PGF and cervical cancer: Accumulating evidence has demonstrated that HPV-16 oncoproteins can promote angiogenesis by up-regulating the expression of a variety of pro-angiogenic factors including fibroblast growth factor binding protein, basic fibroblast growth factor, transforming growth factor-β, tumor necrosis factor-α, angiopoietin-1, hepatocyte growth factor, and placental growth factor in cervical cancer cells [33], [38]–[40].