Lecture 3
Common things that predispose mutations
Protooncogenes are activated, while suppressor genes are inactivated
3 main ways this occurs: chemicals, viruses, radiation
Chemicals:
Which of the three is most common in initiating a cell producing a mutation? Chemicals –
smoking = MCC death in USA due to polycyclic hydrocarbons.
By itself, smoking is MC than virally induced or radiation induced cancers. Smoking causes lung
cancer, squamous cancer of the mouth, larynx, lung, pancreas, bladder, and if it’s not the #1
cause, it’s often #2, such leukemias, cervical ca, and colon.
MCC papillary tumor of the bladder = transitional cancer (smoking)
What if you worked in a dye industry? Aniline
What if you had Wegener’s granulomatosis, put on a drug and got hematuria, did cytology and
saw cells, what drug is pt on? Cyclophosphamide (hemorrhagic cystitis); prevent with mesna,
and can cause transitional cell carcinoma (therefore acts as a carcinogen!)
Lung cancer – MCC = polycyclic hydrocarbons from smoke; most often assoc with smoking is
small cell and squamous;
Viruses:
Virus assoc cancer: a virus with nonpruritic raised red lesions. Dx? Kaposi’s sarcoma (due to HHV
8)
Burkitts; due to Epstein barr varies which also causes nasopharyngeal carcinoma, esp. in
Chinese
liver – Hepatocellular carcinoma due to hepatitis B from Asia; also due to a mold – aflatoxin B;
combo of hep B, cirrhosis, plus aflatoxin makes is common in Asia; can also be caused by hep C
HIV is assoc with primary CNS lymphoma. They will ask: the rapidly increasing incidence of
primary CNS lymphoma can be directly attributed to what?
HIV
HPV causes squamous cancer of cervix, vagina, and vulva, and anus of homosexuals due to
unprotected intercourse; due to HPV 16, 18, 31. This virus causes anal squamous cell carcinoma
in homosexuals. The virus works by making two proteins, E6 which knocks off p53, while E7
knocks of Rb.
Radiation
MC cancer assoc with radiation = leukemi
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