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Questions and Answers
Which human tissue is considered the most sensitive to radiation?
Which human tissue is considered the most sensitive to radiation?
- Bone marrow (correct)
- Salivary glands
- Lungs
- Thyroid
What is a potential consequence of radiation therapy on normal cells?
What is a potential consequence of radiation therapy on normal cells?
- Acquisition of cancer-promoting DNA damage (correct)
- Increased cell division
- Enhanced wound healing
- Improved immune response
What was one effect observed following the atomic bombings in Japan?
What was one effect observed following the atomic bombings in Japan?
- Increase in breast cancer cases
- Reduction in thyroid cancer rates
- Decrease in overall cancer cases
- Peak incidence of leukemia diagnosis (correct)
Which of the following conditions is primarily associated with ionizing radiation exposure?
Which of the following conditions is primarily associated with ionizing radiation exposure?
Which type of scans significantly increase the risk of brain tumors in children?
Which type of scans significantly increase the risk of brain tumors in children?
A mutated gene that enables the cell to proliferate by gaining a function is likely to be classified as which type of gene?
A mutated gene that enables the cell to proliferate by gaining a function is likely to be classified as which type of gene?
Which type of gene loses its function and no longer regulates cell proliferation?
Which type of gene loses its function and no longer regulates cell proliferation?
A gene that allows neoplastic cells to escape programmed cell death is most likely a type of:
A gene that allows neoplastic cells to escape programmed cell death is most likely a type of:
Which of the following processes allows errors in the DNA sequence to go unchecked, contributing to carcinogenesis?
Which of the following processes allows errors in the DNA sequence to go unchecked, contributing to carcinogenesis?
What best describes the study of how gene expression is regulated by factors other than the DNA sequence itself?
What best describes the study of how gene expression is regulated by factors other than the DNA sequence itself?
The basic unit of chromatin, which consists of DNA wrapped around histones, is referred to as:
The basic unit of chromatin, which consists of DNA wrapped around histones, is referred to as:
Which types of changes commonly occur in somatic genetic alterations in cancers?
Which types of changes commonly occur in somatic genetic alterations in cancers?
What characteristic distinguishes epigenetic changes from genetic mutations?
What characteristic distinguishes epigenetic changes from genetic mutations?
Which cancer is primarily associated with the oncogenic effects of hepatitis B and C viruses?
Which cancer is primarily associated with the oncogenic effects of hepatitis B and C viruses?
What is the predominant presentation of chronic Helicobacter pylori infection?
What is the predominant presentation of chronic Helicobacter pylori infection?
Which of the following infectious agents has NOT been linked to carcinogenesis?
Which of the following infectious agents has NOT been linked to carcinogenesis?
What is the impact of immunodeficiency states on cancer frequency?
What is the impact of immunodeficiency states on cancer frequency?
Which process is essential for immune surveillance and tumor rejection?
Which process is essential for immune surveillance and tumor rejection?
In an immunosuppressed host, how does the immune system's response to tumor antigens change?
In an immunosuppressed host, how does the immune system's response to tumor antigens change?
Which type of T-cells are primarily involved in triggering apoptosis when abnormal self antigens are present?
Which type of T-cells are primarily involved in triggering apoptosis when abnormal self antigens are present?
What is a significant consequence of chronic inflammatory states induced by infections?
What is a significant consequence of chronic inflammatory states induced by infections?
What is the primary function of microRNAs in gene expression regulation?
What is the primary function of microRNAs in gene expression regulation?
Which of the following mutations is characteristic of aflatoxin B1-associated hepatocellular carcinoma?
Which of the following mutations is characteristic of aflatoxin B1-associated hepatocellular carcinoma?
What distinguishes initiation from promotion in chemical carcinogenesis?
What distinguishes initiation from promotion in chemical carcinogenesis?
Which type of carcinogen directly alters DNA without needing metabolic conversion?
Which type of carcinogen directly alters DNA without needing metabolic conversion?
What is a common effect of cigarette smoke related to cancer risk?
What is a common effect of cigarette smoke related to cancer risk?
Which statement about chemical carcinogens is false?
Which statement about chemical carcinogens is false?
What role do electron-deficient electrophiles play in chemical carcinogenesis?
What role do electron-deficient electrophiles play in chemical carcinogenesis?
What represents a common pathway of mutation in relation to chemical carcinogens?
What represents a common pathway of mutation in relation to chemical carcinogens?
What impact does hyperglycemia have on epigenetic mechanisms?
What impact does hyperglycemia have on epigenetic mechanisms?
Which characteristic is not true of cancer-related mutations?
