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TNF Neutralization Results in the Delay of Transplantable Tumor Growth and Reduced MDSC Accumulation.

Atretkhany KS, Nosenko MA, Gogoleva VS, Zvartsev RV, Qin Z, Nedospasov SA, Drutskaya MS - Front Immunol (2016)

Bottom Line: Under the influence of inflammatory cytokines, these cells become MDSCs, acquire immunosuppressive phenotype, and accumulate in the affected tissue, as well as in the periphery.TNF is a critical factor for the induction, expansion, and suppressive activity of MDSCs.Both etanercept and infliximab treatments resulted in a delayed growth of MCA 205 fibrosarcoma in hTNF KI mice, significantly reduced tumor volume, and also resulted in less accumulated MDSCs in the blood 3 weeks after tumor cell inoculation.

View Article: PubMed Central - PubMed

Affiliation: Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia; Immunology Department, Faculty of Biology, Beloszersky Institue of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.

ABSTRACT
Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of immature myeloid cells (IMCs) that, under normal conditions, may differentiate into mature macrophages, granulocytes, and dendritic cells. However, under pathological conditions associated with inflammation, cancer, or infection, such differentiation is inhibited leading to IMC expansion. Under the influence of inflammatory cytokines, these cells become MDSCs, acquire immunosuppressive phenotype, and accumulate in the affected tissue, as well as in the periphery. Immune suppressive activity of MDSCs is partly due to upregulation of arginase 1, inducible nitric oxide synthase, and anti-inflammatory cytokines, such as IL-10 and TGF-β. These suppressive factors can enhance tumor growth by repressing T-cell-mediated anti-tumor responses. TNF is a critical factor for the induction, expansion, and suppressive activity of MDSCs. In this study, we evaluated the effects of systemic TNF ablation on tumor-induced expansion of MDSCs in vivo using TNF humanized (hTNF KI) mice. Both etanercept and infliximab treatments resulted in a delayed growth of MCA 205 fibrosarcoma in hTNF KI mice, significantly reduced tumor volume, and also resulted in less accumulated MDSCs in the blood 3 weeks after tumor cell inoculation. Thus, our study uncovers anti-tumor effects of systemic TNF ablation in vivo.

No MeSH data available.


Related in: MedlinePlus

Etanercept efficiently reduces transplantable tumor growth and MDSC accumulation in C57Bl/6 mice. (A) Tumor growth in control mice (blue) and mice undergoing treatment with etanercept (red). Each line represents the growth curve of mean tumor volume ±SD. (B) MDSC accumulation in the blood. Each bar represents mean relative MDSC level in the blood of tumor-bearing mice normalized to tumor-free mice ± SD. (C) Representative dot plots for MDSC staining in the blood from mice without tumors (left), etanercept (middle), or PBS-treated (right) tumor-bearing mice on day 16 after tumor cells inoculation. Cells were first gated as VD−CD45+, and then CD11b+Gr-1+ cells were defined as MDSCs (with Gr-1 antibody clone RB6-8C5 recognizing both Ly6G and Ly6C epitopes). Data are representative of two independent experiments with three to five mice per each group. *p < 0.5, **p < 0.01, and ***p < 0.001.
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Figure 2: Etanercept efficiently reduces transplantable tumor growth and MDSC accumulation in C57Bl/6 mice. (A) Tumor growth in control mice (blue) and mice undergoing treatment with etanercept (red). Each line represents the growth curve of mean tumor volume ±SD. (B) MDSC accumulation in the blood. Each bar represents mean relative MDSC level in the blood of tumor-bearing mice normalized to tumor-free mice ± SD. (C) Representative dot plots for MDSC staining in the blood from mice without tumors (left), etanercept (middle), or PBS-treated (right) tumor-bearing mice on day 16 after tumor cells inoculation. Cells were first gated as VD−CD45+, and then CD11b+Gr-1+ cells were defined as MDSCs (with Gr-1 antibody clone RB6-8C5 recognizing both Ly6G and Ly6C epitopes). Data are representative of two independent experiments with three to five mice per each group. *p < 0.5, **p < 0.01, and ***p < 0.001.

