Vocal fold fibroblasts promote angiogenesis in vocal fold leukoplakia by secreting pro-angiogenic factors

Cancer-associated fibroblasts (CAFs) have been reported to play an essential role in tumor angiogenesis and progression. In this study, we aimed to investigate the impact of vocal fold leukoplakia-associated fibroblasts (VFLFs) on the angiogenesis process in vocal fold leukoplakia (VFL) and their potential secretions of proangiogenic factors.A total of 160 lesions (86 laryngeal carcinoma, 67 vocal fold leukoplakia, 7 vocal fold polyp) were detected under narrow band imaging (NBI) mode to evaluate the relationship between pathology and intraepithelial papillary capillary loop (IPCL) grades. We characterized immortalized vocal fold CAFs, VFLFs, normal fibroblasts (NFs) cell lines using immunofluorescence cytochemistry and real-time quantitative polymerase chain reaction (RT-qPCR). The effects of fibroblast conditioned media (CM) on the proliferative, migrating and tube formation capacity of human umbilical vein endothelial cells (HUVEC) were investigated using the cell counting kit-8 (CCK-8) assay, wound healing assay, transwell migration experiment and Matrigel tube formation experiment. The expression levels of proangiogenic factors in CAFs, VFLFs, and NFs were evaluated by antibody microarray and RT-qPCR.NBI images depicted that angiogenesis was abnormally activated during laryngeal tumorigenesis. Both CAF and VFLF expressed Vimentin, alpha-smooth muscle actin (α-SMA) and fibroblast activation protein (FAP). NF expressed Vimentin and α-SMA, but not FAP. The PCR results showed that mRNA expression levels of Vimentin, α-SMA and FAP in CAFs and VFLFs were significantly increased than those in NFs. CAF-CM and VFLF-CM promoted the proliferative, migrating, and tube formation ability of HUVECs. Secretome profiling of fibroblasts by antibody microarray demonstrated that VFLFs secreted significantly more vascular endothelial growth factor (VEGF), angiogenin, bFGF and HGF than NFs.Overall, we demonstrated that VEGF, angiogenin, bFGF and HGF derived from VFLFs may play crucial roles in the angiogenesis process of laryngeal premalignant and malignant lesions. This may contribute to the exploitation of novel therapeutic strategies for VFL.