ABCB4 and breast cancer: Huang et al. (2018) showed that ABCB4 mediated the efflux transport of doxorubicin and contributed to the acquired resistance of the drug in breast cancer cells. Furthermore, ABCB4 takes part in 5-fluorouracil resistance. Hu et al. (2018) revealed that loss of ABCB4 may enhance the resistance of colon cancer to 5-fluorouracil via inhibiting apoptosis. However, the underlying mechanism of ABCB4 in ccRCC requires further research.