Oncofetal Tumor Antigens

Oncofetal tumor antigens, as the name implies, are found not only on cancerous cells but also on normal fetal cells. These antigens appear early in embryonic development, before the immune system acquires immunocompetence; if these antigens appear later on cancer cells, they are recognized as nonself and induce an immunologic response. Two well-studied onco-fetal antigens are alpha-fetoprotein (AFP) and carcinoem-bryonic antigen (CEA).

Although the serum concentration of AFP drops from milligram levels in fetal serum to nanogram levels in normal adult serum, elevated AFP levels are found in a majority of patients with liver cancer (Table 22-3). CEA is a membrane glycoprotein found on gastrointestinal and liver cells of 2- to 6-month-old fetuses. Approximately 90% of patients with advanced colorectal cancer and 50% of patients with early colorectal cancer have increased levels of CEA in their serum; some patients with other types of cancer also exhibit increased CEA levels. However, because AFP and CEA can be found in trace amounts in some normal adults and in some noncancerous disease states, the presence of these oncofetal antigens is not diagnostic of

Elevation of Alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) in serum of patients with various diseases

Elevation of Alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) in serum of patients with various diseases

No. of % of patients patients with high AFP Disease tested or CEA levels*

Alcoholic cirrhosis NA 0

Hepatitis NA 1

Hepatocellular carcinoma NA 69

Other carcinoma NA 0 CEA > 10 ng/ml

Cancerous

Breast carcinoma 125 14

Colorectal carcinoma 544 35

Gastric carcinoma 79 19

Noncarcinoma carcinoma 228 2

Pancreatic carcinoma 55 35

Pulmonary carcinoma 181 26 Noncancerous

Alcoholic cirrhosis 120 2

Cholecystitis 39 1

Nonmalignant disease 115 0

Pulmonary emphysema 49 4

Rectal polyps 90 1

Ulcerative colitis 146 5

*Altough trace amounts of both AFP and CEA can be found in some healthy adults, none would have levels greater than those indicated in the table.

tumors but rather serves to monitor tumor growth. If, for example, a patient has had surgery to remove a colorectal carcinoma, CEA levels are monitored after surgery. An increase in the CEA level is an indication of resumed tumor growth.

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