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Cancer Antigen Tests
April 17, 2009
Index |
I. Introduction Cancer detection can be done in many ways: DNA probes, DNA sequencing, PCR, tissue biopsies, X-rays, MRIs, CT scans, antigen tests, screens for hormone changes, and physical exams. Each type of testing has its own advantages and disadvantages. We are focusing on antigen tests for cancer. A type of testing that is often misunderstood and misinterpreted. See companion CLS page: Molecular Genetic Tests Other useful lung cancer sites: |
b. What are Cancer Antigen Tests?
Cancer antigen tests are tests for proteins, carbohydrates, and hormones that serve as markers for cancer1. These markers can be found in different fluids and tissues of the body. Antigen tests are done with blood, urine, occasionally with other body fluids, and tissue samples. When a cancer antigen test comes back positive, the antigen was found. Although a positive result does not mean that the cancer is present, it does mean that there is a greater chance of having that cancer1. Cancer antigens are synonymous with tumor markers and biomarkers. Each term has been trendy at one time or another.
c. Why Test?
A common reason for testing is predictive2. Predictive testing is done based on common risk factors which include: age, gender, race, family history, or behavior based risk factors, such as smoking. The increase in risk or prevalence of cancer leads to many being screened for common risk related cancers. Increased levels of the cancer antigen would then warrant further testing to confirm a diagnosis.
Another common reason for cancer antigen testing is to monitor2. Those who have already been diagnosed are often tested to monitor the current cancer state. Cancer antigen tests are also used to monitor treatment. A change in antigen levels could indicate a change in the cancer state, such as remission or advancement of the cancer.
II. Testing Methods
Most cancer antigen testing is done by Chemiluminescence, Electochemiluminescence, or Immunoradioactive Assays. These tests all involve using antibodies that are labeled with a fluorescent tag or a radioactive tag3. The antibodies are specific for the antigen being tested, but can sometimes cross react with other antigens. When the test is positive, fluorescence or light will be seen from the fluorescent or radioactive tags on the antibodies.
III. Testing Requirements
Most of the tests have very strict requirements depending on which company that is used or which machines are used. The best place to find information about the testing requirements is from the manufacture or the machine’s manual and policy procedures. The National Academy of Clinical Biochemistry Laboratory Medicine has a paper that outlines good practices and procedures along with requirements for many of the tests.
IV. Research
a. Gender Based
Current testing/widely used cancer biomarkersMore accurate and sensitive testing is needed. Understanding levels of biomarkers and reasons for their change has shown that new or additional markers need to be incorporated in the detection and diagnosis of specific cancers and their progressive states. Early, specific, and accurate detection of cancer is key in the treatment and survival of the patient. Factors other than cancer have been associated with the rise or fall in levels of current biomarkers, leading to an increased movement to find new ways to approach cancer detection and monitoring. Prostate specific antigen (PSA)- Is urrently the most widely used cancer biomarker. PSA is elevated in persons with prostate cancer and its presence triggers additional investigation. A major problem that arises with testing of PSA deals with specificity. Many times an elevated level is indicative of other issues such as medication use, metabolism, and physical/sexual activity among others. Results obtained from PSA testing can lead to biopsy. This procedure is invasive and uncomfortable for many patients and often times results in no cancer being detected4,5. |
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CA-125- Protein CA 125 is currently used to detect ovarian cancer in women. It has been shown to be elevated in patients with ovarian cancer, but specificity is poor. The use of CA 125 results in 50% of true positive results. Factors such as hormone replacement therapy, endometriosis, early pregnancy, and pelvic inflamitory disease omong others have shown increased levels of CA 1256.
BRACA-1 BRACA-2- Currently the BRACA test is used to screen for mutations in these genes. A positive result is only used to determine hereditary risk of breast cancer and is not diagnostic. Mutation in these genes have been linked to breast and ovarian cancer development5,7.
