Western blot of whole cell T47D lysate prepared from cells that had been incubated in the presence of the synthetic progestin agonist R5020 (500 nM) showing specific immunolabeling of the ~90k PR-A isoform and the ~120 PR-B isoform of the progesterone receptor phosphorylated at Ser294 using Progesterone Receptor (phospho Ser294) antibody [608] (GTX30165). The immunolabeling is blocked by the phosphopeptide used as the antigen (not shown).