Tumour-Conditioned Macrophages Up-Regulate Endothelial-Derived Fibronectin to Facilitate Lung Metastasis in Breast Cancer

Abstract

Primary tumour cell-derived factors modulate distant microenvironment to become pre-metastatic niche, which is conducive for tumour homing, prior to metastasis. It is not known whether tumour secreted factors could alter endothelial function during pre-metastatic niche formation. My data revealed that lung endothelium was more susceptible to invasion by breast cancer cells, MDA-MB-231, compared to endothelium isolated from non-metastatic sites. Tumour cells disrupted the lung endothelial monolayer integrity upon adhesion and created ?gaps? on the monolayer that facilitated trans-endothelial migration. MDA-MB-231-conditioned macrophages became M2 macrophages and secreted factors (including interleukin-6) that enhanced tumour-endothelial interactions mediated by tumour-a5?1 integrins. The stimulated lung endothelium increased fibronectin expression, which is an important component of pre-metastatic niche formation. Endothelial cells from non-metastatic organs were not responsive to the tumour-conditioned macrophages. The enhanced expression of fibronectin on MDA-macrophage-primed FLEC was regulated by the activation of the JNK/cJUN and STAT3 signalling pathways.