Changes in the secretory profile of NSCLC-associated fibroblasts after ablative radiotherapy: Potential impact on angiogenesis and tumor growth

Abstract

In the context of radiotherapy, collateral effects of ablative ionizing radiation (AIR) on stromal components of tumors remains understudied. In this work, cancer-associated fibroblasts (CAFs) isolated from freshly resected human lung tumors were exposed to AIR (1x18Gy) and analyzed for their release of paracrine factors. Inflammatory mediators and regulators of angiogenesis and tumor growth were analyzed by multiplex protein assays in conditioned medium (CM) from irradiated and non-irradiated CAFs. Additionally, the profile of secreted proteins was examined by proteomics. In functional assays, effects of CAF-CM on proliferative and migratory capacity of lung tumor cells (H-520/H-522) and endothelial cells (HUVECs), and on the tube-forming capacity of endothelial cells was assessed. Our data show that exposure of CAFs to ablative doses of ionizing radiation results in a) down-regulation of angiogenic factors SDF-1, angiopoietin and thrombospondin-2; b) up-regulated release of growth factor bFGF from most donors, and c) unaffected (high) expression-levels of HGF and inflammatory mediators IL-6, IL-8, IL-1&#946 and TNF-α. Conditioned medium from irradiated and non-irradiated CAFs did not affect differently the proliferative or migratory capacity of tumor cells (H522 or H522), whereas migratory capacity of endothelial HUVEC cells was partially reduced in the presence of irradiated CAF-CM. Overall we conclude that AIR-induced altered secretion of important tumor regulatory factors by CAFs could affect therapeutic outcome and therefore merits further investigations.