In this work, we will focus on the following factors involved in tumor angiogenesis: VEGF/VEGFR, angiopoietins, and their receptors: Tie-1 and -2, Eph receptors, and their ephrins ligands, HIF1α (hypoxia-inducible factor 1 alpha), MMPs, and delineate their relationship with the important tumor-suppressor PTEN (phosphatase and tensin homologue). Here, HIF1A is linked to neoplasm.