Tumor Antigens
المؤلف:
APURBA S. SASTRY , SANDHYA BHAT
المصدر:
Essentials Of Medical Microbiology 2021
الجزء والصفحة:
3rd edition , p218-219
2025-10-13
340
Two types of tumor antigens have been identified on tumor cells:
1. Tumor-specific transplantation antigens (TSTAs)
2. Tumor-associated transplantation antigens (TATAs).
Tumor-specific Transplantation Antigen
Tumor-specific antigens are present only on tumor cells and are absent in normal cells of the body.
They may result from mutations in tumor cells that generate altered cellular proteins; cytosolic processing of these proteins would give rise to novel peptides that are presented with class I MHC molecules, inducing a cell mediated immune response by tumor-specific cytotoxic T lymphocytes.
TSTAs are induced on tumor cells either by chemical or by physical carcinogens, and also by viral carcinogens.
- In chemically/physically induced tumors, the TSTA is tumor specific. Different tumors possess different TSTA, even though induced by the same carcinogen. Methylcholanthrene and ultraviolet light are the examples of chemical and physical carcinogens that are extensively studied
- In contrast, the TSTA of virus induced tumors is virus specific; all tumors produced by one virus would possess the same antigen. Examples include Epstein– Barr virus which causes nasopharyngeal carcinoma and several types of lymphoma.
Tumor-associated Transplantation Antigens
Tumor-associated antigens (TATAs) are not unique to tumor cells and may also be expressed by normal cells, but at a very low level. Their level gets exponentially high in tumor cells. Examples include (Table 1):
- Oncofetal antigens: They are the proteins that are expressed on normal cells during fetal life, but not expressed in the adult normally
* Reactivation of the embryonic genes that encode these proteins in tumor cells results in their expression on the fully differentiated tumor cells
* Examples include alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA).
- Non-oncofetal TATAs: Examples include carbohydrate antigens (CA 125, CA 19-9), prostate specific antigen and macroglobulin.
Table1. TATAs used as tumor markers for diagnosis of cancers.
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