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ABSTRACT: One way to link chronic inflammation with cancer is through the intrinsic inflammatory pathway, in which genetic alterations that induce malignant transformation also produce a cancer-promoting, inflammatory microenvironment. Signal transducer and activator of transcription 3 (STAT3) contributes to the intrinsic inflammatory pathway in Barrett's esophagus. In human tumors, honokiol (a polyphenol in herbal teas) has growth-inhibitory and proapoptotic effects associated with suppressed activation of STAT3. We used human Barrett's epithelial and esophageal adenocarcinoma cell lines to determine effects of honokiol on cell number, necrosis, apoptosis, and anchorage-independent growth and to explore STAT3's role in those effects. We determined Ras activity and expression of phosphorylated ERK1/2, phosphorylated Akt, and phosphorylated STAT3 in the presence or absence of honokiol. Cells were infected with constitutively active Stat3-C to assess effects of honokiol-induced STAT3 inhibition on apoptosis. Honokiol decreased cell number and increased necrosis and apoptosis in transformed Barrett's cells, but not in nontransformed cells. In adenocarcinoma cells, honokiol also increased necrosis and apoptosis and decreased anchorage-independent growth. Within 30 min of honokiol treatment, transformed Barrett's cells decreased expression of phosphorylated STAT3; decreases in Ras activity and phosphorylated ERK1/2 expression were detected at 24 h. Infection with Stat3-C significantly reduced apoptosis after honokiol treatment. Honokiol causes necrosis and apoptosis in transformed Barrett's and esophageal adenocarcinoma cells, but not in nontransformed Barrett's cells, and the proapoptotic effects of honokiol are mediated by its inhibition of STAT3 signaling. These findings suggest a potential role for targeting the intrinsic inflammatory pathways as a therapeutic strategy to prevent Barrett's carcinogenesis.
AJP Gastrointestinal and Liver Physiology 06/2012; 303(5):G561-9. · 3.43 Impact Factor
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ABSTRACT: Patients who have esophageal eosinophilia without gastroesophageal reflux disease (GERD) nevertheless can respond to proton pump inhibitors (PPIs), which can have anti-inflammatory actions independent of effects on gastric acid secretion. In esophageal cell cultures, omeprazole has been reported to inhibit Th2 cytokine-stimulated expression of eotaxin-3, an eosinophil chemoattractant contributing to esophageal eosinophilia in eosinophilic esophagitis (EoE). The objective of this study was to elucidate molecular mechanisms underlying PPI inhibition of IL-4-stimulated eotaxin-3 production by esophageal cells.
Telomerase-immortalized and primary cultures of esophageal squamous cells from EoE patients were treated with IL-4 in the presence or absence of acid-activated omeprazole or lansoprazole. We measured eotaxin-3 protein secretion by ELISA, mRNA expression by PCR, STAT6 phosphorylation and nuclear translocation by Western blotting, eotaxin-3 promoter activation by an exogenous reporter construct, and STAT6, RNA polymerase II, and trimethylated H3K4 binding to the endogenous eotaxin-3 promoter by ChIP assay. Omeprazole in concentrations ≥5 µM significantly decreased IL-4-stimulated eotaxin-3 protein secretion and mRNA expression. Lansoprazole also blocked eotaxin-3 protein secretion. Omeprazole had no effect on eotaxin-3 mRNA stability or on STAT6 phosphorylation and STAT6 nuclear translocation. Rather, omeprazole blocked binding of IL-4-stimulated STAT6, RNA polymerase II, and trimethylated H3K4 to the eotaxin-3 promoter.
PPIs, in concentrations achieved in blood with conventional dosing, significantly inhibit IL-4-stimulated eotaxin-3 expression in EoE esophageal cells and block STAT6 binding to the promoter. These findings elucidate molecular mechanisms whereby patients with Th2 cytokine-driven esophageal eosinophilia can respond to PPIs, independent of effects on gastric acid secretion.
