Among processes believed to impede the antitumor immune response is the emergence of myeloid cell populations during tumor growth, termed myeloid-derived suppressor cells (MDSC). These immune suppressing cells are distinguished from other myeloid subsets based on their characteristic expression of both CD11b and Gr-1 cell surface markers. Although considerable interest has been dedicated to understanding how MDSC inhibit antitumor immune mechanisms, much less is known regarding the molecular events that govern their development to begin with. Thus, the proposed research will test a novel hypothesis by which these CD11b+Gr-1+ MDSC develop, one which reflects a new functional role for interferon regulatory factor-8 (IRF-8) in tumor immunology. Previous key studies have revealed an essential role for IRF-8, a member of the IRF family of transcription factors, in regulating normal myelopoiesis. The impact of IRF-8 in myelopoiesis has been clearly illuminated by alteration of the gene in mouse models. IRF-8 deficiency leads to myeloproliferative disorders. Collectively, these findings indicate that IRF-8 loss or down-regulation has profound pathologic consequences on myelo-monocytic development and differentiation. Therefore, the primary objective of this proposal is to determine the causal link between IRF-8 expression and CD11b+Gr-1+ MDSC generation, which conceptually may be analogous to the aberrant myelopoiesis observed in IRF-8 null mice. The central hypothesis is that IRF-8 functions to block tumor-induced MDSC development and acquisition of their pro-tumorigenic activities. It is further hypothesized that the neoplastic process alters IRF-8 levels of myeloid progenitors through the inappropriate production and action of certain tumor-derived myelopoietic growth factors. Based on new preliminary data in our tumor models, we have identified abundant levels of G-CSF as a putative tumor-derived factor of MDSC generation. Thus, tumor-induced IRF-8 down-regulation by G-CSF or other STAT3-activating cytokines may underlie a novel pathway for MDSC development. Guided by our recently published data that IRF-8 levels are strongly reduced in, and inversely correlated with, the generation of tumor-induced MDSC, the central hypothesis will be tested by pursuing three specific aims in mouse models: two will be mechanistic and one will be therapeutic in scope: 1) Determine the causal link between IRF-8 expression and MDSC development;2) Identify tumor-induced mechanisms that drive IRF-8 down-regulation and the resultant production of MDSC;and 3) To determine whether blocking MDSC development through IRF-8 over-expression will enhance immunotherapy efficacy. The proposed research will enhance knowledge of the host-tumor interaction and, thus, provide the framework to explore the prognostic or therapeutic significance of elements of this new molecular pathway in cancer clinical settings.
Myeloid-derived suppressor cells (MDSC) are a recently discovered population of white blood cells that accumulate in patients with certain types of solid cancers and are thought to embody a significant barrier to an effective anti-cancer immune response. MDSC are typically identified by their unique expression of two cell surface markers, known as CD11b and Gr-1. Although much interest has been devoted to understanding mechanisms by which MDSC block immunity, much less is known regarding the processes that regulate their development. Our research will explore the concept that these cells arise because cancer cells cause a profound alteration in a 'master gene', called interferon regulatory factor-8 (IRF-8) that is essential for controlling fundamental properties of the myeloid cell family and preventing the generation of MDSC. This work will advance our understanding of mechanisms of immune suppression, and will be highly relevant to cancer and the design of novel prognostic or therapeutic oncologic options.
|Messmer, Michelle N; Netherby, Colleen S; Banik, Debarati et al. (2015) Tumor-induced myeloid dysfunction and its implications for cancer immunotherapy. Cancer Immunol Immunother 64:13-Jan|
|Waight, Jeremy D; Banik, Debarati; Griffiths, Elizabeth A et al. (2014) Regulation of the interferon regulatory factor-8 (IRF-8) tumor suppressor gene by the signal transducer and activator of transcription 5 (STAT5) transcription factor in chronic myeloid leukemia. J Biol Chem 289:15642-52|
|Koorella, Chandana; Nair, Jayakumar R; Murray, Megan E et al. (2014) Novel regulation of CD80/CD86-induced phosphatidylinositol 3-kinase signaling by NOTCH1 protein in interleukin-6 and indoleamine 2,3-dioxygenase production by dendritic cells. J Biol Chem 289:7747-62|
|Messmer, Michelle N; Kokolus, Kathleen M; Eng, Jason W-L et al. (2014) Mild cold-stress depresses immune responses: Implications for cancer models involving laboratory mice. Bioessays 36:884-91|
|Farren, Matthew R; Carlson, Louise M; Netherby, Colleen S et al. (2014) Tumor-induced STAT3 signaling in myeloid cells impairs dendritic cell generation by decreasing PKC?II abundance. Sci Signal 7:ra16|
|Hu, Xiaolin; Bardhan, Kankana; Paschall, Amy V et al. (2013) Deregulation of apoptotic factors Bcl-xL and Bax confers apoptotic resistance to myeloid-derived suppressor cells and contributes to their persistence in cancer. J Biol Chem 288:19103-15|
|Waight, Jeremy D; Netherby, Colleen; Hensen, Mary L et al. (2013) Myeloid-derived suppressor cell development is regulated by a STAT/IRF-8 axis. J Clin Invest 123:4464-78|
|Gil, Margaret; Seshadri, Mukund; Komorowski, Marcin P et al. (2013) Targeting CXCL12/CXCR4 signaling with oncolytic virotherapy disrupts tumor vasculature and inhibits breast cancer metastases. Proc Natl Acad Sci U S A 110:E1291-300|
|Godoy, Heidi E; Khan, A Nazmul H; Vethanayagam, R Robert et al. (2013) Myeloid-derived suppressor cells modulate immune responses independently of NADPH oxidase in the ovarian tumor microenvironment in mice. PLoS One 8:e69631|
|Waight, Jeremy D; Hu, Qiang; Miller, Austin et al. (2011) Tumor-derived G-CSF facilitates neoplastic growth through a granulocytic myeloid-derived suppressor cell-dependent mechanism. PLoS One 6:e27690|