Clinical Chemistry

1. Clinical Chemistry Metabolic effects of tumor markers Mohammed Al-Zubaidi, PhD

2. Definition • Malignant disease is one of the world’s major killers. Hence it is important to know the biochemical diagnosis and monitoring in such patients. • Neoplastic cells of differentiated tissues synthesize compounds (normally thought it does not come from that tissue) and release them to body fluids; these compounds Either • Alter metabolism produce clinical effects Or • Biologically inactive, detectable in body fluids (sometime used as tumor markers)

3. Catecholamines • The sympathetic nervous tissue comprising the adrenal medulla, composed of the chromaffin cells, and sympathetic ganglia, composed of the nerve cells, both of which can synthesize active catecholamines. • Adrenaline is almost exclusively produced by the adrenal medulla, whereas noradrenaline is predominantly formed at sympathetic nerve endings.

4. Catecholamines • Metabolism of catecholamines Tyrosine Tyrosine hydroxylase DOPA decarboxylase Dihydroxyphenylalanine (DOPA) Dihydroxyphenylethylamine (DOPAMINE) Precursor Dopamine beta hydroxylase Catechol-O-methyl transferase Phenethanolamine N-methyltransferase Metadrenaline Adrenaline Noradrenaline Catechol-O-methyl transferase Normetadrenaline 4-hydroxy-3-methoxymandelic acid (HMMA)

5. Catecholamines • Action of catecholamines • Adrenaline : causes dilation of blood vessels in muscles with effects on blood pressure and pulse rate, hyperglycemia due to glycogenolysis. • Noradrenaline : causes vasoconstriction with hypertension and pallor.

6. Catecholamine-secreting tumours • Phaeochromocytomas • Occur in chromaffin tissue. • Associated with MEN syndrome, neurofibromatosis and Von Hippel-Lindau disease, although many are isolated tumours. • Symptoms and signs related to very high concentrations of catecholamines.

7. Diagnosis of phaechromocytomas • Daily measurement of urinary catecholamines (adrenaline, noradrenaline and dopamine) or HMMA. Extra-adrenal tumours may only secret dopamine. • Urine metanephrines measurement are preferable because they are more sensitive than catecholamines and raised in some phaechromocytomas with normal catecholamines concentration.

8. Diagnosis of phaechromocytomas • Raised plasma metanephrine concentration is used ( nearly 100 % sensitivity) for the diagnosis of phaeochromocytoma. However, its concentration may also be raised in renal failure. • The clonidine or pentolinium suppression tests also used in the investigation if urinary catecholamines are positive and imaging studies are negative. Urinary and plasma catecholamines concentration should decrease after administration of the suppressing agents in normal individuals.

9. Neuroblastomas • Neuroblastomas are very malignant tumours of the sympathetic nervous tissue. About 40% occur in the adrenal medulla and 60 % are extra-adrenal. • Plasma catecholamine concentration is higher than those in patients with phaeochromacytomas. • Some neuroblastomas secrete dopamine and homovanillic acid (HVA) and their concentration are raised in the urine.

10. The carcinoid syndrome • Normal metabolism of 5-hydroxytryptamine: Argentaffin cells normally found in tissues derived from the embryonic gut. They synthesize 5-hydroxytryptamine (5-HT; serotonin) from tryptophan, the intermediate product being 5-hydroxytryptophan (5-HTP). 5-HTP inactivated by deamination and oxidation by monoamine oxidase to 5-hydroxyindole acetic acid (5-HIAA).

11. The carcinoid syndrome • Causes of the carcinoid syndrome: Usually associated with high concentration of plasma 5-HT (serotonin). The products of intestinal tumours are inactivated in the liver but those from other sites, such as the bronchus, are released directly into the systemic circulation in an active form and therefore cause symptoms.

12. The carcinoid syndrome • The symptoms and signs of the carcinoid syndrome include: • Diarrhoea • Flushing • Bronchospasm and right-sided fibrotic lesions of the heart. • Diagnosis of the carcinoid syndrome: • Urine test: 5-HIAA is usually very high in the carcinoid syndrome.

13. Multiple endocrine neoplasia • Two or more endocrine glands in the rare syndromes of MEN (pluriglandular syndrome) secret inappropriately high amounts of hormones, from adenomas. • Two main groups of syndromes: • MEN 1 : involve two or more of the following endocrine tissues: • Parathyroid gland • Pancreatic islet cells

14. Multiple endocrine neoplasia • Anterior pituitary gland • Adrenal cortex • MEN 2 includes: • Medullary carcinoma of the thyroid gland • Phaeochromocytoma • Adenoma or carcinoma of the parathyroid gland

15. Multiple endocrine neoplasia • MEN 2 can be subdivided into 2A and 2B • Both MEN 1 and MEN 2 are usually inherited; MEN1 is due to a mutation in the MENIN gene, a tumour-suppressor gene; MEN 2 is the result of proto-oncogene mutation known as RET.

