The human breast cancer-associated protein, the prolactin-inducible protein (PIP), regulates intracellular signaling events and cytokine production by macrophages
The prolactin-inducible protein (PIP) is considered a valuable biomarker that is associated with both benign and malignant pathological conditions of the mammary gland. The function of PIP in breast tumorigenesis remains unknown; however, evidence from our laboratory and others suggest that it regulates host immunity. Studies with PIP-deficient (PIP−/−) mice demonstrated significantly lower numbers of CD4+ T cells in their secondary lymphoid organs, impaired Th1 response, and impaired nitric oxide (NO) production. To further delineate the immunoregulatory role of PIP, we compared the expression of IFN-γR and TLR4, pro-inflammatory cytokine production, and intracellular signaling events by IFN-γ and lipopolysaccharide (LPS)-stimulated macrophages from wild-type (WT) and PIP−/− mice. We showed that although the expressions of IFN-γR and TLR4 were comparable, productions of pro-inflammatory cytokines were decreased in PIP−/− macrophages. This was associated with decreased phosphorylation of mitogen-activated protein kinase (MAPK) and signal transducer of activation of transcription (STAT) proteins in macrophages from PIP−/− mice. Interestingly, the expression of suppressors of cytokine signaling (SOCS) 1 and 3 proteins, known to suppress IFN-γ and LPS signaling, was higher in PIP−/− macrophages compared to those from WT mice. Collectively, our studies show that deficiency of PIP significantly affects intracellular signaling events leading to decreased pro-inflammatory cytokine production, and further confirms a role for PIP as an important immunoregulatory protein. This direct link between PIP and cell-mediated immunity, a key component of the immune system that is critical for cancer control, may have significant therapeutic implications.
KeywordsProlactin-inducible protein Macrophages Lipopolysaccharide Interferon gamma Cell-mediated immunity Breast cancer
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
The University of Manitoba Animal Care and Use Committee approved this project. All the mice used were maintained at the Central Animal Care Services under specific pathogen-free conditions and used according to guidelines stipulated by the Canadian Council for Animal Care.
- 4.Cimino-Mathews A, Foote JB, Emens LA. Immune targeting in breast cancer. Oncology (Williston Park). 2015;29(5):375–85.Google Scholar
- 12.Hassan MI, Bilgrami S, Kumar V, Singh N, Yadav S, Kaur P, et al. Crystal structure of the novel complex formed between zinc alpha2-glycoprotein (ZAG) and prolactin-inducible protein (PIP) from human seminal plasma. J Mol Biol. 2008;384(3):663–72. https://doi.org/10.1016/j.jmb.2008.09.072.CrossRefPubMedGoogle Scholar
- 19.Lewis GH, Subhawong AP, Nassar H, Vang R, Illei PB, Park BH, et al. Relationship between molecular subtype of invasive breast carcinoma and expression of gross cystic disease fluid protein 15 and mammaglobin. Am J Clin Pathol. 2011;135(4):587–91. https://doi.org/10.1309/AJCPMFR6OA8ICHNH.CrossRefPubMedPubMedCentralGoogle Scholar
- 21.Autiero M, Gaubin M, Mani JC, Castejon C, Martin M, El MS, et al. Surface plasmon resonance analysis of gp17, a natural CD4 ligand from human seminal plasma inhibiting human immunodeficiency virus type-1 gp120-mediated syncytium formation. Eur J Biochem. 1997;245(1):208–13.CrossRefPubMedGoogle Scholar
- 23.Schenkels LC, Walgreen-Weterings E, Oomen LC, Bolscher JG, Veerman EC, Nieuw Amerongen AV. In vivo binding of the salivary glycoprotein EP-GP (identical to GCDFP-15) to oral and non-oral bacteria detection and identification of EP-GP binding species. Biol Chem. 1997;378(2):83–8.CrossRefPubMedGoogle Scholar
- 24.Blanchard A, Nistor A, Castaneda FE, Martin D, Hicks GG, Amara F, et al. Generation and initial characterization of the prolactin-inducible protein (PIP) null mouse: accompanying global changes in gene expression in the submandibular gland. Can J Physiol Pharmacol. 2009;87(10):859–72.CrossRefPubMedGoogle Scholar
- 25.Myal Y, Iwasiow B, Cosby H, Yarmill A, R.P.C. S. Mouse mammary tumor virus (MMTV)-targeted gene expression of the human gross cystic disease fluid protein-15/prolactin inducible protein (GCDFP-15/PIP) in the mammary gland of transgenic mice. Transgenics. 1998;2:327–32.Google Scholar
- 30.Yang H, Young DW, Gusovsky F, Chow JC. Cellular events mediated by lipopolysaccharide-stimulated toll-like receptor 4. MD-2 is required for activation of mitogen-activated protein kinases and Elk-1. J Biol Chem. 2000;275(27):20861–6. https://doi.org/10.1074/jbc.M002896200.CrossRefPubMedGoogle Scholar
- 31.Liu D, Zhang T, Marshall AJ, Okkenhaug K, Vanhaesebroeck B, Uzonna JE. The p110delta isoform of phosphatidylinositol 3-kinase controls susceptibility to Leishmania major by regulating expansion and tissue homing of regulatory T cells. J Immunol. 2009;183(3):1921–33. https://doi.org/10.4049/jimmunol.0901099.CrossRefPubMedGoogle Scholar