Mass Spectroscopy and Tumor Markers

Mass Spectroscopy and Tumor Markers Notes

Mass Spectrometry Overview

  • Definition: Mass spectrometry (MS) is an analytical technique used to:

  • Identify unknown compounds.

  • Determine concentrations of known substances.

  • Study molecular structures and chemical compositions.

  • Applications:

  • Detection of drugs, steroids, damaged genes, dioxins, proteins, and metabolites.

Mass Spectrometry Basics

  • Components of a Mass Spectrometer:

  1. Sample Inlet System

  2. Ionization Source

  3. Mass Analyzer

  4. Ion Detection System

  5. Vacuum System

  6. Signal Processor

  7. Readout Display

Ionization Process

  • Ionization Source: Converts molecules to gas-phase ions.

  • Types of Ionization:

    • Electron & Chemical Ionization: Suitable for gases and vapors.

    • Electrospray Ionization (ESI) & Matrix-Assisted Laser Desorption/Ionization (MALDI): Suitable for liquids and solids.

Mass Analyzer

  • Function: Sorts ions by their mass-to-charge ratio (m/z).

  • Types of Mass Analyzers:

    • Sector instruments

    • Time of flight (TOF)

    • Quadrupole

    • Ion traps

Ion Detection System

  • Measures separated ions and sends data to produce a mass spectrum.

  • Mass Spectrum: Plots m/z ratio on x-axis and relative abundance on y-axis.

Mass-to-Charge Ratio

  • Definition: Ratio obtained by dividing the mass of an ion by its charge.

  • Mass Spectrum Characteristics:

  • x-axis: m/z ratio

  • y-axis: relative abundance

Mass Spectrum Example

  • Pentane Example:

  • Ionization produces various cations:

    • CH3+ (m=15 g/mol)

    • CH3CH2+ (m=29 g/mol)

    • CH3CH2CH2+ (m=43 g/mol)

    • CH3CH2CH2CH2+ (m=57 g/mol)

    • CH3CH2CH2CH2CH3+ (m=73 g/mol)

  • Mass spectrum shows m/z against relative abundance.

MALDI Technique

  • Matrix-Assisted Laser Desorption Ionization (MALDI):

  • Sample plate with analyte mixed with matrix, subjected to laser.

  • Lasers evaporate matrix, ionizing analyte.

  • Useful in identifying biomolecules, especially proteins.

Time-of-Flight (TOF) Mass Analyzer

  • Function: Measures time ions take to travel from ion source to detector.

  • Low m/z ions reach the detector faster than high m/z ions.

Diagnostic Sensitivity and Specificity

  • Diagnostic Sensitivity: Ability of a test to correctly identify patients with the disease (True Positive rate).

  • Diagnostic Specificity: Ability to correctly identify patients without the disease (True Negative rate).

  • Predictive Value: Probability that a positive or negative test indicates the presence or absence of the disease.

Biomarkers Overview

  • Definition: Molecules detected in body fluids associated with malignancy.

  • Types of Tumor Markers:

  • Produced by tumors or in response to tumors.

  • Useful for monitoring treatment success or disease stage.

Advantages of Tumor Markers

  • Aid in diagnosing cancer or guide further testing.

  • Monitor response to therapy: decreasing levels indicate effective treatment.

  • Prognostic indicators of cancer aggressiveness.

  • Detect cancer relapse using established markers.

Disadvantages of Tumor Markers

  • High variability in patient samples complicates diagnosis.

  • Not always reliable; normal cells can also produce markers.

  • Presence of tumor markers does not confirm cancer existence.

Detection Technologies

  • Advancements in genomic/proteomic technologies for classification and monitoring of diseases.

  • Use of next-generation sequencing and immunoassays for tumor markers.

Biochemical Grouping of Tumor Markers

  • Categorized into Enzymes, Hormones, Oncofetal Antigens, and Genetic Markers corresponding to specific cancers.

Specific Tumor Markers Examples

  • Enzymes:

  • Alkaline Phosphatase, elevated with liver or bone metastasis.

  • Lactate Dehydrogenase (LDH), an indicator of tumor mass.

  • Hormones:

  • β-Human Chorionic Gonadotropin (hCG)

  • Adrenocorticotropic Hormone (ACTH)

  • Proteins for Breast Cancer:

  • CA 15-3, HER2-neu for prognosis and chemotherapy monitoring.

  • PSA for prostate monitoring.

  • CEA for colorectal cancer detection.

Summary of Application

  • Biochemical tumor markers assist in screening, diagnosis, prognosis, treatment monitoring, and recurrence detection.

  • Immunoassays are common diagnostic tests available in hospitals for tumor markers.