HMOX1 and liver cancer: For example, in the liver cancer cell line HepG2, treatment with β-carotene at 1 to 5 μM inhibits growth signals (such as NF-kB, pAkt, and pERK) and redox signals (such as nuclear factor erythroid 2–related factor 2 (Nrf-2), SOD-2, and heme oxygenase-1 (HO-1)) but triggers apoptotic signals such as cleaved PARP, Bax, and caspase [48].