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Are substances usually proteins, that are produced by the body in response to cancer growth or by the cancer tissue itself and certain benign (noncancerous) conditions Detected in higher than normal amounts in the blood, urine, or body tissues Some tumor markers are specific for one type of cancer, while others are seen in several cancer types Measurements can be useful – when used along with x-rays, or other tests in the detection and diagnosis of some types of cancer Characteristics of an “ideal” tumor marker : Characteristics of an “ideal” tumor marker Highly specific: detectable in only one tumor type Highly sensitive: non-detectable in physiological or benign disease states Long lead-time: sufficient time for alteration of natural course of disease Levels correlate with tumor burden: prognostic & predictive utility of tumor marker Short half-life: frequent serial monitoring of marker levels after 5-6 half-lives Simple and cheap test: applicability as screening test Easily obtainable specimens: acceptability by target population IN REALITY AN IDEAL TUMOR MARKER DOES NOT EXIST Methods of detection of tumor markers : Methods of detection of tumor markers Slide 6: ELISA-…-ENZYME LINKED IMMUNOSORBENT ASSAY Slide 7: ELISA, or enzyme-linked immunosorbent assay, are quantitative immunological procedures in which the Ag- Ab reaction is monitored by enzyme measurements. (or) An enzyme linked immunosorbent assay (ELISA) is a test performed in an immunology laboratory to determine levels of protein in a biological sample Why known as ......? Enzyme Linked Immunosorbent Assay : Why known as ......? Enzyme Linked Immunosorbent Assay Antigen of interest is absorbed on to plastic surface (‘sorbent’). 2. Antigen is recognised by specific antibody (‘immuno’). 3. This antibody is recognised by second antibody (‘immuno’) which has enzyme attached (‘enzyme-linked’). 4. Substrate reacts with enzyme to produce product, usually coloured. BASIC PRINCIPLE OF ELISA : BASIC PRINCIPLE OF ELISA Use an enzyme to detect the binding of antigen (Ag) antibody (Ab). The enzyme converts a colorless substrate (chromogen) to a colored product, indicating the presence of Ag : Ab binding. An ELISA can be used to detect either the presence of Antigens or antibodies in a sample depending how the test is designed. Slide 10: Substrate Different antigens in sample ELISA Qualitative/Quantitative : ELISA Qualitative/Quantitative Qualitative determines antigen or antibody is present or absent Quantitative determines the quantity of the antibody Titer The highest dilution of the specimen usually serum which gives a positive reaction in the test Equipment for performing the ELISA test : Equipment for performing the ELISA test ELISA Plate 96 Wells : ELISA Plate 96 Wells Sandwich ELISA : Sandwich ELISA Sandwich ELISA is used to determine the antigen concentration in unknown samples The sandwich ELISA measures the amount of antigen between two layers of antibodies. The antigens to be measured must contain at least two antigenic sites, capable of binding to antibody, since at least two antibodies act in the sandwich. Slide 16: Cancer detection by ELISA CLINICAL APPLICATIONS : CLINICAL APPLICATIONS SCREENING DIAGNOSIS PROGNOSIS: RECURRENCE, METASTASIS AND SURVIVAL MONITORING TREATMENT RESPONSE Recommendations for ordering tumor marker tests : Recommendations for ordering tumor marker tests Never rely on the result of a single test When ordering serial testing, be certain to order every test from the same laboratory using the same assay kit Be certain that the tumor marker selected for monitoring recurrence was elevated in the patient prior to surgery Consider the half-life of the tumor marker when interpreting the test result Consider how the tumor marker is removed from or metabolized in the blood circulation Consider ordering multiple markers to improve both the sensitivity and the specificity for diagnosis Be aware of the presence of ectopic tumor markers Heterophile antibody CARCINO-EMBRYONIC ANTIGEN (CEA) : CARCINO-EMBRYONIC ANTIGEN (CEA) A complex glycoprotein with a MW of approximately 180,000 daltons First discovered in patients