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What percentage of cancer deaths can be prevented by modifying or avoiding key risk factors?
What is the percentage of cancer deaths attributed to smoking?
What is the benefit of the Mediterranean diet in terms of cancer risk?
What is the effect of having children on breast cancer risk for women?
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What is the International Agency for Research on Cancer's classification of alcohol?
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What is the risk of stomach cancer for Japanese people who migrate to the USA and adopt the American diet?
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What is the effect of unprotected exposure to the sun on DNA?
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How many carcinogens have been identified in cigarette smoke?
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What contributes to carcinogenesis?
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What type of radiation is most closely linked to skin cancer?
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What is a characteristic of ionizing radiation?
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How does UVA radiation damage DNA?
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What is a by-product of aerobic metabolism?
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What type of DNA damage is most closely associated with ionizing radiation?
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What is a characteristic of ultraviolet radiation?
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What is a common feature of radiation-induced carcinogenesis?
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What is the role of Cytochrome P450 enzymes in the liver?
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Which of the following fibrous minerals is a group of fibrous silicate minerals that was used extensively in building materials?
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What type of cancer is associated with exposure to benzene?
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What is the role of oncogenic viruses in carcinogenesis?
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What is the effect of arsenic compounds on the human body?
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Which of the following is an example of a polycyclic aromatic hydrocarbon (PAH)?
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What is the result of hydrolysis of the glycosidic bond between a base and deoxyribose?
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What is a characteristic of hereditary cancers?
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What is a characteristic of autosomal recessive cancer syndromes?
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What is an example of a familial cancer of uncertain inheritance?
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What is an example of an acquired pre-neoplastic condition?
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What is the result of errors during DNA replication and DNA recombination?
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What is a characteristic of cancers that occur in children?
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What is a risk factor for developing cancer?
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Which of the following viruses replicates by integrating its genome into the host DNA?
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What is the result of oxidative respiration and lipid peroxidation in endogenous cellular reactions?
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Which of the following cancers is associated with Human T-cell lymphotropic virus type 1 (HTLV-1)?
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What is the mechanism of replication of some DNA viruses in host cells?
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Which of the following pathogens is associated with Kaposi's sarcoma?
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What is the result of spontaneous chemical reactions in endogenous cellular reactions?
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Which of the following cancers is associated with Epstein-Barr virus (EBV)?
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What is the role of host's translational machinery in the replication of DNA viruses?
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Study Notes
Risk Factors in Human Carcinogenesis
Lifestyle Factors
- Exposure to carcinogens, hormonal modifications, and exposure to viruses influence reproductive life, diet, and environment
- Unprotected exposure to UV radiation alters DNA, leading to skin cancer
- Having children reduces breast cancer risk for women compared to not having children
- Age of first birth and menstrual cycles influence cancer risk
- Stomach cancer is prevalent in Japan, but risk decreases if Japanese people adopt an American diet
- The Mediterranean diet, rich in fruits and vegetables, is beneficial in reducing cancer risks
- Alcohol is a carcinogen, classified by the International Agency for Research on Cancer in 2007
- Smoking accounts for 40% of all cancer deaths, with at least 81 identified carcinogens in cigarette smoke
Additional Influences
- By-products of metabolism and errors during DNA replication contribute to carcinogenesis
- Aerobic metabolism produces mutagenic oxygen radicals
- Polymerases can introduce mutations during DNA replication and repair due to associated error rates
Carcinogenic Agents
Radiation
- Ionizing radiation (alpha and beta particles, gamma rays) damages DNA directly or indirectly through reactive oxygen species
- Ionizing radiation is the most significant damage associated with carcinogenesis, causing double-strand DNA breaks
- Ultraviolet radiation (UVB) is the most effective carcinogen, causing DNA damage through absorption and dimer formation
- UVA indirectly damages DNA via free radical-mediated damage
Chemical Carcinogens
- Many chemicals in the environment and diet play a role in human carcinogenesis
- Cytochrome P450 enzymes are involved in the metabolism of chemicals in the liver and activate carcinogens to ultimate carcinogens
- Examples of chemical carcinogens include polycyclic aromatic hydrocarbons, aromatic amines, and nitrosamines and nitrosamides
- Fibrous minerals like asbestos and erionite act as chemical/physical carcinogens and mutagens
Occupational Cancers
- Beryllium, chromium, radon, nickel, and asbestos are associated with lung cancer
- Arsenic compounds are associated with lung, skin, and hemangiosarcoma
- Benzene is associated with leukemia and Hodgkin's lymphoma
- Cadmium is associated with prostate cancer
Infectious Pathogens
- Early 20th-century studies showed that viruses can cause tumors in animals
- Oncogenic viruses encode viral proteins that block tumor suppressor genes or produce mutated forms of normal genes
- Examples of carcinogenic pathogens include:
- Human papillomavirus (types 16 and 18) associated with cervical cancer
- Kaposi's sarcoma-associated herpesvirus (KSHV) associated with Kaposi's sarcoma
- Hepatitis B virus associated with liver cancer
- Epstein-Barr virus (EBV) associated with nasopharyngeal carcinoma
- Human T-cell lymphotropic virus type 1 (HTLV-1) associated with T-cell leukemia
- Helicobacter pylori associated with gastric cancer
- S. Typhi associated with hepatobiliary and gallbladder carcinoma
Age
- Frequency of cancers increases with age (55-74 years), due to accumulation of somatic mutations
- Children are affected by certain neoplasms, such as lymphoblastic leukemia, lymphoma, and retinoblastoma
Hereditary Cancers
- Hereditary cancers constitute about 5-10% of all human cancers
- Hereditary cancers tend to be bilateral and arise earlier in life
- Autosomal dominant cancer syndromes include:
- Retinoblastoma (60% have defective tumor suppressor gene)
- Familial adenomatous polyposis (100% develop colon cancer by age 50)
- Autosomal recessive cancer syndromes include:
- Xeroderma pigmentosum (defective DNA repair)
- Familial cancers of uncertain inheritance include:
- Cancers of colon, breast, ovary, and brain
Acquired Pre-Neoplastic Conditions
- Some non-neoplastic lesions increase the likelihood of developing cancer
- Examples include:
- Squamous metaplasia and dysplasia of bronchi in smokers (risk for lung cancer)
- Endometrial hyperplasia and dysplasia in women with estrogenic stimulation (risk for endometrial cancer)
- Villous adenoma of colon (risk for colorectal carcinoma)
- Leukoplakia of the oral cavity and vulva (risk for squamous cell carcinoma)
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Description
This quiz covers the factors that contribute to the development of cancer in humans, including lifestyle factors, carcinogenic agents, age, hereditary factors, and pre-neoplastic conditions.