tumor markers 2553 chatchawin

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Tumor Markers

Tumor Markers

Lecturer:

Chatchawin PETCHLERT, Ph.D.

Head, Department of Biochemistry

Deputy Head, Department of Biotechnology

Department of BiochemistryFaculty of Science, Burapha University

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Tumor Markers

DNA structure andorganization within the cell.

The complement of 46

metaphase chromosomes

(human karyotype) is shown

lying next to an intact

nucleus. One chromosome is

blown up to reveal the degreeof chromatin condensation

and associated nucleosome

structures involved in the

organization of eukaryotic

DNA. The red box shows

the molecular structure of the

nucleoside bases which formthe struts of the DNA helix,

and the bonds between the

pyrimidine and purine bases(dashed lines).

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Tumor Markers

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A tumor is an abnormal growth of body tissue. It

originally meant any abnormal swelling, lump or

mass.

Tumors can be cancerous (malignant) or non-

cancerous (benign).

Tumor has become synonymous with neoplasm

except some neoplasms, such as leukemia do not

form tumors.

Tumor


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Department of Biochemistry

Faculty of Science, Burapha UniversityTumor Markers

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The term cancercancer derives from the Latin forcrabdue to the resemblance of the swollen veins around atumour to a crabs limbs.

Cancer is not a single disease; there are over 200 pathologically

distinct neoplastic entities (each depending on the cell/tissue-type

of origin). Nevertheless, all cancers are generally characterized byuncontrolled abnormal cell growth, which eventually forms a cell

mass, or tumour. Tumour development, or tumourigenesis,

generally occurs over a period of years, and cancer incidence is

more prevalent in aged populations. Sooner or later, the tumour

will generally invade and destroy surrounding normal tissues, andcells from the tumour can spread (metastasize) through the

bloodstream or lymphatic system to start new tumours in otherparts of the body.


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Liver cancer Colon cancer Gastric cancer

Skin cancer Breast cancerCervical cancer


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The process of carcinogenesis,that is, the change in cells from normal,

controlled cell division and differentiation

to cells that are transformed, dividing

without check, and are undifferentiated or

abnormally differentiated, does not

appear to occur as a single step. In other

words, transformation is a multistageprocess and involves a sequence of

events from tumour cell initiation, to

promotion, malignant conversion and

progression. Evidence for this comes

from in vitro studies (e.g. cell

transformation studies), animal models

and clinical/epidemiological observationsand, in particular, the long latency period

between cell initiation and the

appearance of a tumour in the target

tissue and the progression to metastaticdisease


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ProtoProto--oncogeneoncogene can become activated to anoncogene by a relatively small modication of itsoriginal function.

There are three basic activation types:

Mutation within a proto-oncogene can cause a

change in the protein structure, causing

an increase in protein (enzyme) activity and/or

loss of gene regulation.


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An increase in protein activity, caused by an increase in gene expression

an increase of protein stability, prolonging its existence and thus its

activity in the cell

a gene duplication resulting in an increased amount of protein in the cell.

A chromosomal translocation causing

inappropriate or constitutive gene expression, that is, in the wrong cell

type or at the wrong time; for example, c-Abl in chronic myeloid leukemia


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Tumour suppressor genesTumour suppressor genes encode for proteins whichgenerally inhibit tumorigenesis, and their existence was

originally inferred from experiments where tumour cells were

fused with normal cells in culture that resulted in non-

tumourigenic hybrids.

Subsequent loss of specic individual chromosomes or

specic regions of a chromosome in the hybrid, and derived

from the normal parental cell, resulted in the re-emergence

of the tumorigenic phenotype.


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Numerous tumour suppressor genes have since beenidentied, and the functions of the associated proteinsfall into several categories:

1. The activities of the cyclin-dependent kinase (CDK) family are in turn regulated by

cyclin-dependent kinase inhibitors (CDIs), which are essential for continuing the cell cycle. Ifthese genes are not expressed the cell cycle will arrest, effectively inhibiting cell division (Fero

et al., 1998).

