Heat Shock Protein 27 Differentiates Tolerogenic Macrophages That May Support Human Breast Cancer Progression

Sanjib Banerjee,Linda M Schiffhauer,David G Hicks,Kristin A Skinner,Asit K De,Chuen-Fu L Lin,Lauren O'Donoghue,Howard N Langstein,David Morrow,Jennifer Strickland,Eileen M Redmond,Carol L Miller-Graziano,Alissa Huston,Michelle Shayne,James Peacock

doi:10.1158/0008-5472.can-10-1778

Sanjib Banerjee, Linda M Schiffhauer + Show 13 more

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https://doi.org/10.1158/0008-5472.can-10-1778

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Abstract

Tumor cells release several factors that can help the progression of the tumor by directly supporting tumor growth and/or suppressing host antitumor immunity. Here, we report that human primary breast tumor cells not only express elevated levels of heat shock protein 27 (Hsp27) at the intracellular level but also release extremely high levels of Hsp27 compared with the same patients' serum Hsp27 levels, predicting an acutely increased concentration of soluble Hsp27 in the human breast tumor microenvironment (HBTM). We demonstrate that Hsp27 levels in the HBTM can be extremely elevated as evidenced by high soluble Hsp27 levels in patients' tumor interstitial fluid. Because increasing numbers of tumor-associated macrophages (TAM) in the HBTM negatively correlate to patients' clinical outcomes and we have previously reported the immunoregulatory activity of soluble Hsp27, here, we tested for any specific effects of soluble Hsp27 on human monocyte to macrophage differentiation. We demonstrate that soluble Hsp27 causes the differentiation of monocytes to macrophages with immuno-tolerizing phenotypes (HLA-DRlow, CD86low, PD-L1high, ILT2high, and ILT4high). We detected the presence of TAMs with similar phenotypes in breast cancer patients. Hsp27-differentiated macrophages induce severe unresponsiveness/anergy in T cells. Moreover, these macrophages lose tumoricidal activity but become extremely proangiogenic, inducing significant neovascularization, a process that is critically important for tumor growth. Thus, our data demonstrate a novel immune escape and tumor growth-supporting mechanism mediated by soluble Hsp27 that may be operative in human breast cancer.

Highlights

Heat shock protein (Hsp) 27, an important member of the small Hsp family, is ubiquitously expressed in various cell types and is involved in actin polymerization, which is the protection of intracellular peptides during the stress and inhibition of mitochondrial apoptosis [1,2,3]
We have shown that rhHsp27 exhibited significant biological activity on human monocytes, causing the secretion of high levels of IL-10 and moderate levels of TNF-a [12]
We have reported that soluble heat shock protein 27 (Hsp27) could inhibit the differentiation of human monocytes to dendritic cells

Summary

Introduction

Heat shock protein (Hsp) 27, an important member of the small Hsp family, is ubiquitously expressed in various cell types and is involved in actin polymerization, which is the protection (chaperoning) of intracellular peptides during the stress and inhibition of mitochondrial apoptosis [1,2,3]. Intracellular expression of Hsp is highly elevated in human breast tumor cells [4,5,6] and correlates to increased resistance to chemotherapeutic drug-induced apoptosis [7, 8]. Elevated serum Hsp levels are reported in breast cancer. A recent report has shown the secretion of Hsp from a human monocytic cell line [11]. We hypothesized that human breast tumor cells expressing elevated levels of intracellular Hsp may secrete high levels of Hsp, increasing its local concentration in the human breast tumor microenvironment (HBTM). Increased Hsp levels in the HBTM may cause a severe reduction in the differentiation of monocytes to DCs. An increase in the number of DCs in human breast tumors is positively correlated with survival [14].

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