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Human Biology (BIOL 104)
Talk Thirteen:
Cancer
Chapter 22
What Is Cancer?
– Cancer is caused, in part, by a breakdown in
control of the cell cycle
– The cell cycle is controlled by proteins in the cell
that give either a “GO”, a “STOP” or a “die”
signal
– Cancer cells divide excessively
- they have too many “GO” signals or
not enough “STOP” signals
- cancer cells can also ignore “die” signals =
apoptosis
Cancer Cells: Growing Out of Control
• Normal plant and animal cells have a cell
cycle control system
• When the cell cycle control system
malfunctions
– Cells may reproduce at the wrong time or
place
– A benign tumor may form
Cancer Cells: Growing Out of Control
• Proto-oncogenes –
• Genes whose products
signal and regulate
normal cell division
• The abnornal, mutated
form of the protooncogene that lead to
cell transformation and
cancer are called
oncogenes.
Cancer Cells: Growing Out of Control
• Oncogenes differ from
proto-oncogenes in three
basic ways
• 1- Timing and quality of
expression
• 2- Structure of protein
products
• 3 – Degree to which their
protein products are
regulated by cellular signals
Remember Regulation of gene expression?
• Gene expression can be
regulated at 5 later steps
too.
• 1 – transcription turned on
or off
• 2- mRNA modified to allow
exit from nucleus
• 3 – Alteration of rate of
translation
• 4 – modification of protein
folding
• 5 – Effector molecules
Cancer Cells: Growing Out of Control
• The mutation of a protooncogene to an oncogene can
alter the cell division signals
at any of the 5 steps and
trigger uncontrolled cell
division
• One type of oncogene codes
for a modified growth factor
that continuously 2nd
messengers and thus always
triggers cell division
• Another causes the cell to
secrete growth factors
allowing the cell to divide
Cancer Cells: Growing Out of Control
• Another codes for altered
2nd messenger that tells the
cell to activate cell division
• Another alters the
regulatory system in the
nucleus
– So the DNA continues
to replicate and this
drives continuous cell
division
Six Hallmarks of Cancer
1.Self-sufficiency in growth signals or response
2.Insensitivity to grown inhibitor signals (antigrowth
signals)
3.Evasion of programmed cell death (apoptosis)
4.Limitless replicative potential (no senescence)
5.Sustained angiogenesis (stimulation of blood vessel
growth)
6.Tissue invasion and metastasis
Progression of cancer
• There are several mechanisms which prevent mutations
causing cancer
• A mismatch leads to a permanent mutation on one DNA
strand if not corrected
Progression of cancer
• A mismatch repair protein (spell-checking protein) acts on a
mutated DNA strand
• Cuts out the DNA and allows the correct base to be added
What cancer affects Tissues
• Tissue: Similarly specialized cells that
perform a common function in the body.
• 4 main tissue types in the human body:
– 1. Epithelial: covers body surface and lines
body cavities.
– 2. Connective: binds and supports body
parts.
– 3. Muscular: Moves body parts
– 4. Nervous-Receives, interprets and sends
signals.
Three types
• A: Adhesion junction
• Cells within tissues and organs
must be anchored to one
another and attached to
components of the
extracellular matrix.
• Anchoring proteins extend
through the plasma membrane
to link cytoskeletal proteins in
one cell to cytoskeletal
proteins in neighboring cells
as well as to proteins in the
extracellular matrix
Three types
• B: Tight junction
• Found in epithelia, they act as
barriers that regulate the
movement of water and solutes
between epithelial layers.
• There is evidence to suggest
that the structures in which
solutes pass through are
somewhat like pores.
• Prevent the highly acidic gastric
fluid in your stomach from
leaking out and digesting
proteins of your own body
instead of those you consume as
food.
Three types
• C: Communicating (GAP)
junctions
•
Allow for direct chemical
communication between adjacent
cellular cytoplasm through diffusion
without contact of the extra cellular
fluid.
•
Protrudes across the cell membrane,
and when 2 adjacent cells interact,
they form the gap junction channel.
•
Play vital roles in the human body,
including their role in the uniform
contractile of the heart muscle.
•
They are also relevant in signal
transfers in the brain, and their
absence shows a decreased cell density
in the brain.
•
Retinal and skin cells are also
dependent on gap junctions in cell
differentiation and proliferation.
Connective Tissue
•
•
•
•
•
•
Binds Organs together
Holds epithelium to the body
Provides Protection and Support
Produces Blood Cells
Stores Fat
CT cells secrete a matrix, this matrix is
composed of fluid and fibers-collagen and
elastin.
Organs and Organ
Systems
•
An organ is a collection of tissues
joined in a structural unit to serve a
common function
•
Organs are composed of main tissue,
parenchyma, and "sporadic" tissues,
stroma.
•
The main tissue is that which is unique
for the specific organ, such as the
specialized cells of the stomach,
•
Sporadic tissues include the nerves,
blood vessels, and connective tissues.
