Background
It has long been suspected that there is a tumour suppressor gene on chromosome 8p, and our array CGH data [1] suggest that it may be close to the WRN and NEUREGULIN1 (NRG1) genes. NRG1 encodes growth factors that function as ligands for the tyrosine kinases ErbB3 and ErbB4, and can both stimulate cell proliferation, differentiation and apoptosis. We previously showed that many breast carcinoma (that is, 39% of cancer cell lines and 6% of breast tumours) have chromosome breakpoints in NRG1, suggesting that the gene plays an important role in tumourigenesis [2, 3], and our initial hypothesis was that the translocations activate expression.