PLoS ONE 01/2012; 7(11):e50037. · 4.09 Impact Factor
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Xiaofang Huo,
Stefanie Juergens, Xi Zhang,
Davood Rezaei,
Chunhua Yu,
Eric D Strauch,
Jian-Ying Wang,
Edaire Cheng,
Frank Meyer,
David H Wang,
Qiuyang Zhang,
Stuart J Spechler,
Rhonda F Souza
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ABSTRACT: Gastroesophageal reflux is associated with adenocarcinoma in Barrett's esophagus, but the incidence of this tumor is rising, despite widespread use of acid-suppressing medications. This suggests that refluxed material other than acid might contribute to carcinogenesis. We looked for potentially carcinogenetic effects of two bile acids, deoxycholic acid (DCA) and ursodeoxycholic acid (UDCA), on Barrett's epithelial cells in vitro and in vivo. We exposed Barrett's (BAR-T) cells to DCA or UDCA and studied the generation of reactive oxygen/nitrogen species (ROS/RNS); expression of phosphorylated H2AX (a marker of DNA damage), phosphorylated IkBα, and phosphorylated p65 (activated NF-κB pathway proteins); and apoptosis. During endoscopy in patients, we took biopsy specimens of Barrett's mucosa before and after esophageal perfusion with DCA or UDCA and assessed DNA damage and NF-κB activation. Exposure to DCA, but not UDCA, resulted in ROS/RNS production, DNA damage, and NF-κB activation but did not increase the rate of apoptosis in BAR-T cells. Pretreatment with N-acetyl-l-cysteine (a ROS scavenger) prevented DNA damage after DCA exposure, and DCA did induce apoptosis in cells treated with NF-κB inhibitors (BAY 11-7085 or AdIκB superrepressor). DNA damage and NF-κB activation were detected in biopsy specimens of Barrett's mucosa taken after esophageal perfusion with DCA, but not UDCA. These data show that, in Barrett's epithelial cells, DCA induces ROS/RNS production, which causes genotoxic injury, and simultaneously induces activation of the NF-κB pathway, which enables cells with DNA damage to resist apoptosis. We have demonstrated molecular mechanisms whereby bile reflux might contribute to carcinogenesis in Barrett's esophagus.
AJP Gastrointestinal and Liver Physiology 06/2011; 301(2):G278-86. · 3.43 Impact Factor
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ABSTRACT: Cancer-related inflammation recently has been proposed as a major physiological hallmark of malignancy. Some genetic alterations known to promote cellular proliferation and induce malignant transformation also may participate in an intrinsic inflammatory pathway that produces a cancer-promoting inflammatory microenvironment. Little is known about this intrinsic inflammatory pathway in Barrett's esophagus. We have used a series of nontransformed and transformed human Barrett's epithelial cell lines developed in our laboratory to explore the potential contribution of interleukin (IL)-6 and signal transducer and activator of transcription (STAT3) (key molecules in the intrinsic inflammatory pathway) to Barrett's carcinogenesis. We determined IL-6 mRNA expression and protein secretion and protein expression of activated phospho-STAT3 and its downstream target myeloid cell leukemia (mcl)-1 (Mcl-1). We used an IL-6 blocking antibody and two JAK kinase inhibitors (AG490 and JAK inhibitor I) to assess whether STAT3 activation is IL-6 dependent. We also used small interfering RNAs (siRNAs) to STAT3 and Mcl-1 to assess effects of STAT3 pathway inhibition on apoptosis. Phospho-STAT3 was expressed only by transformed Barrett's cells, which also exhibited higher levels of IL-6 mRNA and of IL-6 and Mcl-1 proteins than nontransformed Barrett's cells. STAT3 phosphorylation could be blocked by IL-6 blocking antibody and by AG490 and JAK inhibitor I. In transformed Barrett's cells, rates of apoptosis following exposure to deoxycholic acid were significantly increased by transfection with siRNAs for STAT3 and Mcl-1. We conclude that activation of the IL-6/STAT3 pathway in transformed Barrett's epithelial cells enables them to resist apoptosis. These findings demonstrate a possible contribution of the intrinsic inflammatory pathway to carcinogenesis in Barrett's esophagus.
AJP Gastrointestinal and Liver Physiology 12/2010; 300(3):G454-60. · 3.43 Impact Factor
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ABSTRACT: Human Barrett's cancer cell lines have numerous, poorly-characterized genetic abnormalities and, consequently, those lines have limited utility as models for studying the early molecular events in carcinogenesis. Cell lines with well-defined genetic lesions that recapitulate various stages of neoplastic progression in Barrett's esophagus would be most useful for such studies.