16. Ectopic hormone production • Mechanism of production: • Malignant cells may produce ectopic hormones if they partly revert to their early embryonic, pluripotential state. • There are two possible hypotheses, both of them include derepression • Of part of the genome of the tissue cell that codes for the peptides, which are then synthesized in excess. • Of specialized neuroendocrine cells, which are scattered through many tissues.

17. Ectopic hormone production • Hormonal syndromes: Hormones produced at ectopic sites are not under normal feedback control and secretion continues under conditions in which it should be suppressed; such secretion is therefore inappropriate. • Hyponatraemia due to antidiuretic hormone secretion The syndrome of inappropriate ADH secretion has been reported in a wide variety of tumours,although ectopic antidiuretic hormone (ADH) production is commonly associated with the relatively rare small cell carcinoma of the bronchus.

18. Ectopic hormone production • Hypokalaemia due to adrenocorticotropic hormone secretion Ectopic ACTH secretion stimulates the secretion of all adrenocortical hormones except aldosterone. The condition is usually associated with a small cell carcinoma of the bronchus but has occasionally been described in association with a variety of other malignant lesions, especially pulmonary carcinoid tumours.

19. Ectopic hormone production • Hypercalcaemia due to secretion of parathyroid hormone-related protein Hypercalcaemia due to the secretion of parathyroid hormone-related protein (PTHRP) is one of the most common of these syndromes. It is associated with many types of malignant disease, including squamous cell carcinoma of the bronchus.

20. Ectopic hormone production • Polycythaemia due to erythropoietin secretion Polycythaemia due to the secretion of erythropoietin or an erythropoietin-like molecule is a well-recognized complication of renal carcinoma. The syndrome has been reported in association with hepatocellular carcinoma.

21. Ectopic hormone production • Hypoglycaemia due to insulin or an insulin-like growth factor Although rare, hypoglycaemia due to insulin or an insulin-like growth factor (IGF) has been reported in association with various tumours; e.g. very large retroperitoneal or thoracic mesenchymaltumours resembling fibrosarcomas.

22. Ectopic hormone production • Gynaecomastia due to chorionic gonadotrophinsecretion This has been reported in association with various tumours, including carcinoma of the bronchus, breast and liver, due to raised circulating concentrations of chorionic gonadotrophin. • Galactorrhoea Galactorrhoea may also occur due to the ectopic secretion of prolactin or prolactin-like molecules.

23. Ectopic hormone production • Hyperthyroidism due to thyroid-stimulating hormone secretion Some tumours of trophoblastic cells, such as choriocarcinoma, hydatidiform mole and testicular teratoma, have been shown to secrete a thyroid-stimulating hormone-like substance similar to human chorionic gonadotrophin (hCG).

24. Tumour markers For the measurement of a tumour marker to be clinically useful, the result should clearly separate those patients with from those without a tumour. Therefore (although in practice this is not the case), a tumour marker should ideally be: • 100 percent sensitive: levels should be raised if the tumouris present • 100 percent specific: levels should not be raised if the tumouris not present.

25. Tumour markers Tumour markers may be used for the following: • To screen for disease • To diagnose of a tumour • To determine the prognosis • To monitor the response to treatment • To identify the recurrence of a tumour

26. Examples of tumour markers • Prostate-specific antigen (PSA) Prostate-specific antigen (PSA) is a marker for prostatic carcinoma, a common male tumour; it has a plasma half-life of about 3 days. One of its probable functions is to help liquidize semen. Its level is raised in benign prostatic hyperplasia (BPH) and prostatic carcinoma but also in prostate infection, for example prostatitis, and after rectal examination.

27. Examples of tumour markers Levels of PSA increase with age, which is mainly due to the increase in the volume of the prostate that occurs. Therefore age-adjusted reference ranges should be used. One diagnostic limitation is that the values of PSA overlap in BPH and prostatic carcinoma. After a radical prostatectomy, plasma PSA levels become undetectable at 2–3 weeks.