Research and development
Sarcosine is a metabolite that is currently being used to determine prostate cancer progression. By using a combination of high-throughput liquid-and-gas-chromatography-based mass spectrometry with a urine sample sarcosine was notably increased in prostate cancer that was progressing to metastasis. This is biomarker will help determine the course of treatment best suited for the individual patient10.
b. Lung Cancer
| The cancer antigens used to detect lung cancer are not only used to detect lung cancer but may increase with many different cancers of the human body. In many cases the antigen CA 15-3 that helps indicate lung cancer may be also elevated breast, ovary, colon, and pancreas cancers. Antigen CA 27-29 may show an increase with colon, stomach, kidney, lung, liver, uterus, and pancreas cancers making the antigen test non-definitive and only a first step towards a diagnosis. CA 125 is another antigen that is elevated when a person has lung cancer but is better used for helping with the diagnosis of ovarian cancer.20 |
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Lung cancer research has targeted DNA vaccines that are in the early stages of testing. Most of the studies are being conducted on mouse models which are introducing DNA vaccines for the suppression of the HuD expressing tumor cells. Antibodies against the paraneoplastic encephalomyelitis antigen HUD have a clinical significant correlation towards the limitation of the spread of small-cell lung cancer (SCLC).21
In the recent past lung cancer has been decreased due to less tobacco use, better treatment, and better diagnostics. Lung cancer is still the second most common cancer and the most common cause of cancer related deaths in the U.S.22
Researchers have discovered a DNA target for vaccines against lung carcinoma known as survivin. Survivin is encoded by a telomeric gene on human chromosome 17 and is important in many cell functions. This 14.5 KDa protein plays a major role in inhibiting apoptosis with the suppression of the activating proteolytic cleavage of caspase 3. Survivin is almost undetectable in normal tissue but is highly expressed in most carcinomas thus, making survivin a wonderful target for DNA vaccine therapy. Yet with the great possibilities of the DNA vaccinesfor cancers there are limitations. First, there needs to be more studies to find antigens unique to each tumor type that are not found in normal tissue cells. Second, the poor immunogenicity of DNA vaccines do not induce strong T-cell responses against the tumor so high doses of DNA vaccines are needed.23
c. Gastrointestinal cancer|
Gastrointestinal Cancer Antigens Tumor M2-PK is a synonym for the dimeric form of the pyruvates kinase isoenzyme type M2 (PKM2).13 Immunochemical fecal occult blood test (FOBT) and sandwich ELISA’s (two monoclonal antibodies recognizing Tumor M2-PK specifically) can determine the quantification of Tumor M2-PK in stool and EDTA-plasma samples. Immunochemical fecal occult blood test and PKM2 along with EDTA can be used to screen fecal samples using the guaiac smear method (gFOBT), an over-the-counter (OTC) flushable reagent pad/tissue method, or immunochemical method (iFOBT or FIT) for colorectal tumors and other various cancers (in conjunction with CA19-9, CEA, and CA72-4 increases the sensitivity to detect various cancers). “Studies from various international working groups have revealed a significantly increased amount of Tumor M2-PK in EDTA-plasma samples of patients with renal, lung, breast, cervical and gastrointestinal tumors (esophagus, stomach, pancreas, colon, rectum), as well as melanoma (= skin cancer), which correlated with the tumor stage.”14 Tumor M2-PK with EDTA-plasma is an excellent indicator in the success (when levels remain low during therapy) or failure (when levels increase during therapy) with the choice of various treatments. |
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Pancreatic cancer
Cancer antigen 19-9 (also known as carbohydrate antigen) is the predominant cancer antigen of the GI tract that is frequently elevated in pancreatic cancer, along with CEA, CA242, and CA72-4. CA19-9 is also present in colon cancer, non-malignant Mirizzi’s syndrome (a rare cause of acquired jaundice. It is caused by chronic cholecystitis and large gallstones resulting in stenosis of the common bile duct.)15, bile ducts and liver diseases. Research showed that levels of CA19-9 are an effective tumor marker from secretions of the tumor, after operations and early detection of recurrences. The only draw back is that 5% of Caucasians do not have the Lewis a antigen and do not produce CA19-9, “they have a deficiency of a fucosyltrasferase enzyme that is needed to produce CA19-9 as well as the Lewis antigen.”16 For the 95% of Caucasians who have the Lewis a antigen, blood tests can show CA19-9 (carbohydrate antigen 19-9 or sialylated Lewis (a) antigen) for patients with colon cancer and pancreatic cancer. These are some testing methods for CA19-9: Immunoenzymatic Assay, Chemiluminescent Immunoassay (Siemens Centaur), and Electrochemiluminescent Immunoassay [link]. “ Liver function tests can show a combination of results indicative of bile duct obstruction (raised conjugated bilirubin, -glutamyl transpeptidase and alkaline phosphatase levels). However, it lacks sensitivity and specificity. When a cutoff above 37 U/mL is used, this marker has a sensitivity of 77% and specificity of 87% in discerning benign from malignant disease. CA 19-9 might be normal early in the course, and could be elevated due to benign causes of biliary obstruction.”17 Cancer Antigen 125 (a predominant CA for ovarian cancer) and CEA (a predominant CA for bowel cancer) may appear with CA19-9 in elevated levels of the GI tract for both malignant and benign cancer.