To develop such model cell lines, we started with telomerase-immortalized, non-neoplastic Barrett's epithelial (BAR-T) cells, which are spontaneously deficient in p16, and proceeded to knock down p53 using RNAi, to activate Ras by introducing oncogenic H-Ras(G12V), or both. BAR-T cells infected with either p53 RNAi or oncogenic H-Ras(G12V) alone maintained cell-to-cell contact inhibition and did not exhibit anchorage-independent growth in soft agar. In contrast, the combination of p53 RNAi knockdown with expression of oncogenic H-Ras(G12V) transformed the p16-deficient BAR-T cells, as evidenced by their loss of contact inhibition, by their formation of colonies in soft agar, and by their generation of tumors in immunodeficient mice.
Through these experiments, we have generated a number of transformed and non-transformed cell lines with well-characterized genetic abnormalities recapitulating various stages of carcinogenesis in Barrett's esophagus. These lines should be useful models for the study of carcinogenesis in Barrett's esophagus, and for testing the efficacy of chemopreventive and chemotherapeutic agents.
PLoS ONE 01/2010; 5(9). · 4.09 Impact Factor
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ABSTRACT: Cells that sustain double-strand breaks (DSB) can develop genomic instability, which contributes to carcinogenesis, and agents that cause DSBs are considered potential carcinogens. We looked for evidence of acid-induced DNA damage, including DSBs, in benign Barrett's epithelial (BAR-T) cell lines in vitro and in patients with Barrett's esophagus in vivo. In BAR-T cells, we also explored the mechanisms underlying acid-induced DNA damage. We exposed BAR-T cells to acid in the presence of a fluorescent probe for reactive oxygen species (ROS) and in the presence or absence of disodium 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (which prevents intracellular acidification) and N-acety-l-cysteine (a scavenger of ROS). DSBs were detected by Western blotting and immunofluorescence for histone H2AX phosphorylation and by CometAssay. During endoscopy in patients with Barrett's esophagus, we took biopsy specimens from the metaplastic mucosa before and after esophageal perfusion with 0.1 N HCl for 3 min and sought DSBs by Western blotting for histone H2AX phosphorylation. In BAR-T cells, acid exposure resulted in ROS production and caused a time-dependent increase in levels of phospho-H2AX that continued for at least 48 h. Pretreatment with disodium 4,4'-diisothiocyanatostilbene-2,2'-disulfonate or N-acety-l-cysteine prevented the acid-induced increase in phospho-H2AX levels. DSBs also were detected in biopsy specimens of Barrett's metaplasia following esophageal acid perfusion in all of 6 patients with Barrett's esophagus. Acid exposure causes DSBs in Barrett's epithelial cells through ROS produced as a consequence of intracellular acidification. These findings suggest that acid can be considered a carcinogen in Barrett's esophagus.
Cancer Research 11/2009; 69(23):9083-9. · 7.86 Impact Factor
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Rhonda F Souza,
Xiaofang Huo,
Vivek Mittal,
Christopher M Schuler,
Susanne W Carmack,
Hui Ying Zhang, Xi Zhang,
Chunhua Yu,
Kathy Hormi-Carver,
Robert M Genta,
Stuart J Spechler
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ABSTRACT: Reflux esophagitis is believed to be caused by the caustic effects of refluxed gastric acid on esophageal epithelial cells. However, caustic chemical injuries develop rapidly whereas esophagitis might not appear until weeks after the induction of reflux in animal models. We studied early histologic events in the development of reflux esophagitis in a rat model and performed in vitro experiments to determine whether exposure to acidified bile salts causes esophageal epithelial cells to secrete chemokines that might contribute to inflammation.
At various time points after esophagoduodenostomy, the rat esophagus was removed and inflammatory changes were analyzed by histologic analyses. Human esophageal squamous cell lines were exposed to acidified bile salts to evaluate their effects on cytokine production and immune-cell migration.
Reflux esophagitis started at postoperative day 3 with lymphocytic infiltration of the submucosa that progressed to the epithelial surface-these findings contradicted those expected from a caustic chemical injury. Basal cell and papillary hyperplasia preceded the development of surface erosions. Exposure of squamous cells to acidified bile salts significantly increased the secretion of interleukin-8 and interleukin-1beta; conditioned media from these cells caused significant increases in the migration rates of T cells and neutrophils.
These findings support, but do not prove, an alternative concept for the development of reflux esophagitis in which refluxed gastric juice does not directly damage the esophagus, but rather stimulates esophageal epithelial cells to secrete chemokines that mediate damage of esophageal tissue.