Which characteristic is not true of cancer-related mutations?
What is a common outcome for patients treated with alkylating agents?
What is a common outcome for patients treated with alkylating agents?
What role do polycyclic hydrocarbons play in carcinogenesis?
What role do polycyclic hydrocarbons play in carcinogenesis?
Which of the following statements about chemical promoters is correct?
Which of the following statements about chemical promoters is correct?
What is a significant risk factor for lung cancer in smokers related to the CYP1A1 gene?
What is a significant risk factor for lung cancer in smokers related to the CYP1A1 gene?
Which condition is associated with a 1.5-2-fold risk of developing colorectal cancer?
Which condition is associated with a 1.5-2-fold risk of developing colorectal cancer?
What is the primary effect of ultraviolet (UV) radiation on DNA?
What is the primary effect of ultraviolet (UV) radiation on DNA?
What type of cancers is UVB radiation predominantly associated with?
What type of cancers is UVB radiation predominantly associated with?
Which statement is true regarding individuals at risk for melanoma due to UV radiation exposure?
Which statement is true regarding individuals at risk for melanoma due to UV radiation exposure?
Which condition has shown an increased incidence of breast cancer associated with promoter activity?
Which condition has shown an increased incidence of breast cancer associated with promoter activity?
Which form of radiation is NOT an initiator of carcinogenesis?
Which form of radiation is NOT an initiator of carcinogenesis?
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Study Notes
Carcinogenesis and Mutated Genes
- A mutated gene that "gains a function" and enables cell proliferation is likely to be an oncogene.
- A mutated gene that "loses a function" and can no longer regulate cell proliferation is likely to be a tumor suppressor gene.
- A mutated gene that allows the neoplastic cell to escape cell death is likely to be an apoptosis suppressor gene.
- A mutated gene that allows errors in the DNA sequence to go unchecked and to accumulate is likely to be a DNA repair gene.
Epigenetics
- Epigenetics are factors other than the DNA sequence itself that regulate gene expression.
- These factors can include DNA hypermethylation and demethylation, microRNAs, and modifications to histones.
- MicroRNAs are small RNA molecules that act as post-transcriptional regulators of gene expression.
Chemical Carcinogens
- Mutations caused by chemical carcinogens are generally random.
- Some carcinogens, because of their chemical structure, interact with particular DNA sequences/bases.
- Cigarette smoke is a major cancer risk factor due to its high mutational potency.
- Aflatoxin B1 is a common food contaminate that results in increased risk of hepatocellular carcinoma.
Chemical Carcinogenesis: Initiators and Promoters
- Initiation is the permanent and irreversible genetic alteration of a cell exposed to sufficient dose of chemical carcinogen.
- Promotion is the stimulation and alteration of an already initiated cell by a chemical carcinogen; these changes are reversible.
- All initiating chemical carcinogens are highly reactive electrophiles.
- Direct-acting carcinogens don't require metabolic conversion to become carcinogenic.
- Indirect-acting carcinogens require metabolic conversion of the pro-carcinogen to become carcinogenic.
Radiation Carcinogenesis
- Two forms of radiation energy are carcinogenic: ultraviolet light and ionizing radiation.
- UV radiation is divided into three ranges: UVA, UVB, and UVC.
- UVB is carcinogenic due to the formation of pyrimidine dimers in DNA, which distort the DNA helix and prevent proper pairing.
- Ionizing radiation (electromagnetic and particulate) is carcinogenic due to its ability to damage DNA through the formation of oxygen free radicals.
- Certain human tissues are more sensitive to radiation than others.
- Any cell exposed to enough radiant energy can be transformed into a cancer cell.
Microbial Carcinogenesis
- Hepatitis B and C viruses (HBV, HCV) cause 70-85% of worldwide hepatocellular carcinoma.
- Helicobacter pylori infection is associated with an increased risk of duodenal or gastric ulcers, gastric adenocarcinoma, and MALT lymphoma.
Cancer and Immunosuppression
- Immunodeficiencies are associated with increased cancer frequency due to decreased immune surveillance.
- Immune surveillance involves the constant scanning of the body for abnormal cells and their destruction.
- The Class I MHC antigen processing pathway is critical in immune surveillance.
- All nucleated cells express MHC I antigens on their cell membrane, which present endogenous/self antigens.
- CD8+ (cytotoxic) T-cells bind to MHC I and trigger apoptosis if the presented antigens are abnormal.
Other Important Facts
- Cancer cells can develop resistance to chemotherapy drugs via various mechanisms.
- Tumors can grow large enough to press on surrounding organs, causing pain and dysfunction.
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