EGFR and lung cancer: Because EGFR-TKI-resistant lung cancer cell lines (HCC827 GR, H1993 ER, and H292 ER) acquired resistance via stepwise exposure to EGFR-TKIs over a long-term period [21, 27] and exhibited downregulated signaling activity of EGFR (Figure 1(d)), compensatory activation of mitochondrial OXPHOS in the resistant NSCLC cell lines appears reasonable.