Cancer

CD33 is a transmembrane protein that belongs to the sialic acid-binding immunoglobulin-like lectin (siglec) family. These are immunoreceptor tyrosine-based inhibitory motif (ITIM)-containing molecules capable of recruiting the tyrosine phosphatases SHP-1 and SHP-2 to signal assemblies. ITIMs are also used for the ubiquitin-mediated removal of the receptor from cell surfaces. CD33 is expressed on cells of myelomonocytic lineage.

The c-Kit (CD117) proto-oncogene is a 145 kD receptor tyrosine kinase family closely related to platelet-derived growth factor receptor (PDGFR). It is a transmembrane receptor and the cellular homolog of the HZ4-feline sarcoma virus transforming gene (v-Kit). c-Kit is expressed on hematopoietic stem cells (multipotent hematopoietic stem cells, myeloid and/or erythroid lineage progenitors, and T-and B- cell precursors), mast cells, and acute myeloid leukemia (AML) cells. c-Kit regulates a variety of biological responses such as chemotaxis, cell proliferation, apoptosis, and adhesion.

The extracellular matrix (ECM) is the external framework found between individual cells that comprise higher order structures like tissues and organs. The ECM composition of vertebrates is dominated by a class of molecules known as collagens - each with unique features suited for a particular function and location. Collagen proteins are made up of three subunit polypeptides that vary in length. Through a unique repeated (Gly-X-Y) sequence, these components associate to form a structurally regular triple helix.

B7H4 is a co-stimulatory protein though to function as a negative regulator of T-cell mediated immunity by blocking proliferation, cell cycle progression and interleukin-2 (IL-2) production. Because B7H4-deficient mice are only minimally affected, it appears that B7H4 is involved in fine tuning of the T-cell mediated immune response. B7H4 is expressed on activated T-cells, B-cells, monocytes, and dendritic cells and exists in three different isoforms.

CD68 belongs to a growing family of hematopoietic mucin-like molecules known as lysosomal/endosomal-associated membrane glycoproteins (LAMPs). Other LAMP family members included leukosialin, stem cell antigen CD34, and GlyCAM-1. CD68 encodes a 110-kD transmembrane glycoprotein with high levels of expression in human monocytes and tissue macrophages. CD68 binds lectins through a heavily glycosylated extracellular domain.

PCNA is a nuclear protein essential for DNA replication as well as DNA excision and mismatch repair pathways. It coordinates the recruitment and association of needed components during both of these processes, both of which are essential for cell cycle regulation and cell response to stress.  Through the symmetric association of three identical monomers, PCNA forms a toroidal, ring-shaped structure that encircles DNA. This serves as the scaffold upon which polymerases and other proteins dock and associate.

FLT3 is a Type III tyrosine kinase cell surface receptor found on primitive bone marrow stem cells. The FLT3 ligand is a hematopoietic growth factor that stimulates cells via a set of structurally related tyrosine kinase receptors.  This FLT3 Ligand promotes the differentiation of multiple hematopoietic cell lineages and is expressed as a non-covalently-linked dimer by T-cells, bone marrow, and thymic fibroblasts.

L-selectin is a member of the selectin family of glycoprotein adhesion and homing receptors that recognize sialyated carbohydrate groups and regulate lymphocyte-endothelial cell interactions. It is a type I transmembrane cell adhesion molecule (CAM) and is constitutively expressed on all classes of circulating leukocytes including lymphocytes (excluding memory T-cells), monocytes, and polymorphonuclear (PMN) cells.

GH is a member of the large family of growth factors that includes prolactin, placental lactogens, proliferins, and somatolactin. Additionally, GH is a 191-amino acid, single-chain polypeptide that is synthesized, stored, and secreted by somatotropic cells within the lateral wings of the anterior pituitary gland. Release of GH into the circulation is mediated by the concerted actions of the hypothalamic hormones-GH-releasing hormone (GHRH) and somatostatin (SST), as well as through signals from the periphery-ghrelin and leptin.

GAPDH is a 146kD tetramer glycolytic pathway metabolic enzyme composed of four 30-40 kDa subunits. It is responsible for reversibly phosphorylating its substrate glyceraldehyde 3-phosphate within the glycolytic pathway.  Apart from its role in glycolysis, GAPDH may have other roles such as transcriptional activation. Due to its housekeeping role, GAPDH is highly expressed in almost all tissues, allowing its use as an internal loading control (traditionally for mRNA expression comparisons, but also in protein studies.