First-generation tyrosine kinase inhibitors (TKIs) have been associated with good responses in non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR)-sensitizing mutations. However, this therapeutic strategy inevitably promotes resistance to TKIs. This study aimed to investigate the functional role and mechanism of proscillaridin A in NSCLC with or without EGFR mutations. Cellular function assays showed that proscillaridin A could inhibit cell proliferation, migration and invasion in vitro independent of EGFR mutation status. Real-time PCR of the human chromosome 17 α-satellite region revealed that proscillaridin A significantly suppressed tumour micrometastasis in vivo. In immunofluorescence experiments, we found that proscillaridin A decreased filopodia length in NSCLC cells. Furthermore, proscillaridin A also downregulated EGFR-Src-mediated cytoskeleton-related pathways, including FAK-paxillin signalling, which has been shown to promote cell filopodia formation by regulating small G-proteins. Therefore, we used the GST-PBD pull-down assay to demonstrate that proscillaridin A could decrease Cdc42 activity. Moreover, survival analyses of 591 lung adenocarcinoma patients from the GEO database indicated that the expression levels of Src and paxillin and the risk score of the gene signature based on these two factors were negatively correlated with overall survival and could be used as independent prognostic factors. In conclusion, we speculate that proscillaridin A inhibits lung cancer cell growth and motility by regulating EGFR-Src-associated pathways.
Keywords: EGFR; Proscillaridin A; Src; lung adenocarcinoma; small GTPase.
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