Page 129 - Clinical Biochemistry

Tumor markers definition
 Tumor markers are substances present in and produced by a tumor or by the host in response
to a tumor.
 Measured qualitatively or quantitatively by chemical, immunological, genomic methods.
Tumor markers can be classified according to type of the molecule:
1- Enzymes or isoenzymes
2- Hormones
3- Oncofetal antıgens
4- Carbonhydrate epitopes(antigen) cell surface marker
5- Genetic markers
1- Enzymes or isoenzymes used as tumor marker
Alkaline phosphatase ALP
Placental ALP, elevates in a variety of malignancies, including ovarian, lung, gastrointestinal
cancers and Hodgkin’s disease.
Prostatic acid phosphatase PAP
It is used for staging prostate cancer and for monitoring therapy.
2- Hormones: the hormone may be:
• Product of its associated organ represent abnormal synthesis reflecting unregulated cancer
cell metabolism. Examples include: Calcitonin by thyroid carcinoma.
• Hormone is not a natural product of its associated organ, in this case, it called "ectopic".
Examples include: the production of ACTH and ADH by lung cancers.
3- Oncofetal antıgens
Oncofetal substance produced in large amounts in fetal life but after birth, these antigen
disappear or present in very minute amount in adults but reappear in the tumor.
Most reliable markers in this group are:
α-fetoprotein (AFP) in hepatocellular carcinoma
Carcinoembryonic antigen (CEA) in GIT cancer, ovarian and breast cancer
4- Carbonhydrate epitopes (antigen) cancer antigen(CA)
Large transmembrane glycoprotein which is overexpressed on the cell surface of malignant
cells (cell surface marker).
Examples of important carbohydrate antigen are:
CA 15-3 in Breast cancer
CA 125 in ovarian and endometrial carcinomas
CA 19-9 in colorectal and pancreatic carcinoma