What is Cancer?
You've heard of it of course but, "What, exactly, is cancer?" This section provides
an introduction to what it is, how it starts, and how it spreads.
Cancer is the term we give to a large group of diseases that have one thing in
common: abnormal cells growing out of control. Under normal circumstances, the
number and growth of all our cells is a highly controlled mechanism. The body tells the
cell when to divide and when to stop. But when the control signals in one of these cells
goes wrong and its cell cycle becomes disturbed, it divides and divides. It continues on
multiplying uncontrollably, making more and more of itself, and the result is a large
group of cells called a tumor.
This resulting tumor can be either benign or malignant. A benign tumor does not
spread to other parts of the body and is rarely life-threatening. Many breast lumps, for
example, are benign tumors. A malignant tumor, however, can spread and can be
deadly. When this tumor spreads, its malignant cells break off and travel through the
blood system to other places in the body to settle and multiply, creating a new tumor
called a secondary tumor. If the cancer has spread, doctors usually say it has
'metastasized'. The name given to the cancer, however, is based on where the cancer
started, even if it has spread to other areas of the body. For example, even if lung cancer
has spread to the liver it's still called lung cancer.
How does it all start?
What causes this uncontrollable multiplication of cells in the first place, as well as
how fast it happens, differs from person to person. Cancer starts when one normal cell
becomes cancerous. This happens when something disrupts its DNA, changing the
instructions that control the cell cycle. In other words, the instructions that tell the cell
how to grow, divide, and die have been disrupted. One or more of a variety of factors
could cause this change, including diet, tobacco, sun, radiation, or certain chemicals.
Certain factors, such as tobacco, have been proven to be associated with cancer and are
thus called risk factors.
How do we treat Cancer?
What Is Chemotherapy?
Chemotherapy is the use of drugs to treat cancer. The drugs often are called
"anti-cancer" drugs. It is very difficult for the drugs to tell the difference between normal
human cells and cancer cells. Normal cells grow and die in a controlled way. But cancer
occurs when cells become abnormal and keep dividing, forming more cells without
stopping. Anticancer drugs destroy cancer cells by stopping growth or multiplication at
some point in their cell cycle.
In addition to chemotherapy, other methods sometimes are used to treat cancer.
Your doctor may recommend that you have surgery to remove a tumor or to relieve
certain symptoms that may be caused by your cancer.
What Can Chemotherapy Achieve? Depending on the type of cancer and its stage of
development, chemotherapy can be used:
* To cure cancer.
* To keep the cancer from spreading.
* To slow the cancer's growth.
* To kill cancer cells that may have spread to other parts of the body from the original
tumor. To relieve symptoms that may be caused by the cancer.
Does Chemotherapy Hurt?
Getting chemotherapy by mouth, on the skin, or by injection generally feels the
same as taking other medications by these methods. Having an IV started usually feels
like drawing blood for a blood test. Some people feel a coolness or other unusual
sensation in the area of the injection when the IV is started. Report such feelings to your
doctor or nurse. Be sure that you also report any pain, burning, or discomfort that occurs
during or after an IV treatment.
Will I lose my hair?
The Chemotherapy drugs try to attack cells that are dividing. This kills the tumor
cells, but also kills normal cells that are reproducing. Many chemotherapy drugs kill the
cells that grow hair. This hair loss is not permanent. Almost all patients grow their hair
back when the chemotherapy is finished.
Assignment # _____ Period:
Reading Guide – Cell Cycle and Cancer (Chapter 8)
1. Describe the structure of a chromosome.
2. What is a gene?
3. Describe the cell cycle and what occurs during each step of the cycle.
4. How do enzymes control the cell cycle?
5. Recently, scientists have learned how to “silence” a gene by making a protein that
binds to the specific gene sequence. Why might this be an important discovery in
6. Describe how mutations can affect the cell cycle and possibly cause cancer. (Lecture)
7. What role does melanin play in protecting your body from skin cancer? (p.216)
8. Explain the role of the p53 gene in the cell cycle and how its mutation can cause
9. Discuss some evidence that suggests the environment influences the occurrence of
10. Cancers capable metastasizing are called malignant. If metastases spread through the
blood. What organs do you think cancers would metastasize to first? Explain.
11. How do Chemotherapy drugs work? Include in your explanation why hair follicles
and the digestive system lining are affected by these drugs. (You will have to find outside
sources for this answer)