Colorectal cancer
Carcinoembryonic antigen (CEA) is a cell adhesion glycoprotein. High levels of CEA along with CA195 are found in patients with colorectal carcinoma, an article ‘Preoperative carbohydrate antigen 195 (CA195) and CEA serum levels as prognostic factors in patients with colorectal cancer’, e valuated 214 patients and found that the sensitivity was increased to 49% in patients with both CEA and CA195 present with primary colorectal cancer. Blood testing for elevated levels of CEA are indicative of residual or recurrent metastatic carcinoma. "CEA assay is nonspecific for identifying a primary site, but it does indicate the presence of malignancy. Smokers may have an elevated CEA without malignant disease; smoking may affect accuracy of CEA results. Normal range: < 2.5 ng/ml. Normal range may vary somewhat depending on the brand of assay used. Levels > 10 ng/ml suggest extensive disease and levels > 20 ng/ml suggest metastatic disease.”18 CEA can also be found in conjunction with other markers for gastric, pancreatic, lung, breast, and medullary thyroid carcinomas, as well as, an indicator of success or failure in regards to the recurrence of a tumor.
Gastric cancer
Cancer antigen 72-4 (CA 72-4) is the predominant cancer antigen, along with CEA and CA19-9, having a higher sensitivity rating for gastric cancer. As published in The American journal of surgery article, found that out of one hundred and thirty-three patients that were tested by drawing blood serum [link] samples before (16% CEA, 35% CA 19-9, and 20% CA 72-4), and after (44% CEA, 56% CA 19-9, and 51% CA 72-4) curative surgery, 75 patients (56%) had recurrence of the disease. “The combined assay of CEA, CA 19-9, and CA 72-4 may be useful for early diagnosis of recurrence of gastric cancer; however, only CA 72-4 positivity should be considered a specific predictor of tumor recurrence.”19
d. Blood/Bone cancer
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Cancers of the blood and bone: Hodgkin lymphoma Multiple myeloma Acute lymphocytic leukemia Chronic lymphocytic leukemia Acute myeloid leukemia Chronic myeloid leukemia Non-Hodgkin lymphoma Tests to diagnose and stage non-Hodgkin's lymphoma include:
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Treatment depends on how quickly the cancer spreads the stage of the cancer when you are first diagnosed, and symptoms. Chemotherapy is commonly used. A drug called rituximab (Rituxan) is often used to treat non-Hodgkin's lymphoma. Rituxan is a form of immunotherapy.Radioimmunotherapy may be used in some cases. This involves linking a radioactive substance with an antibody that helps the immune system fight infection, and injecting the substance into the body. In select cases, a stem cell transplant may be needed.
The Ki-67 protein was originally defined by the prototype monoclonal antibody Ki-67,which was generated by immunizing mice with nuclei of the Hodgkin lymphoma cell lineThe Ki-67 protein (also known as MKI67 ) is a cellular marker for proliferation.It is strictly associated with cell proliferation . The fraction of Ki-67-positive tumor cells (the Ki-67 labelling index) is often correlated with the clinical course of cancer .Immunochemistry, flow cytometry are the methods used.
LAP - Leukocyte alkaline phosphatase is a test that tells how much of a protein called alkaline phosphatase (ALP) you have inside your white blood cells .Blood levels of LAP can help in the diagnosis of chronic myelogenous leukemia (CML), leukemoid reaction
Higher-than-normal results may be due to- essential thrombocytosis , l eukemoid reaction . Lower-than-normal results may be due to, Aplastic anemia , Chronic granulocytic leukemia
CD33 - is found on granulocyte and macrophage precursors in the bone marrow, but is not on pluripotent stem cells. The protein is also expressed on, and is a useful marker for, peripheral monocytes. It is also useful for distinguishing myelogenous leukaemia cells from lymphoid or erythroid leukaemias. Flow cytometry and ELISA are the testing methods.
CD20 -Rituximab antibody is a therapeutic reagent directed against the CD20 cell surface antigen.
