To corroborate the existence of slowly migrating bands of mitotic p21, colon carcinoma HCT116, breast cancer MCF7 and MDA-MB-231, osteosarcoma U2OS and cervical carcinoma HeLa cells were untreated or synchronized to prometaphase for Western blot analysis (Figure 1A). The gene discussed is CDKN1A; the disease is osteosarcoma.