This article needs more reliable medical references for verification or relies too heavily on primary sources .(September 2019) |
MUC16 | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Identifiers | |||||||||||||||||||||||||||||||||||||||||||||||||||
Aliases | MUC16 , CA125, mucin 16, cell surface associated | ||||||||||||||||||||||||||||||||||||||||||||||||||
External IDs | OMIM: 606154 HomoloGene: 133291 GeneCards: MUC16 | ||||||||||||||||||||||||||||||||||||||||||||||||||
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Wikidata | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Mucin-16(MUC-16) also known as Ovarian cancer-related tumor marker CA125 is a protein that in humans is encoded by the MUC16 gene. [3] [4] [5] MUC-16 is a member of the mucin family glycoproteins. [6] MUC-16 has found application as a tumor marker or biomarker that may be elevated in the blood of some patients with specific types of cancers, most notably ovarian cancer, or other conditions that are benign. [7] [8]
Mucin 16 is a membrane associated mucin that possesses a single transmembrane domain. [9] A unique property of MUC16 is its large size. MUC16 is more than twice as long as MUC1 and MUC4 and contains about 22,000 amino acids, making it the largest membrane-associated mucin. [10]
MUC16 is composed of three different domains: [11]
The N-terminal and tandem repeat domains are both entirely extracellular and highly O-glycosylated. All mucins contain a tandem repeat domain that has repeating amino acid sequences high in serine, threonine and proline. [12] The C-terminal domain contains multiple extracellular SEA (sea urchin sperm protein, enterokinase, and agrin) modules, [13] a transmembrane domain, and a cytoplasmic tail. [11] The extracellular region of MUC16 can be released from the cell surface by undergoing proteolytic cleavage. [14] MUC16 is thought to be cleaved at a site in the SEA modules. [15]
MUC16 is a component of the ocular surface (including the cornea and conjunctiva), the respiratory tract and the female reproductive tract epithelia. Since MUC16 is highly glycosylated it creates a hydrophilic environment that acts as a lubricating barrier against foreign particles and infectious agents on the apical membrane of epithelial cells. [16] Also, the cytoplasmic tail of MUC16 has been shown to interact with cytoskeleton by binding members of the ERM protein family. [17] The expression of mucin 16 has been shown to be altered in dry eye, cystic fibrosis, and several types of cancers. [18]
MUC16 (CA-125) has been shown to play a role in advancing tumorigenesis and tumor proliferation by several different mechanisms.
Testing of CA-125 blood levels has been proposed as useful in treating ovarian cancer. While the test can give useful information for women already known to have ovarian cancer, CA-125 testing has not been found useful as a screening method because of the uncertain correlation between CA-125 levels and cancer. [19] In addition to ovarian cancer, CA-125 can be elevated in patients who have conditions such as endometrial cancer, fallopian tube cancer, lung cancer, breast cancer, and gastrointestinal cancer. It can also be increased in pregnant women. Because of the wide variety of conditions that can increase serum levels, CA-125 is not used to detect cancer, but it is often used to monitor responses to chemotherapy, relapse, and disease progression in ovarian cancer patients. [20]
MUC16 is also thought to participate in cell-to-cell interactions that enable the metastasis of tumor cells. This is supported by evidence showing that MUC16 binds selectively to mesothelin, a glycoprotein normally expressed by the mesothelial cells of the peritoneum (the lining of the abdominal cavity). [22] MUC16 and mesothelin interactions are thought to provide the first step in tumor cell invasion of the peritoneum. [23] The region (residues 296–359) consisting of 64 amino acids at the N-terminus of cell surface mesothelin has been experimentally established as the functional binding domain (named IAB) for MUC16/CA125. [21] An immunoadhesin (HN125) that consists of the IAB domain of mesothelin and the human Fc portion has the ability to disrupt the heterotypic cancer cell adhesion mediated by the MUC16-mesothelin interaction. [24]
Mesothelin has also been found to be expressed in several types of cancers including mesothelioma, ovarian cancer and squamous cell carcinoma. [25] Since mesothelin is also expressed by tumor cells, MUC16 and mesothelial interactions may aid in the gathering of other tumor cells to the location of a metastasis, thus increasing the size of the metastasis. [23]
Evidence suggests that expression of the cytoplasmic tail of MUC16 enables tumor cells to grow, promotes cell motility and may facilitate invasion. This appears to be due to the ability of the C-terminal domain of MUC16 to facilitate signaling that leads to a decrease in the expression of E-cadherin and increase the expression of N-cadherin and vimentin, which are expression patterns consistent with epithelial-mesenchymal transition. [26]
MUC16 may also play a role in reducing the sensitivity of cancer cells to drug therapy. For example, overexpression of MUC16 has been shown to protect cells from the effects of genotoxic drugs, such as cisplatin. [27]
CA-125 was initially detected using the murine monoclonal antibody designated OC125. Robert Bast, Robert Knapp and their research team first isolated this monoclonal antibody in 1981. [28] The protein was named "cancer antigen 125" because OC125 was the 125th antibody produced against the ovarian cancer cell line that was being studied. [29]
A monoclonal antibody is an antibody produced from a cell lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell.
