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D. Richard



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    MO04 - Lung Cancer Biology I (ID 86)

    • Event: WCLC 2013
    • Type: Mini Oral Abstract Session
    • Track: Biology
    • Presentations: 1
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      MO04.03 - Chromosomal and mutational analysis of the cisplatin resistant phenotype in NSCLC cells (ID 3313)

      16:15 - 17:45  |  Author(s): D. Richard

      • Abstract
      • Presentation
      • Slides

      Background
      Primary and acquired resistance to platinum agents such as cisplatin have become a major obstacle in the management of lung cancer patients, in particular non-small cell lung cancer (NSCLC). The availability of comprehensive genomic data on DNA copy number changes in cisplatin resistant NSCLC is limited, and little is known about the genes driving this chemoresistant phenotype. Detailed molecular portraits through high density genomic DNA arrays and genome wide mutation profiles will aid in understanding the molecular basis of individual responses to new molecular therapies.

      Methods
      A panel of cisplatin resistant (CisR) NSCLC cell lines were recently generated and characterised in our laboratory. In this study, high resolution array-based comparative genome hybridization (aCGH) was performed on a panel of five CisR NSCLC cell lines to examine DNA copy number gains, losses and amplifications. Cellular DNA (500ng) and control DNA was differentially labelled with Cy3 and Cy5, respectively. Labelled test (4µg) and reference DNA were hybridised to a 12-plex 135,000 probe array (Roche NimbleGen) for 18 hours in a MAUI hybridisation station (BioMicro Systems) at 42°C. Fluorescent intensities were extracted and log 2 ratios calculated and normalized using NimbleScan Software (version 2.4). Chromosomal aberrations were identified using the CGH-segMNT algorithm (NimbleScan 2.4). A significance log 2 ratio threshold of <−0.25 for loss and >0.25 for gain was used to identify DNA copy number imbalances. For mutational analysis, Sequenom®, a mass-spectrometry-based SNP genotyping technology, was used to identify mutations in our panel of resistant cell lines. Using a literature search and the Catalogue of Somatic Mutations in Cancer (COSMIC) database, a mutation panel was identified for the detection of 547 frequently occurring and potentially clinically relevant mutations in 49 cancer-related genes. Some of these include KRAS, NRAS, BRAF, PIK3CA, MET, CTNNB1, STK11, AKT, and EGFR. Matrix chips were analysed on a Sequenom® MassArray MALDI-TOF system. Visual inspection and Sequenom® typer software were used to perform genotyping based on mass spectra.

      Results
      Using aCGH arrays, a number of gains, losses and amplifications of various chromosomes were found across a panel of CisR cell lines, relative to corresponding PT cells. The most frequently occurring of these chromosomal imbalances included gains, losses and homozygous deletions on chromosome 3 (MOR, A549, H1299), deletions and amplifications on chromosome 7 (H460, A549, H1299) and deletions and gains on chromosome 15 (MOR, A549, H1299) and chromosome X (MOR, H460, SKMES-1). Deletions on chromosomes 4, 6, 11, 12, 14, and amplification of chromosome 5, were also identified among the different CisR cell lines. The collation and analysis of data arising from mutation analysis of CisR cells using the Sequenom® platform are currently being completed.

      Conclusion
      High-resolution mapping of chromosomal imbalances may offer potential in the identification of genes, including oncogenes and tumour suppressor genes, affected by these imbalances. These findings may further contribute to the delineation of the genomic profile of cisplatin resistant lung cancer, and offer perspectives for the identification of genes contributing to this disease phenotype and in assessing the response to new molecular treatments.

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    P1.01 - Poster Session 1 - Cancer Biology (ID 143)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P1.01-016 - Targeting NF-κB regulated pathways to overcome cisplatin resistance in non small cell lung cancer (ID 3270)

      09:30 - 16:30  |  Author(s): D. Richard

      • Abstract

      Background
      Cisplatin based doublet chemotherapy is the mainstay of non small cell lung cancer (NSCLC) treatment with an initial objective response rate of approximately 40-50%. However, intrinsic and acquired resistance to cisplatin constitutes a major clinical obstacle in lung cancer management and has yet to be fully understood. Inflammatory mediators may play an important role in the development of cisplatin resistance, such as those regulated by NF-κB. We have previously demonstrated that levels of NF-κB are increased in cisplatin resistant cells compared with sensitive Parent cells. We are currently assessing a number of NF-κB regulated targets in cisplatin resistant cell line models, using DHMEQ, a specific NF-κB inhibitor. DHMEQ treatment results in greater cell death in the cisplatin resistant cells compared with Parent. This study will elucidate the efficacy of DHMEQ to overcome cisplatin resistance and identify novel targets within the NF-κB pathway that may improve therapeutic strategies for NSCLC patients.

