Immunohistochemistry was performed on samples obtained from patients whose cancers had relapsed after complete remission following chemotherapy, and the ratio of patients exhibiting elevated expression of MDR1 in relapsing tissues compared with in the treatment-naïve lesions in the TP53 mutant group was 88.5% (54/61 cases), which was significantly higher than the ratio for the TP53 wild-type group (36.4%, 4/11 cases) (p < 0.01) (Fig. 5). The gene discussed is TP53; the disease is cancer.