SIRT1‐mediated deacetylation of FOXO3a transcription factor supports pro‐angiogenic activity of interferon‐deficient tumor‐associated neutrophils

Abstract

Angiogenesis plays an important role during tumor growth and metastasis. We could previously show that Type I interferon (IFN)‐deficient tumor‐associated neutrophils (TANs) show strong pro‐angiogenic activity, and stimulate tumor angiogenesis and growth. However, the exact mechanism responsible for their pro‐angiogenic shift is not clear. Here, we set out to delineate the molecular mechanism and factors regulating pro‐angiogenic properties of neutrophils in the context of Type I IFN availability. We demonstrate that neutrophils from IFN‐deficient (Ifnar1−/−) mice efficiently release pro‐angiogenic factors, such as VEGF, MMP9 or BV8, and thus significantly support the vascular normalization of tumors by increasing the maturation of perivascular cells. Mechanistically, we could show here that the expression of pro‐angiogenic factors in neutrophils is controlled by the transcription factor forkhead box protein O3a (FOXO3a), which activity depends on its post‐translational modifications, such as deacetylation or phosphorylation. In TANs isolated from Ifnar1−/− mice, we observe significantly elevated SIRT1, resulting in SIRT1‐mediated deacetylation of FOXO3a, its nuclear retention and activation. Activated FOXO3a supports in turn the transcription of pro‐angiogenic genes in TANs. In the absence of SIRT1, or after its inhibition in neutrophils, elevated kinase MEK/ERK and PI3K/AKT activity is observed, leading to FOXO3a phosphorylation, cytoplasmic transfer and inactivation. In summary, we have found that FOXO3a is a key transcription factor controlling the angiogenic switch of neutrophils. Post‐translational FOXO3a modifications regulate its transcriptional activity and, as a result, the expression of pro‐angiogenic factors supporting development of vascular network in growing tumors. Therefore, targeting FOXO3a activity could provide a novel strategy of antiangiogenic targeted therapy for cancer.

The Good, the Bad, and the Ugly: Neutrophils, Angiogenesis, and Cancer

“…In agreement with the essential role of neutrophils in tumor angiogenesis, reduced tumor vascularization and growth have been demonstrated after antibody-mediated neutrophil depletion (using anti-Gr-1 or anti-Ly6G antibody) or inhibition of neutrophil infiltration into tumor tissue (e.g., anti-vascular cell adhesion molecule-1 and anti-VCAM-1) in several studies [32,97,100]. Adoptive transfer of anti-angiogenic neutrophils has also been shown to limit tumor angiogenesis in the murine model of melanoma [103][104][105], while the transfer of pro-angiogenic neutrophils supports tumor vascularization in mice [32,105].…”

“…Neutrophil-derived Bv8 and S100 proteins (S100A8 and S100A9) increase tumor proliferation and angiogenesis by supporting neutrophil mobilization, EC activation, and proliferation [46,[141][142][143]. Tumor-associated neutrophils have been shown to produce Bv8 and S100A8 in a mouse melanoma model [105]. Bv8 has been suggested as a modulator of myeloid-cell-dependent tumor angiogenesis, and neutrophils have been reported to produce Bv8 robustly, after stimulation with G-CSF or GM-CSF [142,144].…”

“…Similarly, IFN receptor-deficient mice (Ifnar −/− ) showed elevated tumor angiogenesis and neutrophil infiltration in the tumor tissue [105]. Neutrophils from such mice significantly up-regulated their expression of VEGF, MMP-9, Bv8, and S100A8 [105].…”

“…Recently, another mechanism was shown to regulate the angiogenic potential of tumorassociated neutrophils. Bordbari et al demonstrated that the pro-angiogenic capacity of neutrophils is strictly regulated by the post-translational modification of FOXO3a tran-scription factor that controls transcription of pro-angiogenic genes [105]. SIRT1-mediated deacetylation of FOXO3a was shown to activate this factor, while the phosphorylation, in the absence of SIRT1, led to cytoplasmic transfer and deactivation of FOXO3a [105].…”

“…Bordbari et al demonstrated that the pro-angiogenic capacity of neutrophils is strictly regulated by the post-translational modification of FOXO3a tran-scription factor that controls transcription of pro-angiogenic genes [105]. SIRT1-mediated deacetylation of FOXO3a was shown to activate this factor, while the phosphorylation, in the absence of SIRT1, led to cytoplasmic transfer and deactivation of FOXO3a [105]. Activated FOXO3a has been demonstrated to induce the transcription of pro-angiogenic molecules like VEGF, MMP-9, BV8, and S100A8 in TANs [105].…”