It is well known that Prospero homeobox 1 (PROX1) is a crucial regulator of lymphangiogenesis, that reprograms blood endothelial cells to lymphatic phenotype. However, the role of PROX1 in
tumor progression, especially in angiogenesis remains controversial. Herein, we studied the role of PROX1 in angiogenesis in cell lines derived from
follicular thyroid cancer (
FTC:
FTC-133) and
squamous cell carcinoma of the thyroid gland (SCT:
CGTH-W-1) upon PROX1 knockdown. The genes involved in angiogenesis were selected by
RNA-seq, and the impact of PROX1 on vascularization potential was investigated using human umbilical vein endothelial cells (HUVECs) cultured in
conditioned medium collected from
FTC- or SCT-derived
cancer cell lines after PROX1 silencing. The angiogenic phenotype was examined in connection with the analysis of focal adhesion and correlated with
fibroblast growth factor 2 (
FGF2) levels. Additionally, the expression of selected genes involved in angiogenesis was detected in human
FTC tissues. As a result, we demonstrated that PROX1 knockdown resulted in upregulation of factors associated with vascularization, such as
metalloproteinases (MMP1 and 3),
FGF2,
vascular endothelial growth factors C (VEGFC), BAI1 associated
protein 2 (BAIAP2),
nudix hydrolase 6 (NUDT6),
angiopoietin 1 (ANGPT1), and
vascular endothelial growth factor receptor 2 (KDR). The observed molecular changes resulted in the enhanced formation of capillary-like structures by HUVECs and upregulated focal adhesion in FTC-133 and CGTH-W-1 cells. The signature of selected angiogenic genes' expression in a series of
FTC specimens varied depending on the case. Interestingly, PROX1 and
FGF2 showed opposing expression levels in
FTC tissues and seven thyroid
tumor-derived cell lines. In summary, our data revealed that PROX1 is involved in the spreading of
thyroid cancer cells by regulation of angiogenesis.