Cancer has affected the lives of each and every one of us alive today.
Manypeople have know someone with cancer, yet even those who havent have beenbombarded with constant reminders of its terrible threat. Although cancer isoften referred to as a single condition, it actually consists of more than 100different diseases, all characterized by the uncontrolled growth, reproduction,and spread of abnormal body cells. All of these diseases are individuallyunique, 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 cellsreproduce only when instructed to do so by other cells in their vicinity. Thisconstant collaboration ensures that each tissue maintains a certain size andfunction that is exactly what the body needs.Order now
Cancer cells, on the other hand,violate the entire process. Not only do they ignore the bodys controls onproliferation, they possess the ability to invade nearby tissues, and may evenmetastasize migrate and form tumors in distant sites of the body. How docancer cells achieve this? For decades, this question plagued scientistseverywhere. But over the last 20 years, scientists have uncovered a set of basicprinciples that govern the development of cancer ( Brock, 1993). Within eachcell lies a structure called a nucleus which contains strips of material knownas DNA (dioxyribonucleic acid. ) Each of these strips is divided into hundreds ofgenes, which are the codes and templates for all the functions of the humanbody.
Each gene specifies a sequence of amino acids that must be linked togetherto 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 inducecell growth and reproduction, while tumor suppressor genes inhibit it. Together,they carefully control the proliferation of cells.
However, if a proto-oncogeneis mutated, it can become a carcinogenic oncogene, driving excessivemultiplication. Tumor suppressor genes, on the other hand, contribute to cancerwhen they are inactivated by mutation (Ruddon, 1995). Luckily, cancerous tumorsare not caused by one little mutation in one cell they are caused bymultiple mutations in a number of the cells growth-controlling genes. Thenumber of mutations necessary can be as low as two or quite high, depending onthe specific type of cancer. Generally, these mutations occur either frommistakes during cell reproduction, or due to DNA damage caused by carcinogenssuch as tobacco, certain poisons, and UV rays.
So, why dont we all get cancerfrom these things right away? Consider that one of your cells is damaged bypoison 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. Thisin itself, is fairly unlikely. It normally takes decades for an incipient tumorto collect all the mutations required for its malignant growth, whichexplains why the average age for cancer diagnosis is 67 (Ruddon, 1995). Why,then, do some individuals contract cancer before the typical age of onset? Inmany cases, this is explained by the inheritance of a mutation in a criticalgrowth controlling gene.
Typically, this mutation would be a very rare event. However, in this individual, the mutation is present in ALL the cells of thebody, instead of in some randomly stricken cell. So, the process of tumorformation skips its first, slow step. No one can actually inherit cancer;rather, they inherit a predisposition to develop a cancer, which is why cancersdo tend to run in families, but not all family members are stricken (Brock,1993). The outlook for people with cancer has improved steadily since thebeginning 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 AmericanCancer Society estimates that an additional 25% of cancer deaths could beprevented with earlier diagnosis and treatment (ACS homepage). However, one inthree people in the United States will eventually develop some type of cancer,so routine screening for early detection should be an important part ofeveryones lives (Ruddon, 1995). The earlier cancer is diagnosed and treated,the better the chance of its being cured. Some cancers, such as breast andskin cancers, can be detected by routine self-examination before they become tooserious, while others are only detected by more complicated methods.
Either way,early diagnosis appears to be the key to survival. BibliographyRuddon, Raymond W. 1995. Cancer Biology, 3rd ed. New York: Oxford UniversityPress.
Brock, D. J. H. 1993.
Molecular Genetics for the Clinician. 1st ed. NewYork: Cambridge University Press.