Announcements
Chapter 27, Starving a
Tumor, pg. 565
Chapter 8, Cell Cycle
Control and Cancer, pg. 165-170
Chapter 12, Gene
Mutation, pgs. 248-250
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Objectives:
The content of today's lecture will help you answer
question #1 on
this assignment:
After studying this material you should be able to:
-
Describe the mechanisms by which cell division is
controlled in your
body.
-
List the distinguishing characteristics of a cancer cell
and
describe the ways in which a cell may be triggered to become
cancerous.
-
Describe the changes in genes and gene expression that
lead
to
cancer.
-
Describe the role of proto-oncogenes, oncogenes, and tumor
supressor
genes in the development of cancer.
-
Explain the "two hit" hypothesis for cancer development.
-
Explain how an understanding of the controls of the cell
cycle might
facilitate the development of cancer treatments.
Web
Resources
Characteristics of Cancer Cells
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Loss of cell cycle control
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Heritability
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Transplantability
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Genetic mutability
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Dedifferentiation
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Loss of contact inhibition
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Angiogenesis (in growing tumours)
-
Ability to spread
(metastasize)
The Life of a Cell:
Cell Division, Cell Maturation, and Cell Death (Apoptosis)
from
CancerQuest.org
Cells normally have built in systems that check to be sure the
cell
is OK before initiationg cell division. Proteins check for complete DNA
replication, damaged DNA, and adequate nitrients. If the checks
indicate the cell is not ready to divide it does not.
Cells normally divide when told to do so by some outside
influence,
like a hormone or growth factor. Cells also normally respond to signals
that tell them to stop dividing.
Cancer is often the result of some genetic loss of control of
the
cell cycle. Genetic changes by mutation or chromosome abnormalities in
a cell result in cells that divide when they should not be dividing.
The Genes of Cancer from CancerQuest.org
-
Proto-oncogenes (good) and Oncogenes
(bad)
Proto-oncogenes are normal genes that we all have. They
normally
control cell division or cell death.
-
Oncogenes are "cancer genes" that produce unregulated
cell growth by
stimulating cell division or preventing cell death. They are the result
of mutations in normal cell division control genes. These normal genes
are called proto-oncogenes. (If something goes wrong with them they can
become oncogenes.)
-
Oncogenes act as "dominant" genes in that it takes only
one mutated
copy to produce unregulated cell division.
-
Tumor suppressor genes
-
Tumor supressor genes produce proteins that inhibit cell
division if
conditions are not right. Cells would be kept from dividing if the DNA
were damaged, a needed growth factor or hormone were missing, or if
there were defects in the cell division machinery.
-
Tumor supressor genes loose their ability to control
cell
division
when both copies of the gene are damaged by mutation or
chromosomal abnormalities.
-
Two-Hit Hypothesis - If it takes mutations in both
copies of a tumor supressor gene on homologous chromosomes in a cell
(to
become homozygous recessive), what happens to your chances of
developing
cancer if you are born with one mutated copy?
-
Two-Hit Hypothesis Slide from The National Cancer
Institute
Biomarkers and Early Detection and treatment of Cancer
-
Often times cancer has already spread (metastasized)
before
a tumor
can be detected by physical exam or by imaging techniques.
-
Scientists are now attempting to find biomarkers that wil
help them
detect cancer at an early stage.
-
Biomarkers may provide an avenue to disrupt the abnormal
gene
activity of cancer cells and put the cancer cells back on a track to
normal activity.
-
The use of Gene Chips or Micro Arrays to compare gene
activation in
tumor cells and normal cells.
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