution to prognosis is still uncertain. Moreover, the mechanistic pathways of PDAC progression secondary to smoking are various and lack a summative narration. Herein, we update and summarize the direct and indirect roles cigarette smoking plays on PDAC development, review literature to conclude the impact cigarette smoking has on prognosis, and postulate a comprehensive mechanism for cigarette smoking-induced PDAC.

Alcohol and cigarette smoke components activate human pancreatic stellate cells: implications for the progression of chronic pancreatitis

BACKGROUND

Chronic pancreatitis, a known complication of alcohol abuse, is characterized histopathologically by prominent fibrosis. Pancreatic stellate cells (PSCs) are responsible for producing this fibrous tissue in chronic pancreatitis and are activated by alcohol. Progression of alcoholic chronic pancreatitis (as assessed by calcification and fibrosis) is thought to be facilitated by concurrent smoking, but the mechanisms are unknown. This study aimed to (a) determine whether human PSCs (hPSCs) and rat PSCs express nicotinic acetylcholine receptors (nAChRs), which are known to bind 2 important components of cigarette smoke, namely nicotine and nicotine-derived nitrosamine ketone (NNK), and (b) examine the effects of cigarette smoke components in the presence and absence of alcohol on PSC activation in vitro.

METHODS

Western blotting was used to detect the presence of nAChRs in primary cultures of PSCs. Clinically relevant concentrations of cigarette smoke components (either cigarette smoke extract [CSE], NNK, or nicotine) ± ethanol (EtOH) were used to treat primary cultures of PSCs, and stellate cell activation was assessed by cell migration, proliferation, collagen production, and apoptosis.

RESULTS

We demonstrate, for the first time, that PSCs express nAChRs (isoforms α3, α7, β, ε) and that the expression of the α7 isoform in hPSCs is induced by CSE + EtOH. We also provide novel findings that PSCs are activated by CSE and NNK (both alone and in combination with EtOH) as evidenced by an increase in cell migration and/or proliferation. Further, we demonstrate that activation of PSCs by CSE + EtOH and NNK + EtOH may be mediated via nAChRs on the cells.

CONCLUSIONS

PSCs are activated by clinically relevant concentrations of cigarette smoke components (CSE and NNK), alone and in combination with EtOH. Thus, in alcoholics who smoke, progression of pancreatic fibrosis may be facilitated by the combined effects of alcohol and cigarette smoke components on hPSC behavior.

Impact of Smoking on Pancreatic Cancer Patients Receiving Current Chemotherapy

OBJECTIVE

Smoking may affect pharmacokinetics of chemotherapeutic agents and hemodynamics of the smokers, thereby influencing adverse events and efficacy of chemotherapy in patients with pancreatic cancer (PC). The aim of this study was to clarify how smoking totally affected patients with PC receiving current chemotherapy.

METHODS

We evaluated the impact of smoking status on the performance of chemotherapy and survival in 262 patients with PC including 158 resectable and 104 unresectable PC.

RESULTS

There were more male and younger patients in current smokers than in nonsmokers. In unresectable PC, current smokers had more metastatic tumors than locally advanced tumors compared with nonsmokers. In current smokers receiving chemotherapy, the baseline white blood cell count, neutrophil count, and hemoglobin concentration were significantly higher in current smokers than in nonsmokers. Furthermore, grades 3 to 4 neutropenia was observed more often in nonsmokers than smokers. On the other hand, the performance and efficacy of the planned adjuvant chemotherapy were similar between smokers and nonsmokers. More importantly, there was no significant difference in overall prognosis between smokers and nonsmokers receiving chemotherapy.

CONCLUSIONS

Smoking status has no significant impact on the efficacy of current chemotherapy for both resectable and unresectable PC.

How does cigarette smoking cause acute pancreatitis?

INTRODUCTION

Acute Pancreatitis (AP) is an emerging health problem world-wide and it is a major cause of admissions for gastrointestinal disease in many countries. Amongst the more common causes (alcohol and gallstones), recent evidence has emerged indicating that smoking is an independent risk factor for AP. However, the mechanisms involved in smoking-induced AP have not been completely elucidated. This review puts together all the published evidence in literature to present the clinical and laboratory evidence relating smoking to the causation of AP.

