ESR1 and neoplasm: In addition, proteins that have previously been associated with increased bone metastasis including the calcium-binding protein and fibroblast marker S100A4 as well as the cell adhesion molecule fibronectin [11] were both increased in bone metastases from ER+ and triple-negative PDXs compared with the primary tumour, and γ catenin, previously shown to be dysregulated in ER+ models of bone metastasis [39], was increased in the bone metastatic deposits from ER+ PDXs but not triple negative.