Epithelial-mesenchymal transition is associated with osteopontin-induced EGFR‑TKI resistance in EGFR mutant non-small cell lung cancer.

BACKGROUND

Resistance restricts the long-term therapeutic efficacy of epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) in the treatment of non-small cell lung cancer (NSCLC) with positive EGFR mutations. The present study sought to identify the potential protein osteopontin (OPN) involved in EGFR-TKI resistance and examine its therapeutic mechanism in NSCLC.

METHODS

The expression of OPN in NSCLC tissues was evaluated by immunohistochemistry (IHC). Western blot (WB), quantitative real‑time polymerase chain reaction (qRT-PCR), and immunofluorescence staining were used to analyze OPN and epithelial-mesenchymal transition (EMT)-related protein expression in the PC9 and PC9 gefitinib resistance (PC9GR) cells. Enzyme-linked immunosorbent assays (ELISAs) were used to detect the secreted OPN. Cell Counting Kit-8 (CCK-8) assays and flow cytometry were used to examine the effect of OPN on the gefitinib-induced growth and death of PC9 or PC9GR cells.

RESULTS

OPN was upregulated in the human NSCLC tissues and cells resistant to EGFR-TKIs. The overexpression of OPN inhibited EGFR-TKI-induced apoptosis and was associated with the formation of EMT. By activating the phosphatidylinositol-3 kinase (PI3K)/protein kinase B (AKT)-EMT pathway, OPN contributed to the development of EGFR-TKI resistance. Reducing OPN expression and inhibiting PI3K/AKT signaling improved EGFR-TKI sensitivity significantly more than the use of either agent alone.

CONCLUSIONS

This study showed that OPN increased EGFR-TKI resistance in NSCLC through the OPN-PI3K/AKT-EMT pathway. Our findings may provide a possible therapeutic target for overcoming EGFR-TKI resistance in this pathway.