Mutations in human breast cancer: an overview.

Studies of mammary tumorigenesis in mice infected with the mouse mammary tumor virus and in certain strains of transgenic mice with an activated oncogene have provided strong evidence that multiple mutations contribute to the initiation and progression of malignancies in the breast. The increasing availability of recombinant DNA probes that detect various proto-oncogenes, growth factor genes, and growth factor receptor genes, as well as restriction fragment length polymorphisms in the human population, have made possible a molecular approach for the identification of frequently occurring mutations in primary human breast tumor DNA. The aim of studies using this molecular approach has been to investigate whether specific mutations are highly associated with various clinical parameters, including disease prognosis. Eight mutations have been identified, including amplification of c-myc, c-erbB2, and int-2, as well as loss of heterozygosity on five chromosomes (1q, 3p, 11p, 13q, and 17p). Loss of heterozygosity is thought to unmask recessive mutations of tumor-suppressor genes. In some studies, amplification of either c-myc, c-erbB2, or int-2 has been found to have a significant association with high risk of relapse or poor survival. The current status of these mutations as potentially useful prognostic indicators for the management of the disease is controversial and points to the need for further research in this area.