Podcast
Questions and Answers
Which of the following factors are associated with an increased risk of cancer?
Which of the following factors are associated with an increased risk of cancer?
What role does the Src gene play in relation to cancer?
What role does the Src gene play in relation to cancer?
What infection is commonly linked to cervical cancer?
What infection is commonly linked to cervical cancer?
Which noxious substance is associated with mesothelioma due to its dust being inhaled?
Which noxious substance is associated with mesothelioma due to its dust being inhaled?
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What is a consequence of the chromosomal changes found in many cancers?
What is a consequence of the chromosomal changes found in many cancers?
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Aspergillus oryzae increases the risk of which type of cancer due to its toxin?
Aspergillus oryzae increases the risk of which type of cancer due to its toxin?
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In terms of cancer causation, what does the term 'nature vs nurture' refer to?
In terms of cancer causation, what does the term 'nature vs nurture' refer to?
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What is a recognized bacterial cause of gastric carcinoma?
What is a recognized bacterial cause of gastric carcinoma?
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What is the primary mechanism by which RAS regulates cell proliferation?
What is the primary mechanism by which RAS regulates cell proliferation?
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Which describes an oncogene and its behavior?
Which describes an oncogene and its behavior?
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How does p53 function in normal cells under stress?
How does p53 function in normal cells under stress?
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What is the result of mutation at positions 12 or 61 in RAS?
What is the result of mutation at positions 12 or 61 in RAS?
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Which therapy approach targets genetic instability in cancer cells?
Which therapy approach targets genetic instability in cancer cells?
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What characterizes tumor suppressor genes as opposed to oncogenes?
What characterizes tumor suppressor genes as opposed to oncogenes?
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What is a likely characteristic of cancer cells in terms of apoptosis?
What is a likely characteristic of cancer cells in terms of apoptosis?
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Which of the following mutations is a driver mutation commonly seen in colorectal cancer?
Which of the following mutations is a driver mutation commonly seen in colorectal cancer?
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How does the concept of genetic instability relate to cancer development?
How does the concept of genetic instability relate to cancer development?
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What indicates an inherited predisposition to retinoblastoma?
What indicates an inherited predisposition to retinoblastoma?
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Which statement about hybrid cells from normal and cancerous cells is true?
Which statement about hybrid cells from normal and cancerous cells is true?
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Why does cellular stress induce apoptosis in normal cells?
Why does cellular stress induce apoptosis in normal cells?
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What is the role of tyrosine kinase in cell signaling?
What is the role of tyrosine kinase in cell signaling?
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How does the mutation of p53 affect cancer cells?
How does the mutation of p53 affect cancer cells?
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Study Notes
Cancer Pathobiology: Causes and Mechanisms
- Cancer incidence linked to environmental factors, infectious agents, inherited predisposition, and chromosomal changes.
- Oncogenes, activated in most cancers, are mutated forms of normal genes involved in regulated cell proliferation.
- Geography impacts cancer development and types, showing environmental influence.
- Environmental factors (infection, diet, noxious agents) play a significant role in cancer development.
Infectious Agents and Cancer
- Infectious agents, including viruses (e.g., HPV, EBV, HHV-8/HIV; Hepatitis B) and bacteria (e.g., H. pylori), can cause cancer.
- Peyton Rous's experiment showed dose-dependent sarcoma development in injected chickens, indicating infectious agents spread cancer.
- Viruses can encode hyperactive forms of human genes (e.g., SRC) promoting cell proliferation.
- Some dietary exposures (e.g., Aspergillus oryzae) can cause cancer by generating toxic substances that damage DNA.
Noxious Substances and Cancer
- Exposure to noxious substances like asbestos (naturally occurring silicate) can cause mesothelioma.
- Smoking, diet, and obesity are also significant cancer risk factors.
Genetic Predisposition to Cancer
- Genetic predisposition to specific cancers exists (e.g., retinoblastoma, breast cancer syndrome, Wilms tumor, Gorlin syndrome).
- Familial predisposition suggests a strong genetic component.
- Cancer results from chromosomal changes, as seen in chronic myeloid leukemia with reciprocal translocations.
- Chromosomal translocations involve fusion of genes, creating fusion proteins (e.g., ABL-BCR) that cause constant proliferation.
Oncogenes and Cancer
- Oncogenes are dominant genes, transforming cellular behavior.
- Proto-oncogenes normally regulate cell proliferation; mutations activate them.
- Oncogene activation can result from mutation, amplification, or chromosome rearrangement, leading to uncontrolled cell growth.
- Viruses frequently harbor oncogenes, arising from evolutionary capture of proto-oncogenes.
- RAS protein, a key oncogene, exists in "on" (GTP-bound) and "off" (GDP-bound) states, and mutations can lock it in the "on" position, leading to uncontrolled proliferation.
Tumor Suppressor Genes
- Tumor suppressor genes are recessive and inactivate growth-suppressing activity.
- Loss of function in tumor suppressor genes (e.g., Rb) is common in cancer.
- Multiple mutations typically required for tumor development.
- Tumour suppressor gene loss is more common than oncogene activation.
Genetic Instability in Cancer
- Cancer cells are genetically unstable due to defects in DNA repair pathways, DNA replication error correction, and DNA segregation error correction.
- Multiple rounds of mutations and natural selection drive tumor progression.
- Clonal expansion of cells with advantageous mutations occurs.
Apoptosis and Cancer
- Apoptosis can prevent cancer by eliminating damaged cells to prevent tumorigenesis.
- Normal cells respond to stress (e.g., DNA damage) through pathways that induce apoptosis.
- Cancer cells often have defects in apoptosis pathways, allowing them to persist despite instability.
- P53 (a checkpoint gene) plays a vital role in apoptosis induction, and its inactivation in cancer is common.
Other Important Concepts
- Cell fusion experiments demonstrate that normal cells' tumour suppressor genes can suppress tumour formation.
- Cytogenetic analysis has documented chromosomal abnormalities linked to inherited cancers (e.g., retinoblastoma)
- Driver mutations are recurrent genetic changes found in different cancer patients, implying an evolutionary driver aspect to mutations.
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Description
This quiz explores the multifaceted causes of cancer, including environmental factors, infectious agents, and genetic predispositions. Delve into the roles oncogenes and specific viruses play in cancer development. Understand how geography and diet influence cancer risk and mechanisms.