2. Cell cycle regulation and DNA damage surveillance: the cell cycle can be arrested by

tumour suppressor genes of the p53 and Rb pathways that are activated by aberrant

proliferative stimuli or DNA damage (reviewed by Kohn, 1999; Mirza et al., 2003). After cell

cycle arrest, there is an opportunity to rectify DNA damage where necessary. The role of somemembers of the p53 and Rb pathways is to maintain low levels of inactive TP53 in the absenceof genomic damage allowing normal cell cycle function.


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3. If the DNA damage is irreparable, the cell enters senescence or undergoes apoptosis(programmed cell death), preventing replication of the damaged genome (Malumbres and

Barbacid, 2001). Apoptosis in multicellular organisms involves a series of biochemical

events leading to a characteristic cell morphology and death, characterized by a variety of

morphological changes, including blebbing, changes to the cell membrane such as loss of

membrane asymmetry and attachment, cell shrinkage, nuclear fragmentation, chromatin

condensation and chromosomal DNA fragmentation. Mutations in genes regulating

apoptosis can shift the balance between pro- and anti-apoptotic inuences, and maycontribute to genomic instability, if cells carrying DNA damage are permitted to survive.

Such cells which survive past their use-by-date are capable of replication and they and

their progeny are subject to increased genomic instability, increasing the likelihood of the

cell becoming cancerous or diseased (Schmitt et al., 2007).

4. Some tumour suppressor genes encode for proteins involved in cell adhesion which

prevent tumour cells from dispersing, block loss of contact inhibition, and inhibit metastasis.These proteins are known as metastasis suppressors.


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The scientific term to describe an abnormalproliferation of genetically altered cells.

Neoplasms can be benign or malignant:1) Malignant neoplasmormalignant tumor:synonymous with cancer.

2) Benignneoplasm or benigntumor :atumor (solid neoplasm)that stops growing byitself, does not invade other tissues and doesnot form metastases.

Neoplasm


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Tumor markers are molecules occurring in blood,

urine or body tissue that are associated with

cancer.

A tumormarkermaybemadeby a tumoritself or

by the body in response to the tumor.

Tumor marker measurement or identification isuseful in patient diagnosis or clinical management.

Tumor markers

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Tumor markers can be classified in two groups:

1) Cancer-specific markers

2) Tissue-specific markers

Classification

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Cancer-specific markers arerelatedto the

presence of certaincanceroustissue.

Becausethere is a largeoverlapbetween themanydifferenttumortissuetypes and the

markersproducedthesemarkersmightnotbe

specific in making a diagnosis.

Cancer-specific markers

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Tissue-specific markers are related to specific

tissues which have developed cancer.

These substances are not specifically related tothe tumor, and may be present at elevated levels

when no cancer is present.

Tissue-specific markers

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Tumor marker tests are not used alone to

detect and diagnose cancer because

: most tumor markers can be elevated

in patients who don't have a tumor;

: no tumor marker is entirely specificto a particular type of cancer;

: not every cancer patient has an

elevated tumor marker level, especiallyin the early stages of cancer, when

tumor marker levels are usually stillnormal.

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Tumor markers can be used for one of four

purposes:

(1) screening a healthy population or a high riskpopulation for the presence of cancer;

(2) making a diagnosis of cancer or of a specifictype of cancer;

(3) determining the prognosis in a patient;

(4) monitoring the course in a patient in remission

or while receiving surgery, radiation, orchemotherapy.

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Types ofTumor Markers

1. Enzymes and isoenzymes

2. Hormones

3. Immunoglobulins4. Antigens (oncofetal and CHO)

5. Receptors

6. Oncogene products

7. Genetic markers


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CEA is a protein found in manytypes of cells but

associated with tumors and the developingfetus

(oncofetal antigen).

It is a complex glycoprotein of molecular weight~150-300 kDa, that is associated with the plasma

membrane of tumor cells, from which it may be

released into the blood.

CEA is most useful as a marker for colorectal,

pancreatic, gastric, lung, breast, and ovarian

carcinoma.

Carcinoembryonic antigen(CEA)

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AFP is a normal fetal serum protein synthesized by the

liver, yolk sac, and gastrointestinal tract that sharessequence homology with albumin .

The level of AFP is typicallyhigh in the fetus's blood. It

goesdown in the baby's blood afterbirth. And by a year

of age, it is virtuallyundetectable.

It is a glycoprotein with molecular mass of70 kDa.

