Placenta growth factor overexpression inhibits tumor growth, angiogenesis, and metastasis by depleting vascular endothelial growth factor homodimers in orthotopic mouse models

The role of placenta growth factor (PIGF) in pathologic angiogenesis is controversial. The effects of PlGF on growth, angiogenesis, and metastasis from orthotopic tumors are not known. To this end, we stably transfected three human cancer cell lines (A549 lung, HCT116 colon, and U87-MG glioblastoma) with human plgf-2 full-length cDNA. Overexpression of PlGF did not affect tumor cell proliferation or migration in vitro. The growth of PIGF-overexpressing tumors grown orthotopically or ectopically was impaired in all three tumor models. This decrease in tumor growth correlated with a decrease in tumor angiogenesis. The PIGF-overexpressing tumors had decreased vessel density and increased vessel diameter, but vessel permeability was not different from the parental tumors. Tumors overexpressing PlGF exhibited higher levels of PlGF homodimers and PIGF/vascular endothelial growth factor (VEGF) heterodimers but decreased levels of VEGF homodimers. Our study shows that PlGF overexpression decreases VEGF homodimer formation and inhibits tumor progression.