VEGFA and neoplasm: Moreover, microvessel density was significantly reduced in tumor xenografts developed by T lymphoma cells transfected with antiheparanase ribozyme.52 The molecular mechanism by which heparanase facilitates angiogenic responses has traditionally been attributed primarily to the release of HS-bound growth factors such as VEGF-A and FGF-2,18,53 a direct consequence of heparanase enzymatic activity.