Clinical Chemistry > Tumor Markers > Flashcards

Tumor Markers Flashcards

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1
Q

Cancer

A
  • 2nd leading cause of mortality in developed countries
  • 42% males and 38% females will develop invasive cancer in lifetime
  • Lifetime risk of dying of cancer 23% male and 19% female
  • Rates higher in marginalized groups (racial/ethnic/sexual orientation)
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2
Q

Cancer progression steps

A
  1. Proliferation
  2. Transformation
  3. Invasion
  4. Metastasis
  5. Vascularization (solid tumors)
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3
Q

Cancer staging

A

Stage 1: Epithelium with tumor cells
Stage 2: Invasion of primary tumor thru epithelium and into blood vessels
Stage 3: Migration of tumor into regional lymph nodes
Stage 4: Metastasis and invasion of tumor to distant tissues

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4
Q

Tumor marker

A
  • Biomarker found in the blood or tissue and when elevated is linked to cancer
  • Tumor produces it OR marker is effect of tumor on healthy tissue
  • Examples: hormones, metabolites, receptors, enzymes, oncofetal antigens
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5
Q

Oncofetal antigen

A

Protein produced during fetal development and elevated in individuals with cancer

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6
Q

Enzyme tumor markers

A
  • Elevated non-specifically
  • Largely a result of high metabolic demand of tumor cells
  • Tend to correlate with tumor burden
  • Clinically useful for monitoring therapy success
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7
Q

List serum protein tumor markers

A
  1. Beta-macroglobulin
  2. Immunoglobulins
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8
Q

Beta-macroglobulin

A
  • Found on surface of all nucleated cells
  • Used as non-specific marker of the high cell turnover common in tumors
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9
Q

Immunoglobulins

A
  • Multiple myeloma
  • Provides relatively specific measure of plasma cell production of monoclonal proteins
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10
Q

Endocrine tumor markers
When used?
Diagnose what?
Examples?

A
  • Used in endocrine malignancies
  • Valuable in diagnosing neuroblastomas, pituitary, and adrenal adenomas
  • Examples: ACTH, ADH, calcitonin, cortisol, PTH…etc
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11
Q

Oncofetal antigen tumor marker

A
  • One of first classes of tumor markers
  • Expressed transiently during normal development BUT turned on again in formation of tumors
  • Ag: Carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP)
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12
Q

Carbohydrate and cancer antigen tumor markers

A
  • Monoclonal defined antigens identified from human tumor extracts and cell lines
  • There are Ab created to target specific carb or cancer Ag
  • Best used for monitoring treatment of tumors that secrete these epitopes
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13
Q

Receptor tumor markers
Used for what?
Serological or non-serological?
Helps to do what in therapies?

A
  • Receptors that are used to classify tumors for therapy
  • Non-serological markers
  • Helps to choose between endocrine and cytotoxic therapies
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14
Q

Ideal tumor marker traits

A
  • Tumor specific
  • Absent in healthy individuals
  • Readily detectable in body fluids
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15
Q

List applications of tumor marker detection

A
  1. Numerous markers ID have high enough sensitivity AND specificity to aid diagnosis, prognosis, detection of recurrence, and/or monitoring response to treatment
  2. Used in combo with clinical signs, symptoms, and histology to facilitate clinical decision making
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16
Q

Screening and risk assessment

A
  • Weigh benefits of disease detection vs harms of overtreatment (avoid false positives)
  • No tumor marker can effectively screen asymptomatic populations
  • Most found in normal and benign cells as well as cancer
  • Targeted screening
  • Family history of disease
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17
Q

Family history of disease for cancer

A
  • ID germline mutations (breast, ovarian, colon)
  • Breast and ovarian: BRCA1 and BRCA2
  • Familial colon cancers: APC gene develop cancer by 40 by 99%
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18
Q

Prognosis

A
  • [Tumor marker] generally increases with tumor progression
  • Highest levels with metastasis
  • Levels at diagnosis reflect aggressiveness, may predict outcome/indicate malignancy and metastasis
  • Presence or absence may be valuable
  • Can help determine best treatment options
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19
Q

T/F
Thyroid cancer is more common in men than women

A

False. More common in women than men

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20
Q

Monitoring effectiveness of therapy and disease recurrence

A
  • Tumor marker levels can be used to help monitor therapy and can be followed serially
  • Many tumor markers have lead time of several months vs other methods such as imaging
  • Earlier indication of relapse
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21
Q

How does lack of standardization make comparison of serial tumor marker results difficult?