DISCUSSION

The two main metabolites from cigarette smoke, namely nicotine and NNK are able to induce functional and histological changes within the pancreas consistent with AP. The major mechanisms involved include their action on acinar cells and zymogen secretion through pathways involving CCK and the nicotinic preganglionic receptors. Effects on the pancreatic microvasculature may be mediated through the nitric oxide pathway. There is indirect evidence to suggest that nicotine and acrolein may lead to CFTR dysfunction thereby influencing ductal secretion. However, direct evidence for this effect is needed. The effect of cigarette smoke metabolites on stellate cells and the islets warrants further investigation in the context of pathogenesis of AP.

CONCLUSION

Using a step-wise approach, the review revisits the effects of the various metabolites of cigarette smoke on the constituents of the pancreas (exocrine, endocrine, neurohormonal, stellate cells, ductal system) and highlights their proven, and potential, mechanisms in triggering off an attack of AP.

Epidemiologic and Mechanistic Associations Between Smoking and Pancreatitis

OPINION STATEMENT

Alcohol has long been associated with pancreatitis. Although first described more than three decades ago, smoking has been widely accepted as an important risk factor for all forms of pancreatitis only in the past few years. Empiric data has confirmed smoking as an independent and dose-dependent risk for both acute and chronic pancreatitis. Smoking also increases the risk of recurrences and progression of established chronic pancreatitis. The effects of smoking are enhanced in the presence of alcohol consumption. Indirect evidence suggests that smoking cessation may be beneficial in preventing disease progression. Smoking cessation can therefore be an important strategy for primary as well as secondary prevention of pancreatitis. Therefore, in addition to alcohol, physicians should routinely counsel patients for the benefits of smoking cessation. The mechanisms through which cigarette smoke triggers pathological cellular events, resulting in pancreatitis, are unresolved. Although cigarette smoke contains greater than 4000 compounds, principally nicotine and the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) have been broadly studied with regard to pancreatic diseases. Both nicotine and NNK have been shown to induce morphological changes in the pancreas consistent with those seen in pancreatitis. Furthermore, nicotine affects pancreatic secretion and NNK induces premature zymogen activation, two well-known features of pancreatitis. These cigarette toxins may mediate both pro- and anti-inflammatory pathways and can induce changes in pancreatic acinar cell function at the level of transcription, leading to conditions such as thiamin deficiency and mitochondrial dysfunction. Such circumstances could leave the pancreas prone to the development of pancreatitis. This review summarizes relevant research findings and focuses on the epidemiologic links between smoking and pancreatitis, and the cellular pathways that may be significant in induction and evolution of smoking-related pancreatitis.

Pathologic cellular events in smoking-related pancreatitis

Pancreatitis, a debilitating inflammatory disorder, results from pancreatic injury. Alcohol abuse is the foremost cause, although cigarette smoking has recently surfaced as a distinct risk factor. The mechanisms by which cigarette smoke and its toxins initiate pathological cellular events leading to pancreatitis, have not been clearly defined. Although cigarette smoke is composed of more than 4000 compounds, it is mainly nicotine and the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which have been extensively studied with respect to pancreatic diseases. This review summarizes these research findings and highlights cellular pathways which may be of relevance in initiation and progression of smoking-related pancreatitis.

Mitochondrial oxidative stress-induced epigenetic modifications in pancreatic epithelial cells

Emerging studies have linked prooxidative carbamate compound exposures with various human pathologies including pancreatic cancer. In these studies, our aim was to examine mitochondrial oxidative stress-mediated aberrant chromatin responses in human pancreatic ductal epithelial cells. Posttranslational histone modifications, promoter DNA methylation, and micro-RNA (miRNA) expression patterns were evaluated following induction of mitochondrial oxidative stress by N-succinimidyl N-methylcarbamate exposure. In treated cells, perturbation in mitochondrial machinery led to hypermethylation of p16 and smad4 gene promoters and downregulation of respective gene products. Posttranslational histone modifications that include hypoacetylation of acetylated histone (AcH) 3 and AcH4, hypermethylation of monomethylated histone 3 at lysine 9 and trimethylated histone 4 at lysine 20 ubiquitinated histone (uH) 2A/uH2B, and increased phosphorylation of H2AX and H3 were observed in the treated cells. Altered expression of miRNAs denoted possible location of corresponding genes at oxidatively damaged fragile sites. Collectively, our results provide a direct role of mitochondrial oxidative stress-mediated epigenetic imbalance to perturbed genomic integrity in oxygen radical-induced pancreatic injury. Further, identification and characterization of molecular switches that affect these epigenomic signatures and targets thereof will be imperative to understand the complex role of redox-regulatory network in pancreatic milieu.