Cancer immunotherapy (immuno-oncotherapy) is the stimulation of the immune system to treat cancer, improving on the immune system's natural ability to fight the disease. It is an application of the fundamental research of cancer immunology and a growing subspecialty of oncology.
The CD44 antigen is a cell-surface glycoprotein involved in cell–cell interactions, cell adhesion and migration. In humans, the CD44 antigen is encoded by the CD44 gene on chromosome 11. CD44 has been referred to as HCAM, Pgp-1, Hermes antigen, lymphocyte homing receptor, ECM-III, and HUTCH-1.
P-selectin is a type-1 transmembrane protein that in humans is encoded by the SELP gene.
Antigen Kiel 67, also known as Ki-67 or MKI67, is a protein that in humans is encoded by the MKI67 gene.
Minretumomab (CC49) is a mouse monoclonal antibody that was designed for the treatment of cancers that express the TAG-72 antigen. This includes breast, colon, lung, and pancreatic cancers. Apparently, it never got past Phase I clinical trials for this purpose.
Mesothelin, also known as MSLN, is a protein that in humans is encoded by the MSLN gene.
Mucin short variant S1, also called polymorphic epithelial mucin (PEM) or epithelial membrane antigen (EMA), is a mucin encoded by the MUC1 gene in humans. Mucin short variant S1 is a glycoprotein with extensive O-linked glycosylation of its extracellular domain. Mucins line the apical surface of epithelial cells in the lungs, stomach, intestines, eyes and several other organs. Mucins protect the body from infection by pathogen binding to oligosaccharides in the extracellular domain, preventing the pathogen from reaching the cell surface. Overexpression of MUC1 is often associated with colon, breast, ovarian, lung and pancreatic cancers. Joyce Taylor-Papadimitriou identified and characterised the antigen during her work with breast and ovarian tumors.
CD47 also known as integrin associated protein (IAP) is a transmembrane protein that in humans is encoded by the CD47 gene. CD47 belongs to the immunoglobulin superfamily and partners with membrane integrins and also binds the ligands thrombospondin-1 (TSP-1) and signal-regulatory protein alpha (SIRPα). CD-47 acts as a don't eat me signal to macrophages of the immune system which has made it a potential therapeutic target in some cancers, and more recently, for the treatment of pulmonary fibrosis.
Epithelial cell adhesion molecule (EpCAM), also known as CD326 among other names, is a transmembrane glycoprotein mediating Ca2+-independent homotypic cell–cell adhesion in epithelia. EpCAM is also involved in cell signaling, migration, proliferation, and differentiation. Additionally, EpCAM has oncogenic potential via its capacity to upregulate c-myc, e-fabp, and cyclins A & E. Since EpCAM is expressed exclusively in epithelia and epithelial-derived neoplasms, EpCAM can be used as diagnostic marker for various cancers. It appears to play a role in tumorigenesis and metastasis of carcinomas, so it can also act as a potential prognostic marker and as a potential target for immunotherapeutic strategies.