Gastroenterology 09/2009; 137(5):1776-84. · 11.68 Impact Factor
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ABSTRACT: Apoptosis is an important mechanism for maintaining tissue homeostasis and for preventing the proliferation of cells with mutations that could result in malignancy. Barrett's epithelium has been reported to be more resistant to apoptosis than normal esophageal squamous epithelium. We have explored the contribution of the nuclear factor-kappaB (NF-kappaB) pathway to apoptotic resistance in non-neoplastic, telomerase-immortalized esophageal squamous (NES) and Barrett's (BAR-T) epithelial cell lines. We exposed these cells to UV-B irradiation in doses known to cause DNA damage and to induce apoptosis in normal cells, and studied apoptosis as well as the expression of phospho-H2AX, NF-kappaB, Bcl-2, XIAP, cIAP-1, and survivin proteins. We also used Bay 11-7085 and siRNAs to NF-kappaB and Bcl-2 to assess the effects of NF-kappaB and Bcl2 inhibition on apoptosis. UV-B irradiation at low doses (50 and 100 J/m(2)) caused DNA damage in both NES and BAR-T cells but significantly increased apoptosis only in NES cells. UV-B irradiation caused a decrease in the levels of NF-kappaB, Bcl-2, cIAP-1, XIAP, and survivin in NES cells but increased the levels of those proteins in BAR-T cells. The resistance of BAR-T cells to apoptosis induced by low-dose UV-B irradiation was abolished by Bay 11-7085 and by siRNA for NF-kappaB and was decreased significantly by siRNA for Bcl-2. We conclude that the ability of Barrett's epithelial cells to activate the NF-kappaB pathway when they have sustained DNA damage allows them to resist apoptosis. This capacity to avoid apoptosis despite genotoxic damage may underlie the persistence and malignant predisposition of Barrett's metaplasia.
Cancer Research 02/2009; 69(2):672-7. · 7.86 Impact Factor
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ABSTRACT: We hypothesized that, in esophageal squamous epithelial cells, there are differences among individuals in the signal transduction pathways activated by acid reflux that might underlie the development of Barrett's esophagus. To explore that hypothesis, we immortalized nonneoplastic, esophageal squamous cells from patients with gastroesophageal reflux disease (GERD) with (NES-B3T) and without (NES-G2T) Barrett's esophagus and used those cells to study acid effects on MAPK proteins. During endoscopy in patients with GERD with and without Barrett's esophagus, we took biopsy specimens from the distal squamous esophagus to study MAPK proteins before and after esophageal perfusion with 0.1 N HCl. We used immunoblotting and Western blotting to study MEK1/2 phosphorylation at two activating sites (serines 217/221), MEK1 phosphorylation at an inhibitory site (threonine 286), and MEK1/2 activity. After acid exposure, both cell lines exhibited increased MEK1/2 phosphorylation at the activating sites; the NES-B3T cells had higher levels of MEK1 phosphorylation at the inhibitory site, however, and only the NES-G2T cells showed an acid-induced increase in MEK1/2 activity. Similarly, in the squamous epithelium of patients with GERD with and without Barrett's esophagus, acid perfusion increased MEK1/2 phosphorylation at the activating sites in both patient groups; the Barrett's patients had higher levels of MEK1 phosphorylation at the inhibitory site, however, and only the patients without Barrett's demonstrated an acid-induced increase in ERK1/2 phosphorylation. In esophageal squamous cell lines and biopsies from patients with GERD with and without Barrett's esophagus, we have found differences in MAPK pathways activated by acid exposure. We speculate that these differences might underlie the development of Barrett's metaplasia.