Akt kinase mediates the prosurvival effect of smoking compounds in pancreatic ductal cells

OBJECTIVES

Cigarette smoking is a major risk factor for pancreatic cancer (PaCa). However, the mechanisms of smoking-induced PaCa remain unknown. Here we investigated the effect of smoking compounds on cell death pathways in pancreatic ductal cells, precursors of PaCa.

METHODS

Human pancreatic ductal cells (HPDE6-c7) were cultured with cigarette smoke extract (CSE) or smoking compound 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Apoptosis and autophagy were assessed by DNA fragmentation and immunofluorescence, respectively.

RESULTS

Exposure to CSE or NNK decreased DNA fragmentation and up-regulated BclXL. Akt kinase was activated by smoking compounds through reactive oxygen species-dependent mechanism. Specifically, Akt activation was prevented by inhibition of nicotinamide adenine dinucleotide oxidase. Molecular or pharmacologic inhibitions of Akt prevented the antiapoptotic effect of smoking compounds. Smoking compounds stimulated rapid (1 hour) and transient activation of 5'-adenosine monophosphate-activated protein kinase and formation of autophagic vacuoles, indicating stimulation of autophagy. Repeated exposure to CSE/NNK (48 hours or longer) abolished the early activation of autophagic markers. Inhibition of Akt prevented the antiautophagic effect of long exposure to smoking compounds, indicating that smoking-induced late activation of Akt prevents autophagy.

CONCLUSIONS

Long exposure of pancreatic ductal cells to smoking compounds inhibited apoptosis and autophagy. The results revealed a central role for Akt kinase in mediating key procarcinogenic effects of smoking compounds.

Smoking and Pancreatic Disease

Smoking is a major risk factor for chronic pancreatitis and pancreatic cancer. However, the mechanisms through which it causes the diseases remain unknown. In the present manuscript we reviewed the latest knowledge gained on the effect of cigarette smoke and smoking compounds on cell signaling pathways mediating both diseases. We also reviewed the effect of smoking on the pancreatic cell microenvironment including inflammatory cells and stellate cells.

Gamma-amino butyric acid (GABA) prevents the induction of nicotinic receptor-regulated signaling by chronic ethanol in pancreatic cancer cells and normal duct epithelia

Pancreatic cancer has a high mortality rate and alcoholism is a risk factor independent of smoking. We have shown that nicotinic acetylcholine receptors (nAChR) regulate pancreatic ductal epithelia and pancreatic ductal adenocarcinoma (PDAC) cells in an autocrine fashion by stimulating their production of the stress neurotransmitters noradrenaline and adrenaline that signal through β-adrenergic receptors (β-AR). Our current study has investigated the modulation of this autocrine regulatory loop by chronic ethanol and explored the potential prevention of these effects by γ-amino butyric acid (GABA). Using MTT assays, cell migration assays, Western blotting, immunoassays, and gene knockdown of individual nAChRs in two PDAC cell lines and in immortalized human pancreatic duct epithelial cells, our data show that treatment for seven days with ethanol induced the protein expression and sensitivity of nAChRs α3, α5, and α7 resulting in increased production of noradrenaline and adrenaline, which drive proliferation and migration via cyclic AMP (cAMP)-dependent signaling downstream of β-ARs. Treatment with GABA prevented all of these responses to chronic ethanol, reducing cell proliferation and migration below base levels in untreated cells. Our findings suggest that alcoholism induces multiple cAMP-dependent PDAC stimulating signaling pathways by upregulating the protein expression and sensitivity of nAChRs that regulate stress neurotransmitter production. Moreover, our data identify GABA as a promising agent for the prevention of PDAC in individuals at risk due to chronic alcohol consumption.

