• What is PGR?
  • PGR in Breast Cancer
  • Clinical Trials

PR (PGR)

The progesterone receptor gene (PGR, commonly known as PR) plays a role in pathogenesis of cancers such as endometrial cancer and breast cancer (Kim et al. 2013). PR is located on chromosome 11 (Law et al. 1987). PR is in the nuclear receptor superfamily, is part of the steroid receptor family, and has a six-region structure with a defined functional domain (Grontved and Hager 2012).

PR protein expression is measured using immunohistochemistry (IHC) and PR expression occurs in 55–58% of invasive breast cancers (Nadji et al. 2005; Rhodes et al. 2000) and in 50–72% of endometrial cancers (Merritt et al. 2010; Suthipintawong et al. 2008).

Related Pathways

Contributors: Justin M. Balko, Pharm. D., Ph.D., Ingrid A. Mayer, M.D., M.S.C.I., Mia Levy, M.D., Ph.D., Carlos L. Arteaga, M.D.

Suggested Citation: Balko, J., I. Mayer, M. Levy, C. Arteaga. 2015. PR (PGR). My Cancer Genome https://www.padiracinnovation.org/content/disease/breast-cancer/pgr/?tab=0 (Updated December 7).

Last Updated: December 7, 2015

PR (PGR) in Breast Cancer

Progesterone receptor (PR) protein expression occurs in 55–58% of breast cancers (Nadji et al. 2005; Rhodes et al. 2000). PR (PGR) mutations are not known to be important in breast cancer.

Gene or Protein Invasive Breast Cancer Hormone Receptor Positive (ER+ and/or PR+) Invasive Breast Cancer HER2 positive Invasive Breast Cancer Triple-negative Invasive Breast Cancer
PR expression 55–58% (Nadji et al. 2005; Rhodes et al. 2000) 84% (Dunnwald et al. 2007) 50% (Blows et al. 2011 0%
NOTE: ER = estrogen receptor; PR = progesterone receptor

Testing for PR Expression in Breast Cancer

Because ER and PR expression is predictive for response with endocrine therapy and prognostic for survival outcomes, accurate immunohistochemistry (IHC) measurements for ER and PR expression in breast cancer are important (Hammond et al. 2010a).

Several different methods have been used to measure PR status. Per National Comprehensive Cancer Network (NCCN) guidelines, PR expression in invasive breast cancer or ductal carcinoma in situ (DCIS) tumor tissue should be measured with validated IHC assays (Allred et al. 2009). The ASCO/CAP guideline recommendations for ER and PR testing by IHC in breast cancer patients specify the following algorithm for optimal ER/PR testing (Hammond et al. 2010a; Hammond et al. 2010b):

 

1. Positive for ER or PR if finding of ≥ 1% of tumor cell nuclei are immunoreactive.

2. Negative for ER or PR if finding of < 1% of tumor cell nuclei are immunoreactive in the presence of evidence that the sample can express ER or PR (positive intrinsic controls are seen).

3. Uninterpretable for ER or PR if finding that no tumor nuclei are immunoreactive and that internal epithelial elements present in the sample or separately submitted from the same sample lack any nuclear staining.


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Contributors: Justin M. Balko, Pharm. D., Ph.D., Ingrid A. Mayer, M.D., M.S.C.I., Mia Levy, M.D., Ph.D., Carlos L. Arteaga, M.D.

Suggested Citation: Balko, J., I. Mayer, M. Levy, C. Arteaga. 2013. PR (PGR) in Breast Cancer. My Cancer Genome https://www.padiracinnovation.org/content/disease/breast-cancer/pgr/ (Updated October 11).

Last Updated: October 11, 2013

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