Transformation Of Human Bronchial Epithelial Cells Research Articles

Arsenic induces bronchial epithelial carcinogenesis with mitochondrial dysfunction through AKAP95-mediated cell cycle alterations

Arsenic is a widely existing pollutant in the environment, but the mechanism of occurrence and development of lung cancer by long-term arsenic exposure needs to be elucidated further. How the high and low doses of arsenic induce human bronchial epithelial cell transformation is yet to be elucidated. In the present study, human bronchial epithelial cells were exposed to varying high-dose sodium arsenite (NaAsO2) for the short-term or treated with low dose for long-term. The data showed that both short- and long-term treatment promoted G1/S transition of Beas-2B cells, inducing a significant increase in the expression of AKAP95, cyclin D1, cyclin D2, and cyclin E1. However, silencing AKAP95 by treating cells with siAKAP95 exerted a protective function that inhibited G1/S transition, suggesting a regulatory mechanism of AKAP95 on the cell cycle during cell malignant transformation induced by NaAsO2. In addition, mitochondrial dysfunctions occurred during NaAsO2 exposure. Beas-2B cells exposed to low-dose NaAsO2 for long-term were subcultured for 20 generations, and the exposure time was positively proportional to the growth and migration rate of the cells. The exposed cells were used in a tumor-bearing transplantation experiment (mice), and the results showed that the longer the exposure time, the faster the tumor volume growth rate of As-Beas-2B cells. Tumor tissues were excised for hematoxylin-eosin staining, which showed altered cell morphology and increased volume.

MiR-377-3p-Mediated EGR1 Downregulation Promotes B[a]P-Induced Lung Tumorigenesis by Wnt/Beta-Catenin Transduction.

Polycyclic aromatic hydrocarbons (PAHs), particularly benzo[a]pyrene (B[a]P), found in cigarette smoke and air pollution, is an important carcinogen. Nevertheless, early molecular events and related regulatory effects of B[a]P-mediated cell transformation and tumor initiation remain unclear. This study found that EGR1 was significantly downregulated during human bronchial epithelial cell transformation and mice lung carcinogenesis upon exposure to B[a]P and its active form BPDE, respectively. In contrast, overexpression of EGR1 inhibited the BPDE-induced cell malignant transformation. Moreover, miR-377-3p was strongly enhanced by BPDE/B[a]P exposure and crucial for the inhibition of EGR1 expression by targeting the 3’UTR of EGR1. MiR-377-3p antagomir reversed the effect of EGR1 downregulation in cell malignant transformation and tumor initiation models. Furthermore, the B[a]P-induced molecular changes were evaluated by IHC in clinical lung cancer tissues and examined with a clinic database. Mechanistically, EGR1 inhibition was also involved in the regulation of Wnt/β-catenin transduction, promoting lung tumorigenesis following B[a]P/BPDE exposure. Taken together, the results demonstrated that bBenzo[a]pyrene exposure might induce lung tumorigenesis through miR-377-3p-mediated reduction of EGR1 expression, suggesting an important role of EGR1 in PAHs-induced lung carcinogenesis.

Sustained high expression of NRF2 and its target genes induces dysregulation of cellular proliferation and apoptosis is associated with arsenite-induced malignant transformation of human bronchial epithelial cells