Cigarette smoke promotes drug resistance and expansion of cancer stem cell-like side population

It is well known that many patients continue to smoke cigarettes after being diagnosed with cancer. Although smoking cessation has typically been presumed to possess little therapeutic value for cancer, a growing body of evidence suggests that continued smoking is associated with reduced efficacy of treatment and a higher incidence of recurrence. We therefore investigated the effect of cigarette smoke condensate (CSC) on drug resistance in the lung cancer and head and neck cancer cell lines A549 and UMSCC-10B, respectively. Our results showed that CSC significantly increased the cellular efflux of doxorubicin and mitoxantrone. This was accompanied by membrane localization and increased expression of the multi-drug transporter ABCG2. The induced efflux of doxorubicin was reversed upon addition of the specific ABCG2 inhibitor Fumitremorgin C, confirming the role of ABCG2. Treatment with CSC increased the concentration of phosphorylated Akt, while addition of the PI3K inhibitor LY294002 blocked doxorubicin extrusion, suggesting that Akt activation is required for CSC-induced drug efflux. In addition, CSC was found to promote resistance to doxorubicin as determined by MTS assays. This CSC-induced doxurbicin-resistance was mitigated by mecamylamine, a nicotinic acetylcholine receptor inhibitor, suggesting that nicotine is at least partially responsible for the effect of CSC. Lastly, CSC increased the size of the side population (SP), which has been linked to a cancer stem cell-like phenotype. In summary, CSC promotes chemoresistance via Akt-mediated regulation of ABCG2 activity, and may also increase the proportion of cancer stem-like cells, contributing to tumor resilience. These findings underscore the importance of smoking cessation following a diagnosis of cancer, and elucidate the mechanisms of continued smoking that may be detrimental to treatment.

Tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone initiates and enhances pancreatitis responses

Clinical studies indicate that cigarette smoking increases the risk for developing acute pancreatitis. The nicotine metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a major cigarette smoke toxin. We hypothesized that NNK could sensitize to pancreatitis and examined its effects in isolated rat pancreatic acini and in vivo. In acini, 100 nM NNK caused three- and fivefold activation of trypsinogen and chymotrypsinogen, respectively, above control. Furthermore, NNK pretreatment in acini enhanced zymogen activation in a cerulein pancreatitis model. The long-term effects of NNK were examined in vivo after intraperitoneal injection of NNK (100 mg/kg body wt) three times weekly for 2 wk. NNK alone caused zymogen activation (6-fold for trypsinogen and 2-fold for chymotrypsinogen vs. control), vacuolization, pyknotic nuclei, and edema. This NNK pretreatment followed by treatment with cerulein (40 μg/kg) for 1 h to induce early pancreatitis responses enhanced trypsinogen and chymotrypsinogen activation, as well as other parameters of pancreatitis, compared with cerulein alone. Potential targets of NNK include nicotinic acetylcholine receptors and β-adrenergic receptors; mRNA for both receptor types was detected in acinar cell preparations. Studies with pharmacological inhibitors of these receptors indicate that NNK can mediate acinar cell responses through an nonneuronal α(7)-nicotinic acetylcholine receptor (α(7)-nAChR). These studies suggest that prolonged exposure to this tobacco toxin can cause pancreatitis and sensitize to disease. Therapies targeting NNK-mediated pathways may prove useful in treatment of smoking-related pancreatitis.

The burning question: why is smoking a risk factor for pancreatic cancer?

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease. The prognosis is poor; less than 5% of those diagnosed are still alive five years after diagnosis, and complete remission is still rare. Tobacco smoking is a major risk factor of pancreatic cancer. However, the mechanism(s) through which it causes the disease remains unknown. Accumulating evidence indicates that carcinogenic compounds in cigarette smoke stimulate pancreatic cancer progression through induction of inflammation and fibrosis which act in concert with genetic factors leading to the inhibition of cell death and stimulation of proliferation resulting in the promotion of the PDAC.