Mentions: TNF is important for MDSC development, in turn, MDSCs play a crucial role in tumor progression (9, 35). Genetic studies suggested that TNF may play a pro-tumorigenic role in skin carcinogenesis model (27). Thus, we hypothesized that prolonged in vivo blockade of TNF with pharmacological agents may result in anti-tumor effects. To test this hypothesis, we evaluated the ability of clinically used TNF blockers to prevent transplantable tumor growth in mice. Our initial experiments were carried out in C57Bl/6 mice using etanercept, a soluble fusion protein of human p75 TNF receptor and Fc portion of IgG1 antibody, as an inhibitor of murine TNF, because it is the only clinically available blocker that binds to murine TNF (43). We have chosen MCA fibrosarcoma cell line, since a potent anti-tumor effect of TNF in vivo was originally discovered on methyl-cholantrene-induced tumors (25). Specifically, we used transplantable tumor cell line, MCA205 fibrosarcoma, injected into C57Bl/6 mice, because the resulting tumors are known to be dependent on MDSC accumulation (32). As a control reagent in this first set of experiments, we used infliximab, a chimeric monoclonal antibody against human TNF, which does not bind murine TNF but has the same Fcγ-domain as etanercept (44). The scheme of the experiment is shown in Figure 1. We first examined the growth kinetics of MCA 205 fibrosarcoma (Figure 2A) in C57Bl/6 recipients. Mice treated with infliximab or PBS rapidly developed tumors with the similar kinetics (only infliximab group is shown as a control on Figure 2). Importantly, mice injected with etanercept demonstrated a significant reduction in tumor volume starting from day 10 after tumor inoculation (Figure 2A). We then evaluated the effects of systemic TNF ablation on MDSC accumulation by treating mice with etanercept (Figures 2B,C) and compared MDSC levels in the blood of tumor-bearing and tumor-free mice. As expected, mice under etanercept therapy accumulated significantly less MDSCs in the blood compared to mice under infliximab or PBS treatment, whereas tumor-free mice had very low MDSC levels (Figure 2B and data not shown). Moreover, we observed differences in MDSC levels starting from day 10, when the differences in tumor growth were also significant. Taken together, these data show that TNF neutralization might reduce tumor growth and MDSC accumulation in a transplantable MCA tumor model in mice.


TNF Neutralization Results in the Delay of Transplantable Tumor Growth and Reduced MDSC Accumulation.

Atretkhany KS, Nosenko MA, Gogoleva VS, Zvartsev RV, Qin Z, Nedospasov SA, Drutskaya MS - Front Immunol (2016)

