The fibromatosis signature defines a robust stromal response in breast carcinoma

Breast cancer is a heterogeneous disease, and the influence of stromal gene and protein expression patterns on the biological and clinical heterogeneity of the disease is poorly understood. We previously demonstrated that evaluation of the gene expression patterns of two soft-tissue tumors (desmoid-type fibromatosis (DTF) and solitary fibrous tumor) could be used to identify distinct stromal reaction patterns in breast carcinoma. In the current study, we examined four additional data sets obtained from four different institutions and containing gene expression data from a total of 561 breast cancer patients. We identified a core set of 66 DTF-associated genes that were consistently coordinately expressed in a subset of 25-35% of breast cancers. Breast carcinomas defined by high levels of coordinated expression of DTF core genes tend to be lower grade, express estrogen receptor, and show significantly longer survival across the four data sets. Using multiple tissue microarrays of archival breast cancer specimens obtained from a total of 745 patients, we demonstrated that a subset of breast cancers show coordinate expression of DTF core proteins by stromal cells in the tumor microenvironment. We evaluated the protein expression of a single DTF core protein (SPARC) on a tissue microarray with clinical outcome data and demonstrated that breast cancers with strong stromal protein expression of SPARC show a trend for increased survival. Our data demonstrate that the DTF core gene set is a robust descriptor of a distinct stromal response that is associated with improved clinical outcome in breast cancer patients.