In arsenic toxicity, activation of the erythroid 2-related factor 2 (NRF2) pathway is regarded as a driver of cancer development and progression; however, the mechanisms by which NRF2 gene expression regulates cell cycle progression and mediates pathways of cellular proliferation and apoptosis in arsenic-induced lung carcinogenesis are poorly understood. In this study, we explored the regulatory functions of NRF2 expression and its target genes in immortalized human bronchial epithelial (HBE) cells continuously exposed to 1.0 μM sodium arsenite over approximately 43 passages (22 weeks). The experimental treatment induced malignant transformation in HBE cells, characterized by increased cellular proliferation and soft agar clone formation, as well as cell migration, and accelerated cell cycle progression from G0/G1 to S phase with increased levels of cyclin E-CDK2 complex,decreased cellular apoptosis rate. Moreover, we observed a sustained increase in NRF2 protein levels and those of its target gene products (NQO1, BCL-2) with concurrently decreased expression of apoptosis-related proteins (BAX, Cleaved-caspase-3/Caspase-3 and CHOP) and increased expression of the anti-apoptotic protein MCL-1. Silencing NRF2 expression with small interfering RNA (siRNA) in arsenite-transformed (T-HBE) cells was shown to reverse the malignant phenotype. Further, siRNA silencing of NQO1 significantly decreased levels of the cyclin E-CDK2 complex, inhibiting G0/G1 to S phase cell cycle progression and transformation to the T-HBE phenotypes. This study demonstrated a novel role for the NRF2/NQO1 signaling pathway in mediating arsenite-induced cell transformation by increasing the expression of cyclin E-CDK2, and accelerating the cell cycle and cell proliferation. Arsenite promotes activation of the NRF2/BCL-2 signaling pathway inhibited CHOP increasing cellular resistance to apoptosis and further promoting malignant transformation.

Abstract A12: Quercetin inhibits multiple pathways involved in interleukin 6 secretion from human lung fibroblasts and activity in bronchial epithelial cell transformation induced by benzo[a]pyrene diol epoxide

Abstract The interaction between epithelial and stromal cells through soluble factors such as cytokines plays an important role in carcinogenesis. Breaking this cancer-promoting interaction poses an opportunity for cancer prevention. The tumor-promoting function of interleukin 6 (IL-6) has been documented; however, the underlying mechanisms of this function in lung carcinogenesis are not well elucidated. Here, we show that benzo[a]pyrene diol epoxide (BPDE, the active metabolite of cigarette smoke carcinogen benzo[a]pyrene)-induced human bronchial epithelial cell (HBEC) transformation was enhanced by IL-6 in vitro. The carcinogen/IL-6-transformed cells exhibited higher expression of STAT3 (signal transducer and activator of transcription 3) when compared with cells transformed by BPDE alone. Constitutive STAT3 activation drove cell proliferation and survival through anti-apoptosis gene expression. We further show that quercetin, a dietary compound having preventive properties for lung cancer, decreased BPDE-stimulated IL-6 secretion from human lung fibroblasts through inhibition of the NF-κB and ERK pathways. The inhibition was accomplished at clinically achievable concentrations of the compound. Finally, quercetin blocked IL-6-induced STAT3 activation in HBECs, and IL-6 enhancement of HBEC transformation by BPDE was abolished by quercetin treatment. Altogether, our data reveal novel mechanisms for IL-6 in lung carcinogenesis and for the preventive role of quercetin in the process. Citation Format: Wenshu Chen, Mabel T. Padilla, Xuling Xu, Dhimant Desai, Jacek Krzeminski, Shantu Amin, Yong Lin. Quercetin inhibits multiple pathways involved in interleukin 6 secretion from human lung fibroblasts and activity in bronchial epithelial cell transformation induced by benzo[a]pyrene diol epoxide. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr A12.

Abstract 958: MiR-196b is an epigenetically silenced tumor suppressor for lung cancer

Abstract Silencing of microRNAs by promoter hypermethylation could play a significant role in lung cancer initiation and progression. A pre-malignancy model using carcinogen transformed human bronchial epithelial cells (HBECs) treated with the demethylating agent 5-aza-2’deoxycytidine followed by next-generation sequencing identified miR-196b and miR-34c-5p as being epigenetically regulated. Bisulfite sequencing confirmed silencing via dense promoter hypermethylation that was commonly replicated in malignant cell lines and primary tumors. Functional studies of miR-196b revealed that it was epigenetically silenced by chromatin modification and DNA methylation during transformation of HBECs and re-expression modulated genes involved in cell cycle regulation. Stable re-expression led to a cell cycle arrest mediated in part through transcriptional regulation of the FOS oncogene that was replicated in vivo by a profound reduction in growth of tumor xenografts. Luciferase assays demonstrated that forced expression of miR-196b inhibits FOS promoter and AP-1 reporter activity. A case-control study showed that methylation of miR-196b in sputum was strongly associated with lung cancer (OR = 4.7, p<0.001). These studies identify miR-196 as a tumor suppressor whose silencing early in lung carcinogenesis may provide a selective growth advantage to pre-malignant cells. Targeted delivery of this microRNA could benefit prevention and therapy for the management of lung cancer. Citation Format: Carmen S. Tellez, Daniel E. Juri, Kieu Do, Maria A. Picchi, Teresa Wang, Gang Liu, Avrum Spira, Steven A. Belinsky. MiR-196b is an epigenetically silenced tumor suppressor for lung cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 958.

