Author of

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  P2.03 - Biology (ID 162)

  • Event: WCLC 2019
  • Type: Poster Viewing in the Exhibit Hall
  • Track: Biology
  • Presentations: 2
  • Moderators:
  • Coordinates: 9/09/2019, 10:15 - 18:15, Exhibit Hall

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    P2.03-31 - Chemokine Receptor CXCR7 Reactivates ERK Signaling to Promote Resistance to EGFR Kinase Inhibitors in NSCLC (ID 2817)

    10:15 - 18:15  |  Author(s): Agustin Lahoz
    • Abstract

    Background
    

    Activating EGFR mutations in NSCLC confer sensitivity to reversible EGFR TKIs, including gefitinib and erlotinib. Despite promising initial response, acquired resistance develops mediated by the emergence of the secondary T790M mutation or by focal amplification of MET. An epithelial­to­mesenchymal transition (EMT) is clinically linked to NSCLCs with acquired EGFR TKI resistance. The exact mechanisms of EGFR TKI resistance with EMT phenotype remain elusive.

    Method
    

    We have engineered EGFR­mutated NSCLC cell lines with a mesenchymal phenotype by stably depleting E­Cadherin, overexpressing Snail, or chronically exposing the cells to TGFβ1. The resulting mesenchymal cells are resistant to EGFR TKIs. We employed genomic analyses to identify commonly activated oncogenic drivers that maintain signaling pathways upon EGFR inhibition. We also used EGFR­mutated HCC4006 NSCLC cells grown resistant to gefitinib that developed a mesenchymal phenotype (HCC4006Ge­R). To extend our findings to in vivo, we have utilized matched pre- and post-EGFR TKI treatment samples from NSCLC patient and mouse models of acquired EGFR TKI resistance to test if our approach using these cell lines is instructive.

    Result
    

    We discovered that an atypical GPCR, C­X­C chemokine receptor type 7 (CXCR7), is commonly overexpressed in the cell line models of EGFR TKI resistance with a mesenchymal phenotype. The murine tumors driven by human EGFR exon19 deletion/T790M (TD) with acquired resistance to WZ4002 present mesenchymal phenotype and overexpress CXCR7. 50% of NSCLC patients harboring an EGFR kinase domain mutation who progressed on EGFR inhibitors showed an increase in CXCR7 expression. Using the cell line model of EGFR TKI acquired resistance with a mesenchymal phenotype, we find that CXCR7 activates the MAPK-ERK pathway via b-arrestin. Depletion of CXCR7 abrogates the MAPK pathway and significantly attenuated EGFR TKI resistance in the cells with a mesenchymal phenotype. In the long term, the depletion of CXCR7 resulted in mesenchymal to epithelial transition. Ectopic overexpression of CXCR7 in HCC4006 cells was sufficient in activation of ERK1/2 for the generation of EGFR TKI resistant cells. Furthermore, CXCL12 stimulation resulted in an increase in ERK phosphorylation while EGFR was inhibited in HCC4006Ge-R cells. Similarly, we found we found CXCL12 expression is elevated in patient samples with increased CXCR7 expression.

    Conclusion
    

    Taken together, we discovered that the CXCR7-CXCL12 signaling axis is necessary and sufficient for the maintenance of EGFR TKI resistance with mesenchymal phenotype and CXCR7 inhibition could significantly delay and prevent the emergence of acquired EGFR TKI resistance in EGFR mutant NSCLC.

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    P2.03-38 - Identification of a Novel Synthetic Lethal Vulnerability in Non-Small Cell Lung Cancer by Co-Targeting TMPRSS4 and DDR1 (ID 2191)

    10:15 - 18:15  |  Author(s): Agustin Lahoz
    • Abstract
    • Slides

    Background
    

    Synthetic lethality has been defined as the inability of cells to proliferate when co-targeting two genes, with a synergistically superior inhibition than that found for each individual gene. Consistent co-expression of two genes involved in a similar function is a predictor of synthetic lethality, a strategy that is being applied to find out novel cancer vulnerabilities.

    Method
    

    Large-scale bioinformatics analyses across 5 public databases were used to identify genes consistently co-expressed with TMPRSS4, a novel therapeutic target that we have previously identified in NSCLC. Pyrosequencing was used to evaluate methylation levels in patients and cell lines. Functional in vitro experiments and animal models were used to assess synthetic lethality of TMPRSS4 and DDR1 in NSCLC.

    Result
    

    Consistent co-expression between TMPRSS4 and DDR1 was found in all NSCLC databases evaluated. Similar to TMPRSS4, DDR1 promoter was hypomethylated in NSCLC in 3 independent cohorts and hypomethylation was an independent prognostic factor of disease-free survival. Treatment with 5-azacitidine increased DDR1 levels in cell lines, suggesting an epigenetic regulation. Cells lacking TMPRSS4 were highly sensitive to the cytotoxic effect of the DDR1 inhibitor dasatinib. TMPRSS4/DDR1 double knock-down cells, but not single knock-out cells suffered a G0/G1 cell cycle arrest with loss of E2F1 and cyclins A and B, increased p21 levels and apoptosis. Moreover, double knock-down cells were highly sensitized to cisplatin, which caused massive apoptosis (~40%). In vivo studies demonstrated tumor regression in mice injected with double knock-down-injected cells and lack of 18FDG-uptake by microPET analysis.

    Conclusion
    

    We have identified a novel vulnerability in NSCLC resulting from a synthetic lethal interaction between DDR1 and TMPRSS4. This may help designing therapeutic strategies to impair NSCLC growth by co-targeting both genes.

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