AJP Gastrointestinal and Liver Physiology 08/2008; 295(3):G470-8. · 3.43 Impact Factor
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ABSTRACT: We hypothesized that differences among individuals in reflux-induced oxidant production by esophageal squamous epithelial cells might contribute to the development of Barrett's esophagus. We studied the effects of acid and bile acids on the production of reactive oxygen species (ROS) in esophageal squamous cell lines derived from gastroesophageal reflux disease patients with (NES-B3T) and without (NES-G2T) Barrett's esophagus and in a Barrett's epithelial cell line (BAR-T). Cells were incubated with an ROS-sensitive probe and exposed to acidic medium, neutral bile acid medium, or acidic bile acid medium. ROS were quantified in the presence and absence of diphenyleneiodonium chloride (DPI, an NADPH oxidase inhibitor), N(G)-monomethyl-l-arginine (l-NMMA, a nitric oxide synthase inhibitor), and rotenone (a mitochondrial electron transport chain inhibitor). Acidic bile acid medium induced ROS production in both squamous cell lines; however, only DPI blocked ROS production by NES-B3T cells, whereas both DPI and l-NMMA blocked ROS production by NES-G2T cells. In BAR-T cells, acidic medium and acidic bile acid medium induced the production of ROS; l-NMMA prevented ROS production after exposure to acidic medium, whereas ROS production induced by acidic bile acid medium was blocked by DPI. These studies demonstrate that there are differences between esophageal squamous cells and Barrett's epithelial cells and between esophageal squamous cells from gastroesophageal reflux disease patients with and without Barrett's esophagus in the mechanisms of oxidant production induced by exposure to acid and bile acids.
AJP Gastrointestinal and Liver Physiology 03/2008; 294(2):G411-7. · 3.43 Impact Factor
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ABSTRACT: Acid exerts pro-proliferative effects in Barrett's-associated esophageal adenocarcinoma cells. In non-neoplastic Barrett's epithelial (BAR-T) cells, in contrast, we have shown that acid exposure has antiproliferative effects. To explore our hypothesis that the acid-induced, antiproliferative effects are mediated by alterations in the proteins that regulate the G(1)-S cell cycle checkpoint, we exposed non-neoplastic Barrett's cells to acidic media (pH 4.0) and analyzed G(1)-S checkpoint proteins' expression, phosphorylation, and activity levels by Western blot. We studied acid effects on growth (by cell counts), proliferation (by flow cytometry and bromodeoxyuridine incorporation), cell viability (by trypan blue staining), and apoptosis (by annexin V staining), and we used caffeine and small interfering RNA to assess the effects of checkpoint kinase 2 (Chk2) inhibition on G(1)-S progression. Acid exposure significantly decreased cell numbers without affecting cell viability and with only a slight increase in apoptosis. Within 2 h of acid exposure, there was a delay in progression through the G(1)-S checkpoint that was associated with increased phosphorylation of Chk2, decreased levels of Cdc25A, and decreased activity of cyclin E-cyclin-dependent kinase 2; by 4 h, a continued delay at G(1)-S was associated with increased expression of p53 and p21. Caffeine and Chk2 siRNA abolished the acid-induced G(1)-S delay at 2 but not at 4 h. We conclude that acid exposure in non-neoplastic BAR-T cells causes early antiproliferative effects that are mediated by the activation of Chk2. Thus, we have elucidated a mechanism whereby acid can exert disparate effects on proliferation in neoplastic and non-neoplastic BAR-T cells.
Cancer Research 10/2007; 67(18):8580-7. · 7.86 Impact Factor
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ABSTRACT: Telomeres are repetitive DNA sequences located at the ends of chromosomes. Telomeres are shortened by repeated cell divisions and by oxidative DNA damage, and cells with critically shortened telomeres cannot divide. We hypothesized that chronic gastroesophageal reflux disease (GERD)-induced injury of the esophageal squamous epithelium results in progressive telomeric shortening that eventually might interfere with mucosal healing. To address our hypothesis, we compared telomere length and telomerase activity in biopsy specimens of esophageal squamous epithelium from GERD patients and control patients. Endoscopic biopsies were taken from the esophageal squamous epithelium of 38 patients with GERD [10 long-segment Barrett's esophagus (LSBE), 15 short-segment (SSBE), 13 GERD without Barrett's esophagus] and 16 control patients without GERD. Telomere length was assessed using the terminal restriction fragment assay, and telomerase activity was studied by the PCR-based telomeric repeat amplification protocol assay. Patients with GERD had significantly shorter telomeres in the distal esophagus than controls [8.3 +/- 0.5 vs. 10.9 +/- 1.5 (SE) Kbp, P = 0.043]. Among the patients with GERD, telomere length in the distal esophagus did not differ significantly in those with and without Barrett's esophagus (LSBE 7.9 +/- 0.8, SSBE 8.6 +/- 0.9, GERD without BE 8.7 +/- 1.0 Kbp). No significant differences in telomerase activity in the distal esophagus were noted between patients with GERD and controls (4.0 +/- 0.39 vs. 5.2 +/- 0.53 RIUs). Telomeres in the squamous epithelium of the distal esophagus of patients who have GERD, with and without Barrett's esophagus, are significantly shorter than those of patients without GERD despite similar levels of telomerase activity.