STAT3-regulated exosomal miR-21 promotes angiogenesis and is involved in neoplastic processes of transformed human bronchial epithelial cells

Although microRNA (miRNA) enclosed in exosomes can mediate intercellular communication, the roles of exosomal miRNA and angiogenesis in lung cancer remain unclear. We investigated functions of STAT3-regulated exosomal miR-21 derived from cigarette smoke extract (CSE)-transformed human bronchial epithelial (HBE) cells in the angiogenesis of CSE-induced carcinogenesis. miR-21 levels in serum were higher in smokers than those in non-smokers. The medium from transformed HBE cells promoted miR-21 levels in normal HBE cells and angiogenesis of human umbilical vein endothelial cells (HUVEC). Transformed cells transferred miR-21 into normal HBE cells via exosomes. Knockdown of STAT3 reduced miR-21 levels in exosomes derived from transformed HBE cells, which blocked the angiogenesis. Exosomes derived from transformed HBE cells elevated levels of vascular endothelial growth factor (VEGF) in HBE cells and thereby promoted angiogenesis in HUVEC cells. Inhibition of exosomal miR-21, however, decreased VEGF levels in recipient cells, which blocked exosome-induced angiogenesis. Thus, miR-21 in exosomes leads to STAT3 activation, which increases VEGF levels in recipient cells, a process involved in angiogenesis and malignant transformation of HBE cells. These results, demonstrating the function of exosomal miR-21 from transformed HBE cells, provide a new perspective for intervention strategies to prevent carcinogenesis of lung cancer.

Effects of model airborne pollutants on AhR-dependent gene regulation in normal vs. transformed human bronchial epithelial cells (HBEC)

Effects of model airborne pollutants on AhR-dependent gene regulation in normal vs. transformed human bronchial epithelial cells (HBEC)

Anti-oncogene of opioid binding protein/cell adhesion molecule-like methylation status in malignant transformation of human bronchial epithelial cells induced by glycidyl methacrylate

To analyze the opioid binding protein/cell adhesion molecule-like (OPCML) methylation status at different stages of malignant transformation of human bronchial epithelial (16HBE) cells induced by Glycidyl Methacrylate (GMA) and to explore the effect of OPCML methylation in the process of malignant transformation. Cells were harvested at different stages (the 10th generation, the 20th generation and the 30th generation). To verify the Methylation chip result of OPCML methylation status in the process of malignant transformation, we detected it by methylation-specific-PCR (MSP); Real-time fluorescence Quantitative PCR (qPCR) were applied to measure the gene expression levels of OPCML at different transformed stage, and compared with the control groups (treated with DMSO). Based on the result of methylation chip, the gene of OPCML methylation occurred in all stages, which was consistent to the result of MSP; qPCR showed that the levels of gene expression decreased in the 20th generation and 30th generation. Methylation status of OPCML gene promoter could be considered as a stable and specific biomarker in the transformation process.

Epigenetic silencing of microRNA-218 via EZH2-mediated H3K27 trimethylation is involved in malignant transformation of HBE cells induced by cigarette smoke extract.

