An increased expression of ARNT confers tumour cells a radioresistant phenotype (including Hep3B cells) and provides a clonal survival benefit as demonstrated previously by our group.19 The observation that ARNT overexpression in Hep3B cells is sufficient to stabilise HIF-1α accompanied with HRE-driven reporter gene expression in normoxia fits well with these results.19 The gene discussed is ARNT; the disease is neoplasm.