Transcript Cancer Biology - Zanichelli online per la scuola

David Sadava, David M. Hillis,
H. Craig Heller, May R. Berenbaum
La nuova
biologia.blu
Anatomia e fisiologia dei viventi S
Cancer Biology
What is cancer?
Cancer is a collection of related diseases. In all types
of cancer, some of the body’s cells begin to divide
without stopping and spread into surrounding tissues.
Cancerous tumors are malignant, which means they
can spread into, or invade, nearby tissues.
Unlike malignant tumors,
benign tumors do not spread
into nearby tissues.
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What is cancer?
Carcinomas are formed by epithelial cells.
Sarcomas are cancers that form in bones and soft
tissues (muscle, fat, blood vessels, lymph vessels,
fibrous tissue).
Leukemias are the cancers
that begin in the blood-forming
tissues of the bone marrow.
There are also different types of brain and spinal cord
tumors that are named based on the type of cell in
which they formed.
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What is cancer?
Biological characteristics of cancer cells:
• Grow under control
• Ignore growth signals
• Ignore stop signals
• Become invasive
• Able to evade the immune system
• Less specialized than normal cells
• Have unstable DNA
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Cancer depends on mutations
Cancer cells have more
genetic changes (DNA
mutations) than normal
cells.
Some mutations are in
somatic cells (sporadic
cancers) or in the
germinal line of cells
(hereditary cancers).
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Gene control and cancer
Oncogenes are genes that can potentially cause
cancer.
Tumor suppressor genes are also involved in
controlling cell growth and division because they can
protect a cell from one step of the path to cancer.
DNA repair genes are involved in fixing damaged
DNA.
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What causes cancer?
• Environmental factors— mutagens. Chemical
compounds, tobacco smoke, ultraviolet rays
• Hereditary factors
• Causal factors— duplication DNA mistakes
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What causes cancer?
The human body has a lot of control systems to
protect against inflammation.
Some inflammation can last several days, but if the
inflammation is caused by cancer cells, it persists and
changes from acute to chronic inflammation.
Many chronic inflammatory diseases can increase a
person’s cancer risk.
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What causes cancer?
Genetic testing looks for specific inherited changes
in a person’s chromosomes, genes or proteins.
The test also determines whether family members
have inherited the same mutation as a family member
who is known to carry a cancer-associated mutation.
For example, specific inherited mutations in BRCA1
and BRCA2 genes increase the risk of female breast
and ovarian cancers.
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Can viruses cause cancer?
Viruses are able to cause cancer. They have
oncogenes in their viral genome.
A virus must enter a living cell and hijack its DNA in
the host cell.
RNA viruses
transcribe the
double strand
DNA with the
reverse
transcriptase from a single strand RNA
template.
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How can we prevent cancer?
Many things in our genes, lifestyle and environment
may increase our risk of getting cancer.
A healthy lifestyle could help prevent cancer,
including:
• no smoking
• doing sport
• reduce the use of alcohol
• eat more fruits and vegetables
• avoid HPV or hepatitis
• protect skin from sun
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How do we diagnose cancer?
Diagnosis determines the type
and size of a cancer and find
out if it has spread.
After diagnosis, it is possible to
suggest treatments.
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How is cancer treated?
The main treatments include:
• Surgery— open surgery or minimally invasive
surgery makes it possible to remove a tumor in part
or in whole
• Radiation therapy— external and internal beams of
iodine and cobalt serve to destroy the DNA in
humoral cells
• Chemotherapy— it works by stopping or slowing
the growth of cancer cells
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How is cancer treated?
• Hormone therapy— some hormones stimulate cell
growth; this therapy interferes with the receptors of
these hormones. Tamoxifen is used for treating
breast cancer.
• Targeted therapy— aims at the changes in cancer
cells. The Imatinib is used against a particular type
of leukemia.
• Immunotherapy— helps the immune system fight
cancer
• Stem cell transplant— is a procedure that restores
blood-forming stem cells
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How is cancer treated?
Each therapy and drug must be tested prior to use.
In vitro tests are made of single cells in the
laboratory, outside living organisms.
After a long time the drugs can
be promoted to in vivo tests,
using a whole, living organism.
All these procedures are called
preclinical development, a
stage of research that begins
before clinical trials (testing in
humans).
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What happens if a cancer returns after treatment?
Cancer stem cells are cancer cells that can
regenerate very fast.
Such cells are hypothesized to persist in tumors as a
distinct population and cause relapse and metastasis
by giving rise to new tumors.
A theory proposed to explain the metastatic
preference of cancer cells for specific organs is called
the “seed and soil” theory: interaction between the
cells (seed) and the tissues (soil) determines the
formation of a secondary tumor.
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What happens if a cancer returns after treatment?
Precision medicine is an emerging medical model
and approach to disease treatment and prevention
that takes into account individual variability in genes,
environment, and lifestyle for each person.
In this model, diagnostic testing is often used to select
appropriate therapies based on a patient’s genetic
content and other molecular and cellular analyses.
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