Abnormal expression of miRNAs has been implicated in the pathogenesis of human lung cancers, most of which are attributable to cigarette smoke. The mechanisms of action, however, remain obscure. Here, we report that there are decreased expression of miR-218 and increased expression of EZH2 and H3K27me3 during cigarette smoke extract (CSE)-induced transformation of human bronchial epithelial (HBE) cells. Depletion of EZH2 by siRNA or by the EZH2 inhibitor, 3-deazaneplanocin A, attenuated CSE-induced decreases of miR-218 levels and increases of H3K27me3, which epigenetically controls gene transcription, and BMI1, an oncogene. Furthermore, ChIP assays demonstrated that EZH2 and H3K27me3 are enriched at the miR-218-1 promoter in HBE cells exposed to CSE, indicating that EZH2 mediates epigenetic silencing of miR-218 via histone methylation. In addition, miR-218 directly targeted BMI1, through which miR-218 ablates cancer stem cells (CSCs) self-renewal in transformed HBE cells. In CSE-transformed HBE cells, the protein level of Oct-4 and mRNA levels of CD133 and CD44, indicators of the acquisition of CSC-like properties, were reduced by over-expression of miR-218, and over-expression of miR-218 decreased the malignancy of transformed HBE cells. Thus, we conclude that epigenetic silencing of miR-218 via EZH2-mediated H3K27 trimethylation is involved in the acquisition of CSC-like properties and malignant transformation of HBE cells induced by CSE and thereby contributes to the carcinogenesis of cigarette smoke.

MicroRNA-191, by promoting the EMT and increasing CSC-like properties, is involved in neoplastic and metastatic properties of transformed human bronchial epithelial cells.

Lung cancer is the leading cause of cancer mortality worldwide. A common interest in lung cancer research is the identification of biomarkers for early diagnosis and accurate prognosis. There is increasing evidence that microRNAs (miRNAs) are involved in lung cancer. To explore new biomarkers of chemical exposure in risk assessment of chemical carcinogenesis and lung cancer, we analyzed miRNA expression profiles of human bronchial epithelial (HBE) cells malignantly transformed by arsenite. High-throughput microarray analysis showed that 51 miRNAs were differentially expressed in transformed HBE cells relative to normal HBE cells. In particular, miR-191 was up-regulated in transformed cells. In HBE cells, arsenite induced increases of miR-191 and WT1 levels, decreased BASP1 expression, and activated the Wnt/β-catenin pathway, effects that were blocked by miR-191 knockdown. In addition, a luciferase reporter assay indicated that BASP1 is a direct target of miR-191. By inhibiting the expression of BASP1, miR-191 increased the expression of WT1 to promote activation of Wnt/β-catenin pathway. In transformed cells, inhibition of miR-191 expression blocked the epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC)-like properties of cells and decreased their migratory capacity and neoplastic properties. Thus, these results demonstrate that miR-191 modulates the EMT and the CSC-like properties of transformed cells and indicate that it is an onco-miR involved in the neoplastic and metastatic properties of transformed cells.

Exosomal miR-21 derived from arsenite-transformed human bronchial epithelial cells promotes cell proliferation associated with arsenite carcinogenesis.

Intercellular communications within the cancer microenvironment coordinate the assembly of various cell types. Exosomes are mediators of intercellular communication in immune signaling, tumor promotion, stress responses, and angiogenesis. The present research aimed to determine whether miRNAs secreted from human bronchial epithelial (HBE) cells transformed by 1.0μM arsenite are transferred into normal HBE cells and are functionally active in the recipient cells. The results show that miR-21 is involved in exosome-mediated intercellular communication between neoplastic and normal HBE cells. Exosomes derived from transformed HBE cells stimulated proliferation of normal HBE cells, whereas exosomes from miR-21 depleted cells failed to stimulate proliferation. In normal HBE cells, the expression of phosphatase and tensin homolog, a target gene for miR-21, was increased by exosomal miR-21, indicating that exogenous miRNAs, via exosomal transport, function-like endogenous miRNAs. Concordantly, specific reduction of miR-21 content in exosome-producing transformed cells abolished the stimulation of proliferation by exosomes. Collectively, the data indicate that transformed HBE cells release exosomes containing miR-21, stimulating proliferation in neighboring normal HBE cells and supporting the concept that exosomal miRNAs are involved in cell-cell communication during carcinogenesis induced by environmental chemicals.