with adenocarcinoma of the colon in 1965 Metabolized primarily by the liver with a circulating half-life ranging from 1 to 8 days Hepatic diseases, including extrahepatic biliary obstruction, intrahepatic cholestasis and hepatocellular disease, may impede clearance rate Normally, it is present in the fetal intestine, pancreas and liver during the first 2 trimesters of gestation Normal colonic mucosa and pleural and lactating mammary tissue bind to anti-CEA antiserum; however, the quantity of CEA or CEA-like molecules expressed in these tissues is much less than that observed in malignant tumors Normal range is from 0 to 2.5 to 3.0 ng/ml as determined by radioimmunoassays and increase serum concentrations Slide 21: Benign conditions that cause elevated CEA Cigarette smoking Bronchitis Emphysema Gastritis Gastric ulcer Hepatic disease Pancreatitis Polyps of colon& rectum Diverticulitis Crohn’s disease BPH Renal disease ALPHA FETO-PROTEIN (AFP) : ALPHA FETO-PROTEIN (AFP) An oncofetal protein that was first discovered in 1963 in the serum of mice with hepatoma Normal fetal protein synthesized by the liver, yolk sac, and GIT that shares sequence homology with albumin A major component of fetal plasma, reaching a peak concentration of 3mg/ml at 12 weeks of gestation -- following birth, it clears rapidly from the circulation, having a half-life of 3.5 days Concentration in adult serum <20ng/ml Slide 23: Malignant conditions causing elevation of AFP aside from hepatoma Teratocarcinoma of the testis and embryonal Ca (70%) Carcinoma of the pancreas (23%) Carcinoma of the stomach (18%) Carcinoma of the lung (7%) Carcinoma of the colon (5%) *** In patients with hepatoma, the incidence of elevation of levels of AFP correlates with tumor burden HUMAN CHORIONIC GONADOTROPIN (HCG) : HUMAN CHORIONIC GONADOTROPIN (HCG) A glycoprotein hormone with a MW of 45,000 daltons Composed of 2 polypeptide chain – alpha and beta Circulating half-life is 12 to 20 hours Normally secreted by placental tissue with highest circulating levels occurring at 60 days of gestation Significant elevation occurs during pregnancy and in patients with trophoblastic neoplasms or nonseminomatous germ cell tumors It maybe secreted in small amounts by the testis, pituitary gland and GIT Maybe elevated in some benign conditions – peptic ulcer disease, inflammatory intestinal disease and cirrhosis In patients with trophoblastic disease, levels of HCG correlate with tumor burden, prognosis of patient and response to therapy CA 125 : CA 125 An antigen present on 80% of non-mucinous ovarian carcinomas Defined by a monoclonal antibody (OC125) that was generated by immunizing laboratory mice with a cell line established from human ovarian carcinoma Elevated in other cancers – endometrial, pancreatic, lung, breast, and colon Elevated in benign conditions – menstruation, pregnancy, endometriosis CA 19-9 : CA 19-9 A monoclonal antibody generated against a colon carcinoma cell line to detect a monosialoganglioside found in patients with gastrointestinal adenocarcinoma Elevated in gastric cancer (21-42%), colon cancer (20-40%), pancreatic cancer (71-93%) PROSTATE SPECIFIC ANTIGEN (PSA) : PROSTATE SPECIFIC ANTIGEN (PSA) Found in normal prostatic epithelium and secretions but not in other tissues It is a glycoprotein whose function may be to lyse the seminal clot Highly sensitive for the presence of prostatic cancer Elevation correlated with stage and tumor volume Predictive of recurrence and response to treatment Has prognostic value in patients with very high values prior to surgery are likely to relapse Present in low concentrations in the blood of adult males It is produced by both normal and abnormal prostate cells Benign elevations – prostatitis and BPH Conditions associated with elevated tumor marker levels : Conditions associated with elevated tumor marker levels LESS COMMON TUMOR MARKERS : LESS COMMON TUMOR MARKERS LESS COMMON TUMOR MARKERS : LESS COMMON TUMOR MARKERS LESS COMMON TUMOR MARKERS : LESS COMMON TUMOR MARKERS ECTOPIC TUMOR MARKERS : ECTOPIC TUMOR MARKERS THANK YOU : THANK YOU You do not have the permission to view this presentation. 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