Abstract
BackgroundThis study investigated the role of fibrinogen-like protein 1 (FGL1) in regulating gefitinib resistance of PC9/GR non-small cell lung cancer (NSCLC).MethodsThe effect of different concentrations of gefitinib on cell proliferation were evaluated using the CCK-8 assay. FGL1 expression in the normal human bronchial epithelial cell line Beas-2B, as well as four lung tumor cell lines, H1975, A549, PC9, and PC9/GR, was investigated by using western blotting and qRT-PCR. FGL1 was knocked down using small interfering RNA to evaluate the effects of FGL1 on PC9 and PC9/GR. The correlation between FGL1 expression and gefitinib resistance was determined in vitro via CCK-8 and colony formation assays, and flow cytometry and in vivo via flow cytometry and immunohistochemistry.ResultsFGL1 expression was significantly upregulated in non-small cell lung cancer cells with EGFR mutation and higher in the gefitinib-resistant NSCLC cell line PC9/GR than in the gefitinib-sensitive NSCLC cell line PC9. Further, FGL1 expression in PC9 and PC9/GR cells increased in response to gefitinib treatment in a dose-dependent manner. Knockdown of FGL1 suppressed cell viability, reduced the gefitinib IC50 value, and enhanced apoptosis in PC9 and PC9/GR cells upon gefitinib treatment. Mouse xenograft experiments showed that FGL1 knockdown in PC9/GR tumor cells enhanced the inhibitory and apoptosis-inducing actions of gefitinib. The potential mechanism of gefitinib in inducing apoptosis of PC9/GR cells involves inhibition of PARP1 and caspase 3 expression via suppression of FGL1.ConclusionsFGL1 confers gefitinib resistance in the NSCLC cell line PC9/GR by regulating the PARP1/caspase 3 pathway. Hence, FGL1 is a potential therapeutic target to improve the treatment response of NSCLC patients with acquired resistance to gefitinib.
Highlights
This study investigated the role of fibrinogen-like protein 1 (FGL1) in regulating gefitinib resistance of PC9/GR non-small cell lung cancer (NSCLC)
Upregulation of FGL1 correlates with gefitinib resistance To explore the role of FGL1 in NSCLC cell resistance to gefitinib, we first measured FGL1 expression levels in normal bronchial epithelial cells BEAS-2B, and the four human NSCLC cell lines, A549, H1975, PC9, and PC9/ GR, by western blot analysis and RT-qPCR
These results suggested that FGL1 expression may relate to the mutation status of epidermal growth factor receptor (EGFR) and contribute to gefitinib acquired resistance in NSCLC cells
Summary
This study investigated the role of fibrinogen-like protein 1 (FGL1) in regulating gefitinib resistance of PC9/GR non-small cell lung cancer (NSCLC). Lung cancer is the main cause of cancer-related mortality globally [1]. In China, 7,33,300 lung cancer cases were diagnosed in 2015 [2]. Non-small cell lung cancer (NSCLC) accounts for approximately 85% of lung cancer cases, and approximately 80% of NSCLC patients miss the best opportunity of treatment by the time of diagnosis. With a five-year survival rate of only 15%, prognosis is poor [3]. The frequency of epidermal growth factor receptor (EGFR) gene mutation in non-smoking NSCLC patients is as high as 60% in Asia [4].
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