Fig. 1

Total PR and phospho-Ser294 PR IHC staining in cell lines, tissue sections, and a breast cancer tissue microarray. a Cartoon depiction of PR ligand/kinase-dependent Ser294 phosphorylation, which blocks Lys388 SUMOylation and alters the recruitment of either co-activators or co-repressors, resulting in promoter-selective transcription. b PR Ser294 phosphorylation and total PR protein expression levels were measured in T47D breast cancer cell lines by western blotting, with and without progestin R5020 treatment. c PR levels were also measured in T47D cells on coverslips using IHC methods. d PR Ser294 and total PR protein levels were measured by IHC in a control tissue type (endometrial) to demonstrate effective PR Ser294 (and total PR) antibody specificity and sensitivity. e IHC in breast tumor sections (spots) of a tissue microarray. Six representative images demonstrate H-scoring classification: (column 1) 0% staining, (column 2) 20% positive cells, weak, (column 3) 100% positive cells, strong