Dr.R.Venkateswari Assistant Professor Department of Medical Biochemistry University of Madras, Taramani Campus, Chennai

Transcription

1 Dr.R.Venkateswari Assistant Professor Department of Medical Biochemistry University of Madras, Taramani Campus, Chennai

2 KNOWING CANCER Cancer is a disease in which body cells grow out of control (tumor). Cancer can invade nearby tissue (angiogenesis) and spread to other parts of the body (metastasis). Cancer results from a series of molecular events that fundamentally alter the normal properties of cells. In cancer cells the normal control systems that prevent cell overgrowth and the invasion of other tissues are disabled. These altered cells divide and grow in the presence of signals that normally inhibit cell growth; therefore, they no longer require special signals to induce cell growth and division. As these cells grow they develop new characteristics, including changes in cell structure, decreased cell adhesion, and production of new enzymes. 2

3 Causes of cancer Cancer cells are abnormal cells in which the processes regulating normal cell division are disrupted. That is, cancer develops from changes that cause normal cells to acquire abnormal functions. These changes are often the result of inherited mutations or are induced by environmental factors such as UV light, X-rays, chemicals, tobacco products, and viruses. All evidence suggests that most cancers are not the result of one single event or factor. Rather, around four to seven events are usually required for a normal cell to evolve through a series of premalignant stages into an invasive cancer. 3

4 HALLMARKS OF CANCER 4

5 The abnormalities in cancer cells usually result from mutations in protein-encoding genes that regulate cell division. Over time more genes become mutated. This is often because the genes that make the proteins that normally repair DNA damage are themselves not functioning normally because they are also mutated. Consequently, mutations begin to increase in the cell, causing further abnormalities in that cell and the daughter cells. Some of these mutated cells die, but other alterations may give the abnormal cell a selective advantage that allows it to multiply much more rapidly than the normal cells. 5

6 This enhanced growth describes most cancer cells, which have gained functions repressed in the normal, healthy cells. As long as these cells remain in their original location, they are considered benign; if they become invasive, they are considered malignant. Cancer cells in malignant tumors can often metastasize, sending cancer cells to distant sites in the body where new tumors may form. 6

7 DIAGNOSIS OF CANCER Diagnosis of cancer is an important part in identifying the disease, understanding the stage of cancer and deciding the treatment to patients 7

8 COMMON MEDICAL TESTS IN CANCER CT scan (also called a CAT scan) A CT scan uses energy called radiation to make pictures and shows organs and soft tissues. MRI An MRI uses magnetic fields to make pictures. An MRI can be done on any part of the body and show many angles of the body. It gives a detailed pictures of organs and tissues and are clearer than CAT scans. MRI scan help to see if cancer has spread. People with metal in their body might not be able to have MRIs, for eg. people with pacemakers and metal plating. 8

9 X-Ray X-rays focus a beam of radiation on the body. This makes shadowlike images of organs and tissues. An x-ray of the breast is called a mammogram. These can find and diagnose breast cancer. Special types of x-ray tests may use dyes. These dyes are called contrast materials. The contrast can help a doctor see parts of the body more clearly. PET scans Can tell a tumor from normal tissue affected by cancer treatment. They can show how fast a tumor is growing. And how much of a danger it might be. SPECT scans Shows how blood flows through vessels. This helps doctors see how the organs are working. It also helps find tumors. 9

10 Antibodies in PET and SPECT scans Antibodies are special type of cell messenger made to find cancer cells and stick to their surface. Plus some messengers get another job. They carry a tiny piece of radiation. And deliver it to cancer cells. The radiation lights up the tumor. First, the messengers travel through the bloodstream. When they find a tumor they attach themselves. The radiation they deliver lights up the tumor. This helps the doctor see exactly where the tumor is. 10

11 DIAGNOSIS OF CANCER The development of molecular biological techniques may help in the diagnosis of potential cancers in the early stages, long before tumors are visible. The subtle differences between normal and tumor cells are exploited in the detection and treatment of cancer. Some of these differences are designated as tumor markers and can be either qualitative or quantitative in their nature. The structures produced by tumor cells as well as those produced by host tissues in excessive amounts under the influence of tumor cells can function as tumor markers. Speaking in general, the tumor markers are the specific molecules appearing in the blood, urine, stool, other bodily fluids or tissues and the occurrence of which is associated with cancer. 11

