Download cell cycle regulation and cancer cells

Regulation of the Cell Cycle
Key Concept: Cell Cycle regulation is
necessary for healthy growth.
*Internal and external factors regulate
cell division*
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Both external and internal factors regulate the
cell cycle in eukaryotic cells.
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External factors come from outside the cell.
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They include messages from nearby cells and
from distant parts of the organism’s body.
Internal factors come from inside the cell
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These include several types of molecules found in
the cytoplasm.
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External factors include physical and
chemical signals.
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One example of a physical signal is cell-cell
contact.
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Most mammal cells form a single layer in a culture
dish and stop dividing once they touch other cells.
One example of a chemical signal is called a
Growth factor
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Growth factors are proteins that bind to receptors
that activate specific genes to trigger cell growth.
External factors continued…..
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Some growth factors affect many different
types of cells.
For example, platelets are sticky fragments of bone
marrow cells. They form clots that help stop bleeding.
Platelets store a type of growth factor that helps your
body repair wounds by triggering the growth of many
different cell types.
 Erythropoietin stimulates the
production only of RBC.
 Growth hormone results in bone
growth and affects your protein and
fat metabolism.
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Internal Factors
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When external factors bind to
their receptors, they can
trigger internal factors that
affect the cell cycle.
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2 of the most well studied
internal factors include kinases
and cyclins
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These two proteins help a cell
advance to different stages of the
cell cycle
Apoptosis
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Just as some cells need to grow and divide, other cells
need to die.
Apoptosis is programmed cell death.
 a normal feature of healthy organisms
 caused by a cell’s production of self-destructive
enzymes
webbed fingers
 occurs in
development
of infants
What is Cancer?

Cancer is the general name for a group of
more than 100 diseases. Although there are
many kinds of cancer, all cancers start
because abnormal cells grow out of control.
Untreated cancers can cause serious illness
and death.
How cancer starts….

Cancer starts when cells in a part of the body start
to grow out of control.

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Aka- regulation of the cell cycle breaks down.
Cancer cell growth is different from normal cell
growth.
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Instead of dying, cancer cells continue to grow and form
new, abnormal cells.
They also keep dividing in the absence of growth factors
required for division.
Cell division is uncontrolled in cancer.

Cancer cells can also invade (grow into) other
tissues, something that normal cells cannot
do. Growing out of control and invading other
tissues are what makes a cell a cancer cell.
Cell division is uncontrolled in cancer.

Cancer cells form disorganized clumps called tumors.
 Benign tumors remain clustered and can be removed.
 Malignant tumors metastasize, or break away, and can
form more tumors.
normal cell
cancer cell
bloodstream
But why are tumors so harmful?

1. Cancer cells do not perform the specialized
functions needed by the body

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In the lung, cancer cells do not exchange oxygen and
carbon dioxide
In the brain, they do not transmit the carefully ordered
electrical messages needed to interpret info

Therefore, the body has large clumps of rapidly
dividing cells that require lots of food and blood
supply but contribute nothing to the body’s function.

2. Also, a growing tumor can exert great pressure on
surrounding organs.
Why has the regulation of the cell cycle stopped?

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Cancer cells come from normal cells that have suffered
damage to the genes (DNA) that help make proteins
involved in cell-cycle regulation.
Most cancer cells carry mutations, or errors, in two types
of genes.

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Mutations in these genes can be inherited.

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Oncogenes – accelerate cell cycle
The second type act as cell-cycle brakes
Example: some types of breast cancers
Others can be caused by exposure to radiation or
chemicals

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Example: some skin cancers are due to DNA damage caused by
UV radiation
Carcinogens are substances known to produce or promote the
development of cancer
 Tobacco smoke and air pollutants
Some mutated forms of oncogenes are even carried by viruses;
causes cervical cancer.
Cancer Treatments

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Standard cancer treatment often involves both
radiation and chemotherapy.
Radiation therapy is the use of radiation to kill
cancer cells and shrink tumors.

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It works by damaging a cell’s DNA so much that the cell
cannot divide.
Radiation is usually targeted to a specific region because it
can hurt healthy cells.
Chemotherapy uses certain drugs, often in
combination, to kill actively dividing cells.

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Like radiation, it kills both cancerous and healthy cells.
However, chemotherapy is systemic – drugs travel
throughout the entire body.
How cancers differ

No matter where a cancer may spread, it’s always
named for the place where it started.

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For example, breast cancer that has spread to the liver is
called metastatic breast cancer, not liver cancer. Likewise,
prostate cancer that has spread to the bone is called
metastatic prostate cancer, not bone cancer.
Different types of cancer can behave very differently.

For instance, lung cancer and skin cancer are very
different diseases. They grow at different rates and respond
to different treatments. This is why people with cancer need
treatment that is aimed at their kind of cancer.
Cancer Facts
Presented using information from
The American Cancer Society
www.cancer.org
and
The Mayo Clinic
www.mayoclinic.com
Links to Cancer Deaths
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Lung Cancer is the leading cause of cancer death in
both men and woman, and is one of the hardest
cancers to treat.
Smoking and exposure to secondhand smoke
accounts for 1 in 5 deaths
Smoking is responsible for almost 9 out of 10 lung
cancer deaths.
Cigarette smoking accounts for a least 30% of all
cancer deaths.
About ½ of all Americans who keep smoking will die
because of the habit.
Smoking kills more Americans than alcohol, car
accidents, suicide, AIDS, homicide, and illegal drugs
combined.
Smoking is also linked to the following
cancers:
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lung
larynx (voice box)
oral cavity (mouth,
tongue, and lips)
pharynx (throat)
esophagus (tube
connecting the
throat to the
stomach)
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stomach
pancreas
cervix
kidney
bladder
acute myeloid
leukemia
What about other forms of tobacco?

Chewing tobacco has been linked to multiple
types of cancer, including:
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Esophagus
Mouth
Pancreas
Throat
Inhaled chewing tobacco (snuff) may
increase the risk of cancers, including:
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Esophagus
Mouth
Skin Cancer
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How many people get skin cancer?
Skin cancer is the most common of all
cancers.
It accounts for nearly half of all cancers in the
United States.
More than 2 million cases of non-melanoma
skin cancer are found in this country each
year. Melanoma, the most serious type of
skin cancer, will account for about 68,130
cases of skin cancer in 2010.
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What are the risk factors for skin cancer?
Risk factors for non-melanoma and
melanoma skin cancers include:
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Unprotected and/or excessive exposure to
ultraviolet (UV) radiation (tanning beds)
Fair complexion (especially babies)
Occupational exposures to coal tar, pitch,
creosote, arsenic compounds, or radium
Family history
Multiple or atypical moles
Severe sunburns as a child