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S. Xi
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MINI 34 - RNA and miRNA (ID 162)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:C. Mascaux, L.(. Wang
- Coordinates: 9/09/2015, 18:30 - 20:00, 205+207
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MINI34.13 - Long Noncoding RNA BC070487 Represses ZNFX1 during Tobacco-Induced Lung Carcinogenesis (ID 2912)
19:40 - 19:45 | Author(s): S. Xi
- Abstract
- Presentation
Background:
Limited information exists regarding regulation of gene expression by long noncoding RNAs (lncRNAs) during initiation and progression of tobacco-associated lung cancers. In the present study, an in-vitro model system was used to examine the effects of cigarette smoke on lncRNA expression in human respiratory epithelia and lung cancer cells.
Methods:
Micro-array and qRT-PCR techniques were used to assess lncRNA and gene expression profiles in normal human small airway epithelial cells (SAEC) and immortalized human bronchial epithelial cells (HBEC) cultured in the presence or absence of cigarette smoke condensate (CSC). Quantitative chromatin immunoprecipitation (ChIP), methyl-DNA immunoprecipitation (MeDIP), and cross-link immunoprecipitation (CLIP) techniques were used to assess promoter occupancy, DNA methylation, and interaction of lncRNAs with target proteins. Formaldehyde-Assisted Isolation of Regulatory Elements (FAIRE) assays were used to identify a regulatory sequence for lncRNA BC070487.
Results:
Micro-array analysis demonstrated that under relevant exposure conditions, CSC consistently mediated a 2.5 fold increase in BC070487 expression, and 3.6 fold decrease in its immediate downstream target gene, ZNFX1, in SAEC. qRT-PCR experiments confirmed a 4-7 fold up-regulation of BC070487, with a 4-8 fold down-regulation of ZNFX1 in SAEC and HBEC, as well as Calu-6 and H841 lung cancer cells following CSC exposure. BC070487 expression correlated inversely with expression of ZNFX1 (BC070487: 1.38-10.31 fold up vs ZNFX1: 2.26-26.29 fold down) in primary lung cancers relative to adjacent normal lung parenchyma. Overexpression or depletion of BC070487 inhibited or enhanced expression of ZNFX1, respectively in normal respiratory epithelia and lung cancer cells. CSC as well as BC070487-mediated repression of ZNFX1 coincided with increased occupancy of EZH2, SUZ12, BMI1, and increased levels of H3K27Me3, with decreased H3K4Me3 within the ZNFX1 promoter region. CSC as well as BC070487 overexpression enhanced binding of BC070487 with EZH2, SUZ12 and BMI1 proteins in SAEC and Calu-6 cells. CSC exposure significantly increased DNA methylation in one of three CpG islands spanning the regulatory elements of ZNFX1. In addition, CSC enhanced binding of BC070487 with DNMT3A and DNMT3B with site-specific de novo DNA methylation of ZNFX1 in SAEC and Calu-6 cells. FAIRE assays identified a 800 bp regulatory sequence for BC070487; CSC-mediated activation of BC070487 coincided with increased levels of H3K4Me3, H3K27Ac, H3K36Me3, Sp1, and Ago proteins, with decreased levels of H3K27Me3 and H3K9Me3 within this regulatory region. miR-31, an oncomiR specifically induced by CSC, modulated the transcriptional activity of BC070487 via remodeling the distribution of histone modification marks (Up: H3K4Me3, H3K27Ac, H3K36Me3; Down: H3K27Me3 and H3K9Me3) in the regulatory region of BC070487. Overexpression or depletion of BC070487 increased or inhibited proliferation and invasion of lung cancer cells, and similarly modulated growth of SAEC and HBEC cells. In contrast, ZNFX1 overexpression or depletion decreased or enhanced growth of normal respiratory epithelial cells and lung cancer cells. BC070487 overexpression enhanced growth of lung cancer cells xenografts in athymic nude mice, while forced expression of ZNFX1 arrested growth of these xenografts.
Conclusion:
Collectively, these data suggest that CSC-mediated up-regulation of BC070487 suppresses ZNFX1 to promote pulmonary carcinogenesis.
