Our results implicating Jab1 in the EGFR pathway, in addition to its role in the S100A7 pathway, suggest that Jab1 may be particularly important in the ERα- breast cancer cell and provide insight into the application of new therapeutic strategies (for example, proteasome inhibitors) directed to this important and difficult-to-treat subset of breast cancer. Here, COPS5 is linked to breast carcinoma.