The SUMO-deficient PR gene expression signature is associated with HER2-positive human breast tumors and predicts reduced patient survival. (A) Normalized gene expression levels (for genes in our LD KR > WT gene signature) are presented for each tumor in the patient cohort , organized by ERBB2 status. (B) Gene expression levels were measured by RT-qPCR for CHN2 and RGS2 (both upregulated by SUMO-deficient PR, and members of the LD KR > WT gene signature) and the control gene ACOT6 (equally upregulated by both WT and KR receptors) in BT-474 human breast cancer cells. Cells were pre-treated with MEK kinase inhibitor U0126 prior to progestin or antiprogestin co-treatment. Protein levels were evaluated by western blotting for total PR, PR Ser294 phosphorylation, total ERK1/2, and ERK1/2 phosphorylation. (C) Kaplan-Meier survival curve for distant metastasis free survival for patients whose tumors expressed the combined T47D metagenes (WT or KR, -/+R5020) relative to patient tumors lacking these metagenes. Patient samples include untreated and tamoxifen-treated ER-positive tumors from the Loi et al. dataset . (D) Survival curves as in part C for patients whose tumors expressed the combined T47D metagenes (KR -R5020, or KR +R5020) relative to patient tumors lacking these metagenes. [See also Additional files 4 and 9]. ER, estrogen receptor; KR, K388R PR-B mutant; LD, ligand dependent; SUMO, small ubiquitin-like modifier; WT, wild type.