Enhanced Sensitivity of Nonsmall Cell Lung Cancer with Acquired Resistance to Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors to Phenformin: The Roles of a Metabolic Shift to Oxidative Phosphorylation and Redox Balance

Figure 4

Selective anticancer effect of phenformin in acquired EGFR-TKI-resistant lung cancer. (a) HCC827, HCC827 GR, H1993, and H1993 ER cells were exposed to phenformin (30 and 100 μM) for 72 h, and cell proliferation was monitored by IncuCyte ZOOM. Data represent (, vs. parental cell line). (b) Intracellular aspartate level. HCC827 and HCC827 GR cells were treated with 100 μM phenformin for 24 h, and aspartate levels in cell lysates were determined by LC-MS/MS. Data represent (, vs. vehicle-treated group). (c) Potentiation of redox stress by phenformin in acquired EGFR-TKI-resistant cancer cells. Intracellular NAD⁺/NADH ratio was analyzed in HCC827 and HCC827 GR cells 24 h after exposure with vehicle or 100 μM phenformin. Data represent (, vs. vehicle-treated group). (d) Reversal of antiproliferative effect of phenformin by electron acceptor or aspartate. Cell proliferation was monitored for 72 h in HCC827 and HCC827 GR cells treated with phenformin (30 and 100 μM) in the presence or absence of 1 mM AKB or 10 mM aspartate. Data represent (, , vs. vehicle-treated group). (e and f) In vivo anticancer effect of phenformin on tumor growth of EGFR-TKI-resistant lung cancer. HCC827 and HCC827 GR cells were inoculated into right flank of Balb/c nude mice, and the mice were orally administered with 300 mg/kg phenformin or tap water (vehicle) once a day. (e) Representative images. (f) Tumor volumes were measured every other day. Data represent (, vs. vehicle-treated group).

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