PGR and breast cancer: It has been reported that the progesterone receptor lacks the consensus sequence or half-sequence response element in the PRLR gene PIII promoter and demonstrated that progesterone induces an increase in PRLR mRNA in a non-classical manner by inducing the expression of PRLR through the cooperative activation of Sp1 and CEBPβ at the PIII promoter in mouse cells and T47D breast cancer cells (43).