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Questions and Answers
What is one of the intrinsic factors that can contribute to the development of tumors?
What is one of the intrinsic factors that can contribute to the development of tumors?
Which of the following is a familial condition associated with an increased risk of tumors?
Which of the following is a familial condition associated with an increased risk of tumors?
Which condition is associated with defective DNA repair mechanisms related to sensitivity to radiation damage?
Which condition is associated with defective DNA repair mechanisms related to sensitivity to radiation damage?
Which stage of carcinogenesis involves the advancement of initiated cells into a pre-malignant state?
Which stage of carcinogenesis involves the advancement of initiated cells into a pre-malignant state?
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What role do oncogenes play in neoplasia?
What role do oncogenes play in neoplasia?
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What is the primary gene involved in Familial breast/ovarian cancer?
What is the primary gene involved in Familial breast/ovarian cancer?
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What type of damage can low doses of radiation primarily cause?
What type of damage can low doses of radiation primarily cause?
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Which of the following is NOT an extrinsic factor contributing to tumor development?
Which of the following is NOT an extrinsic factor contributing to tumor development?
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Which tumor suppressor gene is mentioned in relation to neoplasia?
Which tumor suppressor gene is mentioned in relation to neoplasia?
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Which chemical agent is an example of a direct-acting carcinogen?
Which chemical agent is an example of a direct-acting carcinogen?
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What condition is associated with a higher risk of developing malignant tumors?
What condition is associated with a higher risk of developing malignant tumors?
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In the context of chemical carcinogenesis, what is the role of a promoter?
In the context of chemical carcinogenesis, what is the role of a promoter?
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What is the mechanism by which radiation exposure can lead to different types of DNA damage?
What is the mechanism by which radiation exposure can lead to different types of DNA damage?
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Which agent is linked to the development of cancer through its action as a carcinogen?
Which agent is linked to the development of cancer through its action as a carcinogen?
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Which gene is altered in hereditary non-polyposis colon cancer (HNPCC)?
Which gene is altered in hereditary non-polyposis colon cancer (HNPCC)?
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What type of cancer risk is increased in children undergoing radiotherapy for head and neck cancers?
What type of cancer risk is increased in children undergoing radiotherapy for head and neck cancers?
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What type of cancer is primarily associated with polynuclear aromatic hydrocarbons such as coal tar and cigarette smoke?
What type of cancer is primarily associated with polynuclear aromatic hydrocarbons such as coal tar and cigarette smoke?
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Which chemical is converted into an active form by hydroxylation, leading to its cancer-causing potential?
Which chemical is converted into an active form by hydroxylation, leading to its cancer-causing potential?
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Which virus is associated with the development of Burkitt's lymphoma?
Which virus is associated with the development of Burkitt's lymphoma?
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Which of the following factors contributes to increased incidence of malignant tumors based on geographical variation?
Which of the following factors contributes to increased incidence of malignant tumors based on geographical variation?
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Which substance is associated with mesothelioma?
Which substance is associated with mesothelioma?
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Which of the following is a characteristic of oncogenes?
Which of the following is a characteristic of oncogenes?
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Accumulating genetic lesions in tumor cells often involve which type of genetic changes?
Accumulating genetic lesions in tumor cells often involve which type of genetic changes?
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What host factor is associated with an increased risk of cancer as age increases?
What host factor is associated with an increased risk of cancer as age increases?
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What is the primary role of tumour suppressor genes?
What is the primary role of tumour suppressor genes?
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Which gene is commonly associated with hereditary breast cancer susceptibility?
Which gene is commonly associated with hereditary breast cancer susceptibility?
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What type of cancer is linked to mutations in the p53 gene?
What type of cancer is linked to mutations in the p53 gene?
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Which mechanism involves a long time between stimulus exposure and cancer emergence?
Which mechanism involves a long time between stimulus exposure and cancer emergence?
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Familial retinoblastoma is characterized by which of the following?
Familial retinoblastoma is characterized by which of the following?
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What happens to DNA repair gene mutations in relation to oncogenes?
What happens to DNA repair gene mutations in relation to oncogenes?
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Which of the following describes the role of the c-erbB-2 (HER-2) gene?
Which of the following describes the role of the c-erbB-2 (HER-2) gene?
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What is the relationship between the accumulation of gene alterations and cancer development?
What is the relationship between the accumulation of gene alterations and cancer development?
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Study Notes
Neoplasia III: Tumour Development
- Tumour development is a result of alterations in the genetic code.
