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V. Shukla
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MINI 38 - Biology and Prognosis (ID 167)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Thymoma, Mesothelioma and Other Thoracic Malignancies
- Presentations: 1
- Moderators:R. Tsuchiya, M. Wynes
- Coordinates: 9/09/2015, 18:30 - 20:00, 702+704+706
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MINI38.07 - RITA Enhances Mithramycin-Mediated Growth Arrest and Apoptosis of Malignant Pleural Mesothelioma Cells In-Vitro and In-Vivo (ID 2996)
19:05 - 19:10 | Author(s): V. Shukla
- Abstract
- Presentation
Background:
Malignant pleural mesotheliomas (MPM) are relatively rare tumors for which there are no effective treatment options. Previously we reported that mithramycin (MM) dramatically inhibits growth and tumorigenicity of MPM cells in part via depletion of Specificity Protein 1 (SP1) and activation of p53 signaling. We also demonstrated that 24h MM treatment induces G0/G1arrest and senescence with subsequent apoptosis of MPM cells. The present study was undertaken to examine the effects of RITA (Reactivation of p53 and Induction of Tumor cell Apoptosis- a p53 activator and MDM2 inhibitor) with or without MM in cultured MPM cells in vitro and in vivo.
Methods:
NCI-SB-MES1 and NCI-SB-MES7 (MES1 and MES7, respectively) with wild-type p53 were cultured in the presence of mithramycin (24h) and/or RITA (48h). DNA damage, senescence and autophagy were assessed by immunoblot/immunofluorescence analysis of g-H2A-X phosphorylation and foci formation, ß-gal staining, and immunoblot/immunofluorescence analysis of LC3 proteins. Propidium iodide and APO-BrdU techniques were used to determine cell cycle kinetics and quantify apoptosis. qRT-PCR and immunoblot techniques were used to examine signal transduction, cell cycle-related and apoptosis-related protein levels in MPM cells. Murine subcutaneous xenograft models were used to evaluate the combinatorial antitumor effects of RITA and MM in-vivo.
Results:
MM treatment (10-100nM x 24h) mediated dose-dependent depletion of SP1 and markedly increased p53 levels in MPM cells; these effects coincided with DNA damage, G0/G1 arrest, senescence and an autophagy phenotype as evidenced by induction of LC3 puncta/proteins and p-AMPK and inhibition of p-S6 kinase. Senescence or autophagy phenotype coincided with up-regulation of CDKN1A, MDM2/TP53INP1, MAPLC3B, and down-regulation of EZH2, SP1/MTOR. RITA (100-1000nM x48h) alone mediated low-level, dose-dependent growth inhibition in MPM cells. However treatment with subtherapeutic doses of MM for 24h followed by RITA for 48h resulted in synergistic growth inhibition and apoptosis in MPM cells, detected by flow cytometry, as well as immunoblot analysis of cleaved PARP and cleaved caspase 3. Sequential intraperitoneal treatment with MM (1mg/kg/week) followed by RITA (2 mg/kg/3d/week) significantly reduced volumes/masses of subcutaneous MES1 xenografts in athymic nude mice.
Conclusion:
Sequential mithramycin/RITA treatment significantly reduces mesothelioma tumor burden via induction of apoptosis. These findings provide preclinical rationale for evaluation of this drug regimen in MPM patients.
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ORAL 07 - Lung Cancer Pathogenesis (ID 91)
- Event: WCLC 2015
- Type: Oral Session
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:J. Sage, E. Brambilla
- Coordinates: 9/07/2015, 10:45 - 12:15, 102+104+106
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ORAL07.01 - Evaluation of Epigenetic Mechanisms of Pluripotency in Human Respiratory Epithelia (ID 3041)
10:45 - 10:56 | Author(s): V. Shukla
- Abstract
- Presentation
Background:
Smoking is the number one risk factor for lung cancer worldwide. Recent data indicate that stem cells situated throughout the small airway epithelium may initiate cancer formation following direct exposure to inhaled carcinogens. In the present study we sought to generate induced pluripotent stem cells (iPSCs) from normal human small airway epithelial cells (SAECs) in order to investigate epigenetic mechanisms contributing to the cancer stem cell initiation process, and possibly identify novel targets for lung cancer therapy.
Methods:
Several different stocks of SAEC were transduced with Stemcca virus containing OKSM (Yamanaka factors); multiple randomly selected clones were expanded for further analysis. Spectral karyotyping was performed to confirm the purity of pluripotent cells. iPSC cells were injected in SCID mice to study teratoma formation. RNA and DNA were extracted from iPSC and parental SAEC for qRT-PCR and RNA-Seq analyses, as well as pyrosequencing of LINE-1, NBL2 and D4Z4 DNA repetitive elements, and promoter regions of several differentially regulated genes.
Results:
SAEC were reprogrammed to a pluripotent state. Generated iPSCs demonstrated hallmarks of pluripotency including morphology, proliferation, expression of surface antigens, stemness gene expression, and in vivo teratoma formation. Interestingly, no chromosomal aberrations were observed in iPSCs. Pyrosequencing did not demonstrate any significant changes in LINE-1, NBL2 and D4Z4 DNA methylation levels in iPSC compared to parental SAEC, suggesting relatively limited global hypomethylation following reprogramming. Consistent with these observations, cancer-testis genes such as NY-ESO-1, MAGE-A1 and MAGE-A3, which are frequently upregulated by DNA demethylation in lung cancer cells, remained transcriptionally repressed in the iPSC. On the other hand, NANOG and POU5F1 genes were hypomethylated in iPSCs relative to SAEC, correlating with their over-expression in iPSCs. RNA-Seq analysis revealed up-regulation of genes encoding components of Polycomb-Repressive Complex 2 (PRC2), and down-regulation of several tumor suppressor genes such as DKK1, p16 and p21 in iPSC relative to parental SAEC. Several novel pluripotency associated genes were also noted to be up-regulated in pulmonary iPSC, which are the focus of ongoing mechanistic studies.
Conclusion:
This is the first report demonstrating successful reprogramming of human respiratory epithelia to pluripotency. This model may prove useful for elucidating fundamental epigenomic mechanisms of pulmonary carcinogenesis and identification of novel targets for lung cancer therapy.
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