12 TUMOR MARKERS Tumor markers are made by cancer cells. Tumor markers show up in different places in the body. They are found in blood, in urine, and in other parts of the body. They may be signs of cancer. Doctors look at tumor markers to learn about your cancer. They can help doctors decide how to treat. 12

13 What are Tumor markers Tumor markers are biochemical substances usually proteins produced by the body in response to the cancer growth or by the cancer tissue itself Tumor Markers may be detected in blood, urine or tissue samples due to the cause or effect of malignant process. Most tumor markers are produced by normal cells, but their production is much increased in cancerous conditions. 13

14 Definition of Tumor Marker: There have been Numerous attempts to broaden the definition to accommodate the rapidly expanding set of identified tumor markers and include the following: 1. Substances present in, or produced by, a tumor itself or produced by host in response to a tumor that can be used to differentiate a tumor from normal tissue or to determine the presence of a tumor based on measurements in blood or secretions. 2. A molecule, a process or a substance that is altered quantitatively or qualitatively in precancerous or cancerous conditions, the alteration being detectable by an assay. 3. Biochemical indicators of the presence of a tumor. 14

15 An ideal tumor marker An ideal tumor marker should fulfill certain criteria when using it as a test for detection of cancer disease: (1) positive results should occur in the early stages of the disease, (2) positive results should occur only in the patients with a specific type of malignancy, (3) positive results should occur in all patients with the same malignancy, (4) the measured values should correlate with the stage of the disease, (5) the measured values should correlate to the response to treatment, (6) the marker should be easy to measure. Most tumor markers available today meet several, but not all criteria. 15

16 Most tumor markers are proteins. However, more recently, patterns of gene expression and changes to DNA have also begun to be used as tumor markers. Some are associated with only one type of cancer, whereas others are associated with two or more cancer types. There is no "universal" tumor marker that can detect any type of cancer. Sometimes, noncancerous conditions can cause the levels of certain tumor markers to increase. In addition, not everyone with a particular type of cancer will have a higher level of a tumor marker associated with that cancer. Moreover, tumor markers have not been identified for every type of cancer. 16

17 Why to measure tumor markers Measurements of tumor marker level can be useful, when used along with radiograph or other tests in the detection and diagnosis of some type of cancer. Tumor markers can be found in cells, tissues or body fluids. They can be measured quantitatively or qualitatively by chemical, immunological or molecular biological methods to determine the presence of neoplasia. Quantitative as well as qualitative evaluation of these markers is possible through modern techniques of sensitive immunoassays (RIA) and enzyme linked immunosorbent assays (ELISA) using monoclonal or polyclonal antibodies in majority of cases and biochemical and molecular biology techniques in other cases. 17

18 Few markers are specific for a single individual tumor (tumor specific markers). Most are found with different tumors of the same tissue type (tumor associated markers). They are present in higher quantities in cancer tissues or in blood from cancer patients than in benign tumors or in the blood of normal subjects. Few markers are specific to the organ where the tumor resides. 18

19 A technician or specialist comes across a variety of clinical situations where the exact demarcation between a premalignancy and malignancy cannot be ascertained, thus posing a problem in diagnosis, leading to a delay of the treatment of these dangerous lesions. The tumor markers can aid the clinician greatly in such situations, if the clinicopathologic picture is not accurately suggestive of these tumor markers, their interactions and clinical applications as shown relevant by the recent advances in research. 19

20 They may be present as intracellular substances in tissues or may be released into the circulation and appear in serum. Continuing search for suitable tumor markers in serum, tissue and body fluids during neoplastic process is of clinical value in the management of patients with various malignancies. The spectrum of biochemical tumor markers reported to date is very wide. 20

21 How are tumor markers used in cancer care? Doctors use tumor markers to Look for cancer Some tumor markers may act as signs of cancer. They tell doctors that cancer may have started to grow in the body. Doctors can then run tests and learn more Predict how the cancer will act When cancer is found, the level of a tumor marker offers clues. It may suggest how the cancer will act in the body. It may tell what kind of medicine will work best. is can help your doctor pick the right treatment Tell if the cancer treatment is working Most of ten, tumor markers are used to see if treatment is working. If it is, tumor marker levels usually go down. If the levels go up, it may mean that the cancer is not responding to the specific medicine you are taking See if the cancer has returned Tumor markers can show a return of cancer. The sooner cancer is found, the better 21