AFP is elevated in normal pregnancy, benign liverdisease (hepatitis, cirrhosis), as well as in cancer.

AFP is of importance in diagnosinghepatocellular

carcinoma and maybeuseful in screeningprocedures.

Alpha-Fetoprotein (AFP)

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PSA is prostate-specific, notcancer-specific.

It is found in normal prostatic epithelium and secretionsbut not in other tissues. It is a glycoprotein.

A variety of conditionscanraisePSAlevels:prostatitis

(prostate inflammation), benign prostatic hypertrophy

(prostateenlargement), and prostate cancer.

PSA is highlysensitive for the pesence of prostaticcancer.

Prostate-SpecificAntigen(PSA)

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HCG is a glycoprotein consisting of subunits a- and b-subunits, which are non-convalently linked.

The hormone is normally produced by the

syncytiotrophoblastic cells of the normal placenta and is

elevated in pregnancy.

Its most important uses as a tumor marker in trophoblastictumor(tumors of placenta) and some tumors of the testis.

The level of HCG is occasionally elevated in other cancersincluding those of breast, lung, and gastrointestinal tract.

Human chorionic gonadotropin (HCG)

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CA 19-9is synthesized by normal human pancreatic

and biliary ductular cells and by gastric, colon, and

salivary epithelia.

This carbohydrate antigen is a glycolipid with amolecular mass > 200 kDa.

CA 19-9 is a marker for both colorectal, pancreatic

carcinoma and cholangiocarcinoma.

Carbohydrate antigen CA 19-9

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CA1

25 is high molecular mass (> 200

kDa)glycoprotein.

CA 125 is most useful as a marker for ovarian

cancer.

CA 125 is often elevated in patients with ovarian

cancer, its level following the patient's clinical

course. With surgical resection or chemotherapy,the level correlates with patient response.

The CA 125 is elevated in other cancers including

endometrial, pancreatic, lung, breast, and coloncancer, and in menstruation, pregnancy.

Carbohydrate antigen CA 125

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Neuron specific enolase is an isozyme of the

glycolytic pathway that is found only in brain andneuroendocrine tissue.

NSE is found in tumors associated with aneuroendocrine origin, including small lung cancer,neuroblastoma and etc.

Use of NSE has been evaluated in lung cancer andneuroblastoma.

NeuronSpecificEnolase(NSE)

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Samples used for tumor marker estimations

1- Blood, plasma, and serum

2- Pleural fluid, ascetic fluid, or

pericardial fluid

3- Urine

4- CSF


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Gene Expression

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Control of gene expression

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Why Proteins ?

Genome (all genes): What couldhappen

Transcriptome (all mRNAs):

What might be happening

Proteome (all proteins):

What is happening

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What is Proteomics ?

A newly emerging field of life

science research that uses high

throughput (HT) technologies todisplay, identify and/or characterize

all the proteins in a given cell, tissue

or organism.

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Content

Proteomics (2D-PAGEMS) Cell lysis and Protein

extraction / Prefractionationand enrichment

Protein separation/Proteindetection

Image analysis

Protein identification

Proteomics and itsapplications

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2D-Polyacrylamide Gel

Electrophoresis (2D-P

AGE)

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AGE)-+

pH 3.0 10.06.5 103.0 5.5 8.5

100

75

50

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20

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Protein

separation

Protein

staining

sample

preparation

Image analysis Protein identification54



AGE)


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Patient Healthy

Proteomic of CA patient and healthy

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Biomarker discovery

Rheumatoidarthritis Infectiousmeningitis

Prostatedisease Ovarian cancer

Pancreatic cancer Systemiclupuserythematosus

Leukemia Cervical cancer Alzheimersdisease Denguevirusinfection

Hepatocellularcarcinoma HIVinfection

Lung cancer WestNilevirus

Melanoma RenalcellcarcinomaHypertension Breast cancer

Raghothama Chaerkadyand Akhilesh Pandey. Annu Rev Path Mech Dis 2008

3

: 485

-498

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Protein biomarker

Righetti et al., 2005Clin Chim Acta 357 : 123-139 58


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Metabolic Pathways

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Detection of tumor markers by ELISA

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tumor markers 2553 chatchawin

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