ABCB5 and Merkel cell skin cancer: Beyond CD56 ADC targeting, ABCB5 blockage with an anti-ABCB5 mAb has also shown efficacy in reducing MCC drug resistance to carboplatin and etoposide in vivo, attenuated xenograft growth, and increased caspase 3 expression in mice injected with MKL-1 tumor cells [37].