22 Tumor markers can be broadly classified as 1. Oncofetal antigens (e.g. alpha-fetoprotein (AFP), Carcinoembryonic antigen (CEA), Pancreatic oncofetal antigen, fetal sulfoglycoprotein. 2. Tumor associated antigens /Cancer Antigens e.g. CA125, CA19-9, CA15-3, CA72-4 CA50 etc. 3. Hormones e.g. Beta human chorionic gonadotropin, calcitonin, placental lactogen etc. 4. Hormone receptors (e.g. estrogen and progesterone receptors) 5. Enzymes and Isoenzymes (e.g. prostate specific antigen (PSA), prostatic acid phosphatase (PAP), neuron specific enolase (NSE), glycosyl transferases, placental alkaline phosphatase (PALP), terminal deoxy nucleotidyl transferase (TDT), lysozyme, alpha amylase 6. Serum and tissue proteins (beta-2 microglobulin, monoclonal immunoglobulin/para proteins, glial fibrillary acidic protein (GFAP), protein S-100, ferritin, fibrinogen degradation products) 7. Other biomolecules e.g. polyamines 22

23 An ideal tumor marker theoretically should have the following criteria 1. It should be highly sensitive and should have low false negatives. 2. It should be highly specific and should have low false positive. 3. It should have high positive and negative predictive value % accuracy in differentiating between healthy individuals and tumor patients. 5. It should be able to differentiate between neoplastic and non-neoplastic disease and show positive correlation with tumor volume and extent. 6. It should predict early recurrence and have prognostic value. 7. It should be clinically sensitive i.e. detectable at early stage of tumor. 8. Its levels should be preceding the neoplastic process, so that it should be useful for screening early cancer. 9. It should be either a universal marker for all types of malignancies or specific to one type of malignancy. 10. It should be easily assayable and be able to indicate all changes in cancer patients receiving treatment. 23

24 However, evaluation of tumor markers can be of valuable aid in diagnosis, prognosis, staging and in monitoring the growth of the tumor. Once the patient is positive for a particular marker before instituting therapy, the effective clinical use becomes evident only after its continued measurement throughout the patient s clinical course. The rising or declining value of marker concentration in majority of malignancies predicts progression or remission. The diagnostic efficiency of tumor markers depends on variety of factors such as sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). 24

25 Classification of Tumor Markers: Tumor markers can be classified in several ways: according to their chemical structure, their tissue of origin, types of malignancies in which they are elevated, etc. In 1995 Waxman J, based on differences in origin, structure, biological function or their relationship to the event in tumor growth or formation. 1) Oncofetal antigens e.g. AFP, CEA. 2) Hormones e.g. Catecholamines, Calcitonin, β hcg. 3) Glycoprotein s e.g. CA 125, CA 15-3, CA19-9, CA 72-4, PSA. 4) Metabolites e.g. VMA, HIAA. 5) Tumor associated antigens a) Viral antigens e.g. Polyoma, SV 40. b) MHC related antigens e.g. H-2K antigen. c) Enzymes e.g. PAP, NSE, PLAP. d) Oncogene Products e.g. c-myc, c-erb B2. e) Cytogenic products e.g. Philadelphia chromosome. 6) Tumor associated markers a) Proteins e.g. Immunoglobulin s, β-2m. b) Enzymes e.g. Lactate, dehydrogenase, Alkaline phosphatase, Pterodines, Pterines. c) Acute phase proteins e.g. C reactive proteins, Ferritin. d) Inflammatory markers e.g. ESR, viscosity. 7) Ultrastructural components a) Intermediate filament components e.g. Desmin, vimentin 25

26 In 1999, European Group on Tumor markers recommended selected examples of serologic tumor markers and malignant diseases associated with each. 1) Oncofetal Antigens 2) Hormones 3) Glycoprotein s 4) Isoenzymes 5) Cellular components/products 6) Immunoglobulins 26

27 In 2001, Johnson PJ gave molecular classification of circulating tumor markers 1. DNA a. Epigenetic - Promoter hyper methylation. e.g. GSP1, DAP in lung cancer; p15, p216 in liver cancer. b. Endogenous - Mutations. e.g. NADH dehydrogenase 4. c. Mitochondrial genetic e.g. (ND4) in urine in bladder cancer. d. Oncogene -. Mutation. e.g. K-ras in pancreatic cancer, micro satellite alterations in head and neck cancers. e. Exogenous viral e.g. EBV in NPC and burkitts lymphoma; HPV in cervical cancer. 27