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P1.04 - Poster Session/ Biology, Pathology, and Molecular Testing (ID 233)
- Event: WCLC 2015
- Type: Poster
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:
- Coordinates: 9/07/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P1.04-098 - Mithramycin Is a Potential Therapeutic Agent for Elimination of Stem-Like Cells in Lung Cancer (ID 2165)
09:30 - 09:30 | Author(s): S. Xi
- Abstract
Background:
There have been several studies demonstrating existence of cancer stem-like cells in lung cancers, and resistance of such cells to conventional chemotherapy or targeted agents. As such, targeting cancer stem-like cells is a potential strategy to prevent development of drug resistance and tumor recurrence. Previously our group has demonstrated that mithramycin, a specific inhibitor of transcription factor SP1, attenuates induction of side population (a phenotype of cancer stem-like cells) by cigarette smoke condensate, and modulates expression of multiple genes regulating stem-cell related pathways in lung cancer cells. The present study was performed to further examine the effects of mithramycin on stem cell signaling pathways, and ascertain if mithramycin can eliminate stem-like cells in lung cancer following exposure to conventional chemotherapeutic or targeted agents.
Methods:
Stem-like cell populations in cultured H358 and H2228 lung adenocarcinoma cells were identified based on expression of stem cell markers, ALDH1 and CD133 using ALDEFLUOR[TM] assay and flow cytometry, respectively. Sphere-formation assays were used to examine clonogenic growth of stem-like cells. qRT-PCR techniques were used to evaluate expression levels of stemness-related genes. Western blot techniques were utilized to assess activation of stemness-related (WNT/β-catenin and NOTCH) signaling pathways.
Results:
Small CD133[+] or ALDH1[+] fractions were detected in untreated H2228 and H358 cells, respectively. Consistent with notion that stem-like cells are present in these two lines, H2228 and H358 cells formed pulmospheroids when cultured in stem cell media in low attachment plates; these phenotypic changes were accompanied by increased expression of stemness-related genes including Oct4, Sox2 and Nanog. Cisplatin treatment enriched CD133[+] fraction in H2228 cells and ALDH[+] fraction in H358 cells. Mithramycin abolished this enrichment, and mediated dose-dependent decreases in Oct4, Sox2 and Nanog expression in a dose-dependent manner. Preliminary analysis demonstrated that mithramycin decreased total as well as active forms of β-catenin, but did not affect levels of cleaved NOTCH1, suggesting that mithramycin eliminates lung cancer stem-like cells partially through suppression of WNT/β-catenin signaling. The effects of mithramycin on lung cancer stem-like cells induced by targeted agents are currently under investigation.
Conclusion:
Mithramycin suppresses stemness-related signaling, and is a potential therapeutic agent for elimination of stem-like cells emerging in lung cancers after cisplatin therapy.
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P2.04 - Poster Session/ Biology, Pathology, and Molecular Testing (ID 234)
- Event: WCLC 2015
- Type: Poster
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:
- Coordinates: 9/08/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P2.04-051 - The Pluripotency Factor Musashi-2 Is a Potential Target for Lung Cancer Therapy (ID 2973)
09:30 - 09:30 | Author(s): S. Xi
- Abstract
Background:
Recent studies have demonstrated that mithramycin represses multiple pathways critical for stem cell signaling and pluripotency in lung cancer cells. This phenomenon coincides with decreased side population (SP) fraction, and dramatic dose-dependent growth arrest of lung cancer cells in-vitro and in-vivo. The present study was performed to further examine the effects of mithramycin on stem cell signaling in an attempt to identify novel targets for lung cancer therapy.
Methods:
Microarray, quantitative RT-PCR (qRT-PCR) and immunoblot techniques were used to examine stem cell gene expression and proliferation of human lung cancer cells and normal/immortalized human respiratory epithelial cells (SAEC/NHBE/HBEC) cultured in the presence or absence of mithramycin, or lung cancer cells following stem cell gene knockdown. Micro-array and qRT-PCR techniques were used to assess effects of systemic mithramycin exposure on stem cell gene expression in subcutaneous lung cancer xenografts in athymic nude mice. qRT-PCR and immunoblot techniques were used to examine endogenous levels of selected stem cell genes in induced pluripotent stem cells (iPSC) derived from SAEC, as well as primary lung cancers and paired normal respiratory tissues. siRNA techniques were used to knockdown Msi-2 to confirm potential mechanisms of action of mithramycin-mediated cytotoxicity in lung cancer cells.
