Antigen: phosphopeptide corresponding to amino acid residues surrounding the phospho-Ser²⁹⁴ of human progesterone receptor · Host: mouse · Application(s): WB and IHC (frozen sections) · There is accumulating evidence to suggest that progesterone plays an essential role in the regulation of growth and differentiation of mammary glands and thus may play a key role in breast cancer.¹ The biological response to progesterone is mediated by two distinct forms of the human progesterone receptor (PR-A and PR-B forms). In most cell contexts, the B form functions as a transcriptional activator, whereas the A form functions as a transcriptional inhibitor of steroid hormones.^2,3 Recently it has been demonstrated that there is differential hormone dependent regulation of the phosphorylation of the A and B forms of the receptor.⁴ Treatment of T47D breast cancer cells with progestin agonist increases the phosphorylation of Ser¹⁹⁰ and Ser²⁹⁴ with different kinetics. These phosphorylation events may differentially affect the transcriptional activity of the receptor.

1 Edwards, D.P. Regulation of signal transduction pathways by estrogen and progesterone. Annu Rev Physiol 67 335-376 (2005).

2 Attia, G.R., Zeitoun, K., Edwards, D., et al. Progesterone receptor isoform A but not B is expressed in endometriosis. J Clin Endocrinol Metab 85 2897-2902 (2000).

3 Lin, V.C.L., Woon, C.T., Aw, S.E., et al. Distinct molecular pathways mediate progesterone-induced growth inhibition and focal adhesion. Endocrinology 144 5650-5657 (2003).

4 Clemm, D.L., Sherman, L., Boonyaratanakornkit, V., et al. Differential hormone-dependent phosphorylation of progesterone receptor A and B forms revealed by a phosphoserine site-specific monoclonal antibody. Mol Endocrinol 14 52-65 (2000).

Edwards, D.P. Regulation of signal transduction pathways by estrogen and progesterone. Annu Rev Physiol 67 335-376 (2005).

Attia, G.R., Zeitoun, K., Edwards, D., et al. Progesterone receptor isoform A but not B is expressed in endometriosis. J Clin Endocrinol Metab 85 2897-2902 (2000).

Clemm, D.L., Sherman, L., Boonyaratanakornkit, V., et al. Differential hormone-dependent phosphorylation of progesterone receptor A and B forms revealed by a phosphoserine site-specific monoclonal antibody. Mol Endocrinol 14 52-65 (2000).

Lin, V.C.L., Woon, C.T., Aw, S.E., et al. Distinct molecular pathways mediate progesterone-induced growth inhibition and focal adhesion. Endocrinology 144 5650-5657 (2003).

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