The shedded ectodomain of Lyve-1 expressed on M2-like tumor-associated macrophages inhibits melanoma cell proliferation

Abstract

Targeting immune cells that support tumor growth is an effective therapeutic strategy in tumor entities such as melanoma. M2-like tumor-associated macrophages (TAM) sustain tumor growth by secreting anti-inflammatory cytokines, proteases and growth factors. In this study, we show that a protein derived from M2-like macrophages namely the shedded ectodomain of Lyve-1 (sLyve-1) decreases human HT144 and murine B16F1 melanoma cell proliferation significantly by acting as a decoy receptor for low-molecular weight hyaluronic acid (LMW-HA) although the LMW-HA/Lyve-1 interaction on lymphatic endothelial cells has been described to induce lymphangiogenesis. This is in line with our finding that the number of LYVE-1+ TAM decreases in higher human melanoma stages and that the early growth of B16 transplant tumors is enhanced in Lyve-1 knockout mice when compared to wild-type mice due to an increased melanoma cell proliferation. LYVE-1 expressing TAM are however true M2 macrophages as they co-express typical M2-markers such as CD163 and CD206. The results of the present study highlight the necessity to carefully determine the net effect particular TAM subpopulations have on tumors before establishing a treatment to target these immune cells.

Semaphorin 7A Promotes Macrophage-Mediated Lymphatic Remodeling during Postpartum Mammary Gland Involution and in Breast Cancer

“…Specifically, TAMs can express pro-lymphangiogenic factors that can signal to the pre-existing lymphatic vessels and/or tumors and have been shown to mobilize what have been called “monocyte-derived lymphatic endothelial cell progenitors (MLECP)” which are LYVE-1 positive and integrate into lymphatic vessels prior to sprouting(29). While lymphatic marker expression on TAMS and activated macrophages has been reported (25–30, 35, 42), it has not been investigated in the normal adult mammary gland. Since alternatively-activated macrophages make up the majority of the macrophages in the adult mammary gland during postpartum involution (11, 17), we suspected that these “involution macrophages” may be like the MLECPs observed in tumors and/or capable of “lymphatic mimicry”.…”

ADP secreted by dying melanoma cells mediates chemotaxis and chemokine secretion of macrophages via the purinergic receptor P2Y12

“…Therefore, the aim of the current study was to identify novel markers on TAM that can be used as therapeutic targets. Previously, we could show that several M2 macrophage markers expressed by TAM of melanoma in situ can be induced in pBM by MDI in vitro 21 . By gene expression analysis of pBM (MDI) , we identified the purinergic receptor P2Y12 as the highest up-regulated gene.…”

“…Human P2Y12 cDNA (clone IRAUp969F0383D) and murine P2Y12 cDNA (IRAVp968D0977D, both from SourceBioscience, Nottingham, UK) was amplified by PCR and cloned into vector lentivirus ADR3 as described previously 21 . For lentiviral transfection, HEK293/T17 producer cells were transfected with the ADR3 vector carrying the P2Y12 gene and 3rd generation lentiviral plasmids (pMD2.G L1, pRSV rev L2, pMDLg/pRRE L3 and pCDNA3.1/p35 E 71) using X-treme GENE 9 DNA transfection reagent (Roche, Mannheim, Germany).…”

Lymphatic Endothelial Cell Progenitors in the Tumor Microenvironment

“…In relation to M-LECP, many TAMs expressing scavenger receptors also express the lymphatic marker LYVE-1 [36,96]. TAMs with dual expression of M2 and LEC markers were identified in human clinical melanoma and a mouse B16 melanoma model [33]. TAMs expressing CD206 and another LEC marker, VEGFR-3, were found in syngeneic 4T1 breast tumors [36] as well as in other tumor models [96,123].…”

“…In human clinical tumors, M-LECP have been similarly identified by co-staining for LEC markers and CD68 that is broadly expressed in most myeloid cells [41], or CD14, a specific monocytic marker [121]. For instance, VEGFR-3-positive cells co-expressing CD14 and CD68 were shown in clinical cervical cancers [97], and LYVE-1 + /CD68 + macrophages were detected in human melanoma [33]. We recently showed [112] that 100% of LYVE-1 + and PDPN + cells infiltrating clinical breast cancers co-expressed classic monocyte-macrophage markers CD14, CD11b, CD18, MD2, MyD88, and Toll-like receptor 4 (TLR4) ( Table 7.1).…”