2. Introduction
Uncontrolled growth of cells results in tumors
The tumors are of two types.
1. Benign tumors : They usually grow by expansion and remain
encapsulated in a layer of connective tissue. Normally benign tumors
are not life-threatening e.g. moles, warts. These types of benign
tumors are not considered as cancers.
2. Malignant tumors or cancers : They are characterized by
uncontrolled proliferation and spread of cells to various parts of the
body, a process referred to as metastasis . Malignant tumors are
invariably life-threatening e.g. lung cancer, leukemia
Tumor markers:
The biochemical indicators employed to detect the presence of
tumor are collectively referred to as tumor markers. They are
produced either by tumor itself or by host in response to presence
of cancers
These includes oncofetal antigens, hormones, enzymes and
proteins.
3. Characteristics of ideal
tumor markers
1. A tumor marker should be present in or produced by tumor itself
2. A tumor markers should not be present in healthy tissues
3. Plasma levels of tumor markers should be at minimum level in healthy subject
and in benign conditions.
4. A tumor markers should be specific for tissue, it should have different
immunological properties when it is synthesized in other tissues.
5. Plasma levels of tumor markers should be in proportion to the size and activity
of tumor
6. A tumor marker should be present at plasma at detectable level even though
tumor size is very small.
4. Classification of tumor markers
a) Onco-fetal antigens:
Eg. AFP(ALPHA FETO PROTEIN), CEA( CARCINOEMBRYONIC
ANTIGEN), squamous cell carcinoma antigen (SCC) ETC
b)Hormones : eg. Beta-HCG (HUMAN CHORIONIC
GONADOTROPHIN), ACTH ( ADRENO CORTICO THYROTROPIC
HORMONE), Prolactin, GH (Growth hormone), calcitonin
ETC.
c)proteins:
Eg. IMMUNOGLOBULIN’s, Beta-2 micro-globulins, C-peptide,
ferritin, BJP( BENCE JONES PROTEIN) in urine ETC.
d) Enzymes :
eg. alkaline phosphatase(ALP),ACP (Acid phosphatase),
Prostate Specific antigen (PSA)
5. Some Clinically Important
Tumor Markers
1)AFP (alpha fetoprotein)
It is a Glycoprotein,
normally synthesized by yolk sac in early fetal life. Elevation in
serum levels of AFP mainly indicates the cancers of liver and germ
cells of testis and, to some extent, carcinomas of lung, pancreas and
colon.
AFP is not specific for the detection of cancers. Elevated levels of
AFP are observed in cirrhosis, hepatitis and pregnancy.
Normal value in adult: <15ng/L
Levels above 1000 ng/L are almost always associated with cancer
(except in pregnancy).
6. 2) CEA (carcinoembryonic antigen)
glycoprotein, normally produced by the embryonic tissue of liver, gut and
pancreas. The presence of CEA in serum is detected in several cancers (colon,
pancreas, stomach, lung)
CEA level is markedly increased in colorectal cancers.
Normal serum level: 5ng/mL
Smoker less than 10ng/ml
Malignancy is more than 20ng/ml
3) Beta Chain of Chorionic Gonadotropin (Beta-HCG)
is a glycoprotein, synthesized by placenta.
Normal value is less than 5 IU/L for males and non-pregnant females.
It is increased in germ cell tumors .
7. ze
4. Cancer Antigen 125 (CA-125)
It is a glycoprotein maker for ovarian, endometrial cancers
. Normal blood level of CA125 is less than 35 U/mL.
5. Prostate Specific Antigen (PSA
It is produced by secretory epithelium of prostate gland. It is normally secreted into seminal
fluid, where it is necessary for the liquefaction of seminal coagulum
is increased in prostate cancers
Normal blood level of total PSA <4 ng/L.
Persons with a borderline total PSA (between 4-10 ng/L),
suggestive of prostatic cancers when levels raise above 100 ng/L
10. Lab diagnosis
RADIO IMMUNE ASSAY
ENZYME ASSAY
FLUORESCENCE ASSAY
CHEMILUMINISCENCE ASSAY
Note: Tumor markers are sometimes elevated in nonmalignant conditions. Not every
tumor will cause a rise in the level of its associated marker, especially in the early
stages of some cancers. When a marker is used for cancer screening or diagnosis, the
physician must confirm a positive test result by using imaging studies, tissue biopsies,
and other procedures.
11. References
TEXTBOOK OF BIOCEMISTRY 4th EDITION
(Dr. U. Satyanarayana , Dr. U. Chakrapani
)
TEXTBOOK OF BIOCHEMISTRY For Medical
Students 6TH EDITION (DM VASUDEVAN ,
SREEKUMARI S , KANNAN VAIDYANATHAN )
