Neutrophils responsive to endogenous IFN-β regulate tumor angiogenesis and growth in a mouse tumor model

Abstract

Angiogenesis is a hallmark of malignant neoplasias, as the formation of new blood vessels is required for tumors to acquire oxygen and nutrients essential for their continued growth and metastasis. However, the signaling pathways leading to tumor vascularization are not fully understood. Here, using a transplantable mouse tumor model, we have demonstrated that endogenous IFN-β inhibits tumor angiogenesis through repression of genes encoding proangiogenic and homing factors in tumor-infiltrating neutrophils. We determined that IFN-β-deficient mice injected with B16F10 melanoma or MCA205 fibrosarcoma cells developed faster-growing tumors with better-developed blood vessels than did syngeneic control mice. These tumors displayed enhanced infiltration by CD11b + Gr1 + neutrophils expressing elevated levels of the genes encoding the proangiogenic factors VEGF and MMP9 and the homing receptor CXCR4. They also expressed higher levels of the transcription factors c-myc and STAT3, known regulators of VEGF, MMP9, and CXCR4. In vitro, treatment of these tumor-infiltrating neutrophils with low levels of IFN-β restored expression of proangiogenic factors to control levels. Moreover, depletion of these neutrophils inhibited tumor growth in both control and IFN-β-deficient mice. We therefore suggest that constitutively produced endogenous IFN-β is an important mediator of innate tumor surveillance. Further, we believe our data help to explain the therapeutic effect of IFN treatment during the early stages of cancer development.

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

“…angiogenesis, immunosurveillance and invasive growth became increasingly clear 4,28,29 even though the controversial discussion regarding the phenotype of granulocytic myeloidderived suppressor cells and TANs is not yet resolved. 30,31 Nevertheless, neutrophils represent an independent prognostic marker in a broad variety of neoplasias.…”

“…Thus, we challenged C57BL/6 or BALB/c and syngeneic Ifnb1 2/2 mice with B16F10 melanoma or 4T1 mamma carcinoma cells, respectively. Both, B16F10 4 and 4T1 cells exhibited significantly faster tumor growth in Ifnb1 2/2 mice, accompanied by a massive infiltration of neutrophilic granulocytes into the tumors (Supporting Information Fig. S1).…”

“…4 Normally, the life span of neutrophils is short at steady state, but increased under proinflammatory conditions. By extrapolation, we hypothesized that the life span of TANs might be increased under conditions where IFN-b is absent.…”

“…Besides its recently demonstrated effects on angiogenic processes, 4 activation of tumor specific CD8 1 T cells, 49 and its contribution to DCmediated cross-presentation of tumor antigens, 50 it apparently plays an important role in the regulation of the life span and apoptosis of tumor-promoting neutrophilic granulocytes. This again highlights the tremendous therapeutic potential of IFN-b.…”

“…4 The massive enrichment of neutrophils in tumors of mice that lacked endogenous IFN-b enhanced tumor growth by improving tumor angiogenesis. 4 In accordance, phenotypic alterations of TANs regarding their proangiogenic capacity were observed in Ifnb1 2/2 mice.Thus far, we attributed the tumor specific accumulation of neutrophils to an IFN-b regulated increased chemoattraction …”