mesothelin
Meaning of mesothelin: A surface protein the cells that make it barely seem to need, which is precisely what makes it a usable target on tumors.
Definition of mesothelin
Mesothelin is a protein anchored to the surface of the cells lining the chest, abdominal and heart cavities. Certain cancers carry it in far greater amounts than any normal tissue does, and a soluble fragment shed from it can be measured in blood. That contrast has made the protein both a marker followed in the laboratory and a target for treatments aimed at tumor cells.
What does it normally do?
Very little that has been pinned down. It sits on mesothelium, the single layer of cells lining the cavities that hold the lungs, the gut and the heart. It is built as a larger protein that is then cut in two, one piece staying tethered to the cell surface and the other released into the surroundings. Animals bred without it develop and reproduce normally, which argues that nothing important depends on it alone. It does bind to another large surface protein, and that attachment may help cells stick to the lining of the abdomen, but its role in health remains genuinely open. Confident statements about what it does for a cell run ahead of the evidence.
Which cancers carry it?
| Cancer | How mesothelin figures |
|---|---|
| Mesothelioma | Present in most tumors of the epithelial type |
| Pancreatic cancer | Strongly present, while the normal pancreas carries almost none |
| Ovarian cancer | Present in a large share of cases |
| Lung adenocarcinoma | Present in a proportion of tumors |
| Bile duct cancer | Present in some tumors |
How is it used?
In two ways. As a blood test, the shed fragment gives a number that tends to climb as mesothelioma grows and fall when treatment works, so it is used chiefly to follow disease already diagnosed. It works poorly as a screening test, because a normal level does not rule the disease out, one subtype of the tumor produces almost none of it, and unrelated conditions including reduced kidney function push the level up. As a treatment target, the near absence of the protein from healthy tissue is the attraction, and antibody-based drug carriers, engineered immune cells and vaccines have all been directed at it in pancreatic cancer and ovarian cancer as well as in mesothelioma. The lining cells that do carry it are the reason inflammation of those surfaces is a recognized effect of such treatments.
Also known as
Used in a sentence
Mesothelin staining was strongly positive throughout the tumor cells.
Good to know
Blood mesothelin rises in conditions other than cancer, reduced kidney function among them, and the sarcomatoid form of mesothelioma produces little of it, so a normal result does not exclude the disease.
Word origin
Where “mesothelin” comes from
The name comes from mesothelium, built on the Greek mesos, meaning middle, for the lining layer these cells form.