The Basics of Cancer Genetics

by Kylie Disch and Lexi Mang, CAPS BIO 202 SI Leaders

The basic definition of cancer is a disease that is characterized by uncontrolled cell growth. Our bodies have mechanisms to control cell growth under normal conditions, but sometimes the machinery does not work. These situations are called mutations, and can be substitutions, chromosomal rearrangements, deletions, etc. Most cancers are somatic, meaning that they are not part of the cells that are part of reproduction. Only about 5% of these mutations can be passed to offspring.

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All cancer cells have two basic properties:

● Cell growth and division that is unregulated (abnormal)

● Metastatic spread (grows past where it started, to other parts of the body)

Most cancers cause the growth of tumors, which can be classified as benign (unregulated mass of cells that cause no serious harm) or malignant (metastasized cells invade other tissue and cause life-threatening problems). Both types have to start out from the same type of cell and accumulate numerous mutations.

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Parts of our normal machinery to ensure cell growth include:

● Proto-oncogenes that encode for proteins necessary to go through the cell cycle. Mutated alleles of these are called oncogenes and code for the hyperactivity of these proteins.

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● Tumor suppressor genes that encode for proteins that regulate whether a cell keeps going through the cell cycle or not. Mutations in these cause for uncontrolled cell proliferation.

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There is one gene that stands out in the world of cancer genetics, and that is TP53. Over 50% of human tumors have some sort of mutation or deletion of this gene. The role of TP53 is to make p53, a protein that checks for any damage in the DNA and allows for repair, or if it cannot be repaired, it sends the cell into apoptosis (programmed cell death).

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Some things to keep in mind about cancer:

● The older you get, the more times your body has had to replicate your DNA, meaning there is a higher risk of mutations, and consequently cancer, as you age.

● Carcinogens also put you at risk (these are agents that can cause cancer, such as radiation). Every day we walk out in the sun, we are exposed to UV radiation, which damages our DNA. Fortunately, our bodies are effective at catching this and fixing it, but sometimes mutations can keep this from happening. This is when you develop skin cancers (this is why sunscreen is important!)

● Some viruses, such as human papillomavirus (HPV) can put you at risk by encoding a protein, E6, which binds and inactivates p53.

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For more information about this, some great resources include: PubMed, a research article database available free to UNM students through the university libraries, your 202 SI leaders, your biology or biochemistry professors, and various websites also include extensive research sections, such as The American Cancer Society.


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