Cancer has affected the lives of each and every one of us alive today. Many
people have know someone with cancer, yet even those who havent have been
bombarded with constant reminders of its terrible threat. Although cancer is
often referred to as a single condition, it actually consists of more than 100
different diseases, all characterized by the uncontrolled growth, reproduction,
and spread of abnormal body cells. All of these diseases are individually
unique, yet the basic processes that produce cancers are very similar (Ruddon,
1995). The human body consists of over 30 trillion cells, living in a complex,
interdependent harmony. They regulate each others proliferation; normal cells
reproduce only when instructed to do so by other cells in their vicinity. This
constant collaboration ensures that each tissue maintains a certain size and
function that is exactly what the body needs. Cancer cells, on the other hand,
violate the entire process. Not only do they ignore the bodys controls on
proliferation, they possess the ability to invade nearby tissues, and may even
metastasize migrate and form tumors in distant sites of the body. How do
cancer cells achieve this? For decades, this question plagued scientists
everywhere. But over the last 20 years, scientists have uncovered a set of basic
principles that govern the development of cancer ( Brock, 1993). Within each
cell lies a structure called a nucleus which contains strips of material known
as DNA (dioxyribonucleic acid.) Each of these strips is divided into hundreds of
genes, which are the codes and templates for all the functions of the human
body. Each gene specifies a sequence of amino acids that must be linked together
to make a particular protein; the protein then carries our the work of the gene.

Two types of genes, which are only a small fraction of the genetic material,
play particularly important roles in triggering cancer. Proto-oncogenes induce
cell growth and reproduction, while tumor suppressor genes inhibit it. Together,
they carefully control the proliferation of cells. However, if a proto-oncogene
is mutated, it can become a carcinogenic oncogene, driving excessive
multiplication. Tumor suppressor genes, on the other hand, contribute to cancer
when they are inactivated by mutation (Ruddon, 1995). Luckily, cancerous tumors
are not caused by one little mutation in one cell they are caused by
multiple mutations in a number of the cells growth-controlling genes. The
number of mutations necessary can be as low as two or quite high, depending on
the specific type of cancer. Generally, these mutations occur either from
mistakes during cell reproduction, or due to DNA damage caused by carcinogens
such as tobacco, certain poisons, and UV rays. So, why dont we all get cancer
from these things right away? Consider that one of your cells is damaged by
poison and becomes mutated. In order for this cell to turn into a cancer cell,
the rest of the necessary mutations must also occur in this very same cell. This
in itself, is fairly unlikely. It normally takes decades for an incipient tumor
to collect all the mutations required for its malignant growth, which
explains why the average age for cancer diagnosis is 67 (Ruddon, 1995). Why,
then, do some individuals contract cancer before the typical age of onset? In
many cases, this is explained by the inheritance of a mutation in a critical
growth controlling gene. Typically, this mutation would be a very rare event.

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However, in this individual, the mutation is present in ALL the cells of the
body, instead of in some randomly stricken cell. So, the process of tumor
formation skips its first, slow step. No one can actually inherit cancer;
rather, they inherit a predisposition to develop a cancer, which is why cancers
do tend to run in families, but not all family members are stricken (Brock,
1993). The outlook for people with cancer has improved steadily since the
beginning of the 20th century, when few cancer victims survived for very long.

Today, 51% of cancer patients survive for 5 years or more, and the American
Cancer Society estimates that an additional 25% of cancer deaths could be
prevented with earlier diagnosis and treatment (ACS homepage). However, one in
three people in the United States will eventually develop some type of cancer,
so routine screening for early detection should be an important part of
everyones lives (Ruddon, 1995). The earlier cancer is diagnosed and treated,
the better the chance of its being cured. Some cancers, such as breast and
skin cancers, can be detected by routine self-examination before they become too
serious, while others are only detected by more complicated methods. Either way,
early diagnosis appears to be the key to survival.

Ruddon, Raymond W. 1995. Cancer Biology, 3rd ed. New York: Oxford University
Press. Brock, D.J.H. 1993. Molecular Genetics for the Clinician. 1st ed. New
York: Cambridge University Press.