Hornerin, an S100 family protein, is functional in breast cells and aberrantly expressed in breast cancer

Abstract

BackgroundRecent evidence suggests an emerging role for S100 protein in breast cancer and tumor progression. These ubiquitous proteins are involved in numerous normal and pathological cell functions including inflammatory and immune responses, Ca2+ homeostasis, the dynamics of cytoskeleton constituents, as well as cell proliferation, differentiation, and death. Our previous proteomic analysis demonstrated the presence of hornerin, an S100 family member, in breast tissue and extracellular matrix. Hornerin has been reported in healthy skin as well as psoriatic and regenerating skin after wound healing, suggesting a role in inflammatory/immune response or proliferation. In the present study we investigated hornerin’s potential role in normal breast cells and breast cancer.MethodsThe expression levels and localization of hornerin in human breast tissue, breast tumor biopsies, primary breast cells and breast cancer cell lines, as well as murine mammary tissue were measured via immunohistochemistry, western blot analysis and PCR. Antibodies were developed against the N- and C-terminus of the protein for detection of proteolytic fragments and their specific subcellular localization via fluorescent immunocytochemisty. Lastly, cells were treated with H2O2 to detect changes in hornerin expression during induction of apoptosis/necrosis.ResultsBreast epithelial cells and stromal fibroblasts and macrophages express hornerin and show unique regulation of expression during distinct phases of mammary development. Furthermore, hornerin expression is decreased in invasive ductal carcinomas compared to invasive lobular carcinomas and less aggressive breast carcinoma phenotypes, and cellular expression of hornerin is altered during induction of apoptosis. Finally, we demonstrate the presence of post-translational fragments that display differential subcellular localization.ConclusionsOur data opens new possibilities for hornerin and its proteolytic fragments in the control of mammary cell function and breast cancer.

Proteomic comparison defines novel markers to characterize heterogeneous populations of extracellular vesicle subtypes

“…3D, Table S1, and Datasets S2 and S3). This list includes various keratins (classically considered contaminants of proteomic analyses), collagen (C04A), fibronectin, an ECM protein previously described in trophoblast or tumor cell-derived exosomes (17,24), and hornerin, a S100 family member also found in the ECM of breast tumors (25). In addition, Complement (C3 and C4A), PEDF and prothrombin (F2), probably come from the serum used for culture and associate extracellularly with EVs after their secretion.…”

The Role of Exosomes in Breast Cancer

“…A number of S100 genes were found to be involved in breast cancer progression, with S100A11 (S100 calcium binding protein A11) 4 and S100A14 (S100 calcium binding protein A14) associated with patient outcome (40 ). The S100 protein hornerin, which has been detected in exosomes (41 ), was found to be expressed in breast cancer tissue, including mammary epithelial cells and stromal cells, and found to undergo proteolytic cleavage and differential subcellular compartmentalization. Premalignant, malignant, and metastatic MCF10A cells were developed by transfecting the primary cell line with active H-Ras; cells were then selected according to increased tumor growth from xenograft tumors.…”

“…Furthermore, increased expression and fragmentation of hornerin was observed in breast cancer cells following the induction of apoptosis/necrosis with H 2 O 2 . Hornerin, possibly transported via exosomes, may play a role in promoting apoptosis and suppressing tumor progression (41 ).…”

Relevance Rank Platform (RRP) for Functional Filtering of High Content Protein–Protein Interaction Data*

“…5B). HRNR interaction was identified from a protein band corresponding to about 60 kDa protein size, representing a known fragment of HRNR that is processed from full length 250 kDa protein (24) (Figs. 4B and 5B, red line).…”