Glypican-3 is a protein that, in humans, is encoded by the GPC3 gene. The GPC3 gene is located on human X chromosome (Xq26) where the most common gene encodes a 70-kDa core protein with 580 amino acids. Three variants have been detected that encode alternatively spliced forms termed Isoforms 1 (NP_001158089), Isoform 3 (NP_001158090) and Isoform 4 (NP_001158091).
OX-2 membrane glycoprotein, also named CD200 is a human protein encoded by the CD200 gene. CD200 gene is in human located on chromosome 3 in proximity to genes encoding other B7 proteins CD80/CD86. In mice CD200 gene is on chromosome 16.
Trophoblast glycoprotein, also known as TPBG, 5T4, Wnt-Activated Inhibitory Factor 1 or WAIF1, is a human protein encoded by a TPBG gene. TPBG is an antagonist of Wnt/β-catenin signalling pathway.
Tumor-associated glycoprotein 72 (TAG-72) is a glycoprotein found on the surface of many cancer cells, including ovary, breast, colon, lung, and pancreatic cancers. It is a mucin-like molecule with a molar mass of over 1000 kDa.
Glypican 2 (GPC2), also known cerebroglycan, is a protein which in humans is encoded by the GPC2 gene. The GPC2 gene is at locus 7q22.1 and encodes for a 579 amino acid protein. The C-terminus of GPC2 has the GPI attachment site, at G554, and the N-terminus encodes a signal peptide, from M1 to S24. Multiple GPC2 mRNA transcripts have been identified. GPC2-201 is the isoform overexpressed in pediatric cancers. Tumor-associated exon 3 of GPC2 shows the lowest expression in normal tissues compared with other exons.
A431 cells are a model human cell line used in biomedical research.
Tyrosine-protein kinase transmembrane receptor ROR1, also known as neurotrophic tyrosine kinase, receptor-related 1 (NTRKR1), is an enzyme that in humans is encoded by the ROR1 gene. ROR1 is a member of the receptor tyrosine kinase-like orphan receptor (ROR) family.
Mucin-1(MUC-1) is a heterodimer transmembrane protein of the mucin family encoded in humans by the MUC1 gene. It is cleaved into two chains: mucin-1 subunit alpha and mucin-1 subunit beta. These subunits differ in size due to proteolytic cleavage of the translated precursor protein in the endoplasmic reticulum. The larger subunit of MUC-1 is characterized by numerous O-glycosylated bonds and a terminal sialic acid, creating a net negative charge on MUC-1. The smaller subunit contains a juxtamembrane region of the extracellular area, a transmembrane domain, and the cytoplasmic tail. The extracellular domain of MUC-1 is composed of 20 identical amino acid tandem repeats (TR). Each tandem repeat contains two serine and three threonine amino acid residues, providing five sites for potential O-glycosylation. MUC-1 protein is estimated to weigh 120 to 225 kDA.
CKLF like MARVEL transmembrane domain-containing 6, previously termed chemokine-like factor superfamily 6, is a transmembrane protein encoded in humans by the CMTM6 gene. This gene is located in band 22.3 on the short arm of chromosome 3. CMTM6 protein belongs to the CKLF-like MARVEL transmembrane domain-containing family of proteins. This family consist of 9 member proteins: CKLF and CMTM1 through CMTM8. The CMTM family proteins are involved in autoimmune diseases, cardiovascular diseases, the male reproductive system, haematopoiesis, and cancer development. CMTM6 protein regulates immune responses to normal and abnormal cells.
SK-OV-3 is an ovarian cancer cell line derived from the ascites of a 64-year-old Caucasian female with an ovarian serous cystadenocarcinoma. The SK-OV-3 cell line is also hypodiploid, with a modal number of chromosomes of 43, occurring in 63.3% of cells. SK-OV-3 are positive for many of the antigens used to identify cancers of epithelial origin in clinical practice, including vimentin (VIM), high molecular weight cytokeratin (HMWK), low molecular weight cytokeratin (LMWK), epithelial membrane antigen (EMA) and leucocyte common antigen (LCA).