Abstract
Non-small cell lung cancer (NSCLC) is characterized by hyperexpression and/or gain-of-function mutations of the epidermal growth factor receptor (EGFR), resulting in an elevated overall kinase activity. Gefitinib is remarkably effective in patients with the L858R or ΔE746-A750-mutated of EGFR. However, drug resistance tends to develop because of the emergence of T790M mutation on EGFR. New strategies other than repressing kinase activity are thus required to treat NSCLC, thereby circumventing the resistance. In this study, arsenic trioxide (ATO) at 2 μM significantly inhibited the proliferation of the gefitinib-resistant NCI-H1975 cells of the EGFR L858R/T790M mutant compared with a modest inhibition in the gefitinib-sensitive HCC827 cells of ΔE746-A750 mutant and A549 cells of wild-type EGFR. Moreover, ATO significantly inhibited the overall kinase activity of EGFR primarily through quantitatively diminishing the EGFR in NCI-H1975 cells to an extent comparable with that reached by gefitinib in HCC827 cells. Furthermore, ATO promoted autophagic degradation of EGFR in NSCLC cells by directly binding to P62, which interacted with EGFR, preferentially the L858R/T790M mutant providing a plausible explanation for a more favorable effect of ATO on NCI-H1975 cells. Accordingly, the effect of ATO was further confirmed in the NSCLC xenograft mouse models. Our results reveal a new target for ATO with a unique molecular mechanism, i.e., ATO suppresses the overall catalytic potential of EGFR, significantly those with the L858R/T790M mutant in NCI-H1975 cells, through an autophagic degradation by interacting with P62. This study potentially offers an innovative therapeutic avenue for the NSCLC with L858R/T790M-mutated EGFR.
Highlights
Lung cancer is a major cause of cancer death worldwide[1,2]
Results showed that arsenic trioxide (ATO) and gefitinib significantly inhibited the proliferation of NCIH1975 and HCC827 cells (Fig. 1a, S1A), respectively, confirming that NCI-H1975 is sensitive to ATO and HCC827 to gefitinib
Patients harboring the epidermal growth factor receptor (EGFR)-activating mutations benefit from the kinase inhibitor gefitinib but may have to confront the drug resistance caused by the secondary mutations[7,25]
Summary
Mao et al Cell Death and Disease (2018)9:963 developed to treat NSCLC harboring the L858R/T790M mutant[8,9]. Circumventing the resistance to TKI is the most formidable challenge in treating NSCLC. Clinical studies have demonstrated that the addition of arsenic trioxide (ATO) into the nebulized liquid for the treatments of lung cancer patients reduced the tumor size in ~61.9% (13/21) of the cases, with no apparent side effects[17]. Intrapleural administration of ATO in NSCLC patients with advanced large pleural effusion significantly improved the characteristics of pleural effusion 18. These observations suggested that ATO might contribute to the treatment of NSCLC, even though the exact effect and molecular mechanisms remain unknown
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