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33 Cards in this Set

  • Front
  • Back
4 phases of malignant tumor growth?
malignant transformation, growth of transformed cell, local invasion, distant metastasis
agents that induce neoplastic change?
chemical carcinogens, radiant energy, oncogenic microbes (viruses chiefly)
describe initiation in chemical carcinogenesis
exposure to inappropriate dose of a carcinogenic agent (initiator) thus altering cell, rendering it likely to give rise to a tumor, however, it alone cannot give rise to a tumor. rapid, irreversible, has memory, permanent mutation to the DNA.
describe promotion in chemical carcinogenesis
can induce tumors in initiated cells but are non tumorgenic by themselves. effect is reversible and unlikely that they affect the DNA
direct vs indirect carcinogenesis?
direct requires no metabolic conversion while indirect does
describe the chemistry of the direct acting carcinogens and ultimately formed carcinogens that allows them to react with DNA, RNA, and protein
highly reactive electrophiles (have electron deficient atoms) and can react with nucleophilic (electron rich) sites in the cells (ie DNA, RNA, and proteins with DNA being the main target)
most carcinogens are metabolized by what?
cytochrom p450 dependent mono oxygenase. note that metabolism can lead to detox of the procarcinogen/carcinogen or activation of it
what must happen for the change in DNA to become fixed and permanent?
it must undergo one replication cycle
what specefic gene mutation is frequently noted in chemically indued cancers?
RAS gene mutations
describe the characteristics of promoters of carcingoenisis and give some examples
non electrophillic, do not damage DNA. phorbol esters, phenols, hormones, drugs (phenobarbital). TPA is most widely used tumor promoter, it activates PKC that pis cell proliferating and diferentiating molecules
describe the action of direct acting alkylating agents in carcinogenesis
releatively weak, exs are cyclophosphamide, chlorambucil, busulfan, melphalan. induce lymphomas, leukemias, and others, interaction with and damage to the DNA renders them therapeutic and carcinogenic
describe the action of polycyclic aromatic hydrocarbons.
indirect carcinogens, activated by p450, most potent carcinogen, formed during combustion of tobacco with cig smoking, contribute to lung and bladder cancer
describe the action of aromatic amines and azo dyes
metabolized in liver via cyt p450 and excreted in urine. act on transitional epi of bladder, B naphthylamine implicates a 50 fold increase in bladder CA
describe the action of aflatoxin B1.
produced by aspergillus flavus, from corn, rice, peanuts, causes hepatocellular carcinoma
describe the actions of nitrosamines and amides
carcinogen formed in GI tract in humans, implicated in CA of the stomach, from preservatives and are converted to nitrites by bacteria
cancers caused by asbestos?
bronchogenic carcinoma, mesothelioma, GI cancer
CA caused by vinyl chlorides?
hemangiosarcomas of liver
cancer caused by estrogens?
endometrial carcinoma in post menopausal women
describe the acylating agents as carcinognes
dimethylcarbamyl chloride, do not need metabolic conversion and are weal carcinogens,many are also therapeutic agents
degree of cancer risk from UV exposure depends upon?
type of rays, intensity of exposure, quantity of melanin
effects of UV light on cells?
inhibition of cell division, inactivation of enzymes, induction of mutation, cell death
carcinogensis from UV is attributed to what? damage is repaired by?
pyrimidine dimers repaired by nucleotide excision repair. note mutations in oncogenes and tumor suppressors especially RAS and p53 have been notes
initiation in UV damage? promotion?
UV light IS the initiating mechanism and CMI changes is the promoter
what disease is especially likely to induce skin cancer and why?
xeroderma pigmentosum from a defect in the nucleotide excision repair of DNA
what are some types of ionizing radiation that are carcinogenic and give the specefic CA caused by each
X rays cause skin cancer. uranium miners have increase in lung cancer. atom bomb survivors of fallout got AML, CML after 7 years and some got thyroid, breast, colon, and lung Ca, after longer pds. thorotrast is used as a radiologic imaging contrast material and can cause angiosarcoma. therapeutic irradiation is carcinogenic - 9% of head and neck radiation in infacny and child hood developed thyroid cancer
how do DNA oncogenic viruses cause CA on a molecular level?
genomes of the oncogenic DNA viruses integrate into and form stable associations with the host genome
what types of HPV are responsible for squamous cell cancer of the cervix?
85% from types 16, 18. less frequently by 31, 33, 35, and 51.
HPV that causes benign squamous papillomas (warts)?
1,2,4, and 7. note 6 and 11 cause warts with low malignant potential
describe aspects of integration and other carcinogenic activities of HPV.
integration site is clonal (site of integration is identical in all cells of a given cancer), viral DNA is interrupted at E1/E2 ORF, in 16 and 18 viral protein E6 binds and facilitates the degradation of p53 while E7 binds tumor suppressor protein pRb
EBV is seen in what cancers?
african burkitts, B cell lymphoma, hodgkins lymphoma, nasopharyngeal carcinoma
molecule that allows infection of nasopharynx epithelium and B lymphocytes to be infected with EBV.
CD21 molecules
common genetics of Burkitt's lymphoma?
t (8;14) or less common variant translocation that leads to dysregulated expression of the c-myc oncogene
how does hep B virus cause hepatocellular cancer?
not sure- genome does not encode oncoproteins and pattern of integration is not constant. liver injury and regenerative hyperplasia increases the risk for genetic mutation