Human
estrogen receptor (ER) is a 66 kDa protein that acts as an estrogen-dependent,
nuclear hormone receptor. Studies have shown ER is present in the nuclei of
epithelial cells in normal breast and endometrial tissues, as well as a subset
of breast carcinomas. The SP1 clone is a high affinity rabbit monoclonal
antibody directed against an epitope of the C-terminus of the ER protein. (1)
SP1 has been shown to stain formalin-fixed paraffin-embedded tissues. The
robustness of SP1 has been demonstrated by successful immunohistochemistry using
lower temperatures for antigen retrieval (e.g. 80 or 95ºC), and in some
instances, staining can be obtained even without antigen retrieval. (2-3)