A marker is a substance that when produced or found on something can indicate certain conditions or circumstances. Tumor markers act like beacons of flagging the existence and development of cancer in the bodies of human beings or animals.
Tumor markers could be common molecules in the body showing high quantities than normal or modified molecules that point specifically to a given kind tumor in the body. due to technological developments, Tumor markers have been identified and quantified thus enabling early diagnosis, measurement of extent as well as traction of treatment progress.
Analysis of tumor markers in a chemistry laboratory may require samples such as urine, serum, plasma, and aspirates. The cells can also be examined microscopically to identify if they possess the markers being suspected or have any alterations that can point to them being tumorous.
Some of the common tumor markers for different kinds of cancer include:
- CA 15-3 and CA 27-29
- CA 19-9
Cancer antigen 125 also known as mucin 16 is a glycoprotein that is found elevated in the blood of patients with ovarian cancer. this molecule is a membrane-associated mucin with a single transmembrane domain; it is a large protein consisting of about 22000 amino acids. it is a component of the eye surfaces including the cornea and the conjunctiva, as well, it makes up the female reproductive tract epithelia.
This glycoprotein is used to confirm the presence of ovarian cancer due to the established correlation in its levels and the development of cancer in the ovaries. it is not however used as a test factor during screening as it brings inconclusive results as there are other noncancerous conditions that can result in elevated levels of CA-125 in the blood. It is tested from a blood sample and the normal values should be less than 46 units per milliliter.
CA 15-3 and CA 27-29
CA 15-3 and CA 27-29 are associated since they epitopes of the same protein which is coded by the gene MUC1. The elevation of the levels of this marker in a serum together with Alkaline phosphatase can point to the onset of breast cancer or a recurrence after treatment. Elevated levels have been noted in about 59.9% of preoperative breast cancer cases and 81% of advanced metastatic breast cancer cases.
Even though the levels of this marker can be elevated in noncancerous cases such as vitamin B12, it is considered a more sensitive way of detecting and monitoring breast cancer compared to other tumor markers such as CEA. Upon treatment, the level of CA 15-3 drops, however, they can increase following dead cells shedding their markers into the blood circulation. CA27.29 is applied when confirming the presence of cancer in a patient as it is less likely to be positive in a patient who has no tumor in their breast.
PSA (Prostate-Specific Antigen)
Prostate-Specific Antigen as the name suggests is a glycoprotein enzyme that originates from the epithelial cells of the prostate gland. it is sometimes referred to as the gamma-seminoprotein or kallikrein-3. It is majorly produced for the purpose of liquifying the ejaculate as well as dissolving the cervical mucus so that the sperm cells can swim freely into the uterus.
In men with normal prostate functionality, the levels of this enzyme in the blood circulation are low. however, when the prostates are affected by cancerous cells or other disorders that affect the health of the prostate gland, the levels are elevated above 10 nanograms per milliliter (normal range is between 4 and 10 ng/ml). Screening is done on the patient’s serum.
CEA (Carcinoembryonic Antigen)
CEA antigen is a complex protein produced in the gastric and intestinal tissue during the development of a fetus where works together with other related glycoproteins to aid in the process of cellular adhesion. its formation halts immediately before birth and circulates at very low levels in the blood. when the gastric and intestinal cells become cancerous,
Its level in the blood circulation goes above 20 nanograms per milliliter, quantities that can be picked in the biochemistry laboratory upon analysis of patient serum. It, therefore, can be used as a tumor marker for colorectal, lung, stomach, thyroid, pancreases, breast and ovarian cancers.
Alpha-fetoprotein is a major plasma globulin that is found in high levels in the circulation of fetuses and infants compared to children and adults. the levels fall pre-birth and keep falling till they are significantly low by the time one gets to be an adult. even though it role in humans is not so clear, it is postulated that is is important in preventing virilization of male fetuses while still in the womb.
In cases of liver, ovarian and testicular cancer, the levels go way above 5 nanograms per milliliter in adults. This only applies to nonpregnant women since pregnancy can cause elevated serum levels of alpha-fetoproteins.
B2M (Beta 2-microglobulin)
Beta 2-microglobulin is a protein which exists in three alpha forms and is a component of the Major Histocompatibility Complex which is present in all the nucleated cell in the body. Other than the presentation of antigens, this protein is associated with iron uptake and metabolism in the body including transportation of the absorbed iron, utilization of recycled iron from damaged red blood cells through regulation of the expression of hepcidin. When it fails to do this, iron molecules will flood the blood system resulting in iron overload or iron poisoning.
When a serum sample from a patient is analyzed in a biochemistry laboratory, levels above 2 milligrams per liter are flagged to be indicative of multiple myeloma or lymphoma.
Cancer Antigen 19-9 is a cell to cell recognition tetrasaccharide molecule normally attached to the glycans on the surface of cells. when pancreatic cells get cancerous, they shed this molecule into the blood circulation and therefore its elevated levels can be detected. it is normally used to detect and determine the extent of cancer progression in the organs found in the abdomen including gallbladder, bile duct, and the stomach.
Other than cancer, the levels of the tumor marker can be elevated in inflammation of the pancreas, death of the liver cells and other diseases that affect the gall bladder. this can result in false-positive results. It is therefore of great importance to use it in combination with other tests to determine the presence or absence of tumors in the relevant organs.
Beta-hCG Tumor Markers
Beta- hCG is also known as the human chorionic gonadotrophin the beta subunit. It is a 32 kilodalton glycoprotein that is indicated in testicular carcinomas, Germ cell tumors, and choriocarcinomas. this tumor marker is expressed together with syncytiotrophoblastic giant cell.
BTA (Bladder Tumor Antigen)
Bladder cancer is a common malignancy with more than 25% of cases being muscular invasive. some of the causes of bladder cancer include repeated bladder traumer and parastic infections such as those of schistosoma. testing for BTA is anon invasive urine analytic procedure that is used to detect the presence and progress of this disease. in combination with urine cytology, bladder tumors can be managed better.
The test for this turmor marker has been developed into a dipstick immunoassay (a rapid diagnostic test) making the testing process cheap, rapid and affordable. other than bladder cancer, it can also be used in detection of kidney and ureter cancers.
Calcitonin Tumor Markers
Calcitonin is a 32 aminoacid hormone produced and released by the parafollicular cells of the thyroid gland. its main roles in the body include prevention of bone disolution and promotion of calcium reabsorption in the kidneys. when the levels of the hormone increase beyong the normal range,
It can be indicative of medulary thyroid cancer and other thyroid diseases such as perifollicular hyperplasia and multiple endocrine neoplasia type 2 which are generally predisposing factors to medullary thryroid tumor.
Gastrin Tumor Markers
Gastrin is a prptide hormone in the stomach that stimulates the parietal cells in the stomuch to produce hydrochloric acid, it also aids in gastric motility. the levels are high in cases such as Zolliner-Ellison syndrome, ingestion of antiacid and chronic atrophic gastritis which damage the stomach lining to some degree
A gastrinoma of the pancrease or duodenum can lead to secretion of high levels of this tumor marker into the blood. a pentagastrin test is therefore very useful in detection and evaluation of tumor progress indicated by the gastrin hormone.