Cancer is a series of diseases in which all involve changes to the normal process of the cellular replication. Fundamentally, all cancer has a genetic basis. The process of developing cancer is not simple and involves many factors. In most cases multiple genes are involved in the progression of cancer. Ultimately defects to these genes add up, with cell losing its ability to control its reproduction. Overgrowth of the tissue soon follows, which is the origin of a cancerous tumor.
There are two broad categories of genes which can lead to cancer if they are damaged. These two categories are oncogenes, and tumor suppressor genes. The development of cancer often involves damage to both types of genes. This is known as the “Multi Hit Hypothesis”, and is the leading model for cancer development. The Multi Hit Hypothesis simply means that a cell must suffer a series of mutations to it’s DNA structure in order to become cancerous. One small change to the DNA is rarely enough to cause a cancer.
In this article we will take a look at tumor suppressor genes and their role in the development of cancer.
Tumor suppressor genes are bits of DNA which which code for proteins that function to restrict cell growth. These proteins also function to aid in the repair or auto-destruction of cells with damaged DNA. When these proteins are damaged, the cell has a reduced ability to control its growth. This leads to uncontrolled cell growth, and is one of the factors in the development of cancer.
In the last few decades many specific tumor suppressor genes have been isolated by scientists. The first tumor suppressor gene to be discovered was the RB gene. Changes to the RB gene can result in a cancer known as retinoblastoma. A retinoblastoma is a cancer is seen commonly in children and involves the eyes. Mutations to the RB gene can happen randomly, but are also passed along to children from the parents in some cases.
The other famous (at least for geeky scientists) tumor suppressor gene is known as p53 gene. Changes to p53 gene are found in almost all human cancers. They are very commonly seen as random mutations in people with brain tumors, leukemia, breast, lung, and colon cancer.
Like all genes, tumor suppressor genes are bits of DNA which are used to encode specific proteins. These proteins are used in the regulation and control of the cellular reproduction cycle. It is the damage to the proteins, not the actual DNA itself which causes the development of cancer. Because of this, anything which can damage the protein, even after it is made can have the same functional effect as damaging the DNA in the first place. There are some viruses which are known to produce chemicals which can damage the protein products of tumor suppressor genes. These viral proteins will attach to RB and p53 protein products and inactivate them. A common example of this happens with the human papilloma virus.
Tumor suppressor genes play a key role in the development of cancer. As science marches on and we continue to unlock the secrets of our DNA, we will undoubtedly learn more about how they function in cancer growth. Treatments for cancer can only follow once we have a solid idea how they start. This makes the understanding of tumor suppressor genes key to finding effective therapies for cancer.