      Methods
      NF-κB downstream targets and signalling mediators were examined using NF-κB signalling and target pathway qPCR arrays (168 genes) in the H460 CisR and Parent cell line model. Targets identified are currently undergoing validation using qPCR and western blot. Biological and functional relevance of these targets in the development of cisplatin resistance will be examined further using DHMEQ and siRNA knockdown strategies. In addition, a xenograft murine model will be utilised to assess the effect of DHMEQ alone and in combination with cisplatin on tumour growth in vivo.

      Results
      Data from qPCR arrays have demonstrated that a number of genes are differentially regulated between the CisR and Parent cell lines. These include genes which activate the NF-κB signalling cascade (TLR3, TLR4), regulators of the pathway (BIRC3, CASP1), transcription factors (Myc) and NF-κB responsive genes (TNF, CXCL8). A number of these genes will be modulated to determine their involvement in cisplatin resistance. In addition, DHMEQ is being used in combination studies to determine, whether it can re-sensitise cells to cisplatin therapy. At present a dosing study is ongoing to establish the effect of DHMEQ on xenograft tumours derived from Parent and CisR cells. The results of which will be presented.

      Conclusion
      Preliminary data indicates that NF-κB and a number of its downstream targets are deregulated in cisplatin resistant cells. This project aims to validate the role of these NF-κB regulated genes in cisplatin resistant NSCLC. It will also determine whether DHMEQ may be a novel targeted agent for the treatment of NSCLC. The data obtained in this study will ultimately benefit patients by providing insights into novel druggable targets and new clinical strategies to re-sensitise patients to cisplatin therapy.

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    P1.02 - Poster Session 1 - Novel Cancer Genes and Pathways (ID 144)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P1.02-008 - hSSB1: an essential regulator of genomic integrity in lung cancer (ID 2045)

      09:30 - 16:30  |  Author(s): D. Richard

      • Abstract

      Background
      Lung cancer remains a leading cause for cancer mortality worldwide. A key feature of lung cancer development is genomic instability resulting from an accumulation of DNA lesions. In normal settings, these DNA lesions, such as double strand breaks and oxidised DNA, are rapidly repaired to prevent cytotoxicity and loss of genetic information. However, the molecular basis for the loss of genome integrity during cancer development remains to be determined. Herein, we have examined the involvement of hSSB1 in maintenance of genome stability and its potential role in lung cancer progression. hSSB1 is a critical component of the repair of DNA double strand breaks. As part of this study, we examined if hSSB1 is also involved in the repair of oxidative stress-induced DNA modifications. The most common nucleotide modification, 8-oxo-7,8-dihydro-guanine (8-oxoG), is repaired by the enzyme OGG1. Failure to repair these modifications results in mismatch mutations which are common in cancer. Therefore, understanding the molecular basis for genomic instability is key to the development of future therapeutics with clinical relevance.

      Methods
      To determine if hSSB1 expression is associated with lung cancer progression, a tissue microarray (TMA) with cores from 550 patients was stained with an anti-hSSB1 antibody. Kaplan-Meier survival curves were generated with the clinical data and patient prognosis was correlated with hSSB1 expression levels. To determine an in vitro association with lung cancer, A549 lung cancer cells were treated with hSSB1 specific siRNA. Cell survival was determined by microscopy and MTT assay. To examine the role of hSSB1 in repair of oxidised DNA, U2OS cells were treated with 500 µM H~2~O~2~. Cells treated with H~2~O~2~ were fixed, stained with antibodies for hSSB1 and 8-oxoG and examined by deconvolution microscopy. Lysates were collected from H~2~O~2~ treated U2OS cells and subjected to immunoprecipitation and Western blot analysis. Genomic DNA isolated from scrambled or hSSB1 siRNA U2OS cells treated with H~2~O~2~ were immobilised on nylon membrane and stained with antibodies for 8-oxoG.

