Download What Is Cancer

Bio A– Cell division
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. The type of cancer depends on the
type of cell that is growing.
Normal body cells grow, divide, and die in an orderly fashion. During the early years of a person's life, when
they are growing, normal cells divide more rapidly until the person becomes fully grown. After that, cells in
most parts of the body divide only to replace worn-out or dying cells and to repair injuries.
Normal cells communicate with each other by releasing chemicals that neighboring cells can detect. When
there is a gap between cells, like when you cut yourself or break a bone, the cells send out a message that
encourages cells to grow and fill that gap. Once the gap is filled, the cells stop dividing… or at least they
should.
Cancer cells are cells that don’t listen to or don’t have the normal signals that stop cell division. Basically it is
like they are driving down the street and every traffic light is stuck on green. Without any signal to stop them,
they just keep dividing. The cells start to pile up on each other and we get something called a tumor. You can
think of them as “rogue” cells – Cells that no longer follow the rules and continue to grow and divide without
stopping.
Cancer cells are your cells. They are not some foreign invader like bacteria or viruses. As a result your
immune system often doesn’t recognize that anything is wrong. Remember your immune system works by
identifying cells and molecules that don’t belong to you.
Cancer cells develop because of changes in the DNA called mutations. Remember that DNA contains all the
recipes to make any protein that your body needs. Just like changing a cooking recipe, when you change a
gene you change the outcome. Is it possible to improve upon the recipe? SURE! BUT it is much more likely
that your change will have a negative effect. DNA mutations are caused by a number of things. Chemicals in
our environment, UV light, radiation exposure and simple cell errors that no one can prevent or control.
Mutations are a natural part of life. They happen in all of us and the longer we are here on earth, the more
mutations we accumulate in our cells. We hope that they have little to no effect, which is common. But if the
mutation is in just the right place (or rather wrong place) cancer can be the result.
In the case of cancer, those signals we mentioned above that tell cells when to stop dividing and when the start
dividing are proteins. So, if you change the DNA for one of these proteins, you might change the message it is
supposed to convey. A protein whose message was “divide only when you are repairing an injury” might be
changed to “just keep growing!” A protein whose message was “ok, you can stop dividing now” might
disappear all together leaving nothing to stop the cells. Normal proteins that encourage cells to divide when
necessary are called proto-oncogenes. They are tightly regulated. If they are mutated so that they are “on” all
the time they become oncogenes and they can be the cause of cancer. Likewise, proteins that stop cell
division normally are called tumor suppressors. If these are mutated so the message is lost, cells don’t stop
dividing and tumors result.
When cells start growing uncontrollably they usually form a tumor, a solid ball of abnormal cells. Often they
start off as benign, meaning not dangerous. They grow and form a tumor, but the tumor is not interfering with
the normal function of the surrounding cells. It is not until they interfere with neighboring tissue that they
become cancer. These tumors are called malignant tumors. Some cancers, like leukemia, do not form
tumors. Instead, these cancer cells are part of the blood and the blood-forming organs like the bone marrow.
They don’t “clump up” into a tumor and instead travel around the blood stream.
Bio A– Cell division
Often, cancer cells travel to other parts of the body where they begin to grow and replace normal tissue. This
process is called metastasis. Regardless of where a cancer may spread, however, it is always named for the
place it began. For instance, if you have a tumor in your liver and one little liver-cancer cell breaks away and
travels up to your kidney to form a new tumor, it is still liver cancer. Doctors can recognize the origin of the
tumor by looking for special characteristics of the cells that identify them as a particular type of cell.
Remember the “ID tags” on the surface of the cell membrane? Well, it is these “tags” that make each type of
cell unique. So no matter where we find the cell, we can tell where it came from.
Different types of cancer can behave very differently. For example, lung cancer and breast cancer are very
different diseases. They grow at different rates and respond to different treatments. That is why people with
cancer need treatment that is aimed at their particular kind of cancer.
There are several major categories of treatment for cancer. Surgery counts on being able to literally cut out
the tumor and some surrounding tissue to remove the cancer. Obviously the more isolated the tumor, the
more successful the surgery. If the tumor has started infiltrating the surrounding healthy tissue, the surgeon
will have to remove some of that healthy tissue as well. All it takes is a few cells left behind and the tumor can
return.
Chemotherapy uses drugs to attack specifically rapidly dividing cells like cancer cells. Chemotherapy often
makes a patient extremely sick because these drugs will also attack any normal cells who are supposed to
divide quickly (ie: skin cells, lining of the stomach, hair follicles) This explains why individual on chemotherapy
often lose their hair. The treatment is rough, but the hope is that the cancer cells will all be killed before the
body gets too sick.
Radiation therapy directs a very specific amount of radiation at the cancer in an attempt to kill only those cells.
As we mentioned above, radiation causes mutations. So if we damage the DNA of the cancer cells so badly
that the cells die, then that is very good for the patient. But we must target the radiation at the cancer cells
only to minimize the damage to DNA of healthy cells.
Additional treatments include hormone therapy for certain types of cancers like prostate cancer. Reserachers
are looking at drugs that block formation of new blood vessels. Remember cancer cells are cells that need
oxygen, glucose and other nutrients too. So a new tumor needs blood vessels to deliver these materials. If we
block the vessels from forming, we can “starve” out the cancer cells. Also, since the key is directing the
treatment at the cancer cells only, researchers are looking at using viruses that target and infect only cancer
cells. We know viruses only infect one cell (that’s why we always end up with the same symptoms when
infected with the cold virus) so if we can use this to our advantage, we can kill cancer cells and leave healthy
cells alone! Each treatment comes with its own risks and often several treatments are combined for improved
success. The bottom line is, however, that these are your cells. Anything that harms them is likely to harm
you too! So the more research we can do to find a way to target only the cancer cells, the better.
Bio A– Cell division
Read the article attached and answer all.
1. How does cancer relate to our unit on Mitosis? Explain.
2. In what three situations should normal healthy cells divide?
3. Why doesn’t your immune system step up to the plate and kill cancer cells like it does an ear infection or
a cold virus?
4. What are mutations and what can we do to minimize how many we get?
5. What is the difference between an oncogene and a tumor suppressor gene?
6. How does leukemia differ from other cancers?
7. Differentiate between benign and malignant tumors.
8. If a patient appears in a doctor’s office with three tumors in three different parts of the body, how will
the doctor identify what type of cancer the patient has? Explain.
Bio A– Cell division
9. Why do chemotherapy patients lose their hair?
10. Make a table to compare the benefits and risks of the three major types of treatments for cancer.
11. What might be an expected side effect of a drug that block the ability to form new blood vessels?
12. Why is cancer so difficult to cure compared to other illnesses?