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90 Cards in this Set
- Front
- Back
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categories of oncogenic agents
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- chemical carcinogens
- radiation - oncogenic viruses and other microbes |
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which gene helps cells recognize abnormal DNA
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p53
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after p53 has helped the cells detect abnormal DNA, what are the possible outcomes of that cell
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- DNA repair
- apoptosis |
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promotors cause _______________
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clonal expansion of the initiated cell
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one of the first people to see occupational diseases through his study of chimney sweeps' cancer
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Sir Percival Pott
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what are the categories of chemical carcinogens
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- direct-acting: alkylating agents, acylating agents
- procarcinogens that require metabolic activation: polycyclic and heterocyclic aromatic hydrocarbons, aromatic amines, amides, azo dyes |
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which carcinogens are activation indepedent complete carcinogens
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direct-acting alkylating agents
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alkylating agents, in general, are ___________
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weak carcinogens
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some alkylating agents are used as ___________________ but can induce _____________________________
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anti-cancer drugs; lymphoma, leukemia, and other forms of cancer
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name alkylating agents that are used as anti-cancer drugs
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cyclophosphamide, chlorambucil, busulfan, melphalan
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powerful immunosuppressive agents used in treatment of immunologic disorders
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cyclophosphamide
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risk of induced cancer from alkylating agents is ________
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low
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how do alkylating agents exert therapeutic effects
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interacting with and damaging DNA
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what effects of alkylating agents render them carcinogenic
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interacting with and damaging DNA (same as their therapeutic effects)
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some of the most potent carcinogens
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polycyclic aromatic hydrocarbons
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polycyclic armomatic hydrocarbons require ________________
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metabolic activation
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name 3 ways polycyclic aromatic hydrocarbons are produced
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- combustion of tobacco (cigarette smoking)
- produced from animal fats from broiled, smoked meats - combustion of fossil fuels |
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carcinogenicity of some aromatic amines and azo dyes is exerted in the _____________
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liver
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what enzyme system converts aromatic amines and azo dyes into an 'ultimate carcinogen'
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cytochrome p-450 oxygenase
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__________ is responsible for a 50-fold increased risk of bladder cancer in heavily exposed workers in analine dye and rubber industries
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beta-naphtylamine
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food colorants
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azo dyes
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what carcinogens are possibly formed in the gi tract of humans
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nitrosamines and amides
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one form of cancer that may be induced by nitrosamines and amides
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gastric carcinoma
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nitrosamines and amides are derived ______________________________.
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in the stomach from nitrostable amines and nitrates used as a preservative, which can be converted to nitrites by bacteria
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carcinogen associated with bronchogenic carcinoma, mesothelioma, gastrointestinal cancer
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asbestos
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carcinogen associated with hemangiosarcoma
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vinyl chloride, poly vinyl chloride
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arsenic is associated with
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skin cancer
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there is a carcinogen produced by a fungus. name the fungus and the carcinogen. this carcinogen is associated with _______________
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Aspergillus flavus, aflatoxin B1; hepatocellular carcinoma
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aflatoxin interacts with _______ in the production of hepatocellular carcinoma
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HBV
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radiant energy can transform what types of cells
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any cell type
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how does radiation lead to neoplasia
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radiation ionizes water in cells, which leads to free radicals
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radiation effects can be _______________ with other potential carcinogenic influences
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additive or synergistic
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epidemiological evidence that uv rays from the sun increase incidence of ________________________________
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squamous cell carcinoma, basal cell carcinoma, melanoma of the skin
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what people have the highest incidence of skin cancers
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fair skin, repeated sun burns
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factors affecting risk of skin cancer
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- type of uv rays
- intensity of exposure - quantity of light-absorbing 'protective mantle' of melanin in the skin |
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wavelenghth ranges of uv rays? which is responsible for induction of most cutaneous cancers?
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uva, uvb, uvc; uvb-->cutaneous cancers
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effects of UVA rays
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- penetrates deep ---> damages dermis, subdermis
- creates free radicals |
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why are UVC rays not considered significant
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they are filtered out by the ozone layer
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carcinogenicity of UV radiation is attributed to formation of ______________________
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pyrimidine dimers in the DNA
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name the pathway that usually repairs DNA damage
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nucleotide excision repair (NER) pathway
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steps of NER pathway
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1- recognition of DNA lesion
2- incision of the damaged strand on both sites of the lesioin 3- removal of the damaged nucleotide 4- synthesis of a nucleotide patch 5- ligation |
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what happens when the NER pathway is overwhelmed?