Beta-adrenergic signaling in the development and progression of pulmonary and pancreatic adenocarcinoma

Small airway epithelial cells from, which most pulmonary adenocarcinomas (PACs) derive, and pancreatic duct epithelia, from which pancreatic ductal adenocarcinomas (PDACs) originate, share the ability to synthesize and release bicarbonate. This activity is stimulated in both cell types by the α7nicotinic acetylcholine receptor (α7nAChR)-mediated release of noradrenaline and adrenaline, which in turn activate β-adrenergic receptor (β-AR) signaling, leading to the cAMP-dependent release of bicarbonate. The same signaling pathway also stimulates a complex network of intracellular signaling cascades which regulate the proliferation, migration, angiogenesis and apoptosis of PAC and PDAC cells. The amino acid neurotransmitter γ-aminobutyric acid (GABA) serves as the physiological inhibitor of this cancer stimulating network by blocking the activation of adenylyl cyclase. This review summarizes experimental, epidemiological and clinical data that have identified risk factors for PAC and PDAC such as smoking, alcoholism, chronic non neoplastic diseases and their treatments as well as psychological stress and analyzes how these factors increase the cancer-stimulating effects of this regulatory cascade in PAC and PDAC. This analysis identifies the careful maintenance of balanced levels in stimulatory stress neurotransmitters and inhibitory GABA as a key factor for the prevention of PDAC and suggests the marker-guided use of beta-blockers, GABA or GABA-B receptor agonists as well as psychotherapeutic or pharmacological stress reduction as important tools that may render currently ineffective cancer intervention of PAC and PDAC more successful.

Ethanol differentially regulates snail family of transcription factors and invasion of premalignant and malignant pancreatic ductal cells

Pancreatic cancer is one of the deadliest of cancers with a dismal 5-year survival rate. Epidemiological studies have identified chronic pancreatitis as a risk factor for pancreatic cancer. Pancreatic cancer cells also demonstrate increased expression of the transcription factor Snail, a key regulator of epithelial-mesenchymal transition. As ethanol is one of the major causes of pancreatitis, we examined the effect of ethanol on Snail family members in immortalized human pancreatic ductal epithelial (HPDE) cells and in pancreatic cancer cells. Ethanol induced Snail mRNA levels 2.5-fold in HPDE cells, with only 1.5-fold mRNA induction of the Snail-related protein slug. In contrast, ethanol increased Slug mRNA levels 1.5- to 2-fold in pancreatic cancer cells, with minimal effect on Snail. Because Snail increases invasion of cancer cells, we examined the effect of ethanol on invasion of HPDE and pancreatic cancer cells. Surprisingly, ethanol decreased invasion of HPDE cells, but had no effect on invasion of pancreatic cancer cells. Mechanistically, ethanol increased adhesion of HPDE cells to collagen and increased expression of the collagen binding α2- and β1-integrins. In contrast, ethanol did not affect collagen adhesion or integrin expression in pancreatic cancer cells. Also in contrast to HPDE cells, ethanol did not attenuate ERK1/2 phosphorylation in pancreatic cancer cells; however, inhibiting ERK1/2 decreased pancreatic cancer cell invasion. Overall, our results identify the differential effects of ethanol on premalignant and malignant pancreatic cells, and demonstrate the pleiotropic effects of ethanol on pancreatic cancer progression.

GABA (γ-aminobutyric acid), a non-protein amino acid counters the β-adrenergic cascade-activated oncogenic signaling in pancreatic cancer: a review of experimental evidence

GABA is a bioactive constituent of fruits, vegetables, cereals and is believed to play a role in defense against stress in plants. In animals, it acts as an inhibitory neurotransmitter in brain while also expressed in non-neuronal cells. Studies have implicated the regulator of fight or flight stress responses, β-AR signaling cascade, as mediators of cancer growth and progression in in vitro and in vivo models of pancreatic malignancies. Pancreatic cancer is the fourth leading cause of cancer mortality in western countries. This malignancy is generally unresponsive to conventional radio- and chemotherapy, resulting in mortality rate near 100% within 6 months of diagnosis. We review a series of experiments from our laboratory and those of others examining the contribution of this signaling network to pancreatic and other human malignancies. Stimulation of the β-adrenergic receptor by lifestyle and environmental factors, as well as a pre-existing risk of neoplasm, activates downstream effector molecules that lead to pro-oncogenic signaling and thereby aid cancer growth. GABAergic signaling mediated by the serpentine receptor GABA(B) acts as an antagonist to β-adrenergic cascade by intercepting adenylyl cyclase. These evidences enhance the pharmacological value of human diets rich in GABA for use as an adjuvant to standard therapies.

