Progesterone-binding cyst protein (PBCP = GCDFP-24) and steroid hormone receptors as markers of differentiation in breast cancer. Inverse relation of distribution in normal and malignant tissue of the same breast.

Progesterone-binding cyst protein (PBCP, identical to Gross Cystic Disease Fluid Protein; GCDFP-24) has been evaluated as a possible marker of differentiation in breast tissues. In 17 women with verified operable breast cancer, we have quantitated the cytosol content of PBCP, steroid hormone receptors (estrogen receptor[ER], progesterone receptor[PR] and androgen receptor[AR] as well as albumin in specimens from the primary tumor and from the adjacent non-malignant tissue of the same breast. A significantly higher amount of PBCP (p less than 0.001) and albumin (p less than 0.003) was found in the non-malignant tissue. Conversely, the content of steroid receptors was significantly higher (p less than 0.001) in the malignant tumor, compared to the non-malignant breast tissue. A significant correlation (p = 0.005) between PBCP content in the malignant tumor and in the non-malignant tissue was found. In malignant tissue, ER was significantly correlated with AR (p = 0.007) and to age at operation (p = 0.006). Our results are in agreement with recent reports on other tissue parameters, which indicate qualitative and quantitative differences between the malignant and the non-malignant counterpart with regard to regulation of cell growth and the expression of differentiation markers. This study provides evidence for PBCP as a marker of differentiation to be implemented in further clinical and basic research on breast cancer.