28 2. RNA a. Cell based - Tissue specific markers. e.g. PSA m RNA. b. Endogenous e.g. 20m RNA in breast cancer. c. Cell free - Circulating m RNA. e.g. tyrosinase m RNA in melanoma. d. Exogenous viral - Viral RNA. e.g. EBV coded RNA in NPC. 3. Translational Protein a. Native protein e.g. PSA in prostate cancer, CEA in colonic. b. Conventional markers. c. Glycon - Aberrant glycosylation. e.g. monosialytactec APF in HCC. 28

29 Based upon methods of detection of tumor markers, they are classified into 6 major groups 1) Immunological 2) Flow cytometry 3) Cytogenetic analysis 4) Genetic analysis 5) Proteomics 29

30 Oncofetal proteins Oncofetal proteins are antigens that are normally produced during the embryonic development and their production is limited or completely absent/stopped in adults. Elevated concentrations in adults result from reactivation of certain genes that control cellular growth and are directly connected to malignant process. CEA is one of the first known tumor markers associated with colorectal cancer Alpha-fetoprotein (AFP) associated with hepatocellular carcinoma. 30

31 Hormones and/or Carcinoplacental antigens: The synthesis and secretion of hormones can sometimes be altered due to malignancies. Quantitative and qualitative alterations of the synthesis and hormone secretion can therefore be the indicators of a malignant process and can be monitored as tumor markers. e.g. calcitonin and parathyroid hormone in breast cancer, lipotropin in carcinoid tumors, calcitonin, insulin, parathyroid hormone in thymic malignomas. 31

32 Enzymes: Certain enzymes can also be used as tumor markers when they are produced more intensely in malignancies. Elevated Prostatic acid phosphatise serum concentrations; can be observed in the patients with prostatic cancer. Alkaline phosphatise, an iso-enzyme, is synthesized in the liver, bones or placenta. Elevated serum concentrations in patients with malignant disease usually indicate a metastatic spread of the disease into the liver and/or bones, and/or the presence of primary bone tumors such as osteosarcoma. Chromogranin A (CgA) is made by neuroendocrine tumors that include carcinoid tumors, neuroblastoma, and small cell lung cancer. The blood level of CgA is often elevated in patients with these diseases. Neuron specific enolase (NSE) is a cytoplasmic glycolytic enzyme that was primarily detected in the cells of neuroectodermal origin and in neuronal cells. Elevated levels of NSE may also be found in medullary thyroid cancer, melanoma, and pancreatic endocrine tumors. Among other nonspecific markers in this group, lactic dehydrogenase (LDH) is an enzyme that is quite often elevated in the sera of patients with malignant lymphomas and germ tumors (seminomas); elevated ã glutamyl transpeptidase (GGT) indicates cholestasis; and thymidine kinase (TK) helps to evaluate the disease spread in the patients with leukemia, lymphoma, brain tumors, small cell lung cancer, and breast cancer. 32

33 Tumor-associated antigens Tumor associated antigens is a heterogeneous group of markers that comprises various membrane structures of tumor cells. Carcinomic antigen 15-3 (CA 15-3) is produced in the secretory epithelium of the breast, lungs, gastrointestinal tract, uterus etc and can be found frequently in the excretions of healthy adults. Carcinomic antigen 125 (CA 125) is a characteristic marker for ovarian cancer Carcinomic antigen 19-9 (CA19-9) is a glycolipid and is frequently elevated in the serum of patients with gastrointestinal tumors. Carcinomic antigen (CA 27-29) is another marker that can be used to follow patients with breast cancer and can be elevated in cancers in the colon, stomach, kidney, lung, ovary, pancreas, uterus, and liver. Prostate specific antigen (PSA) is a serine protease, produced in the prostate tissue and associated with prostate cancer. BCR-ABL is an abnormal gene seen in chronic myeloid leukemia (CML) cancer cells. Bladder tumor antigen (BTA) is found in the urine of many patients with bladder cancer. NMP22 is a protein found in the nucleus of cells and elevated in bladder cancer. BRAF gene defect (mutations) can be found in melanoma, thyroid cancer, and colorectal cancer. 33

