The progesterone receptor (PR) is a nuclear hormone receptor that mediates the effects of progesterone, a steroid hormone critical for regulating female reproductive functions, including menstrual cycle regulation, embryo implantation, and pregnancy maintenance. PR exists as two main isoforms, PR-A and PR-B, transcribed from the same gene via alternative promoters. PR-B is a full-length receptor with a unique N-terminal domain, while PR-A lacks part of this region. Both isoforms bind progesterone but exhibit distinct transcriptional activities: PR-B primarily drives progestin-responsive gene expression, whereas PR-A often acts as a repressor of PR-B and other steroid receptors. PR is predominantly expressed in reproductive tissues (e.g., uterus, ovaries), mammary glands, and certain hormone-responsive cancers, such as breast and endometrial cancers.
PR antibodies are essential tools in research and diagnostics, particularly in breast cancer subtyping. Clinically, PR status (alongside estrogen receptor, ER) guides endocrine therapy decisions, as PR-positive tumors often respond better to anti-hormonal treatments like tamoxifen. These antibodies are widely employed in immunohistochemistry (IHC) to assess PR expression levels and cellular localization in tissue samples, aiding in prognosis and therapeutic stratification. In research, PR-specific antibodies enable studies on receptor dynamics, post-translational modifications, and isoform-specific functions via techniques like Western blot, immunofluorescence, and chromatin immunoprecipitation. Antibody specificity is critical, as cross-reactivity with other steroid receptors or failure to distinguish isoforms may skew results. Recent studies also explore PR's role in non-reproductive contexts, such as neuroprotection and immune modulation, expanding the utility of PR antibodies in diverse biomedical fields.