In breast cancer cells, Circular RNA Forkhead box O3 (circ-Foxo3) has been demonstrated to facilitate ubiquitination and degradation of mutant p53 tumor suppressor protein (p53) by binding p53 and the E3 ubiquitin ligase mouse double minute 2 (MDM2) as the tumor suppressor. The gene discussed is TP53; the disease is breast carcinoma.