Proscillaridin A inhibits lung cancer cell growth and motility through downregulation of the EGFR-Src-associated pathway.

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