Etanercept efficiently reduces transplantable tumor growth and MDSC accumulation in C57Bl/6 mice. (A) Tumor growth in control mice (blue) and mice undergoing treatment with etanercept (red). Each line represents the growth curve of mean tumor volume ±SD. (B) MDSC accumulation in the blood. Each bar represents mean relative MDSC level in the blood of tumor-bearing mice normalized to tumor-free mice ± SD. (C) Representative dot plots for MDSC staining in the blood from mice without tumors (left), etanercept (middle), or PBS-treated (right) tumor-bearing mice on day 16 after tumor cells inoculation. Cells were first gated as VD−CD45+, and then CD11b+Gr-1+ cells were defined as MDSCs (with Gr-1 antibody clone RB6-8C5 recognizing both Ly6G and Ly6C epitopes). Data are representative of two independent experiments with three to five mice per each group. *p < 0.5, **p < 0.01, and ***p < 0.001.
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Figure 2: Etanercept efficiently reduces transplantable tumor growth and MDSC accumulation in C57Bl/6 mice. (A) Tumor growth in control mice (blue) and mice undergoing treatment with etanercept (red). Each line represents the growth curve of mean tumor volume ±SD. (B) MDSC accumulation in the blood. Each bar represents mean relative MDSC level in the blood of tumor-bearing mice normalized to tumor-free mice ± SD. (C) Representative dot plots for MDSC staining in the blood from mice without tumors (left), etanercept (middle), or PBS-treated (right) tumor-bearing mice on day 16 after tumor cells inoculation. Cells were first gated as VD−CD45+, and then CD11b+Gr-1+ cells were defined as MDSCs (with Gr-1 antibody clone RB6-8C5 recognizing both Ly6G and Ly6C epitopes). Data are representative of two independent experiments with three to five mice per each group. *p < 0.5, **p < 0.01, and ***p < 0.001.
Mentions: TNF is important for MDSC development, in turn, MDSCs play a crucial role in tumor progression (9, 35). Genetic studies suggested that TNF may play a pro-tumorigenic role in skin carcinogenesis model (27). Thus, we hypothesized that prolonged in vivo blockade of TNF with pharmacological agents may result in anti-tumor effects. To test this hypothesis, we evaluated the ability of clinically used TNF blockers to prevent transplantable tumor growth in mice. Our initial experiments were carried out in C57Bl/6 mice using etanercept, a soluble fusion protein of human p75 TNF receptor and Fc portion of IgG1 antibody, as an inhibitor of murine TNF, because it is the only clinically available blocker that binds to murine TNF (43). We have chosen MCA fibrosarcoma cell line, since a potent anti-tumor effect of TNF in vivo was originally discovered on methyl-cholantrene-induced tumors (25). Specifically, we used transplantable tumor cell line, MCA205 fibrosarcoma, injected into C57Bl/6 mice, because the resulting tumors are known to be dependent on MDSC accumulation (32). As a control reagent in this first set of experiments, we used infliximab, a chimeric monoclonal antibody against human TNF, which does not bind murine TNF but has the same Fcγ-domain as etanercept (44). The scheme of the experiment is shown in Figure 1. We first examined the growth kinetics of MCA 205 fibrosarcoma (Figure 2A) in C57Bl/6 recipients. Mice treated with infliximab or PBS rapidly developed tumors with the similar kinetics (only infliximab group is shown as a control on Figure 2). Importantly, mice injected with etanercept demonstrated a significant reduction in tumor volume starting from day 10 after tumor inoculation (Figure 2A). We then evaluated the effects of systemic TNF ablation on MDSC accumulation by treating mice with etanercept (Figures 2B,C) and compared MDSC levels in the blood of tumor-bearing and tumor-free mice. As expected, mice under etanercept therapy accumulated significantly less MDSCs in the blood compared to mice under infliximab or PBS treatment, whereas tumor-free mice had very low MDSC levels (Figure 2B and data not shown). Moreover, we observed differences in MDSC levels starting from day 10, when the differences in tumor growth were also significant. Taken together, these data show that TNF neutralization might reduce tumor growth and MDSC accumulation in a transplantable MCA tumor model in mice.

Bottom Line: Under the influence of inflammatory cytokines, these cells become MDSCs, acquire immunosuppressive phenotype, and accumulate in the affected tissue, as well as in the periphery.TNF is a critical factor for the induction, expansion, and suppressive activity of MDSCs.Both etanercept and infliximab treatments resulted in a delayed growth of MCA 205 fibrosarcoma in hTNF KI mice, significantly reduced tumor volume, and also resulted in less accumulated MDSCs in the blood 3 weeks after tumor cell inoculation.

View Article: PubMed Central - PubMed

Affiliation: Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia; Immunology Department, Faculty of Biology, Beloszersky Institue of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.

ABSTRACT
Myeloid-derived suppressor cells (MDSCs) represent a heterogeneous population of immature myeloid cells (IMCs) that, under normal conditions, may differentiate into mature macrophages, granulocytes, and dendritic cells. However, under pathological conditions associated with inflammation, cancer, or infection, such differentiation is inhibited leading to IMC expansion. Under the influence of inflammatory cytokines, these cells become MDSCs, acquire immunosuppressive phenotype, and accumulate in the affected tissue, as well as in the periphery. Immune suppressive activity of MDSCs is partly due to upregulation of arginase 1, inducible nitric oxide synthase, and anti-inflammatory cytokines, such as IL-10 and TGF-β. These suppressive factors can enhance tumor growth by repressing T-cell-mediated anti-tumor responses. TNF is a critical factor for the induction, expansion, and suppressive activity of MDSCs. In this study, we evaluated the effects of systemic TNF ablation on tumor-induced expansion of MDSCs in vivo using TNF humanized (hTNF KI) mice. Both etanercept and infliximab treatments resulted in a delayed growth of MCA 205 fibrosarcoma in hTNF KI mice, significantly reduced tumor volume, and also resulted in less accumulated MDSCs in the blood 3 weeks after tumor cell inoculation. Thus, our study uncovers anti-tumor effects of systemic TNF ablation in vivo.

No MeSH data available.


Related in: MedlinePlus