Angiogenesis, mediated by miR-21, is involved arsenite-induced carcinogenesis

Evidence for arsenite-induced lung cancer in humans is strong, but the molecular mechanisms by which arsenite causes cancer remain to be established. Angiogenesis is a fundamental characteristic of cancer and is necessary in its multi-step progression. In this investigation, the mechanism for arsenite-induced angiogenesis was evaluated. Tumors formed from human bronchial epithelial (HBE) cells transformed by arsenite developed new blood vessels, which were prevented by the knockdown of miR-21, and cultures of human umbilical vein endothelial cells (HUVEC) exposed to arsenite developed endothelial tubes, a characteristic of angiogenesis. Also found in transformed HBE cells were up-regulation of a microRNA, miR-21, and increased levels of vascular endothelial growth factor (VEGF), which promotes angiogenesis. Down-regulation of miR-21 in these cells inhibited the arsenite-induced increases of VEGF levels. Thus, we conclude that arsenite induces tumor angiogenesis through processes mediated by miR-21.

The Function and Significance of SELENBP1 Downregulation in Human Bronchial Epithelial Carcinogenic Process

BackgroundOur quantitative proteomic study showed that selenium-binding protein 1 (SELENBP1) was progressively decreased in human bronchial epithelial carcinogenic process. However, there is little information on expression and function of SELENBP1 during human lung squamous cell cancer (LSCC) carcinogenesis.MethodsiTRAQ-tagging combined with 2D LC-MS/MS analysis was used to identify differentially expressed proteins in the human bronchial epithelial carcinogenic process. SELENBP1, member of selenoproteins family and progressively downregulated in this process, was selected to further study. Both Western blotting and immunohistochemistry were performed to detect SELENBP1 expression in independent sets of tissues of bronchial epithelial carcinogenesis, and ability of SELENBP1 for discriminating NBE (normal bronchial epithelium) from preneoplastic lesions from invasive LSCC was evaluated. The effects of SELENBP1 downregulation on the susceptibility of benzo(a)pyrene (B[a]P)-induced human bronchial epithelial cell transformation were determined.Results102 differentially expressed proteins were identified by quantitative proteomics, and SELENBP1 was found and confirmed being progressively decreased in the human bronchial epithelial carcinogenic process. The sensitivity and specificity of SELENBP1 were 80% and 79% in discriminating NBE from preneoplastic lesions, 79% and 82% in discriminating NBE from invasive LSCC, and 77% and 71% in discriminating preneoplastic lesions from invasive LSCC, respectively. Furthermore, knockdown of SELENBP1 in immortalized human bronchial epithelial cell line 16HBE cells significantly increased the efficiency of B[a]P-induced cell transformation.ConclusionsThe present data shows for the first time that decreased SELENBP1 is an early event in LSCC, increases B[a]P-induced human bronchial epithelial cell transformation, and might serve as a novel potential biomarker for early detection of LSCC.

Abstract 2910: Suppressing excessive reactive oxygen species accumulation by RIP1 potentiates BPDE-induced transformation of human bronchial epithelial cells.

Abstract Cell survival signaling is important for the malignant phenotypes of cancer cells. Although the role of receptor-interacting protein 1 (RIP1) in cell survival signaling is well documented, whether RIP1 is directly involved in cancer development has never been studied. In this report, we found that RIP1 expression is substantially increased in human non-small cell lung cancer (NSCLC) tissues and cell lines. RIP1 expression in human bronchial epithelial cells (HBECs) was significantly induced by cigarette smoke extract (CSE) or benzo[a]pyrene diol epoxide (BPDE), the active form of the tobacco-specific carcinogen benzo (a) pyrene (BaP). In RIP1 knockdown HBECs, BPDE-induced cytotoxicity was significantly increased, which was associated with induction of cellular reactive oxygen species (ROS), mainly hydrogen peroxide (H2O2), and activation of mitogen-activated protein kinases (MAPKs) including JNK, ERK and p38. Scavenging ROS suppressed BPDE-induced MAPK activation and inhibiting ROS or MAPKs substantially blocked BPDE-induced cytotoxicity, suggesting ROS-mediated MAPK activation is involved in BPDE-induced cell death. The H2O2-reducing enzyme catalase is destabilized in an ERK- and JNK-dependent manner in RIP1 knockdown HBECs and application of catalase effectively blocked BPDE-induced H2O2 accumulation and cytotoxicity. Importantly, BPDE-induced transformation of HBECs was significantly reduced when RIP1 expression was suppressed. Altogether, these results strongly suggest an oncogenic role for RIP1, which promotes malignant transformation through protecting DNA-damaged cells against carcinogen-induced cytotoxicity associated with excessive ROS production. Citation Format: Qiong Wang, Wenshu Chen, Xiuling Xu, Bilan Li, Weiyang He, Mabel T. Padilla. Suppressing excessive reactive oxygen species accumulation by RIP1 potentiates BPDE-induced transformation of human bronchial epithelial cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2910. doi:10.1158/1538-7445.AM2013-2910