A
  • Differences in Ab specificity
  • Analyte heterogeneity
    -Assay design
  • Lack of standardized reference material
  • Calibration
  • Kinetics
  • Reference range variation
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22
Q

T/F
The wide range of tumor marker concentrations encountered clinically must be considered in the lab

A

True

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23
Q

List test methods for tumor markers

A
  1. Immunoassays
  2. HPLC
  3. Immunohistochemistry/immunofluorescence
  4. Enzyme assays
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24
Q

List specific tumor markers that are tested

A
  1. AFP
  2. Cancer Antigen 125 (CA-125)
  3. Carcinoembryonic Ag (CEA)
  4. Human Chorionic Gonadotropin (hCG)
  5. Prostate Specific Ag (PSA)
  6. CA-15-3
  7. Immunoglobulin Free Light Chains (FLC)
  8. Human Epididymis Protein 4 (HE4)
  9. Neuron-Specific Enolase (NSE)
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25
**Immunoassays** How common? Advantages? Unique factors?
- Common method - **Advantages**: automated testing and ease of use - **Unique factors** Assay linearity, Ag excess (hook effect), and potential for heterophile Ab
26
Immunoassay linearity
- Span of analytic concentrations over which linear relationship exists btwn analyte and signal - **Samples exceeding linear range much more likely with tumor markers** - Dilutions done: be careful of diluent used and be aware of calculation errors
27
Hook effect
- When analyte concentrations exceed the analytical range excessively (potential for Ag excess) such that you see **decrease in signal at high analyte concentrations**, so need to dilute analyte. Common in **sandwich** type assays - Label Ab become saturated at high [Ag]
28
Heterophile Ab
- High interference in immunoassays - These are Ab against reagents - Subsets of heterophile Ab: human anti-animal, human anti-mouse
29
Common analytic concerns with tumor marker immunoassays
- Icterus (bilirubin) - Lipemia - Hemolysis - Ab cross-reactivity - Carry-over
30
**HPLC** Function? Extractions separated by which factors?
- Used to detect small molecules such as catecholamine metabolites in urine and plasma, endocrine metabolites. Detect hormones and metabolites secreted by tumors. - Extractions separated by charge, size, and polarity
31
What are catecholamines and metabolites used to diagnose?
- Neuroblastoma - Pheochromocytoma - Carcinoid tumors
32
Neuroblastoma
- Common childhood malignant tumor - High levels of plasma epinephrine, norepinephrine, and dopamine
33
Pheochromocytoma
- Rare tumor associated with hypertension - Elevated plasma metanephrines, urine vanillylmandelic acid, free catecholamines
34
Carcinoid tumors
- Serotonin-secreting tumors from small intestine - Serotonin metabolite (5-hydroxyindoleacetic acid)
35
HPLC advantages and disadvantages
**Advantages**: - Not subject to hook effect - No lot-to-lot variation - No heterophile Ab interference **Disadvantages**: - More labor intensive - More experience and skill required than automated
36
**Immunohistochemistry/immunofluorescence** Sample type? Sample collection method? Method?
- Use solid tissue tumor markers not found in circulation - Fine needle aspiration or biopsy - Specific Ab incubated with tissue sections to detect Ag, colorimetric or. fluorescent secondary Ab
37
Enzyme assays
- Used before widespread use of immunoassays + oncofetal assays - Most elevated enzymes can't be used to specifically ID a type of tumor, **but PSA is exception** - Examples: ALP, LDH, PSA
38
**Alpha-fetoprotein (AFP)** What is it? Synthesized where? Expression pattern? When is it elevated?
- Abundant serum carcinoembryonic protein - Normally synthesized by fetal liver - Re-expressed in certain types of tumors - Often elevated in patients with **hepatocellular carcinoma (HCC)** and germ cell tumors