•
Functionally related organs often
cooperate to form whole organ systems.
•
A hollow organ is a visceral organ that
forms a hollow tube or pouch, such as
the stomach or intestine, or that
includes a cavity, like the heart or
urinary bladder
•Used with permission from imgarcade.com
Organ Systems
•
Circulatory System: The main function of
this system is to transport nutrients and
gasses to cells and tissues throughout body.
This is accomplished by the circulation of
blood.
•
Cardiovascular: comprised of the heart,
blood, and blood vessels. The beating of the
heart drives the cardiac cycle which pumps
blood throughout body.
•
Cardiovascular organs:
– heart, blood vessels, blood
•
Lymphatic: This system is a vascular
network of tubules and ducts that collect,
filter, and return lymph to blood circulation.
•
As a component of the immune system, the
lymphatic system produces and circulates
immune cells called lymphocytes.
•
Lymphatic organs:
– lymph vessels, lymph nodes, thymus,
spleen, tonsils
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Progression of cancer
• A tumor is said to be benign if it is contained in one
location and has not broken through the basement
membrane to which normal cells are attached
• Benign tumors often cause no health problems to an
individual
• Can grow big enough to interrupt the functioning of
normal tissue
• Removal is generally successful as they are not
intermingled with other tissue
The Characteristics of Cancer
•A cancer cell’s structure is abnormal.
• Cancer is a result of a series of mutations in
the cell’s genes
–
–
–
–
Larger cell nucleus and less cytoplasm
Loss of structural specialization
Cytoskeleton shrinks
Plasma membrane proteins could be lost or
altered
– New plasma membrane proteins may appear
– Changes passed on to cell’s descendants
•
Progression
of
cancer
Figure
12.17
(1)
Malignant tumors invade normal tissue
• Do not just push healthily cells out of the way
•
Progression
of
cancer
Figure
12.17
(2)
Tumor cells produce protein-degrading enzymes
that breaks down the connective tissue that holds
cells together
Progression
of
cancer
Figure
12.17
(3)
Malignant tumors invade normal produce
• As
that
allow them to invade other tissue, they spread to
other locations
• Metastasis – one or more transformed cells spread
to the rest of the body via the blood system.
The Characteristics of Cancer
•A Cancer cells break away from
their home tissue.
•B The metastasizing cells become
attached to the wall of a blood
vessel or lymph vessel. They secrete
enzymes that break down part of
the wall. Then they enter the
vessel.
•C Cancer cells creep or tumble
along inside blood vessels, then
leave the bloodstream the same
way they got in. They start new
tumors in new tissues.
The Skin: an example of an organ system
• The skin is the largest organ
in the human body.
• For the average adult human, the
skin has a surface area of between
1.5-2.0 square meters (16.1-21.5 sq
ft.), most of it between 2–3 mm
(0.10 inch) thick.
• On average it weighs about 9 pound
• The average square inch (6.5 cm²)
of skin holds:
•
•
•
•
650 sweat glands
20 blood vessels
60,000 melanocytes
more than 1,000 nerve endings
The Skin: an example of an organ system
• Skin performs the following
functions:
• Protection: an anatomical barrier
from pathogens and damage
between the internal and external
environment in bodily defense;
• Sensation: contains a variety of
nerve endings that react to heat
and cold, touch, pressure, vibration,
and tissue injury
• Heat regulation: Dilated blood
vessels increase perfusion and heat
loss, while constricted vessels
greatly reduce cutaneous blood flow
and conserve heat.
The Skin: an example of an organ system
• Control of evaporation: the skin
provides a relatively dry and semiimpermeable barrier to fluid loss.
– Loss of this function contributes to the
massive fluid loss in burns.
• Aesthetics and communication:
Some trained professionals see our
skin and can assess our mood,
physical state and attractiveness.
• Storage and synthesis: acts as a
storage center for lipids and water,
as well as a means of synthesis of
vitamin D by action of UV on certain
parts of the skin.
The Skin: an example of an organ system
• Excretion: sweat contains urea,
however its concentration is
1/130th that of urine, hence
excretion by sweating is at most a
secondary function to temperature
regulation.
• Absorption: the cells comprising
the outermost 0.25–0.40 mm of the
skin are "almost exclusively supplied
by external oxygen", although the
"contribution to total respiration is
negligible".
• Water resistance: The skin acts as
a water resistant barrier so
essential nutrients aren't washed
out of the body.
Figure 12.19a
Figure 12.19b
Cancer Prevention and Survival
• Cancer prevention includes changes in
lifestyle
– Not smoking
– Avoiding exposure to the sun
– Eating a high-fiber, low-fat diet
– Visiting the doctor regularly
– Performing regular self-examinations
- Chemoprevention
Issues
• So, what do you thing of stems cells now if they can
be used to:
– Hopefully grow new organs
– Treat all forms of cancer
– Possibly treat all major diseases
– Stop a lot of pain and suffering
The end!
Any questions?