It has been found that cytosolic p21WAF1/KIP1 effectively blocks procaspase-3 mediated cell death in a human liver cancer cell line and that this interaction occurs on the mitochondria, suggesting the pivotal role of cytoplasmic p21WAF1/KIP1 in inhibition of apoptosis in cancer cell lines [55, 56]. The gene discussed is CDKN1B; the disease is liver cancer.