CXXC5 and neoplasm: Next, we investigated the role of the CXXC5–CRL4B–NuRD complex in tumor development and progression in vivo by implanting MCF-7 cells that had been engineered to stably express empty vector, control shRNA, CXXC5, CXXC5 + shCUL4B, CXXC5 + shMTA1, shCXXC5, or shCXXC5 + shTSC1 onto the abdominal mammary fat pad of 6-week-old ovariectomized female athymic BALB/c mice implanted with E2 pellets (n = 5).