- Tumour development can be caused by intrinsic factors (inherited) and extrinsic factors (environmental).
- Intrinsic factors include inheritance, host factors (age, immune system, hormones).
- Extrinsic factors include radiation, chemicals, viruses.
Objectives
- Understanding inherited susceptibility to tumour development (Xeroderma pigmentosum, Ataxia telangiectasia)
- Understanding the inheritance of certain tumours (Familial adenomatous polyposis, Breast cancer, Retinoblastoma)
- Understanding the functions of oncogenes and tumour suppressor genes (TSG) and changes in neoplasia.
- Understanding the role of certain oncogenes (ras, c-myc, c-erbB-2 (HER-2)) and TSG (retinoblastoma, p53)
- Understanding the stages in carcinogenesis (initiation, promotion)
- Identifying agents that cause tumours and their mechanisms of action (radiation (UV, ionizing), chemicals (polycyclic hydrocarbons, aromatic amines, nitrosamines), viruses (Epstein Barr, hepatitis), other factors (hormones, aflatoxins, parasites)
- Understanding occupations associated with tumour development (asbestos exposure, dye industry)
- Understanding medical conditions increasing the risk of malignancy (ulcerative colitis, cirrhosis, Hashimoto's thyroiditis, chronic atrophic gastritis)
- Understanding geographical variation in malignant tumour incidence (gastric cancer, breast cancer, Burkitt's lymphoma)
Mechanisms of Carcinogenesis
- Tumour development and progression involve a long period between exposure to a stimulus and the emergence of clinical cancer.
- Carcinogenesis stages: Initiation, Promotion, Progression
- Initiating stimulus-effect is modified through genetic factors, DNA repair.
- Promotion leads to local tissue response and immune response.
- Progression is influenced by the number and type of genes.
- Tumour development is a complex process involving the accumulation of alterations in multiple genes and factors.
Hallmarks of Cancer
- Evading apoptosis
- Self-sufficiency in growth signals
- Insensitivity to anti-growth signals
- Sustained angiogenesis
- Limitless replicative potential
- Tissue invasion & metastasis
Intrinsic factors
- Inheritance: Inherited conditions increase tumour risk due to DNA repair deficiencies.
- Host factors: Age, immune system, hormones affect risks and development of tumours.
Defective DNA Repair
- Individuals with inherited DNA repair defects have a significantly increased risk of cancer.
Radiation
- Exposure to radiation, especially ionizing radiation, increases the risk for certain cancers (e.g., lung cancer in miners, thyroid cancer in children treated for head and neck cancer).
Chemicals
- Carcinogens interact with DNA in various ways, including causing specific base damage and single-strand breaks; resulting in mutations.
- Initiator (chemicals): Causes permanent changes for tumour formation.
- Promoter (chemicals): Stimulates tumour development in already initiated cells; they themselves are not tumorigenic.
Oncogenes
- Derived from proto-oncogenes, genes involved in normal cell growth and differentiation.
- Alterations (mutation, amplification, translocation) can activate oncogenes and contribute to uncontrolled cell growth.
- Specific examples: c-myc, Ras, c-erbB-2 (HER-2).
Tumour Suppressor Genes
- Normal function is to inhibit cell proliferation and promote cell death, protecting against tumours.
- Loss or alteration of these critical genes can eliminate growth suppression and increase cancer risk.
- Examples: p53, retinoblastoma (RB) genes.
DNA Repair Genes
- Critical for accurately copying DNA during cell division, preventing mutations.
- Defects in DNA repair genes increase the likelihood of other gene mutations, contributing to cancer development.
- Specific examples: BRCA1, BRCA2.
p53
- A key tumour suppressor gene.
- Encodes a protein that helps regulate cell division and DNA repair processes, initiating apoptosis if damage is too substantial.
- Commonly mutated in various cancer types.
- Important in multiple crucial processes, including cell cycle regulation, DNA repair, and apoptosis.
Other Agents
- Asbestos: Causes mesothelioma.
- Aflatoxins: Linked to liver cancer.
- Schistosoma: Associated with bladder cancer.
- Helicobacter: Linked to gastric cancer (and lymphoma).
- Hormones: Estrogen is linked to breast cancer; androgens are connected to liver cancer.
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Description
This quiz explores the genetic alterations leading to tumour development, highlighting both intrinsic and extrinsic factors. You'll learn about inherited susceptibilities and the roles of oncogenes and tumour suppressor genes in neoplasia. Test your understanding of carcinogenesis and tumour-causing agents.
