Lecture 18

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Questions and Answers

What percentage of cancer deaths can be prevented by modifying or avoiding key risk factors?

20%

30% (correct)

40%

50%

What is the percentage of cancer deaths attributed to smoking?

40% (correct)

30%

50%

20%

What is the benefit of the Mediterranean diet in terms of cancer risk?

Has no effect on cancer risk

Has an unknown effect on cancer risk

Decreases the risk of cancer (correct)

Increases the risk of cancer

What is the effect of having children on breast cancer risk for women?

Decreases breast cancer risk Signup and view all the answers

What is the International Agency for Research on Cancer's classification of alcohol?

Carcinogen Signup and view all the answers

What is the risk of stomach cancer for Japanese people who migrate to the USA and adopt the American diet?

Decreases Signup and view all the answers

What is the effect of unprotected exposure to the sun on DNA?

Causes DNA alterations that can lead to skin cancer Signup and view all the answers

How many carcinogens have been identified in cigarette smoke?

At least 81 Signup and view all the answers

What contributes to carcinogenesis?

Both by-products of metabolism and errors during DNA replication Signup and view all the answers

What type of radiation is most closely linked to skin cancer?

Ultraviolet radiation Signup and view all the answers

What is a characteristic of ionizing radiation?

It induces ionization of molecules Signup and view all the answers

How does UVA radiation damage DNA?

Through the generation of reactive oxygen species Signup and view all the answers

What is a by-product of aerobic metabolism?

Oxygen radicals Signup and view all the answers

What type of DNA damage is most closely associated with ionizing radiation?

Double-strand DNA breaks Signup and view all the answers

What is a characteristic of ultraviolet radiation?

It damages DNA through the formation of dimers Signup and view all the answers

What is a common feature of radiation-induced carcinogenesis?

It can occur through both direct and indirect mechanisms Signup and view all the answers

What is the role of Cytochrome P450 enzymes in the liver?

To activate carcinogens to ultimate carcinogens Signup and view all the answers

Which of the following fibrous minerals is a group of fibrous silicate minerals that was used extensively in building materials?

Asbestos Signup and view all the answers

What type of cancer is associated with exposure to benzene?

Leukemia Signup and view all the answers

What is the role of oncogenic viruses in carcinogenesis?

They encode viral proteins that block tumor suppressor genes Signup and view all the answers

What is the effect of arsenic compounds on the human body?

They cause lung, skin, and hemangiosarcoma Signup and view all the answers

Which of the following is an example of a polycyclic aromatic hydrocarbon (PAH)?

Not mentioned in the text Signup and view all the answers

What is the result of hydrolysis of the glycosidic bond between a base and deoxyribose?

Formation of a mutation Signup and view all the answers

What is a characteristic of hereditary cancers?

They tend to be unilateral and arise earlier in life Signup and view all the answers

What is a characteristic of autosomal recessive cancer syndromes?

Characterized by chromosomal or DNA instability Signup and view all the answers

What is an example of a familial cancer of uncertain inheritance?

Cancer of the colon, breast, ovary, and brain Signup and view all the answers

What is an example of an acquired pre-neoplastic condition?

Squamous metaplasia and dysplasia of bronchi in smokers Signup and view all the answers

What is the result of errors during DNA replication and DNA recombination?

Formation of a mutation Signup and view all the answers

What is a characteristic of cancers that occur in children?

They are never bilateral and arise at an early age Signup and view all the answers

What is a risk factor for developing cancer?

Increasing age Signup and view all the answers

Which of the following viruses replicates by integrating its genome into the host DNA?

Hepatitis B virus Signup and view all the answers

What is the result of oxidative respiration and lipid peroxidation in endogenous cellular reactions?

Production of ROS that can react with DNA and lipids Signup and view all the answers

Which of the following cancers is associated with Human T-cell lymphotropic virus type 1 (HTLV-1)?

T-cell leukemia Signup and view all the answers

What is the mechanism of replication of some DNA viruses in host cells?

Replication as episomes within host cells Signup and view all the answers

Which of the following pathogens is associated with Kaposi's sarcoma?

Kaposi's sarcoma-associated herpesvirus (KSHV) Signup and view all the answers

What is the result of spontaneous chemical reactions in endogenous cellular reactions?

Mutations in DNA Signup and view all the answers

Which of the following cancers is associated with Epstein-Barr virus (EBV)?

Nasopharyngeal carcinoma Signup and view all the answers

What is the role of host's translational machinery in the replication of DNA viruses?

Production of viral proteins Signup and view all the answers

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.