Delayed apoptosis of tumor associated neutrophils in the absence of endogenous IFN‐β

Abstract

The importance of neutrophils in tumor immune surveillance, invasive growth and angiogenesis becomes increasingly clear. Many of neutrophil activities are controlled by endogenous IFN-b. Here, we provide evidence that endogenous IFN-b is regulating the apoptosis of pro-angiogenic tumor infiltrating neutrophils by influencing both, the extrinsic as well as the intrinsic apoptosis pathways. Accordingly, the life span of tumor associated neutrophils (TANs) is remarkably prolonged in tumor bearing Ifnb1 2/2 mice compared to wild type controls. Lower expression of Fas, reactive oxygen species, active Caspase 3 and 9, as well as a change in expression pattern of proapoptotic and antiapoptotic members of the Bcl-2 family and the major apoptosome constituent Apaf-1 is observed under such conditions. In line with inhibition of apoptosis and the prolonged neutrophil survival, in the absence of endogenous IFN-b, a strong enhancement of G-CSF expression and PI3 Kinase phosphorylation is detected. These data explain the increased longevity of tumor infiltrating neutrophils and the accumulation of such cells in tumors. Taken together, our findings add to the important role of Type I IFN in immune surveillance against cancer.Neutrophilic granulocytes are the most abundant white blood cells in circulation, that are released from the bone marrow as terminally differentiated, nondividing cells. 1 Besides their role in immunity, neutrophils strongly influence growth, metastasis, 2 angiogenesis 3,4 and immune surveillance 5 of tumors. In contrast to cells of the adaptive immune system, neutrophils need no activation to acquire an effector phenotype. In accordance with their pleiotropic function, neutrophils are equipped with a large array of effector molecules like proteolytic enzymes, antimicrobial proteins/peptides and are able to produce reactive oxygen species. 6 Due to their potential toxicity against host tissue, the life span of such cells is strictly regulated. 7 In the absence of noxious or inflammatory stimuli, neutrophils are removed from circulation by apoptosis shortly after their emigration from the bone marrow. However, several proinflammatory cytokines have been shown to influence the longevity of neutrophils. 8 Type I interferons (IFNs) were first identified as factors responsible for the phenomenon of viral interference. In the meantime, they are recognized to influence a broad variety of biological processes, such as maintenance of cellular homeostasis, 9 hematopoiesis, 10 lymphocyte development 11 and apoptosis of dendritic 12 or CD4 1 T cells 13 besides their role in infections. In addition, Type I IFNs display strong antitumor effects by exhibiting direct antiproliferative and proapoptotic effects on tumor cells 14 as well as supporting systemic immunity against tumor targets by up-regulation of MHC class I expression, enhancement of cytotoxic T cell responses and activation of natural killer cells and macrophages. 15 Nevertheless, the mechanism of how Type I IFNs contribute to immune surveillance against tumo...

Tumor-associated neutrophils display a distinct N1 profile following TGFβ modulation: A transcriptomics analysis of pro- vs. antitumor TANs

“…Interestingly, it has been proposed that there can be phenotypic or functional plasticity, where neutrophils infiltrating a tumor are modulated by cues present in the tumor environment. 23 This has been well exemplified by recent works showing that TANs can be modulated and polarized toward an N1 phenotype by type-1 interferons [24][25][26] or a pro-tumorigenic (N2) phenotype by the presence of TGFb 7 as demonstrated by the observation that systemic inhibition of TGFb using a specific Alk5 kinase inhibitor called SM16 in mice caused a shift toward a pro-inflammatory and antitumor phenotype (N1).…”

“…7 In contrast, in the presence of type-I IFNs or absence of TGFb, TANs display an antitumor N1 phenotype with increased tumor cytotoxicity, high neutrophil extracellular traps (NETs) expression, high ICAM1, and TNF-a expression. 9,24,26 Using transcriptomic analysis 29 , we have previously shown that N2-polarized TANs display a dramatically different transcriptomic profile than both myeloid-derived suppressor cells (G-MDSCs) and naive bone marrow neutrophils (BMN), including the expression of a wide range of cytokines (CCL17, CCL2, CCL5). By secreting CCL17, TANs were further shown to recruit regulatory T-cells to the tumor site, thus inducing immunologic self-tolerance and impaired immune response to tumor cells.…”

“…As specific markers discriminating between pro-and antitumor neutrophils have yet to be identified, the isolation and phenotyping of these neutrophil populations is still not possible without interventions such as IFNb or anti-TGFb treatments. 7,24 The identification of characteristic markers will allow in the future the specific isolation of these neutrophils subpopulations directly from the developing tumor without the need of such manipulations. Importantly, although we have described differences between early and late-tumor TANs, there was no exact similarity to the N1-N2 polarization.…”

The Essential Role of Type I Interferons in Differentiation and Activation of Tumor-Associated Neutrophils

“…This phenomenon, together with the enhanced infiltration of lungs by these cells, leads to improved metastatic load in IFN-deficient mice (20). N2 neutrophils are characterized with immature nucleus shape and reduced tumor cell killing capacity (34); they were also shown to recruit regulatory T cells in tumors by expression of CCL17 (35). Accordingly, in clinical studies, the percentage of neutrophils in blood and neutrophil/lymphocyte ratio was shown to be negative predictors of patient outcome in different types of cancer (36, 37).…”

Neutrophils: Critical components in experimental animal models of cancer

“…The researchers concluded that adaptive immune cells are not involved in the IFNβ-dependent inhibition of tumor angiogenesis by repeating the experiments in Ifnb1 −/− Rag2 −/− and Rag2 −/− mice that lack T and B-cells [103, 105]. Moreover, in the Ifnb1 −/− mice model deficiency of IFNβ delays the apoptosis of pro-angiogenic neutrophils infiltrating the tumor [106]. …”