      Results
      Significantly, TMA staining of lung cancer tissues indicated universal overexpression of hSSB1. Survival curves generated from the patient data indicated a poorer prognosis for patients with increased hSSB1 expression versus lower expressing tumours. Interestingly, in vitro inhibition of hSSB1 using siRNA significantly reduced cell survival. These data highlight the potential prognostic value of hSSB1 expression. As oxidative stress is prevalent in lung cancers, we also tested whether hSSB1 is capable of repairing 8-oxoG DNA lesions. Following oxidative DNA damage, hSSB1 localises rapidly to chromatin. hSSB1 also directly interacts with OGG1 to facilitate OGG1 recruitment to chromatin and repair of DNA damage. Importantly, cells lacking hSSB1 display ineffective repair of 8-oxoGs.

      Conclusion
      Our data highlight a potential role for hSSB1 in lung cancer progression and a novel role in maintenance of genome integrity. As tumours have increased genomic instability, elevated hSSB1 expression in lung cancer may enable tumours to cope with genomic instability. Taken together, these data present hSSB1 both as a prognostic marker and a novel therapeutic target.

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    P1.05 - Poster Session 1 - Preclinical Models of Therapeutics/Imaging (ID 156)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P1.05-024 - PARP inhibition increases sensitivity of NSCLC cells to cisplatin (ID 3300)

      09:30 - 16:30  |  Author(s): D. Richard

      • Abstract

      Background
      Primary and acquired resistance to platinum agents is a serious clinical problem in lung cancer. Its mechanisms are probably multifactorial and remain poorly understood. Enhanced DNA repair can lead to increased cell viability in the face of DNA damage and has been proposed to be important in mediating platinum resistance. PARPs (poly(ADP-ribose) polymerases) are a family of nuclear enzymes that regulate the repair of DNA single-strand breaks (SSBs). Cisplatin sensitivity and DNA repair mechanisms following treatment with the PARP inhibitor, PJ34, was investigated in this study.

      Methods
      A panel of isogenic cisplatin resistant (CisR) NSCLC cells lines (MOR, SKMES-1, H1299) previously generated in our laboratory were used. The cisplatin resistant phenotype was initially assessed by treating CisR and parental (PT) cells with increasing doses of cisplatin (0-80uM) for 72h, after which time, cell proliferation was measured (BrdU). The effects of PJ34 on cell survival were also examined in a similar dose-response study. IC~25~ concentrations were calculated for each cell line using GraphPad statistical software. Cells were treated with PJ34 (IC~25~) alone, or in combination with cisplatin and cell survival/proliferation measured after 72h. Under similar experimental conditions, RNA was isolated from cells from which cDNA was reverse transcribed. All cell lines were screened for PARP1, PARP2, BRCA1, BRCA2 and ERCC1 mRNA at basal levels, and in response to treatment (RT-PCR). To investigate DNA double strand break (DSB) repair capacity in our panel of cell lines in response to PARP inhibition and cisplatin, phosphorylated γH2AX foci was examined by High Content Analysis (HCA) following treatment of cell lines for 24h. Cisplatin-DNA adduct formation (Pt-GpG) was studied following treatment of cells for 24h. Cells (1x10[6]/ml) were spotted on Superfrost® Gold glass slides. Immunofluorescence staining of specific DNA platination products, and quantification of adducts, was performed using an antibody that specifically recognises cisplatin-GpG DNA adducts.

      Results
      MOR and H1299 CisR cells were significantly more resistant to cisplatin (10µM and 20µM) compared to PT cells. SKMES-1 CisR cells were also significantly more resistant at 10µM, 20µM and 40µM cisplatin. While PJ34 had no effect on NSCLC cells when treated as a single agent, cell proliferation was significantly inhibited in MOR and H1299 cells when used in combination with cisplatin. No effect however was observed in our panel of CisR cell lines. While baseline expression levels of PARP1/2, BRCA1/2 and ERCC1 mRNA levels were similar in PT and CisR cell lines, BRAC1/2 mRNA expression was increased in cells treated with cisplatin alone, and in combination with PJ34 in PT cells but not in CisR cells. The formation of γH2AX foci and measurement of cisplatin-GpG DNA adducts in response to PARP inhibition and cisplatin are currently being investigated.

      Conclusion
      Data from this study show that inhibition of NSCLC cells with the PARP inhibitor, PJ34, sensitises lung cancer cells to the cytotoxic effects of the platinum drug, cisplatin. Further studies are warranted to investigate the role of PARP inhibitors in cisplatin resistant NSCLC cells.