Additionally, consistent with our finding of rapid PR protein loss (i.e., by turnover) of activated (deSUMOylated and phosphorylated) receptors, we detected phospho-PR gene signatures in breast tumors clinically designated as PR-low to PR-null (luminal B) and identified novel gene sets (HER2, PAX2, AHR, AR, and RUNX) uniquely regulated by modified PRs that are associated with cancer stem cell biology. This evidence concerns the gene PGR and breast neoplasm.