To further elucidate the critical role of Topo IIα in mediating the response of NSCLC cells to osimertinib or EGFR-TKIs, we compared basal levels of Topo IIα between osimertinib-resistant cell lines and their matched parental cell lines and found that Topo IIα levels were in general higher in the tested osimertinib-resistant cell lines than in their corresponding parental cell lines (Figure 5, A and B). This evidence concerns the gene EGFR and non-small cell lung carcinoma.