Abstract 3298: Arsenic induces human bronchial epithelial cell transformation featured with tumor-initiating cells

Abstract Arsenic is a well-known human carcinogen. Chronic exposure to arsenic is associated with cancers in various tissues, including skin, urinary bladder, lung, liver, kidney and prostate. However, the mechanism underlying arsenic-induced carcinogenesis remains elusive. Here, we demonstrate that long-term (six month) exposure to low levels of sodium arsenite (0.25 µ M) in human bronchial epithelial cell line (BEAS-2B) results in altered morphology, increased cell proliferation and anchorage-independent colony formation in soft agar, indicative of malignant transformation of these cells. Moreover, tumorigenesis analysis revealed that s.c. inoculation of the arsenic-transformed cells can induce tumors in nude mice. The tumors can be observed after 2-3 weeks even only 500 arsenic-transformed cells were injected, suggesting that these transformed cells induced by long-term and low-dose arsenic treatment are highly tumorigenic. Additional studies indicated that some of these arsenic-transformed cells exhibit characteristics of tunor-initiating cells (TICs) or cancer stem cells (CSCs), such as overexpression of Oct3/4, Nanog, Sox2, Klf4, and C-myc. Tumor sphere formation assay, a general procedure in defining TICs or CSCs, suggested that about 5% of these arsenic-transformed cells can form tumor spheres in non-adherent plates. The tumor sphere forming cells were enriched through serial passage of the cells collected from tumor spheres. Flow cytometry sorting showed that 90% of these sphere cells are CD49f positive, whereas CD133, CD44, EpCAM, and c-kit were not detected. Overexpression of CD49f was confirmed by immunoblotting, which indicated an increased CD49f level in the arsenic-transformed cells relative to the non-transformed BEAS-2B cells. Finally, the ability of sphere formation and colony formation in soft agar was compared between the cells showed the strongest and the weakest CD49f expression and suggested that the cells with the strongest CD49f expression are more capable of forming tumor spheres and colonies. In conclusion, our data suggested that the transformed cells induced by arsenic have features of TICs or CSCs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3298. doi:1538-7445.AM2012-3298

Abstract 385: Potentiating MUC1 expression in human bronchial epithelial cells by cigarette smoke carcinogens through induction of TNF-α secretion from macrophages