Results:
Preliminary microarray analysis of cultured lung cancer cells and xenografts demonstrated that mithramycin decreased expression of musashi-2 (Msi-2), a RNA binding protein which mediates self-renewal in normal stem cells and aggressive phenotype of several human cancers. Subsequent qRT-PCR and immunoblot experiments confirmed that mithramycin depletes Msi-2 in lung cancer cells in a time and dose-dependent manner. Expression levels of Msi-2 were significantly elevated in non-small cell as well as small-cell lung cancer lines relative to normal/immortalized human respiratory epithelial cells (p < 0.001). Consistent with these findings, Msi-2 mRNA levels in primary lung cancers were significantly higher than those detected in adjacent paired normal lung parenchyma (p< 0.0003). Msi-2 expression was enriched in SP fractions of cultured lung cancer cells, and was significantly increased in SAEC following reprogramming to pluripotency. si-RNA-mediated knock-down of Msi-2 decreased expression of Oct4, Nanog and Myc, and transiently inhibited proliferation of lung cancer cells. Attempts to permanently knockdown Msi-2 by shRNA techniques thus far have been unsuccessful, suggesting a strong selective pressure to maintain Msi-2 expression in these cells.
Conclusion:
Mithramycin depletes Msi-2 in lung cancer cells. Pharmacologic depletion of this pluripotency factor may be a novel strategy for lung cancer therapy.
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P3.05 - Poster Session/ Prevention and Tobacco Control (ID 217)
- Event: WCLC 2015
- Type: Poster
- Track: Prevention and Tobacco Control
- Presentations: 1
- Moderators:
- Coordinates: 9/09/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P3.05-012 - Hookah Smoke Mediates Cancer-Associated Alterations in Normal Human Respiratory Epithelial Cells (ID 2767)
09:30 - 09:30 | Author(s): S. Xi
- Abstract
Background:
Cigarette smoking is the leading cause of lung cancers worldwide, and numerous countries have initiated public health programs to curtail cigarette abuse. Although hookah tobacco is perceived to be a safe alternative to cigarettes, the effects of hookah smoke in human respiratory epithelial cells and lung cancer cells are currently unknown. The present study was undertaken to examine if hookah smoke mediates cancer-associated alterations in normal respiratory epithelia and lung cancer cells.
Methods:
Human small airway epithelial cells (SAEC), cdk4/hTERT-immortalized human bronchial epithelial cells (HBEC) and lung cancer cells (Calu-6 and A549) were cultured in normal media in the presence or absence of waterpipe condensates (WPC) or cigarette smoke condensates (CSC) under relevant exposure conditions. MTS, quantitative RT-PCR and western blot techniques were used to examine the effects of hookah smoke on cell proliferation, mRNA/ microRNA expression and the histone code relative to those induced by cigarette smoke.
Results:
Five day WPC exposures mediated variable effects in cultured respiratory epithelia and lung cancer cells. In SAEC and HBEC, WPC mediated dose-dependent growth inhibition. In Calu-6 cells, low dose WPC (0.1mg/ml and 0.5mg/ml) enhanced proliferation, whereas higher concentrations of WPC (1.0mg/ml and 2.0mg/ml) inhibited growth. High concentrations of WPC (2.0mg/ml) inhibited proliferation of A549 cells. Similar to CSC, WPC decreased H4K16Ac and H4K20Me3 levels in SAEC and HBEC. In addition, like CSC, WPC increased miR-31 and decreased miR-487b expression in SAEC, HBEC and lung cancer cells. Furthermore, WPC increased expression of Cyp1b1 in SAEC cells, enhanced expression of ABCG2, Lin28B, Myc, SALL4, CTCF, JARID2 and Cyp1a1 in HBEC cells, up-regulated ABCG2 and Cyp1a1 in Calu-6 lung cancer cells, and induced dose-dependent up-regulation of Cyp1a1 and Cyp1b1 in A549 lung cancer cells. WPC exposure significantly decreased expression of Dkk-1 in HBEC and Calu-6 cells. Cigarette smoke induced similar changes in these cells.
Conclusion:
These preliminary findings demonstrate that hookah smoke mediates cancer-associated alterations in human respiratory epithelial cells, and suggest that waterpipe tobacco is not a safe alternative to cigarettes.
