Given the strong rationale linking CD133 expression to more aggressive cellular behaviour, including resistance to chemotherapy and radiotherapy, several studies have addressed its correlation with clinico-pathological characteristics of cancer patients: in particular, a direct correlation between CD133 expression and advanced stage of disease as well as poor grade of differentiation has been shown in hepatocellular carcinoma [23]. The gene discussed is PROM1; the disease is hepatocellular carcinoma.