TP53 and neoplasm: However, when TP53 is mutated, chemotherapy-induced inactivation of this pathway and the accumulation of LRPPRC and MDR1 promote drug resistance.195 Mutated p53 binds to the miR-223 promoter and reduces its transcriptional activity, and the introduction of exogenous miR-223 makes tumor cells carrying mutated TP53 sensitive to treatment.258