The body is a society whose members are cells, The body is a society whose members are cells, organized into tissuesorganized into tissues

Cancer cells grow when they should notCancer cells grow when they should not Cancer cells invade other tissuesCancer cells invade other tissues These are the behaviors of free growing cells, like These are the behaviors of free growing cells, like

bacteriabacteria

Types of Tumors

Benign MalignantGrow slowly

as a single massGrow rapidly and

invade other tissues

90% of mutagens are carcinogens90% of mutagens are carcinogens

An environmental insult leads to DNA damageAn environmental insult leads to DNA damage This results in a mutation…a change in DNA sequenceThis results in a mutation…a change in DNA sequence This mutation often alters cell proliferationThis mutation often alters cell proliferation The cancer cells grows out of controlThe cancer cells grows out of control

One mutation alone does not lead to cancerOne 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 slowlyCancer cells develop slowly

Smoking leads to lung Smoking leads to lung cancercancer

10 to 20 years10 to 20 years Radiation exposure (the Radiation exposure (the

bomb) causes leukemiasbomb) causes leukemias

5 to 8 years5 to 8 years

Cancer as a function of age

Genes implicated in cancer

• Oncogenes• Tumor supressor genes• DNA repair genes

Genes supressores de tumoresGenes supressores de tumores

Estes genes inibem normalmente o crescimento, a Estes genes inibem normalmente o crescimento, a diferenciação ou a divisão celularesdiferenciação ou a divisão celulares

A mutação provoca uma perda de funçãoA mutação provoca uma perda de função Ambas as cópias do gene são mutadas (recessivos)Ambas as cópias do gene são mutadas (recessivos) Examplo: gene RbExamplo: gene Rb

Mutações no Rb provocam retinoblastomasMutações no Rb provocam retinoblastomas

Mutações no gene Rb podem conduzir ao retinoblastoma

X X X XX X X

XX

O p53 é um gene supressor de tumores

Most people with an alelle of p53 mutated develops cancer