Loss of MAP2K7 resulted in a 75–97% reduction in endogenous pJNKT183/Y185 levels in MCF-7 and T-47D cells, indicating that MKK7 mediates a substantial proportion of JNK phosphorylation in proliferating ER+ breast cancer cells (Fig. 2F-I). This evidence concerns the gene MAPK8 and breast carcinoma.