title: Osteopontin splice variants expressed by breast tumors regulate monocyte activation via MCP-1 and TGF-β1.
abstract: Osteopontin (OPN), a multifunctional glycoprotein, has three transcripts that have distinct roles in tumors in vitro. Whether OPN transcripts have different functions in tumor processes in vivo is unclear. It has been reported that immune cell-derived OPN can promote tumor formation. We propose a hypothesis that tumor-derived OPN may facilitate tumor immune escape by affecting immune cell differentiation and function. In this study, we constructed lentiviral expression vectors of OPN transcripts and transfected them into the MCF-7 cell line. MCF-7 cells transfected with OPN transcripts were injected into the armpit of nude mice, and tumor growth was monitored. The results showed that all OPN transcripts promoted local tumor formation, but that there was no significant difference among transcripts. We also investigated the effect of the OPN expressed by tumor cells on monocyte differentiation by coculturing monocytes with tumor supernatant. We found OPN-c upregulated CD163 levels compared with OPN-a and OPN-b; however, none of the transcripts affected HLA-DR and CD206 levels. All OPN transcripts significantly inhibited TNF-α and enhanced IL-10 production by monocytes. Furthermore, we found that the overexpression of OPN transcripts significantly upregulated TGF-β1 and MCP-1 production by tumor cells. Using neutralizing antibody and recombinant cytokines, we found that OPN overexpressed by tumor cells regulates the production of TNF-α and IL-10 by monocytes partly via MCP-1 and TGF-β1, respectively. Collectively, our results show that OPN transcripts have no distinct role in breast cancer formation in vivo. We also demonstrate that OPN regulates the alternative activation of monocytes via TGF-β1 and MCP-1, which may represent an additional mechanism for tumor immune escape.
authors: Institute of Basic Medical Sciences, Jinan, China.
authors: Jintang
authors: J
authors: Sun
authors: Alei
authors: A
authors: Feng
authors: Songyu
authors: S
authors: Chen
authors: Yun
authors: Y
authors: Zhang
authors: Qi
authors: Q
authors: Xie
authors: Meixiang
authors: M
authors: Yang
authors: Qianqian
authors: Q
authors: Shao
authors: Jia
authors: J
authors: Liu
authors: Qifeng
authors: Q
authors: Yang
authors: Beihua
authors: B
authors: Kong
authors: Xun
authors: X
authors: Qu
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics* / Q000276:immunology* / Q000473:pathology; D045744:Cell Line, Tumor; D018932:Chemokine CCL2 / Q000502:physiology*; D015972:Gene Expression Regulation, Neoplastic / Q000276:immunology; D014644:Genetic Variation / Q000276:immunology; D006801:Humans; D057131:Immune Evasion / Q000235:genetics; D051379:Mice; D008819:Mice, Nude; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D053495:Osteopontin / Q000096:biosynthesis / Q000235:genetics*; D012326:RNA Splicing / Q000235:genetics / Q000276:immunology*; D053773:Transforming Growth Factor beta1 / Q000502:physiology*
chemical_list: C111835:CCL2 protein, human; D018932:Chemokine CCL2; D053773:Transforming Growth Factor beta1; D053495:Osteopontin