The four stromal signatures (ESTIMATE42, Hallmark EMT, and the two breast cancer-specific stromal signatures40,46) increased synchronously with HER2-targeted therapy alone; after chemotherapy, however, the non-breast cancer signatures remained elevated, while the breast cancer stromal signatures plummeted, perhaps because these signatures capture gene expression related to stromal interaction with the active tumor or that is affected differentially by chemotherapy. This evidence concerns the gene ERBB2 and breast cancer.