More breast cancer genes?

A new gene associated with a high risk of breast cancer, termed BRCAX, may exist on chromosome 13q. Tumours from multicase Nordic breast cancer famili es, in which mutations in BRCA1 and BRCA2 had been excluded, were analyzed using comparative genomic hybridization in order to identify a region of in terest, which was apparently confirmed and refined using linkage analysis o n an independent sample. The present commentary discusses this work. It als o asks why there should exist genetic variants associated with susceptibili ty to breast cancer other than mutations in BRCA1 and BRCA2, and what might be their modes of inheritance, allele frequencies and risks. Replication s tudies will be needed to clarify whether there really is a tumour suppresso r gene other than BRCA2 on chromosome 13q.