Neurotransmitter receptors as central regulators of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) has a near 100% mortality because it is generally detected at an advanced stage and responds poorly to existing therapeutics. This review summarizes current evidence suggesting important roles of neurotransmitter receptors in the regulation of this malignancy. Experimental evidence indicates that the alpha(7)-nicotinic acetylcholine receptor (alpha(7)nAChR) stimulates PDAC via stress neurotransmitter-mediated activation of beta-adrenergic signaling while the alpha(4)beta(2)nAChR inhibits PDAC via GABA-mediated inhibition of adenylyl cyclase activation. In analogy to molecular mechanisms that govern nicotine addiction, chronic exposure to nicotine or its nitrosated derivative nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone render the stimulatory alpha(7)nAChR hyperactive while desensitizing the inhibitory alpha(4)beta(2)nAChR. Accordingly, PDAC intervention strategies should include the diagnosis of unphysiological neurotransmitter levels and aim to restore any imbalance in stimulatory and inhibitory neurotransmitters.

Ethanol consumption as inductor of pancreatitis

Alcohol abuse is a major cause of pancreatitis, a condition that can manifest as both acute necroinflammation and chronic damage (acinar atrophy and fibrosis). Pancreatic acinar cells can metabolize ethanol via the oxidative pathway, which generates acetaldehyde and involves the enzymes alcohol dehydrogenase and possibly cytochrome P4502E1. Additionally, ethanol can be metabolized via a nonoxidative pathway involving fatty acid ethyl ester synthases. Metabolism of ethanol by acinar and other pancreatic cells and the consequent generation of toxic metabolites, are postulated to play an important role in the development of alcohol-related acute and chronic pancreatic injury. This current work will review some recent advances in the knowledge about ethanol actions on the exocrine pancreas and its relationship to inflammatory disease and cancer.

Desmoplasia of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer and is characterized by remarkable desmoplasia. The desmoplasia is composed of extracellular matrix (ECM) proteins, myofibroblastic pancreatic stellate cells, and immune cells associated with a multitude of cytokines, growth factors, and ECM metabolizing enzymes. The mechanisms of participation of this complex matrix process in carcinogenesis are only starting to be appreciated. Recent studies showed key roles for stellate cells in the production of ECM proteins as well as cytokines and growth factors that promote the growth of the cancer cells all present in the desmoplastic parts of PDAC. In addition, interactions of ECM proteins and desmoplastic secreted growth factors with the cancer cells of PDAC activate intracellular signals including reactive oxygen species that act to make the cancer cells resistant to dying. These findings suggest that the desmoplasia of PDAC is a key factor in regulating carcinogenesis of PDAC as well as responses to therapies. A better understanding of the biology of desmoplasia in the mechanism of PDAC will likely provide significant opportunities for better treatments for this devastating cancer.

Nicotine stimulates pancreatic cancer xenografts by systemic increase in stress neurotransmitters and suppression of the inhibitory neurotransmitter gamma-aminobutyric acid

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer mortality in Western countries. We have shown previously that four representative human PDAC cell lines were regulated by beta-adrenoreceptors via cyclic adenosine 3',5'-monophosphate (cAMP)-dependent signaling. In the current study, we have tested the hypothesis that nicotine stimulates the growth of PDAC xenografts in nude mice by increasing the systemic levels of the stress neurotransmitters adrenaline and noradrenaline, which are the physiological agonists for beta-adrenoreceptors and that inhibition by gamma-aminobutyric acid (GABA) of the adenylyl cyclase-dependent pathway downstream of adrenoreceptors blocks this effect. The size of xenografts from PDAC cell line Panc-1 was determined 30 days after inoculation of the cancer cells. Stress neurotransmitters in serum as well as cAMP in the cellular fraction of blood and in tumor tissue were assessed by immunoassays. Levels of GABA, its synthesizing enzymes GAD65 and GAD67 and beta-adrenergic signaling proteins in the tumor tissue were determined by western blotting. Nicotine significantly increased the systemic levels of adrenaline, noradrenaline and cAMP while increasing xenograft size and protein levels of cAMP, cyclic AMP response element-binding protein and p-extracellular signal-regulated kinase 1/2 in the tumor tissue. Nicotine additionally reduced the protein levels of both GAD isozymes and GABA in tumor tissue. Treatment with GABA abolished these responses to nicotine and blocked the development of xenografts in mice not exposed to nicotine. These findings suggest that the development and progression of PDAC is subject to significant modulation by stimulatory stress neurotransmitters and inhibitory GABA and that treatment with GABA may be useful for marker-guided cancer intervention of PDAC.

