Questions and Answers
What is the term used to describe the ability to notice distinct characteristics of cancer cells from other surrounding tissues?
Differentiation
Which type of cancer originates from melanocytes?
Melanoma
What occurs when a damaged DNA cannot be repaired in normal cells exposed to mutagens?
Mutation
Which class of substances are alkylating agents and aromatic hydrocarbons examples of?
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What is the main consequence of the inhibition of apoptosis in carcinoma cells?
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In carcinogenesis, what do mutagens lead to after damaging the DNA in normal cells?
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What is a characteristic of an ideal tumor marker?
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Which of the following is NOT a way to promote apoptosis in cancer cells?
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Which genetic mutation can lead to uncontrolled cell division?
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Which chemical compound is known to cause Hepatic Carcinoma?
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Which virus is associated with causing Kaposi’s sarcoma?
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How do ideal tumor markers respond to treatment?
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Which type of genes are responsible for slowing down cell division, repairing DNA mutations, and promoting apoptosis?
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What is the primary function of tumor suppressor genes when they are not mutated?
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Which type of mutation results in a loss or reduction in the function of tumor suppressor genes?
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What is the role of proto-oncogenes in normal cells?
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What type of gene conversion can result in proto-oncogenes becoming oncogenes?
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Which characteristic is NOT commonly associated with an ideal tumor marker?
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What is a key feature of tumor markers that are produced by the body in response to tumor cells?
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What is the primary purpose of utilizing tumor markers in cancer diagnosis?
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What does the inhibition of tumor suppressor genes primarily result in?
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What is the consequence of mutations in proto-oncogenes that convert them into oncogenes?
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Study Notes
Physical Carcinogens
- X-ray, Gamma ray, and UV ray can cause:
- Formation of pyrimidine dimers
- Apurinic sites with consequent break in DNA
- Formation of free radicals and superoxides leading to DNA break and somatic mutations
- Increase risk of leukemia in childhood if exposed during fetal life
Proto-Oncogenes and Oncogenes
- Proto-oncogenes are responsible for the synthesis of:
- Growth factors
- Transcription factors
- Receptor factors
- Proteins for gene expression
- Proto-oncogenes can be converted to oncogenes through:
- Point mutation
- Chromosomal translocation
- Gene amplification
- Examples of oncogenes:
- jun (Transcription Factor)
- fos (Transcription Factor)
- myc (DNA Binding Protein)
- ras (GTPase)
- rat (Protein Kinase)
- abl (Tyrosine Kinase)
- sis (Platelet-Derived Growth Factor)
Tumor Suppressor Genes (Anti-Oncogenes/Recessive Oncogenes)
- Normal genes that:
- Slow down cell division
- Repair DNA mutations
- Responsible for apoptosis
- Mutation can result in loss or reduction of function, allowing cells to grow abnormally and cause cancer
- Examples of tumor suppressor genes:
- RB1 (Retinoblastoma Gene 1)
- P53 (Phosphoprotein)
- WT (Wilm's Tumor)
- FAP (Familial Adenomatous Polyposis)
- BRCA (Breast cancer gene)
Tumor Markers
- Biochemical indicators of the presence of a tumor
- Produced by tumor cells (tumor-derived) or by the body in response to tumor cells (tumor-associated)
- Detected in plasma and body fluids such as urine, CSF, and pleural fluid
- Characteristics of an ideal tumor marker:
- Specific production in premalignant or malignant tissue
- Early in the progression of disease
- Sensitive and produced at detectable levels in all patients with a specific malignancy
- Expression in an organ site-specific manner
- Evidence of presence in bodily fluids obtained non-invasively
- Levels related quantitatively to tumor volume, biological behavior, and disease progression
- Relatively short half-life, reflecting temporal changes in tumor burden and response to therapy
Cancer
- Types of cancer classified by origin:
- Epithelial (Carcinoma)
- Blood cells (Leukemia)
- Lymphatics (Lymphoma)
- Connective Tissue (Sarcoma)
- Melanocyte (Melanoma)
Carcinogenesis
- Normal cells exposed to chemicals, viruses, or radiation can damage DNA
- Damaged DNA can be repaired, but failure to repair leads to mutation
- Mutation can lead to:
- Activation of oncogenes
- Inhibition of tumor suppressor genes
- Inhibition of apoptosis
Etiology (Mutagens)
- Substances that increase the rate of mutation, enhancing the incidence of cancer
- Examples of mutagens:
- Chemicals:
- Alkylating Agents
- Aromatic Hydrocarbons
- Aromatic Amines
- Nitroso Compounds
- Viruses:
- HPV (human papillomavirus)
- HSV (herpes simplex virus)
- HBV (hepatitis B virus)
- HCV (hepatitis C virus)
- HIV (human immunodeficiency virus)
- HTLV (human T-lymphotropic virus type 1)
- EBV (Epstein-Barr Virus)
- Chemicals:
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