Effects of VEGFR1+ hematopoietic progenitor cells on pre-metastatic niche formation and in vivo metastasis of breast cancer cells

Du Meng,Min Meng,Shangke Huang,Minna Luo,Xin Jing,Xinhan Zhao,Rui Liu,Anqi Luo,Guanying Wang,Shan Shao

doi:10.1007/s00432-018-2802-6

Abstract

The pre-metastatic niche has been shown to play a critical role in tumor metastasis, and its formation is closely related to the tumor microenvironment. However, the underlying molecular mechanisms remain unclear. In the present study, we successfully established a mouse model of lung metastasis using luciferase-expressing MDA-MB-435s cells. In this model, recruitment of vascular endothelial growth factor receptor-1 (VEGFR1)+CD133+ hematopoietic progenitor cells (HPCs) was gradually increased in lung but gradually decreased after the formation of tumor colonies in lung. We also established a highly metastatic MDA-MB-435s (MDA-MB-435s-HM) cell line from the mouse model. Changes in protein profiles in different culture conditions were investigated by protein microarray analysis. The levels of CXC chemokine ligand 16, interleukin (IL)-2Rα, IL-2Rγ, matrix metalloproteinase (MMP)-1, MMP-9, platelet-derived growth factor receptor (PDGFR)-α, stromal cell-derived factor (SDF)-1α, transforming growth factor (TGF)-β, platelet endothelial cell adhesion molecule (PECAM)-1 and vascular endothelial (VE)-cadherin were significantly greater (> fivefold) in the culture medium from MDA-MB-435s-HM cells than in that from MDA-MB-435s cells. Moreover, the levels of MMP-9, PDGFR-α, and PECAM-1 were significantly greater in the co-culture medium of MDA-MB-435s-HM cells and CD133+ HPCs than in that from MDA-MB-435s-HM cells. Differentially expressed proteins were validated by enzyme-linked immunosorbent assay, and expression of their transcripts was confirmed by quantitative real-time polymerase chain reaction. Moreover, inhibition of MMP-9, PDGFR-α, and PECAM-1 by their specific inhibitors or antibodies significantly decreased cell migration, delayed lung metastasis, and decreased recruitment of VEGFR1+CD133+ HPCs into lung. Intra-hepatic growth of HPCs enhanced the invasive growth of MDA-MB-435s-HM cells in the liver. Our data indicate that VEGFR1+CD133+ HPCs contribute to lung metastasis.

Highlights

Tumor metastasis is a dynamic and complex process involving a series of critical steps including epithelialto-mesenchymal transition (EMT) of cancer cells, local invasion of primary tumor, tumor cell intravasation into the circulatory system, extravasation and seeding at the pre-metastatic niche, and invasion and growing in the secondary sites—most frequently in the lung and liver (Arvelo et al 2016; Zingg et al 2018)
The results showed that the levels of CXCL16, IL-2Rα, IL-2Rγ, matrix metalloproteinase (MMP)-1, MMP-9, platelet-derived growth factor receptor (PDGFR)-α, stromal cellderived factor (SDF)-1α, transforming growth factor (TGF)-β, platelet endothelial cell adhesion molecule (PECAM)-1, and vascular endothelial (VE)-cadherin in the supernatant of MDA-MB-435s-HM cells were significantly higher than those in the supernatant of MDA-MB-435s cells (> fivefold, P < 0.01, Fig. 4a–j)
To address whether the differential expression of the above cytokines/chemokines/MMPs was affected at the translational or transcriptional level, we further examined the mRNA expression of IL-2Rα, MMP-1, MMP-9, PDGFR-α, TGF-β, PECAM-1, and VE-cadherin in the cells by qRT-PCR

Summary

Introduction

Tumor metastasis is a dynamic and complex process involving a series of critical steps including epithelialto-mesenchymal transition (EMT) of cancer cells, local invasion of primary tumor, tumor cell intravasation into the circulatory system, extravasation and seeding at the pre-metastatic niche, and invasion and growing in the secondary sites—most frequently in the lung and liver (Arvelo et al 2016; Zingg et al 2018). It has been demonstrated that tumor metastasis involves close collaboration of multiple cell types [cancer cells, immune cells, cancerassociated fibroblasts (CAFs) and bone marrow-derived cells (BMDCs)], inflammatory cytokines and chemokines, matrix metalloproteinases (MMPs), etc. Chronic deregulation of cytokine expression and activity can result in tumor initiation, growth, and metastasis (Peinado et al 2017; Itatani et al 2016; Guan et al 2018; Hou et al 2017). MMPs have been found to contribute to tumor invasion and metastasis and to control cell growth, inflammation, and angiogenesis via multiple signaling pathways (Liu and Cao 2016; Mrozik et al 2018; Giles et al 2016). Recent studies found a new role for MMPs in building a favorable microenvironment for tumor metastasis (Itatani et al 2016; Liu and Cao 2016)

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