Chromosome missegregations were observed in approximately one-third of the cell divisions in the vehicle-treated tumour (Fig. 5a, b), confirming previous observations that the BRCA1−/−;TP53−/− tumours are CIN.39 Exposure to Cpd-5 alone did not have a significant effect on the level of missegregations in these tumours, while treatment with docetaxel led to a minor increase (Fig. 5b). Here, BRCA1 is linked to neoplasm.