Abstract Although an important role of inflammation in the development of lung cancer has been recognized, how inflammation promotes lung epithelial cell transformation and lung cancer development has not been well elucidated. Cigarette smoke (CS), the major cause of lung cancers, potently elicits chronic pulmonary inflammation. Our recent studies have found that CS significantly induces Muc1 (MUC1 for human and Muc1 for nonhuman species) expression in mouse bronchial epithelial cells and macrophages, and MUC1 facilitates Benzo(a)pyrene diolepoxide (BPDE)-induced human lung epithelial cell transformation. In this study, we investigated the role of inflammatory cells in regulating CS carcinogen-induced MUC1 expression in bronchial epithelial cells. BPDE and N-Nitroso-N-methylurea (MNU), an active CS carcinogen and a mimic, strongly induced tumor necrosis factor-alpha (TNF-α) secretion from human macrophages. The TNF-α induction was effectively blocked when ERK, JNK, and NF-κB were blocked, suggesting these pathways are involved in the induction of TNF-α from macrophages by BPDE and MNU. Interestingly, knockdown of MUC1 in macrophages suppressed BPDE- or MNU-induced TNF-α secretion, suggesting MUC1 plays a role in modulating carcinogen-induced and macrophage-mediated inflammatory responses. Conditioned media from BPDE- or MNU-treated macrophages potently induced MUC1 expression in human bronchial epithelial cells (HBECs), which was inhibited by a TNF-α neutralizing antibody, suggesting that TNF-α derived from macrophages contributes to CS carcinogen-induced MUC1 expression in HBECs. Thus, our results establish a dual role of MUC1 in CS-induced and inflammation-associated lung cancer development: to facilitate TNF-α secretion from macrophages and to potentiate transformation of HBECs. Note: This work is supported by NIH/NIEHS grant 1R01ES017328. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 385. doi:1538-7445.AM2012-385

MUC1 Contributes to BPDE-Induced Human Bronchial Epithelial Cell Transformation through Facilitating EGFR Activation

Although it is well known that epidermal growth factor receptor (EGFR) is involved in lung cancer progression, whether EGFR contributes to lung epithelial cell transformation is less clear. Mucin 1 (MUC1 in human and Muc1 in animals), a glycoprotein component of airway mucus, is overexpressed in lung tumors; however, its role and underlying mechanisms in early stage lung carcinogenesis is still elusive. This study provides strong evidence demonstrating that EGFR and MUC1 are involved in bronchial epithelial cell transformation. Knockdown of MUC1 expression significantly reduced transformation of immortalized human bronchial epithelial cells induced by benzo[a]pyrene diol epoxide (BPDE), the active form of the cigarette smoke (CS) carcinogen benzo(a)pyrene (BaP)s. BPDE exposure robustly activated a pathway consisting of EGFR, Akt and ERK, and blocking this pathway significantly increased BPDE-induced cell death and inhibited cell transformation. Suppression of MUC1 expression resulted in EGFR destabilization and inhibition of the BPDE-induced activation of Akt and ERK and increase of cytotoxicity. These results strongly suggest an important role for EGFR in BPDE-induced transformation, and substantiate that MUC1 is involved in lung cancer development, at least partly through mediating carcinogen-induced activation of the EGFR-mediated cell survival pathway that facilitates cell transformation.

Abstract 1994: Tobacco carcinogen-induced transformation of HBECs is associated with chromatin-mediated reprogramming of the epigenome

Abstract An in vitro model, hTERT/cdk4, immortalized human bronchial epithelial cells (HBECs), was used to identify key molecular changes driving cell transformation and the clonal outgrowth of preneoplastic lung epithelial cells. Low-dose weekly treatment (12 weeks) of HBECs with genotoxic, but not cytotoxic doses of the carcinogens methylnitrosourea (MNU), benzo(a)pyrene-diolepoxide 1 (BPDE), or both induced transformation. Transformation efficiency (0.2-3%) differed between HBECs and was associated with DNA repair capacity, increased levels of DNMT1 protein, promoter hypermethylation, EMT, and stem-like cell phenotype. Agilent 44K arrays were used to determine genome-wide changes in gene expression associated with transformation. Comparison of expression between HBEC1 and HBEC2 to cells transformed by BPDE, MNU, or the combination revealed 287-321 and 320-493 genes with increased or decreased (≥ 3-fold change) expression. Approximately 214 and 331 of the genes with decreased expression in HBEC1 and HBEC2 had CpG islands that extended through their transcriptional start site. HBEC2 MNU/BPDE transformed cells were treated with DAC or TSA to assess globally whether chromatin remodeling alone, or in combination with DNA methylation mediated gene silencing. Only 128 of 331 silenced genes in HBEC2 MNU/BPDE transformed cells responded to DAC alone. Promoter methylation arrays and genome-wide ChIP-chip for inactive chromatin marks were used to elucidate mechanisms of global gene silencing in HBEC2 MNU/BPDE transformed cells. Array analysis revealed 216 genes with reduced expression are enriched for H3K27me3 and 23 novel genes with reduced expression are hypermethylated in HBEC2 MNU/BPDE transformed cells. Our in vitro model suggests that the re-programming of the epigenome during carcinogen-induced transformation is initially mediated by chromatin remodeling with ensuing DNA methylation sustaining gene silencing. The authors’ work is supported by a research grant from National Institutes of Health (R01 ES008801). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1994. doi:10.1158/1538-7445.AM2011-1994