GABA B receptor is a novel drug target for pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer death. Smoking, diabetes, and pancreatitis are risk factors. It has been shown that the growth of PDAC and pancreatic duct epithelial cells is regulated by beta-adrenoreceptors (beta-ARs). The activity of beta-ARs in the central nervous system is counteracted by gamma-aminobutyric acid (GABA) via GABA B receptor-mediated inhibition of adenylyl cyclase. The aim of the study was to investigate if GABA B R inhibits beta-AR signaling in PDAC and pancreatic duct epithelial cells, thus blocking driving forces of cancer progression, such as cell proliferation and cell migration.

METHODS

Intracellular cAMP was measured by immunoassays, DNA synthesis by BrdU incorporation assays, activation of ERK1/2 by ERK activation assays, and Western blots and metastatic potential by cell migration assays in the human PDAC cell lines PANC-1 and BXPC-3 and immortalized human pancreatic duct epithelial cells HPDE6-C7. The expression of norepinephrine, PKAR IIalpha, and GABA in PDAC microarrays was assessed by immunohistochemistry. RESULTS.: Stimulation of the GABA B R by GABA or baclofen inhibited isoproterenol-induced cAMP signaling below base levels. ERK1/2 activity in response to isoproterenol was blocked by GABA, an effect enhanced by transient overexpression of the GABA B R and abolished by GABA B R knockdown. DNA synthesis and cell migration were stimulated by isoproterenol, responses blocked by GABA and baclofen. Norepinephrine and PKAR IIalpha were overexpressed while GABA was underexpressed in human PDAC tissue arrays.

CONCLUSIONS

The data suggest the stimulation of GABA B R signaling as a novel target for the treatment and prevention of pancreatic cancer.

Lifetime history of tobacco consumption and K-ras mutations in exocrine pancreatic cancer

OBJECTIVES

We analyzed the relation between mutations in codon 12 of the K-ras oncogene and lifetime consumption of tobacco in patients with exocrine pancreatic cancer (EPC).

METHODS

Incident cases of EPC were prospectively identified and interviewed during hospital admission about smoking and other factors. Exact logistic regression was used to compare EPC cases (N = 107) with and without K-ras mutations (case-case study).

RESULTS

Mutated cases were nonsignificantly less likely to have been smokers than wild-type cases: the odds ratio adjusted by age and sex was 0.54 (95% confidence interval, 0.10-2.69; P = 0.613). With respect to never smokers, adjusted odds ratios for former and current smokers were 0.79 and 0.36, respectively (P = 0.193). Pack-years smoked, years of smoking, and cigarettes smoked per year also tended to be higher in nonmutated than in mutated cases. Neither age at onset of smoking nor the time between quitting and diagnosis were associated with K-ras.

CONCLUSIONS

Tobacco does not play a major part in the acquisition of K-ras mutations in the pancreatic epithelium. Although both smoking and K-ras mutations have important roles in the etiopathogenesis of EPC, the 2 processes may act independently.

The role of protein kinases in pancreatic carcinogenesis

BACKGROUND

Pancreatic cancer is a devastating disease with a very poor prognosis.

METHODS

Protein kinases are aberrantly expressed in pancreatic ductal adenocarcinoma as analyzed by microarray-based expression analysis and have an impact for pancreatic cancer. Many regulatory proteins have an impact on cancer progression similar to the kinases. The list contains several regulators of kinases derived from the cell cycle control or the mitogen-activated protein (MAP)-kinase pathway.

CONCLUSION

Both signalling pathways are essential for tumor progression and pancreatic ductal adenocarcinoma (PDAC) malignancy.