MLH1 or MSH2-deficient tumour cells have been reported to be resistant to a large number of anticancer drugs (Aebi et al, 1997; Fink et al, 1998b) and to radiotherapy (Fritzell et al, 1997; Xu et al, 2001), and as a result, MMR status may be an important resistance factor. This evidence concerns the gene MLH1 and neoplasm.