Numerous in vitro and in vivo studies(Powell et al, 2010) using differentclasses of PARP inhibitors have reported enhancement of the cytotoxicity ofradiation in a number of tumour types, including colorectal cancers (Calabrese et al, 2004) and gliomas (Dungey et al, 2009; Russo et al, 2009). The gene discussed is PARP1; the disease is colorectal cancer.