If expressed, the truncated BRCA1 has been shown to cause chemoresistance, decreased susceptibility to apoptosis, decrease in vivo tumour growth suppression, as well as inhibition of “protective” estrogen receptor transcriptional activity, suggesting that truncated BRCA1 proteins function by inhibiting the activity of wild-type BRCA1 [84]. This evidence concerns the gene BRCA1 and neoplasm.