Rituximab is a therapeutic reagent directed against the human CD20 cell surface antigen. This antibody has been used to detect Rituximab bound to the surface of the Raji B cell line, however detection of Rituximab bound 'in vivo' to B CLL cells has not been demonstrated. It is possible that complement deposition on Rituximab opsonised cells inhibits binding of the anti-Rituximab antibody to cell bound Rituximab. Flow cytometry, ELISA are the testing methods
CD52 -Human CD52 is a glycosylphosphatidylinositol (GPI) anchored antigen expressed in a number of different tissues. CD52 is expressed at high density by lymphocytes, monocytes, eosinophils, thymocytes and macrophages. It is expressed by most lymphoid derived malignancies, although expression on myeloma cells is variable. Flow cytometry method is used for used for Alemtuzumab sensitivity test
CBFB/MYH11 FUSION PROTEIN -The protein encoded by this gene is the beta subunit of a heterodimeric core binding transcription factor belonging to the PEBP2/CBF transcription factor family which master regulates a host of genes specific to hematopoiesis and osteogenesis. The beta subunit is a non-DNA binding regulatory subunit; it allosterically enhances DNA binding by alpha subunit as the complex binds to the core site of various enhancers and promoters, including murine leukemia virus, polyomavirus enhancer, T cell receptor enhancers and GM CSF promoters. Alternative splicing generates two mRNA variants, each encoding a distinct carboxyl terminus. In some cases, a pericentric inversion of chromosome 16 [inv(16)(p13q22)] produces a chimeric transcript consisting of the N terminus of core-binding factor beta in a fusion with the C terminal portion of the smooth muscle myosin heavy chain 11. This chromosomal rearrangement is associated with acute myeloid leukemia of the M4Eo subtype.ELISA method is used for CBFB/MYH11 FUSION PROTEIN test
Resources/References: Blood/Bone Cancer
- Hoffman R, Benz Jr. EJ, Shattil SJ, et al., eds. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, Pa: Churchill Livingston; 2005:803-804.
- Goldman L, Ausiello D. Cecil Textbook of Medicine. 22nd ed. Philadelphia, Pa: WB Saunders; 2004:987-988.
- http://www.drugs.com/enc/leukocyte-alkaline-phosphatase-lap.html
V. Future
The future for serological cancer antigen testing is limited without making the tests more specific and sensitive to the cancer antigens. With increased specificity and sensitivity antigen tests may become more useful for practitioners and clinical laboratories. If the tests become more accurate, moving the tests into ELISA or EIA waived testing would be both quicker and more cost effective than the current procedures. Until the tests are improved, their current and future uses are limited.
The future for cancer antigen testing in general is still wide open. New tests using RT-qPCR looking for the turned on gene is one direction. Also the study of proteomics is another possible way to go.
VI. Resources/References:
1. Handy, Beverly. The Clinical Utility of Tumor Markers. Labmedicine February 2009 Vol: 40 Number 2. http://labmed.ascpjournals.org/ content/40/2/99.full#F1.
2. Tietz. Fundamentals of Clinical Chemistry. Saunders 6th Edition 2008. Pgs 337-362.
3. Tietz. Fundamentals of Clinical Chemistry. Saunders 6th Edition 2008. Pgs 63-83.
4. Prostate-specific antigen testing accuracy in community practice
Richard M Hoffman, 1,2 Frank D Gilliland,3 Meg Adams-Cameron,2 William C Hunt,2 and Charles R Key2. BMC Fam Pract. 2002; 3: 19.
Published online 2002 October 24. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=137591
5. National Cancer Institute http://www.cancer.gov/cancertopics/pdq/screening/ovarian/HealthProfessional/page3
6. Johns Hopkins Pathology: Ovarian cancer http://ovariancancer.jhmi.edu/ca125qa.cfm#accuracy
7. Lab Tests Online http://www.labtestsonline.org/understanding/analytes/brca/faq.html
8. Identification of biomarkers for ovarian cancer using strong anion-exchange ProteinChips: Potential use in diagnosis and prognosis. Katherine R. Kozak et. al PNAS October 14, 2003 vol. 100 no. 21 12343-12348 http://www.pnas.org/content/100/21/12343.full
9. PCA3: A Genetic Marker of Prostate CancerPCRI Insights August, 2006 vol. 9, no. 3
By Alejandra B.Torres and Leonard S.Marks, MD* Urological Sciences Research Foundation (USRF) *also: David Geffen School of Medicine at UCLA,
Department of Urology www.prostate-cancer.org/.../Torres_PCA3.html
10. Metabolomic profiles delineate potential role for sarcosine in prostate cancer progression. Sreekumar A , Poisson LM , Rajendiran TM , Khan AP , Cao Q , Yu J , Laxman B , Mehra R , Lonigro RJ , Li Y , Nyati MK , Ahsan A , Kalyana-Sundaram S , Han B , Cao X , Byun J , Omenn GS , Ghosh D , Pennathur S , Alexander DC , Berger A , Shuster JR , Wei JT , Varambally S , Beecher C , Chinnaiyan AM .
