Angiopoeitin-2 is a multimeric ligand involved in the angiopoietin-Tie signaling system that binds the Tie2 receptor and is characterized as a modulator of endothelial permeability and barrier function. It is predominantly expressed by endothelial cells and some smooth muscle cells, with increased expression in many inflammatory and angiogenic conditions, such as inflammation-induced vascular remodeling and tumor angiogenesis. Ang-2 expression has been documented in a range of human cancers, including glioblastoma, melanoma, prostate adenocarcinoma, and renal cell carcinoma.

Basic fibroblast growth factor, also known as FGF2 and FGF-β, is a growth factor and signaling protein encoded by the FGF2 gene. FGFb binds to and exerts its effects via the fibroblast growth factor receptor (FGFR). It possesses broad mitogenic and cell survival activities, and is involved in a variety of biological processes, including embryonic development, cell growth, morphogenesis, tissue repair, tumor growth and invasion.

Heparin-binding epidermal growth factor (HB-EGF), part of the EGF family of growth factors, is a mitogenic and chemotactic glycoprotein. HB-EGF is essential for normal cardiac valve formation and heart function as well as cutaneous wound healing. Research suggests that HB-EGF plays a critical role in the formation of many types of tumors as well as neurogenesis once the propeptide is induced by brain hypoxia or ischemia.

Hepatocyte growth factor (HGF) is a pleiotropic growth factor secreted by mesenchymal stromal cells, which targets and acts upon epithelial cells, endothelial cells, haemopoietic progenitor cells and T cells. HGF regulates cell growth, cell motility, and morphogenesis by activating a tyrosine kinase signaling cascade after binding to its receptor, tyrosine-protein kinase Met (c-MET). HGF is involved in the regulation of growth, motility, and morphogenesis of various cell types, and plays an important role in wound-healing, tissue or organ regeneration, angiogenesis, and carcinogenesis.

Placental growth factor (PLGF) is a member of the vascular endothelial growth factor (VEGF) family of cytokines, which play important roles in the development and growth of the vascular or lymphatic endothelia. PlGF is a potential prognostic marker for tumor progression in several types of cancer, including renal, colorectal, gastric, breast, and lung. PlGF also plays a role in inflammatory conditions such as artherosclerosis and rheumatoid arthritis, where measurement of serum levels can enhance biomarker analysis of disease progression. In addition, PlGF is elevated in individuals with Sickle Cell Disease (SCD) and thought to play a role in the pathophysiology of pulmonary hypertension in patients with SCD.

Vascular endothelial growth factor (VEGF) is a 27KDa signaling protein produced by cells that stimulates vasculogenesis and angiogenesis. VEGF is a heparin binding protein and exists as a disulfide linked homo-dimer. It has at least 6 isoforms produced by alternative splicing. The Simoa Human VEGF assay detects the 165 amino acid form of the factor (VEGF-165), which is the most common form in tissues. VEGF induces endothelial cell proliferation, promotes cell migration, inhibits apoptosis, and induces permeabilization of blood vessels. VEGF is also involved in vasodilation through induction of endothelial nitric oxide synthase and the subsequent increase in nitric oxide production. Serum concentration of VEGF is high in bronchial asthma and diabetes mellitus. When VEGF is over-expressed, it can contribute to disease; cancers that can express VEGF are able to grow and metastasize.