JWA regulates N-methyl-N'-nitro-N-nitrosoguanidine induced malignant transformation in human bronchial epithelial cells

To investigate the role and possible mechanism of JWA in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) inducing human bronchial epithelial (HBE) cells' neoplastic transformation. JWA overexpression vector and its stable transfection HBE cells were established. The characteristics of transformed HBE cells were determined by methyl thiazolyl tetrazolium (MTT) assay and the soft agar colony formation assay. The expressions of JWA and P53 were detected by Western blot. The growth rates of the HBE cells which were treated with MNNG were significantly accelerated than the JWA overexpression HBE cells and controlled HBE cells (P < 0.05). The soft agar colony formation of JWA overexpression HBE cells with and without MNNG treatment (8.06% and 10.14%) was significantly lower than that of the normal HBE cells with MNNG treatment (26.80%) (P < 0.01). After exposure of MNNG, the P53 expressions were gradually increased in HBE cells with the increased passages. However, the expression of P53 in JWA over expressed HBE cells showed a different manner. P53 reached an over expression peak at early stage (the first passage), and then with a gradually down-regulated expression spectrum with increased passages of the cells. JWA might be a key molecule and play an important role in MNNG inducing neoplastic transformation in HBE cells through regulation of the expression of P53.

Microarray Analyses Uncover UBE1L as a Candidate Target Gene for Lung Cancer Chemoprevention

Retinoids, natural and synthetic derivatives of vitamin A, are active in cancer therapy and chemoprevention. We reported previously that all-trans-retinoic acid (RA) treatment prevented carcinogen-induced transformation of immortalized human bronchial epithelial (HBE) cells. To identify cancer chemopreventive mechanisms, immortalized (BEAS-2B), carcinogen-transformed (BEAS-2B(NNK)), and RA-chemoprevented (BEAS-2B(NNK/RA)) HBE cells were used to conduct microarray analyses independently. Species increased in chemoprevented as compared with immortalized HBE cells (group I) and those augmented in chemoprevented as compared with transformed HBE cells (group II) included known RA-target genes as well as previously unrecognized RA-target genes in HBE cells. Unexpectedly, both groups were also enriched for interferon-stimulated genes. One interferon-stimulated gene of particular interest was UBE1L, the ubiquitin-activating enzyme E1-like protein. UBE1L expression was also induced after prolonged RA-treatment of immortalized HBE cells. UBE1L mRNA was shown previously as repressed in certain lung cancer cell lines, directly implicating UBE1L in lung carcinogenesis. Notably, UBE1L immunoblot expression was reduced in a subset of malignant as compared with adjacent normal lung tissues that were examined. Immunohistochemical analyses were performed using a new assay developed to detect this species using rabbit polyclonal anti-UBE1L antibodies independently raised against the amino- or carboxyl-termini of UBE1L. Studies done on paraffin-embedded and fixed tissues revealed abundant UBE1L, but low levels of cyclin D1 expression in the normal human bronchial epithelium, indicating an inverse relationship existed between these species. To study this further, cotransfection into HBE cells of wild-type or mutant UBE1L species was accomplished. In a dose-dependent manner, wild-type but not mutant UBE1L species repressed cyclin D1 expression. This implicated UBE1L in a retinoid chemoprevention mechanism involving cyclin D1 repression described previously. Taken together, these findings directly implicate UBE1L as a candidate-pharmacologic target for lung cancer chemoprevention. These findings also provide a mechanistic basis for the tumor suppressive effects of UBE1L through cyclin D1 repression.