39
AFP regulation and physiology
- AFP is a glycoprotein related to albumin that normally functions as a transport protein - AFP involved in regulating fetal oncotic pressure - During development, AFP peaks at 1/10 albumin level at 30 wks gestation - Infants: high levels that decline to adult levels at 7-10 mths old
40
AFP clinical usefulness and interpretation
- Used for diagnosis, staging, prognosis, and treatment monitoring of HCC - AFP can be elevated in benign conditions such as pregnancy, non-malignant liver disease, other malignancy (testicular cancer)
41
Hepatocellular carcinoma (HCC)
- Tumor originating in liver - Can be caused by chronic disease such as cirrhosis, hepatitis - Elevated AFP (non-specific)
42
Testicular cancer
Subtypes: - **seminomatous**: it forms directly from malignant germ cells - **nonseminomatous**: differentiate into embryonal carcinoma, teratoma, choriocarcinoma, yolk sac tumors
43
**T/F** AFP is used with hCG to classify nonseminomatous tumors
True
44
AFP methodology and clinical application
- **Methodology:** Automated immunoassays, Sandwich assays with mAb or poly-Abs - **Clinical app:** primary tumor marker for HCC and nonseminomatous testicular cancer (monitor, detect residual tumor, or relapse). AFP part of maternal serum screening for neural tube defects and chromosomal abnormalities
45
**CA-125** What is it? Regulation and physiology?
- Murine mAb against serious ovarian carcinoma cell line - Expressed in ovary/human ovarian carcinoma cells. May be elevated in patients with **endometriosis**, 1st tri of pregnancy, or during menstruation
46
**CA-125** Clinical Usefulness? Methodology?
- Serological marker for ovarian cancer - Immunoassays use OC125 and M11 Ab on many different, non-interchangeable methods
47
**CA-125** Clinical application
- Distinguish between benign masses and ovarian cancer - Monitor therapy - Evaluate pt response to treatment + predict current cancer - **Post-menopausal women** with high levels and palpable mass, positive predictive value of 90% - CA-125 can predict surgery success and efficacy of chemotherapy - Elevated post-treatment means poor prognosis
48
**CEA** What is it? Regulation and physiology? Functions? Elevated in which demographic?
- It is a prototypical oncofetal Ag expressed during development and **re-expressed in tumors**. Most widely used for colorectal tumors but also found in lung, breast, and GI tumors - It's a large heterogenous glycoprotein part of Ig superfamily - Functions in apoptosis, immunity, cell adhesion. May be involved in metastasis - Increased CEA in heavy smokers and some pt following radiation treatment
49
**CEA** Clinical usefulness? Methodology? Clinical applications?
- Main use as marker for **colorectal cancer** - Immunoenzymatic sandwich assays, anti-CEA mouse mAb - Used for surgical monitoring and chemotherapy
50
**hCG** What is it? Regulation and physiology?
- It's a dimeric hormone secreted by trophoblasts and functions to promote implantation of blastocyte and placenta, maintains corpus luteum in 1st tri of pregnancy - Elevated in trophoblastic tumors, choriocarcinoma, and germ cell tumors of ovary/testes - Glycoprotein with alpha and beta subunits that is degraded into multiple fragments - Intact or beta-hCG elevated in malignancies - Most assays detect multiple hCG fragments
51
**hCG** Clinical usefulness? Methodology? Clinical application?
- Prognostic for ovarian cancer and diagnostic for classification of testicular cancer - Most useful marker for detection of **gestational trophoblastic diseases** - **Methods**: Total beta-hCG assay most useful bc detects both intact and free beta-hCG - **Clinical app**: Testicular cancer, elevated in pt with nonseminomatous
