CRISPR/Cas9 screens also defined the importance of the MSH2 gene and mismatch repair in cisplatin resistance in bladder cancer [63] and the role of ABCB1 gene (also named multidrug resistance1, MDR1, which encodes a transmembrane glycoprotein transporting multiple types of chemotherapeutic drugs out of cells) in breast cancer resistance to doxorubicin [64, 65]. Here, ABCB1 is linked to breast cancer.