As previously reviewed (Smith, 2011b), comparison of the extent of exogenous heme clearance with HPX levels supported that HPX recycles after heme delivery to the liver (Muller-Eberhard et al., 1968; Drabkin, 1971), which was subsequently shown directly using radioactive heme-125I-HPX in rats (Smith and Morgan, 1978, 1979) and confirmed in human hepatoma cells (Smith and Hunt, 1990). The gene discussed is HPX; the disease is hepatocellular carcinoma.