Study identifies molecular differences between primary breast cancer and its metastases

A multi-institutional national study has identified unique molecular features responsible for the development and progression of metastatic breast cancer. One of the key features involves changes in the immune system that are due, in part, to methylation of the HLA-A gene; methylation is the addition of a small chemical group to a DNA molecule. Focal deletions, or the loss of part of the HLA-A gene, were also found and were mutually exclusive from samples with DNA methylations. In this study, methylation and focal deletions resulted in fewer immune cells being available to attack cancer cells.