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Neoplasia. 2014 Oct 23;16(10):771-88. doi: 10.1016/j.neo.2014.08.013. eCollection 2014 Oct.

Tissue-infiltrating neutrophils constitute the major in vivo source of angiogenesis-inducing MMP-9 in the tumor microenvironment.

Author information

1
Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA, USA.

Abstract

According to established notion, one of the major angiogenesis-inducing factors, pro-matrix metalloproteinase-9 (proMMP-9), is supplied to the tumor microenvironment by tumor-associated macrophages (TAMs). Accumulated evidence, however, indicates that tumor-associated neutrophils (TANs) are also critically important for proMMP-9 delivery, especially at early stages of tumor development. To clarify how much angiogenic proMMP-9 is actually contributed by TAMs and TANs, we quantitatively evaluated TAMs and TANs from different tumor types, including human xenografts and syngeneic murine tumors grown in wild-type and Mmp9-knockout mice. Whereas host MMP-9 competence was required for full angiogenic potential of both normal and tumor-associated leukocytes, direct comparisons of neutrophils versus macrophages and TANs versus TAMs demonstrated that macrophages and TAMs secrete 40- to 50-fold less proMMP-9 than the same numbers of neutrophils or TANs. Correspondingly, the levels of MMP-9-mediated in vivo angiogenesis induced by neutrophils and TANs substantially exceeded those induced by macrophages and TAMs. MMP-9-delivering TANs were also required for development of metastasis-supporting intratumoral vasculature, characterized by ≥ 11-μm size lumens and partial coverage with stabilizing pericytes. Importantly, MMP-9-producing TAMs exhibit M2-skewed phenotype but do not express tissue inhibitor of metalloproteinases-1 (TIMP-1), a novel characteristic allowing them to secrete TIMP-1-free, neutrophil-like MMP-9 zymogen unencumbered by its natural inhibitor. Together, our findings support the notion whereby TANs, capable of immediate release of their pre-stored cargo, are the major contributors of highly angiogenic MMP-9, whereas tumor-influxing precursors of macrophages require time to differentiate, polarize into M2-skewed TAMs, shut down their TIMP-1 expression, and only then, initiate relatively low-level production of TIMP-free MMP-9 zymogen.

KEYWORDS:

BM, bone marrow; BMD, bone marrow–derived; CM, conditioned medium; IL, interleukin; KO, knockout; M-CSF, macrophage colony-stimulating factor; MMP, matrix metalloproteinase; PB, peripheral blood; PBD, peripheral blood–derived; TAM, tumor-associated macrophage; TAN, tumor-associated neutrophil; TIMP, tissue inhibitor of metalloproteinases

PMID:
25379015
PMCID:
PMC4212255
DOI:
10.1016/j.neo.2014.08.013
[Indexed for MEDLINE]
Free PMC Article

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