CUL4A and breast cancer: MDR-1 could be detected in tumor cells from 12.6% primary NPC patients and 32.6% recurrent NPC patients.[27] A recent study showed the evidence that overexpression of CUL4A in breast cancer cells increased expressions of MDR-1 mRNA and protein levels and induced drug resistance.[28] These findings indicates an important role of CUL4A in chemotherapeutic drug resistance, and MDR1 might be a downstream protein in a subset of NPC patients.