Targeting PKCι-PAK1 in EGFR-mutation positive non-small cell lung cancer.

BACKGROUND: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) induce significant responses in EGFR-mutation positive non-small cell lung cancer (NSCLC). However, universal progression is observed. METHODS: The effect of the anti-rheumatoid agent, auranofin, a selective inhibitor of oncogenic protein kinase C iota (PKCι) signaling and IPA-3, a non-ATP competitive p21-activated kinase 1 (PAK1) inhibitor in treatment-naïve and EGFR TKI-resistant EGFR-mutation positive NSCLC cell lines was investigated. PC9 and HCC827 cells were used. The four EGFR-TKI resistant cell lines were established from PC9. Cell viability assays, drug combination studies, and western blotting were performed. The combination index, and RTK or non-RTK expression were performed. RESULTS: The combination of IPA-3 and auranofin was highly synergistic in all 6 cell lines (combination indexes ranged from 0.37-0.62). The activities on EGFR, CDCP1, AXL, MET, and downstream effector pathways, including PAK1, PKCι, ERK, AKT, STAT3, Src, and YAP1 were abrogated. CONCLUSIONS: The combination of auranofin with IPA-3 could be a potential therapy for EGFR-mutation positive NSCLC resistant to EGFR TKIs. Auranofin with IPA-3 could become a therapeutic solution for EGFR-mutation positive NSCLC patients resistant to EGFR TKIs.