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unrepaired DNA damage leads to transcriptional errors and cancer
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xeroderma pigmentosum is characterized by
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extreme photosensitivity and 2000 fold increased risk of skin cancer
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molecular basis of xeroderma pigmentosum
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inherited inability to repair UV induced DNA damage
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xeroderma pigmentosum is a __________________, caused by ____________________________.
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genetically heterogeneous condition; mutation of one of the genes involved in NER pathway
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UVB rays cause mutations in __________________________.
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oncogenes and tumor suppressor genes, such as RAS and p53
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in NER, which proteins recognize damaged DNA
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XPC and HR23 (possibly XPE)
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after damaged DNA is recognized, what is the next step in NER
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a complex containing THIIF is formed at the lesion
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_________ and __________ (which are ___________) unwind the DNA near the lesion
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XPB and XPD; helicases
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protein required for recruitment of additional components to repair DNA
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XPA
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what proteins cleave the damaged region of DNA
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endonucleases XPF/ERCC1 and XPG
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cleaved region of damaged DNA is filled by
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DNA polymerases delta and epsilon
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defects in bypass repair synthesis of UV damage is caused by
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DNA polymerase η (eta)
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organ transplant recipients develop cutaneous malignancies ______________________
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250-times rate of general population
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tumor induction time in humans after overexposure to ionizing radiation
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5-20 years
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first malignancy associated with exposure to x-rays
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carcinoma of the skin
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most frequent radiation-induced cancer
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leukemia
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second-most frequent radiation-induced cancer
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thyroid cancer - only in the young
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intermediate category of radiation-induced cancers
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breast, lungs, salivary glands
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tissues relatively resistant to radiation-induced neoplasia
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skin, bone, gi tract,
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bacterium associated with gastric tumors
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Helicobacter pylori
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human DNA viruses that can cause cancer
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HPV, epstein-barr virus (EBV), HBV, kaposi sarcoma herpes virus (KSHV)
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oncogenic RNA virus
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HCV
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HPV's have been implicated in what cancers?
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particularly squamous cell carcinoma of the uterine cervix, also oral and laryngeal cancers
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which HPV's are associated with cervical cancer
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16 and 18 (less commonly 31, 33, 35, 51)
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genital warts
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HPV 6 and 11
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EBV has been implicated in the pathogenesis of:
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1- african form burkitt lymphoma
2- b-cell lymphomas 3- some cases of hodgkins lymphoma 4- nasopharyngeal carcinomas |
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b-cell lymphomas caused by ____________ are particularly found in people with ______________________.
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EBV; HIV infection, or undergoing immunosuppressive treatment after organ transplant
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what does EBV infect
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epithelial cells of oropharynx and b lymphocytes
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EBV gains entry into B cells via _______________
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CD21 molecule
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EBV infection of B cells is _________
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latent
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LMP-1 binds to and activates a signaling molecule that is normally activated by _________________.
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CD40 receptor of B cell
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histological appearance of burkitt lymphoma
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starry sky
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HBV encodes a regulator element called _________. what is its effect?
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HBx protein; it disrupts normal growth control of infected liver cells. also binds to p53, appears to interfere with its growth suppressing activities
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how do HBV infections become cancer
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1- chronic liver cell injury ---> regenerative hyperplasia with risk of subsequent genetic changes
2- HBx |
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oncogenic RNA viruses
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- HCV
- human t-cell leukemia virus 1 (HTLV-1) |
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HTLV-1 is associated with
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t-cell leukemia-lymphoma
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HTLV-1 has tropism for ___________
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CD4+ T cells
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transmission of HTLV-1
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transmission of infected t cells via sexual intercourse, blood products, breast feeding
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leukemia develops in what % of individuals infected with HTLV-1
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3-5%
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latent period of HTLV-1 before leukemia
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40-60 years
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HTLV-1 causes ______________________ through the effects of _________ protein.
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expansion of nonmalignant polyclonal cell population; TAX
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effects of TAX protein
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activates the transcription of several host cell genes involved in proliferation and differentiation of T cells
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antibiotic treatment of H. pylori leads to __________________
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regression of gastric lymphoma
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genes associated with virulence of H. pylori
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CagA and VacA
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disease causing strains of H. pylori contain
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pathogenicity island
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effect of VacA
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apoptosis
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malignancy associated with H. pylori infection
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gastric adenocarcinoma
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gastric lymphomas arise in _____________________
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mucosa-associated lymphoid tissue
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in gastric carcinomas caused by H. pylori, tumor growth is initially dependent on ____________________
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immune stimulation by H. pylori
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