Cancer develops when cells grow out of control and do not die. Normally cells grow and divide to replace old cells, but cancer cells continue growing abnormally. Cancer is caused by damage to DNA, which directs cell activities. Damaged DNA is not repaired in cancer cells, which can be inherited or caused by environmental exposures like smoking. Male cancer death rates have declined for lung, colon, and rectal cancers but increased for prostate cancer between 1930-2000. The lifetime risk of developing cancer for men in the US is 1 in 2. Cancer results from genetic mutations, usually in somatic cells, from cell division, external agents, or random events. Theories of cancer development include changes to proto-oncogenes, tumor suppress

1. Cancer

2. • What is Cancer?
– Cancer develops when cells in a part of the body begin to
grow out of control. Although there are many kinds of
cancer, they all start because of out-of-control growth of
abnormal cells.
– Normal body cells grow, divide, and die in an orderly
fashion. During the early years of a person's life, normal
cells divide more rapidly until the person becomes an adult.
After that, cells in most parts of the body divide only to
replace worn-out or dying cells and to repair injuries.
– Because cancer cells continue to grow and divide, they are
different from normal cells. Instead of dying, they outlive
normal cells and continue to form new abnormal cells.
– Cancer cells develop because of damage to DNA. This
substance is in every cell and directs all its activities. Most
of the time when DNA becomes damaged the body is able to
repair it. In cancer cells, the damaged DNA is not repaired.
People can inherit damaged DNA, which accounts for
inherited cancers. Many times though, a person’s DNA
becomes damaged by exposure to something in the
environment, like smoking.
• Source - ACS

3. • Male Cancer Death Rates

4. Rate Per 100,000
100
80 Cancer Death Rates, for Women
60
Lung
Uterus
Breast
40
Colon & rectum
Stomach
20
Ovary
Pancreas
0
1935
1945
1950
1960
1965
1970
1975
1980
1985
1990
1995
2000
1930
1940
1955
*Age-adjusted to the 2000 US standard population.
Source: US Mortality Public Use Data Tapes 1960-2000, US Mortality Volumes 1930-1959,
National Center for Health Statistics, Centers for Disease Control and Prevention, 2003.

5. Lifetime Probability of Developing Cancer,
Men, US, 1998-2000
Cance
r
All sites 1 in 2
Source: DevCan: Probability of Developing or Dying of Cancer Software, Version 5.1 Statistical Research and
Applications Branch, NCI, 2003. http://srab.cancer.gov/devcan

6. • What is the molecular basis of cancer?
– Cancer is a genetic disease.
• Mutations in genes result in altered proteins
– During cell division
– External agents
– Random event
• Most cancers result from mutations in somatic cells
• Some cancers are caused by mutations in
germline cells

7. • Theories of cancer genesis
– Standard Dogma
• Proto-oncogenes (Ras – melanoma)
• Tumor suppressor genes (p53 – various cancers)
– Modified Dogma
• Mutation in a DNA repair gene leads to the accumulation of
unrepaired mutations (Loeb, 1974) (xeroderma
pigmentosum)
– Early-Instability Theory
• Master genes required for adequate cell reproduction are
disabled, resulting in aneuploidy (Philadelphia chromosome)

8. • Problem posing
– Can we understand the mechanism(s) of
cancer by examining the expression patterns
of genes in the cancer cell?
– Can we use gene expression patterns to
determine the properties of a cancer?
–