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BMC Cancer. 2017 Jan 5;17(1):11. doi: 10.1186/s12885-016-3018-2.

PGE2 promotes breast cancer-associated lymphangiogenesis by activation of EP4 receptor on lymphatic endothelial cells.

Author information

1
Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, N6A5C1, Canada.
2
Department of Biology, Brandon University, Brandon, Manitoba, R7A 6A9, Canada.
3
Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, N6A5C1, Canada. pklala@uwo.ca.
4
Department of Oncology, University of Western Ontario, London, Ontario, N6A5C1, Canada. pklala@uwo.ca.
5
Children's Health Research Institute, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, N6A5C1, Canada. pklala@uwo.ca.

Abstract

BACKGROUND:

Lymphatic metastasis, facilitated by lymphangiogenesis is a common occurrence in breast cancer, the molecular mechanisms remaining incompletely understood. We had earlier shown that cyclooxygenase (COX)-2 expression by human or murine breast cancer cells promoted lymphangiogenesis and lymphatic metastasis by upregulating VEGF-C/D production by tumor cells or tumor-associated macrophages primarily due to activation of the prostaglandin receptor EP4 by endogenous PGE2. It is not clear whether tumor or host-derived PGE2 has any direct effect on lymphangiogenesis, and if so, whether EP4 receptors on lymphatic endothelial cells (LEC) play any role.

METHODS:

Here, we address these questions employing in vitro studies with a COX-2-expressing and VEGF-C/D-producing murine breast cancer cell line C3L5 and a rat mesenteric (RM) LEC line and in vivo studies in nude mice.

RESULTS:

RMLEC responded to PGE2, an EP4 agonist PGE1OH, or C3L5 cell-conditioned media (C3L5-CM) by increased proliferation, migration and accelerated tube formation on growth factor reduced Matrigel. Native tube formation by RMLEC on Matrigel was abrogated in the presence of a selective COX-2 inhibitor or an EP4 antagonist. Addition of PGE2 or EP4 agonist, or C3L5-CM individually in the presence of COX-2 inhibitor, or EP4 antagonist, restored tube formation, reinforcing the role of EP4 on RMLEC in tubulogenesis. These results were partially duplicated with a human dermal LEC (HMVEC-dLyAd) and a COX-2 expressing human breast cancer cell line MDA-MB-231. Knocking down EP4 with shRNA in RMLEC abrogated their tube forming capacity on Matrigel in the absence or presence of PGE2, EP4 agonist, or C3L5-CM. RMLEC tubulogenesis following EP4 activation by agonist treatment was dependent on PI3K/Akt and Erk signaling pathways and VEGFR-3 stimulation. Finally in a directed in vivo lymphangiogenesis assay (DIVLA) we demonstrated the lymphangiogenic as well as angiogenic capacity of PGE2 and EP4 agonist in vivo.

DISCUSSION/CONCLUSIONS:

These results demonstrate the roles of tumor as well as host-derived PGE2 in inducing lymphangiogenesis, at least in part, by activating EP4 and VEGFR-3 on LEC. EP4 being a common target on both tumor and host cells contributing to tumor-associated lymphangiogenesis reaffirms the therapeutic value of EP4 antagonists in the intervention of lymphatic metastasis in breast cancer.

KEYWORDS:

Angiognesis; Breast cancer; Cyclooxygenase (COX)-2; Directed in vivo lymphangiogenesis assay (DIVLA); EP4 antagonist; EP4 receptors; Lymphangiogenesis; Lymphatic endothelial cells; Metastasis; PGE2

PMID:
28056899
PMCID:
PMC5217626
DOI:
10.1186/s12885-016-3018-2
[Indexed for MEDLINE]
Free PMC Article

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