Cancer Biochemistry

Tumour marker

• Any substance that can be related to the presence or progress of a tumour.

• Hormones: human gonadotrophin (HCG) secreted by choriocarcinoma

• Enzymes: prostate specific antigen (PSA) in prostate carcinoma

• Tumour antigens: carcinoembryonic antigen (CEA) in colorectal carcinoma

The use of tumour markers

Monitoring treatment• Surgery, chemotherapy, radiotherapy

Assessing follow-up• To monitor the marker long after the levels have

appeared to stabilized

Diagnosis• Detection in blood, biopsy

Prognosis• To be of value in prognosis, the

concentration of the tumour marker in plasma should be correlate with tumour mass.

• Eg: HCG correlates well with the tumour mass in choriocarcinoma

• HCG and AFP correlate with the tumour mass in testicular teratoma

• Paraproteins correlate with the tumour mass in multiple myeloma.

Screening for the presence of disease• Specific high-risk population• Eg: hormone calcitonin, which is

increased in all patients with medullary carcinoma of thyroid, may be used to screen close relatives.

The important tumour markers:

• Alkaline phosphatase (ALP)• Lactate dehydrogenase (LDH)• Prostatic acid phosphatase (PAP)• Prostate specific antigen (PSA)• Human chorionic gonadotropin (HCG)• Alpha-fetoprotein (AFP)• Carcino-embryonic antigen (CEA)

• CA-15 : marker for breast carcinomas• CA-125 : marker for ovarian and

endometrial carcinoma• Calcitonin (secreted by cells of thyroid

gland. Increased in medullary tumour of thyroid gland)

*carcinoma: cancer arising from epithelial tissue.

sarcoma: cancer from connective tissue

• ALP- Primary or secondary liver cancer- Secondary bone cancer- Lung cancer- Cancer of GIT and ovary- Hodgkin’s disease

• PAP-malignant conditions: cancer of prostate,

multiple myeloma, osteogenic sarcoma.-benign conditions: prostatic hypertrophy

(BPH) or enlarged prostate, osteoporosis and hyperparathyroidism.

• PSA-superior marker for prostatic cancer.

• Human Chorionic Gonadotropin (HCG)-placental hormon. Synthesized by

syncytiotrophoblastic cells of placental villi.-choriocarcinoma. About 50% of cases of

choriocarcinoma follow hydatidiform mole pregnancy and HCG is used to screen these women.

-ideal tumour marker for diagnosing and monitoring gestational trophoblastic tumours and germ cell tumours of testes and ovary.

• Alpha-Feto Protein (AFP)-like CEA, AFP is another oncofetal antigen.

AFT is synthesized in liver, yolk sac and GI tract in fetal life and released into serum of fetus.

-AFP is the more specific and ideal tumour marker for primary carcinoma of the liver (hepatocellular carcinoma)

-serum AFP and HCG are best available tumour markers for germ cell type of tumours.

• Cancer antigen 125 (CA-125)-used for screening and diagnosis of ovarian

carcinoma-not specific for ovarian carcinoma

• CA 15-3 & CA-27.29- useful as tumour marker in breast carcinoma

• CA 19-9-useful as tumour marker in pancreatic cancer

and biliary tract cancers.

Hormones

• produced by many tumors• natural product or represent abnormal

synthesis• eg: insulin by islet cell tumor, calcitonin by

medullary thyroid carcinoma, catecholamines by pheochromocytoma

• ectopic hormones - ACTH and ADH by lung cancer