OAZ2 and colorectal carcinoma: In these models, the mRNA of ornithine decarboxylase 2 (OAZ2) enzyme is targeted by miR-34a; therefore, the suppression of miR-34a/OAZ2 signal expression by chemotherapeutic agents increases the activation of MDR-associated ATP-binding cassette (ABC) transporters and anti-apoptosis pathways, thus leading to the development of MDR in CRC models [407].