Brittany's Partial Paper

Brittany Williamson
Developmental Pathway
Spring 2009

Development of Cancer

Cancer is a disease that has claimed the life of many innocent people. It is the second most common cause of death in the United States, only exceeded by heart disease. In 2008, over 500,000 people died from cancer in the US, but this disease is a common health issue world wide, as almost 7.6 million people were killed by cancer in 2008 (ACS). Cancer identifies a group of diseases that are characterized by uncontrolled growth of abnormal cells that also have the ability to spread. The abnormal growth can occur virtually anywhere on the body, including the brain, bone, breast, skin, pancreatic, and many other sites. This grave disease has been researched and followed for years, and as knowledge on the deadly disease has been gained, many causes of the disease have been determined. These causes have been linked to external factors, like radiation, chemicals, or tobacco, and internal factors like inherited mutations, hormones, or immune conditions. Some cancers are even linked to viruses, one specific example of this is the Hepatitis B virus which leads to mutations that can accelerate the development of carcinogens.
Cells are the basic fundamental units of life, and they each carry specific jobs based on their location. They work to transport nutrients, oxygen, excrete wastes, and reproduce, including many other functions. To ensure these duties are performed and enable the body to function properly, cells are continually replaced. Old ones are killed, and new ones are continually reproduced. The procedure of reproduction of a cell is a process of cell division, mitosis for somatic cells and meiosis for sex cells. The processes of a cell, and its reproduction, are regulated by the deoxyribose acid (DNA) contained in the nucleus of the cell (Cell Biology). Each DNA molecule contains genes that direct the synthesis of proteins; these proteins carry out most of the biochemical activities of a cell (book). Each gene instructs a cell for its specificity, whether its to make a different protein, produce a hormone or growth factors that allow for intercellular communications, or even instructs the cell to produce regulatory proteins (Book). Cells are closely controlled by the regulatory proteins, and for a cell to reproduce it must receive the signal from regulatory proteins. If a gene experiences a mutation, changes will occur to the cells and proteins the gene codes to produce (mutation rate).
Mutations can lead to a cell ignoring signals to stop reproducing, to specialize, or even to die and be shed. In each case, the continual growth of a specific cell produces a tumor, which can be classified as benign (non-cancerous) or malignant (cancerous). There are specific types of mutation that can occur to a gene. Each gene is made of a sequence of bases that code for specific amino acids (Likelihoods). If a mutated gene produces a malfunctioning protein, for example, that signals a cell’s growth factor receptor to be turned on constantly, the cell is receiving the message to continually reproduce, when no growth factor is actually present. This leads to the cell uncontrollably growing. When this is paired with another mutation, the inability to produce the tumor suppressing genes, the tumor is likely going to be malignant (mutation rate). The selection of mutagens cancer chooses may depend on the type of change of the amino acid. Since cancer occurs over many years there are great changes to chromosomes, in some late-cancer detections there have been as many as 50 chromosomal rearrangements, which would inevitably lead to even more changes to the nucleotide sequence of DNA in that tumor (Targeted).
The genetic pathway to cancer can be complicated, and there are some types of cancers that researchers do not fully understand the genetics of, like pancreatic cancer (pancreatic). Researchers have been able to identify some specific genes that are frequent targets, which is a monumental movement in the early detection of cancer (Likelihood).
One of the specific genes that researchers have identified as a cancer target is p53, on chromosome 17. This gene is a tumor suppressor gene, and is associated with almost 150 cancer types with a total of 14,971 mutations (Beroud). The risk of mutation of the p53 gene is increased with many external factors, and one of the most critical factors is acquiring the Hepatitis B virus.
Hepatitis B

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