The Michigan Center for Translational Pathology, Ann Arbor, USA.
11. Tiny backpacks for cellsPolymer patches could ferry drugs, assist in cancer diagnosisAnne Trafton, News Office
November 6, 2008 http://web.mit.edu/newsoffice/2008/cellbackpack-1106.html
12. Nanotubes sniff out cancer agents in living cellsChemical engineers use carbon nanotubes to monitor chemotherapy, detect toxins at the single-molecule levelAnne Trafton, News Office
December 14, 2008 http://web.mit.edu/newsoffice/2008/nano-sensor-1214.html
13-14. http://en.wikipedia.org/wiki/Tumor_M2-PK
15. Robertson A, Davidson B (2007). "Mirizzi syndrome complicating an anomalous biliary tract: a novel cause of a hugely elevated CA19-9". European journal of gastroenterology & hepatology 19 (2): 167–9. doi : 10.1097/MEG.0b013e3280122879 http://en.wikipedia.org/wiki/CA19-9#cite_note-Asco-3
16. Locker G, Hamilton S, Harris J, Jessup J, Kemeny N, Macdonald J, Somerfield M, Hayes D, Bast R (2006). “ ASCO 2006 update of recommendations for the use of tumor markers in gastrointestinal cancer ". J. Clin. Oncol. 24 (33): 5313–27. doi : 10.1200/JCO.2006.08.2644 . PMID 17060676 http://jco.ascopubs.org/cgi/content/full/24/33/5313 . http://en.wikipedia.org/wiki/CA19-9#cite_note-Asco-3
17. Frank J. Domino M.D.etc. (2007). 5 minutes clinical suite version 3. Philadelphia, PA: Lippincott Williams & Wilkins. http://en.wikipedia.org/wiki/Pancreatic_cancer#cite_note-11
18. Andicoechea A , Vizoso F , Alexandre E , Cuesta E , Cruz Díez M , Miera L , García-Muñiz JL , Martínez E , Ruibal A . “ Preoperative carbohydrate antigen 195 (CA195) and CEA serum levels as prognostic factors in patients with colorectal cancer.” 1998 Jul-Sep;13(3):158-64. http://www.ncbi.nlm.nih.gov/pubmed/10079391 http://training.seer.cancer.gov/module_diagnostic/unit03_tumor_markers.html
19. MARRELLI Daniele (1) ; PINTO Enrico (1) ; DE STEFANO Alfonso (1) ; FARNETANI Maurizio (2) ; GAROSI Lorenzo (3) ; ROVIELLO Franco (1) ; Clinical utility of CEA, CA 19-9, and CA 72-4 in the follow-up of patients with resectable gastric cancer; The American journal of surgery ISSN 0002-9610 CODEN AJSUAB; Published Elsevier, New York, NY, ETATS-UNIS (1905) (Revue), 2001, vol. 181, no1, pp. 16-19 (10 ref.) http://cat.inist.fr/?aModele=afficheN&cpsidt=940705
20. Tumor markers. Feb .9 2009 5:56 pm. http://www.healthatoz.com/healthatoz/Atoz/common
21. Ohwada, A. et al. DNA Vaccination against HuD Antigen Elicits Antitumor Activity in a Small-Cell Lung Cancer Murine Model. 11 Feb. 2009. 7:54 pm. http://ajrcmb.atsjournals.org/cgi/content/full/21/1/37
22. http://www.alimta.com/pat/aboutnonsmallcell.jsp
23. Viswanathan, Kartik. The use of DNA vaccines in the treatment of prostate and lung carcinoma as an alternative to traditional chemotherapy. MMG 445 Basic Biotechnology e Journal. 2005.1:1.Feb.11 2009. http://www.msu.edu/course/mmg/445