34 Special serum proteins: Feritin which binds iron intracellularly and found in the liver, spleen, and bone marrow.; observed in the patients with acute leukemia, lymphomas (especially Hodgkin s lymphomas), lung, liver, and prostatic cancer. Thyroglobulin is an intracellular glycoprotein responsible for the production and storage of thyroxine; detected in the patients with well differentiated follicular thyroid carcinoma. Beta-2-microglobulin (B2M) is a protein that is identical with the HLA light chain and thus appears on the cell membrane of almost all differentiated cells.; observed in the patients with lung, breast, pancreatic, colorectal cancer, as well as lymphomas and chronic lymphoid leukemia (CLL). S-100 protein was first isolated from bovine brain. a good indicator of traumas to CNS, S-100 can be applied as tumor marker in the patients with neurilemmoma, neurinoma, glioblastoma, astrocytoma, and meningeoma. HER2 (or HER2/neu, erbb-2, or EGFR2) is a protein that is present in larger amounts on the surface of breast cancer cells and also found in stomach and esophageal cancers. 34

35 Other markers Polyamines like spermine, spermidine and putrescine were detected in elevated concentrations in urine in cases of a rapid regeneration of cells of certain tissue. Nucleosides, as dimethylguanosine and pseudouridine are components of RNA that enter the circulation in larger amounts in cases of enhanced cellular proliferation. Tissue polypeptide antigen (TPA) is likewise a nonspecific marker of enhanced cellular proliferation. Immunoglobulins are not classic tumor markers but instead are antibodies, which are blood proteinsnormally made by immune system cells to help fight germs. Bone marrow cancers such as multiple myeloma and Waldenstrom macroglobulinemia often cause a person to have too much of one type of immunoglobulin in the blood. 35

36 Application of tumor markers Utilization of tumor markers in oncology are: I. For Follow-Up of the Disease 1. Determination in body fluids a) To monitor the treatment response b) To detect early the disease recurrence c) To evaluate the extent of disease d) To differentiate benign from malignant conditions e) As screening method for some types of cancer 2. Immunoscintigraphy and Lymphoscintigraphy 3. Immunohistochemistry a) To set the diagnosis b) To determine the prognosis c) To predict the treatment response II. For Treatment 1. Direct cytotoxicity of specific monoclonal antibodies (MoAb) a) Binding of complement to specific MoAb b) Binding of cytotoxic cells to specific markers-receptors 2. Binding of drugs to specific MoAb 3. Binding of toxins to specific MoAb 4. Binding of radioactive isotopes to specific MoAb 5. Inhibition of growth factor receptors 36

37 Determination of Tumor Markers The determination of tumor markers in clinical oncology is helpful in many processes: in the process of diagnose setting and prognose prediction, in determining the disease extent and planning the treatment, as well as in the early detection of disease recurrence or metastasis. In body fluids, tumor markers are found in low concentrations and for their determination highly sensitive technology is needed. The techniques that are being used are more or less based on the same principle i.e. the determination of antigenantibody complexes. Most widely used techniques are the radioimmune assay, the enzyme-immune assay, and the luminometric-immune assay, which differ in the compound bound to the detection antibodies, and in the method of detection of the formed complexes. 37

38 Drawbacks of tumor markers: A simple blood test that could find cancers in their earliest stages could prevent the deaths of millions of people. But very few tumor markers are useful for finding cancer at a very early stage. There are a few reasons/drawbacks for this which are as follows: 1. Almost everyone has a small amount of these markers in their blood, so it s very hard to spot early cancers by using these tests. 2. The levels of these markers tend to get higher than normal only when there s a large amount of cancer present. 3. Some people with cancer never have high tumor marker levels. 4. Even when levels of these markers are high, it doesn t always mean cancer is present. For example, the level of the tumor marker CA 125 can be high in women with Gynaecologic conditions other than ovarian cancer. 38

39 Measurements of tumor marker levels can be useful when used along with x-rays or other tests in the detection and diagnosis of some types of cancer. However, measurements of tumor marker levels alone are not sufficient to diagnose cancer for the following reasons: Tumor marker levels can be elevated in people with benign conditions. Tumor marker levels are not elevated in every person with cancer especially in the early stages of the disease. Many tumor markers are not specific to a particular type of cancer; the level of a tumor marker can be raised by more than one type of cancer. 39

40 Currently, the main use of tumor markers is to assess a cancer s response to treatment and to check for recurrence. Scientists continue to study these uses of tumor markers as well as their potential role in the early detection and diagnosis of cancer. The patient s doctor can explain the role of tumor markers in detection, diagnosis, or treatment for that person. 40

41 THANK YOU 41