Consistent with the results in Fig. 1, the myofibroblast-like cells were found in drug-resistant tumors in EGFRL858R*Tp53+/+ and EGFRL858R*Tp53+/− mice, more intense eosin staining, a higher N/C ratio and irregular in the nuclear morphology were found in the lungs from EGFRL858R*Tp53+/− mice than in those from EGFRL858R*Tp53+/+ mice, implying that partial loss of p53 led to the induction of drug resistance during cancer therapy (Fig. 5C). The gene discussed is TP53; the disease is cancer.