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The body is a society whose members are cells,
organized into tissues
Cancer cells grow when they should not
Cancer cells invade other tissues
These are the behaviors of free growing cells, like
bacteria
Types of Tumors
Benign
Grow slowly
as a single mass
Malignant
Grow rapidly and
invade other tissues
90% of mutagens are carcinogens
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An environmental insult leads to DNA damage
This results in a mutation…a change in DNA sequence
This mutation often alters cell proliferation
The cancer cells grows out of control
One mutation alone does not lead to cancer
There are 1016 cell divisions in a human lifetime
Rate of spontaneous mutation = 10-6 /gene/division
Every gene will have 1010 mutations in an average lifetime
Cancer cells develop slowly
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Smoking leads to lung cancer
10 to 20 years
Radiation exposure (the bomb)
causes leukemias
5 to 8 years
Cancer as a function of age
Genes implicated in cancer
• Oncogenes
• Tumor supressor genes
• DNA repair genes
Genes supressores de tumores
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Estes genes inibem normalmente o crescimento, a
diferenciação ou a divisão celulares
A mutação provoca uma perda de função
Ambas as cópias do gene são mutadas (recessivos)
Examplo: gene Rb
Mutações no Rb provocam retinoblastomas
Mutações no gene Rb podem conduzir ao retinoblastoma
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O p53 é um gene supressor de tumores
Most people with an alelle of p53 mutated develops cancer