28. Examples of tumour markers The PSA is bound in the plasma to either a1-antichymotrypsin or a2-macroglobulin. The concentration of bound or complexed PSA is higher in prostate carcinoma, whereas that of free PSA is higher in BPH. The ratio of free to total PSA is lower in men with prostatic carcinoma.

29. Examples of tumour markers Plasma PSA concentrations greater than 10 μg/L are strongly suggestive of carcinoma, although carcinoma may be present even if values fall within the reference range. A PSA above 20 μg/L is suggestive of prostatic carcinoma that has spread beyond the prostate gland.

30. Examples of tumour markers • Carcinoembryonicantigen Carcinoembryonic antigen may be produced by some malignant tumours, especially colorectal carcinomas. If the initial plasma concentration is raised, serial plasma CEA estimations may sometimes help to monitor the effectiveness of, or recurrence after, treatment. Plasma concentrations correlate poorly with tumourmass, but a very high concentration usually indicates a bad prognosis.

31. Examples of tumour markers • Alfa-Fetoprotein Alfa-Fetoprotein (AFP) is an oncofetal protein, the synthesis of which is suppressed as the fetus matures. Concentrations may be very high in the plasma of patients with certain tumours such as hepatocellular carcinoma (primary hepatomas and hepatoblastomas) and teratoma.

32. Examples of tumour markers • Human chorionic gonadotrophin Human chorionic gonadotrophin (hCG) is normally produced by the placenta, but also by trophoblastic cells of gonadal and extragonadal germ cell tumours. Ectopic secretion has been observed in some bronchial carcinomas. The measurement of hCG can be used to screen for choriocarcinoma in women who have had a hydatidiformmole. Plasma concentrations may be raised in patients with malignancy of the gonads such as seminomas

33. Examples of tumour markers • Carbohydrate antigens Carbohydrate antigens (CAs) are a group of tumourmarkers, raised plasma concentrations of which may be used to monitor the response to treatment and the recurrence of certain tumours.

34. Examples of tumour markers • CA-125concentration may be raised in the plasma of patients with ovarian carcinoma. It can also be raised in pregnancy, fibroids, liver and pancreatic disease, endometriosis and pelvic inflammatory disease. Additionally, it can also be raised in other malignant diseases such as lung, breast or colon carcinoma.

35. Examples of tumour markers • CA-15-3concentration may be raised in the plasma of some patients with advanced breast carcinoma, although it can also be raised in cirrhosis, and with ovarian cysts. • CA-19-9concentration may be raised in the plasma of patients with pancreatic or colorectal carcinoma and those with obstructive liver disease.

36. Examples of tumour markers None of the CA tumour markers fulfils the criteria of an ideal marker, as none is sufficiently sensitive or specific to be used to screen for early disease. Furthermore, some advanced tumours dedifferentiate and fail to produce a marker despite continued growth and spread. These tumour markers may, however, be useful in the monitoring of patients with tumours and in the assessment of therapy.

37. Other tumour markers • Serum paraprotein and urinary Bence Jones protein • Plasma lactate dehydrogenase (LDH): the activity can be raised in certain haematological tumours such as lymphomas. • Placental alkaline phosphatase: true placental alkaline phosphatase and placental-like isoenzyme levels are raised in seminoma and dysgerminoma. Levels are not usually raised in teratomata.

38. Other tumour markers In conjunction with AFP and hCG, it is useful in the diagnosis and monitoring of extragonadal and gonadal germ cell tumours. However, plasma levels are also elevated in smokers. • Thyroglobulin: this high-molecular-weight protein is produced in the follicular cells of the thyroid. Its concentration is raised in follicular or papillary carcinoma of the thyroid. Spuriously low levels may be found in the presence of thyroglobulin antibodies, which interfere with the assay.

39. Other tumour markers • Neuronal-specific enolase: plasma levels may be raised in small cell lung carcinoma and neuroblastoma; it is derived from neurodectal tissue. • Inhibin: this is secreted by the granulosa cells of the ovary and by the Sertoli cells of the testis. It can be used as a plasma tumour marker of ovarian granulosa cell tumours and testicular Sertoli cell tumours.

40. Other tumour markers • Squamous cell carcinoma antigen: this is a plasma tumour marker of potential use in squamous cell carcinoma of the cervix. • Chromogranin A is released from neuroendocrine cells such as in phaeochromocytoma and carcinoid tumours. • Protein S100B is a calcium-binding protein. It is expressed in brain astrocytes and glial cells and also in melanocytes and may be useful in monitoring therapy in malignant melanoma.

41. Other tumour markers • Human epididymis protein (HE4) is being used as a tumour marker for ovarian carcinoma.