AJP Gastrointestinal and Liver Physiology 07/2007; 293(1):G19-24. · 3.43 Impact Factor
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ABSTRACT: For patients with Barrett's esophagus, physicians commonly prescribe antisecretory medications in dosages above those required to heal reflux esophagitis because acid has been shown to have proproliferative and antiapoptotic effects on Barrett's cancer cells and on Barrett's mucosal explants. For a number of reasons, these model systems may not be ideal for determining the effects of acid on benign Barrett's epithelial cells, however. We studied the effects of acid on proliferation and apoptosis in a nonneoplastic, telomerase-immortalized Barrett's epithelial cell line.
Barrett's cells were treated with two 3-minute exposures to acidic media. Cell growth was determined using cell counts, proliferation was studied by flow cytometry, cell viability was determined by trypan blue staining, and apoptosis was assessed by TUNEL and Annexin V. The expression levels of p53 and p21 were determined by Western blotting. p53 siRNA was used to study the effect of p53 inhibition on total cell numbers after acid exposure.
Acid exposure significantly decreased total cell numbers at 24 h without affecting either cell viability or apoptosis. Acid exposure resulted in cell cycle prolongation that was associated with greater expression of p53, but not p21. The acid-induced decrease in total cell numbers was abolished by p53 RNAi.
Acid exposure has p53-mediated, antiproliferative effects in nonneoplastic Barrett's epithelial cells. These findings contradict the results of prior in vitro and ex vivo studies. We speculate that the prescription of antisecretory medications in dosages beyond those required to heal gastroesophageal reflux disease (GERD) symptoms and endoscopic signs could be detrimental. Controlled, prospective clinical trials are needed to determine the optimal level of acid suppression for patients with Barrett's esophagus.
The American Journal of Gastroenterology 02/2007; 102(1):10-20. · 7.28 Impact Factor
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Ruben D Ramirez,
Shelley Sheridan,
Luc Girard,
Mitsuo Sato,
Young Kim,
Jon Pollack,
Michael Peyton,
Ying Zou,
Jonathan M Kurie,
J Michael Dimaio, [......],
Alice L Smith,
Rhonda F Souza,
Laura Gilbey, Xi Zhang,
Kenia Gandia,
Melville B Vaughan,
Woodring E Wright,
Adi F Gazdar,
Jerry W Shay,
John D Minna
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ABSTRACT: By expressing two genes (hTERT and Cdk4), we have developed a method to reproducibly generate continuously replicating human bronchial epithelial cell (HBEC) lines that provide a novel resource to study the molecular pathogenesis of lung cancer and the differentiation of bronchial epithelial cells. Twelve human bronchial epithelial biopsy specimens obtained from persons with and without lung cancer were placed into short-term culture and serially transfected with retroviral constructs containing cyclin-dependent kinase (Cdk) 4 and human telomerase reverse transcriptase (hTERT), resulting in continuously growing cultures. The order of introduction of Cdk4 and hTERT did not appear to be important; however, transfection of either gene alone did not result in immortalization. Although they could be cloned, the immortalized bronchial cells did not form colonies in soft agar or tumors in nude mice. The immortalized HBECs have epithelial morphology; express epithelial markers cytokeratins 7, 14, 17, and 19, the stem cell marker p63, and high levels of p16(INK4a); and have an intact p53 checkpoint pathway. Cytogenetic analysis and array comparative genomic hybridization profiling show immortalized HBECs to have duplication of parts of chromosomes 5 and 20. Microarray gene expression profiling demonstrates that the Cdk4/hTERT-immortalized bronchial cell lines clustered together and with nonimmortalized bronchial cells, distinct from lung cancer cell lines. We also immortalized several parental cultures with viral oncoproteins human papilloma virus type 16 E6/E7 with and without hTERT, and these cells exhibited loss of the p53 checkpoint and significantly different gene expression profiles compared with Cdk4/hTERT-immortalized HBECs. These HBEC lines are a valuable new tool for studying of the pathogenesis of lung cancer.
Cancer Research 01/2005; 64(24):9027-34. · 7.86 Impact Factor
