Altered expression of prolactin receptor-associated signaling proteins in human breast carcinoma

Abstract

Prolactin receptor signaling can modulate proliferation, survival, motility, angiogenesis, and differentiation in breast cancer. Increased serum prolactin is associated with a significantly increased risk of breast cancer in post-menopausal women. The purpose of this study was to examine the expression of prolactin receptorassociated signaling proteins in breast cancer vs benign breast tissue. Breast tissue microarrays representing 40 cases of benign and malignant pathologies were obtained from the Cooperative Human Tissue Network. Standard immunohistochemistry for prolactin and prolactin receptor-associated proteins was performed. Both positive regulators (c-Myb, Nek3, Vav2) and negative regulators (PIAS3, SIRP) of prolactin receptor signaling were examined. Virtual slides were created from the stained breast tissue microarrays. Labels were scored by region of interest and labeling indices incorporating percent target labeled and label intensity were created. Quantitative determinations of labels were made using the Clarient image system. The unpaired t-test was used to compare labels from benign and malignant tissues. Visual scoring data showed upregulation of Nek3 (P ¼ 0.000377), PIAS3 (P ¼ 0.000257), and prolactin (P ¼ 0.002576) in breast cancer vs normal/hyperplastic epithelium. c-Myb showed a trend toward upregulation, but this did not achieve statistical significance (P ¼ 0.107374). SIRP (P ¼ 0.002060) was downregulated. Vav2 showed a trend toward downregulation (P ¼ 0.107456), but this did not achieve statistical significance. Clarient analysis corroborated upregulation in cancer of Nek3 (P ¼ 0.000013), PIAS3 (P ¼ 0.000067), and prolactin (P ¼ 0.017569). In conclusion, regulators of prolactin receptor signaling show heterogeneity in their expression in benign vs malignant breast tissue. Since these species are known to regulate prolactin-mediated actions, these results suggest multiple targets for modulating prolactin receptor-mediated growth and differentiation in breast cancer. The neuroendocrine hormone prolactin contributes to breast cancer progression through both endocrine and autocrine/paracrine loops. Prolactin acts through its cell-surface receptor, the prolactin receptor, and triggers a network of prolactin receptor-associated signaling proteins. In normal tissues, prolactin stimulates lobulo-alveolar expansion and differentiation as a prelude to milk synthesis and secretion. 1 In malignant tissues, however, prolactin fails to trigger differentiation, and instead enhances breast epithelial survival and motility. [2][3][4] Both normal and malignant breast epithelia, besides responding to pituitary-secreted (endocrine) prolactin, synthesize prolactin RNA from an upstream promoter at the autocrine/paracrine level. 4 As mutations of the prolactin receptor are very infrequent in breast cancer, we hypothesized that dysregulation of local prolactin production or prolactin receptor-associated signaling machinery may contribute to some of the altered actions of prolactin in this disease.This study focus...

New concepts in prolactin biology

“…This hypothesis was nicely confirmed at the experimental level using models over-expressing or, in contrast, down-regulating STAT5 expression/activity in human prostate cancer tumors xenografted into immunodeficient mice (Dagvadorj et al 2008). Finally, for the breast, upregulation of PRL labeling paralleled those of NEK3 and PIAS3, two regulators of PRLR signaling (McHale et al 2008).…”

“…In the absence of known negative regulator of extrapituitary PRL production, this issue remains impossible to assess (Ben-Jonathan et al 1996). In conclusion, extrapituitary PRL is very difficult to identify by other means than immunohistochemical analyses of human biopsies, which at best allows semi-quantitative evaluation of its production level (Nevalainen et al 1997, Reynolds et al 1997, McHale et al 2008. These limitations clearly hamper reliable tracking of time-or state-dependent S BERNICHTEIN and others .…”

“…Recent investigations involved immunohistochemical analyses of PRL expression in mammary and prostate biopsies, where its expression levels were compared between cancer and healthy tissue or benign lesions (Li et al 2004, McHale et al 2008. Despite the difficulties linked to the use of this approach for quantification purposes, the level of PRL expression was clearly found to be higher in cancer for both tissues.…”

Protein Inhibitor of Activated STAT3 (PIAS3) Protein Promotes SUMOylation and Nuclear Sequestration of the Intracellular Domain of ErbB4 Protein

“…Interestingly, the prognostic significance of nuclear ErbB4 immunoreactivity in breast cancer cells also seems to be different from the prognostic significance of ErbB4 at the cell surface or in the cytosol (16,17). The role of PIAS3 in cancer has not been extensively studied, but increased PIAS3 expression in breast cancer has been reported (45,46). Therefore, it is interesting to speculate whether the increased expression of PIAS3 in breast cancer could provide a mechanism for nuclear accumulation of ErbB4 ICD with functional consequences on ErbB4 signaling.…”

The Prolactin Receptor Transactivation Domain Is Associated with Steroid Hormone Receptor Expression and Malignant Progression of Breast Cancer

“…For IHC, detection of an antibody-antigen complex used a horseradish peroxidaseeconjugated secondary antibody, followed by diaminobenzidine labeling, as previously described. 48 Visual scoring of the immunofluorescence-labeled images was performed as previously described, 48 with modification. Scoring was restricted to assessment of label intensity on a 0 to 3 scale (0, absent; 1, dim; 2, bright; and 3, very bright).…”