52
**Prostatic Specific Ag (PSA)** What is it? Function?
- It's a glycoprotein produced in epithelial cells of the acini and ducts of the prostate gland - Functionally regulates seminal fluid viscosity, and dissolves cervical mucus cap to allow sperm to enter
53
PSA regulation and physiology
- Healthy men have low circulating PSA levels - Most circulating forms are bound - Total PSA screens/monitors prostate cancer - Detect total and free/unbound
54
**PSA** Clinical use? Methodology Clinical app
- Informed decision-making, screening higher risk individuals (1st degree relative, black) - **Methods**: Immunoassay, enzyme, fluorescence, chemiluminescence. Hook effect and heterophile Ab interference factors - **Clinical app**: monitor prostate cancer/therapy, post-prostatectomy: serial PSA undetectable if cancer is localized
55
**CA-15-3** Regulation and physiology? Clinical usefulness? Methodology? Clinical app?
- **Regulation**: Mucin 1 transmembrane protein normally expressed in glandular or luminal epithelial cells. Encodes tumor assoc Ag CA 15-3 and CA27.29 - **Clinical use**: Manage breast cancer pts, early detection, response to therapy with metastatic breast cancer - **Methods**: Immunoenzymatic sandwich assays - **Clinical app**: Serial testing breast cancer pts
56
**CA 19-9** Regulation and physiology? Clinical usefulness? Methodology? Clinical app?
- **Regulation**: Modified Lewis (Le a) blood group Ag. But Le a-b don't express CA 19-9 bc lack fucosyltransferase - **Clinical use**: Pancreatic cancer, serial. Elevated in GI and benign malignancices - **Methods**: Immunoenzymatic sandwich assays - **Clinical app**: Best validated biomarker for **pancreatic cancer**
57
Pancreatic cancer caveat in relation to CA 19-9?
NOT ALL Lewis antigen negative pts with pancreatic cancer are non-secretors of CA 19-9
58
**Immunoglobulin Free Light Chains (FLC)** Regulation and physiology? Clinical usefulness? Methodology? Clinical app?
- **Regulation**: Multiple myeloma has increased levels, Waldenstrom macroglobulinemia (IgM), monoclonal Ig - **Clinical use**: Serum protein electrophoresis look for M-spike. Calc kappa/lambda light chain ratios - **Methods**: Serum kappa or lambda measured by nephelometry - **Clinical app**: Minimizes neeed to quantitate/perform urine protein electrophoresis, baseline FLC gives diagnostic value in plasma cell dyscrasias, allows monitoring of patients previously thought to have non-secretory myeloma
59
**Human epididymis protein 4 (HE4)** Regulation and physiology? Clinical usefulness? Methodology? Clinical app?
- **Regulation**: Function unknown. Overexpressed in ovarian cancer - **Clinical use**: Higher sensitivity for ovarian cancer detection than CA-125, part of risk for ovarian malignancy algorithm - **Methods**: Immunoenzymatic sandwich assays - **Clinical app**: Ovarian cancer, improved specificity over CA-125, latter of which can be elevated in endometriosis
60
**Neuron-Specific Enolase (NSE)** Regulation and physiology?
- Enolase catalyzes 2-phosphoglycerate to phosphoenolpyruvate - NSE predominant gamma isoenzyme. - Present in RBCS - reject hemolyzed samples - Measure in CSF or serum. - Differential diagnosis of neurodegenerative disorders - Elevated in CSF may indicate Creutzfeldt-Jakob disease
61
**Neuron-Specific Enolase (NSE)** Clinical usefulness? Methodology? Clinical app?
- **Clinical usefulness**: Follow-up marker or auxiliary test for small cell lung carcinoma, carcinoid tumors, pancreatic islet tumors, or neuroblastomas - **Methods**: Homogenous immunofluorescent sandwich assay - **Clinical app**: Auxiliary test for neuroendocrine tumors
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