PGR and breast carcinoma: A putative role in breast cancer based on the AKR1C enzymes metabolizing progesterone into a 4-pregnene was described by Ji et al. These authors speculated that loss of AKR1C1 and AKR1C2, but not AKR1C3 in breast cancer, resulted in decreased progesterone catabolism which, in combination with increased PR expression, may augment progesterone signaling by its nuclear receptors64.