To further clarify the specific mechanism of action of CXXC5 in breast cancer development, we subsequently coimmunoprecipitated total protein extracts of MCF-7 and MDA-MB-231 cells with antibodies against CXXC5, and then immunoblotting with antibodies against DDB1, CUL4B, ROC1, MTA1, MTA2, RbAp46/48, HDAC1, HDAC2, or MBD2/3 was performed to confirm the interaction among CXXC5, the CRL4B complex, and the NuRD complex. The gene discussed is HDAC2; the disease is breast cancer.