 Soon after the protein product was confirmed, DCC knockout mice were created.As DCC−/− mutations are rapidly fatal due to a lack of nervous system development, DCC+/− mice were assessed for increased tumour development over two years, and no increase in tumour predisposition was detected.The discovery of a specific function for DCC that seemed to have little to do with cell cycle control, the low somatic mutation rate and the absence of cancer predisposition in DCC heterozygotes were fairly discouraging evidence for DCC's putative tumour suppressor status.