Author of

• 13580

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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)

  • 13643

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    P1.04-063 - Exposure to IL-1β Leads to EMT via Distinct Mechanisms in Acute and Chronic Inflammation in NSCLC (ID 3034)

    09:30 - 09:30  |  Author(s): Z. Jing
    • Abstract

    Background:
    Dysregulated inflammation is associated with the development and progression of lung cancer. Pulmonary diseases characterized by increased inflammation, including emphysema and pulmonary fibrosis, are strongly related to heightened risk of lung cancer. Moreover, lung cancer patients with increased levels of inflammatory mediators or inflammatory cells have poor outcomes. It has been shown that dysregulated inflammatory cytokines in the tumor microenvironment can promote cancer metastasis. However, the mechanisms of this effect in lung cancer have not been fully understood. Interleukin 1β (IL-1β), a key pro-inflammatory cytokine, is associated with tumor aggressiveness and poor patient outcomes in NSCLC. Herein, we report that treatment of IL-1β leads to epithelial-to-mesenchymal transition (EMT) in NSCLC cell lines. Delineation of the underlying molecular pathway(s) may potentiate novel therapeutic strategies.
    
    Methods:
    We treated NSCLC cell lines with IL-1β acutely (3 days) and chronically (21 days) in vitro and identified EMT mediators using RNA interference and chemical inhibitors. Histone modifications and DNA methylation were analyzed with chemical inhibitors, ChIPassays and methylation-specific PCR. We utilized transwell migration, cell proliferation and anchorage-independent cell growth assays to evaluate the functional phenotypes
    
    Results:
    We found that following acute IL-1β exposure (within 7 days), the activator protein 1 (AP-1) transcription factor components, including Fra-1 and c-jun, mediate EMT. AP-1 functions downstream of ERK1/2 and JNK signaling and resides upstream of the transcription factors Slug and Zeb2. Importantly, inhibition of slug, zeb2, fra-1 or ERK1/2 and JNK signaling by RNA interference or chemical inhibitor is sufficient to abolish IL-1β-induced E-cadherin repression. This occurs concomitantly with decreased cell migration and invasion. Surprisingly, following prolonged IL-1β exposure (21 days), cells do not revert back to the epithelial state despite inhibition of these acute EMT mediators. We also found that following withdrawal of IL-1β after twenty one-day exposure, the treated cells are able to maintain their mesenchymal phenotype for more than 30 days before reverting back to an epithelial phenotype. We refer to this prolonged but reversible EMT program that persists in the absence of the original inflammatory stimulus as EMT “memory.” Further studies showed that fra-1 is only required to establish but not to maintain EMT memory. Chemical inhibition of a variety of enzymes involved in histone modifications and DNA methylation indicates the repression of E-cadherin is mediated by different mechanisms depending on the duration of IL-1β exposure. H3K27Me3 and histone acetylation mediate E-cadherin repression during acute EMT but DNA methylation is responsible for the downregulation of E-cadherin in EMT memory. In fact, we have found increased CpG island methylation in the E-cadherin promoter region in EMT memory. In vitro functional studies further showed that EMT memory enables cancer cells to enhance their motility but gradually regain proliferative advantage.
    
    Conclusion:
    We conclude that lung cancer cells utilize distinct mechanisms for EMT in response to acute and chronic inflammation. We also demonstrate that dynamic alteration of histone modification and DNA methylation can lead to prolonged but reversible EMT, subsequently creating a time window for cancer cells to migrate to distant organs and eventually undergo mesenchymal-epithelial transition to form macro-metastases.