Transcript of "Introduction to the Biology of Cancer"
Transcript of the downloadable video "Introduction to the Biology of Cancer" by Lauren Pecorino, Senior Lecturer in Cancer Biology at the University of Greenwich
Let's begin with the question "What is cancer?"
Cancer is defined as a set of diseases characterized by abnormal growth and the ability to spread from a primary site to other sites in the body (metastasis).
Let’s examine this definition more closely. We are aware that there are many types of cancer and that there are differences between them. Take skin vs. lung cancer. Both have different causes: Ultraviolet light from the sun causes skin cancer whereas cigarette smoking causes lung cancer. Treatment also differs. Therefore the definition states that cancer is a set of diseases.
The definition also states that cancer is characterized by abnormal cell growth and the ability to spread or metastasize. Abnormal cell growth alone, such as a wart or a benign tumor, is not evidence of cancer. It is the presence of a malignant tumor that defines cancer.
Let's compare cancer to other diseases. Anemia is a disease of the blood, and Alzheimer's Disease is a disease of the brain.
Cancer is a disease of your genes.
Carcinogens are agents that cause cancer. Most carcinogens are mutagens, agents that cause mutations.
Mutations are changes in the instructions carried by genes that can be passed down to daughter cells.
As a result of mutations specific cell functions may be affected.
Examples of carcinogens include UV from the sun, x-rays, and cigarette smoke.
Note that most mutations that cause cancer are acquired during your lifetime and are not passed down from generation to generation.
To understand the biology of cancer we must examine characteristics that are different between a healthy cell and a cancer cell. Since cancer is characterized by abnormal growth and spread, it is important to understand how these 2 features occur.
There are 5 processes that are involved in controlling total cell numbers and cell migration. They are cell growth, cell suicide, blood vessel formation, Metastasis, and indirectly DNA repair.
In healthy patients, these processes are precisely regulated. Cancer patients, however, have mutations in genes that affect these 5 processes involved in controlling total cell numbers and migration.
Let’s briefly introduce each process starting with cell growth, shown here in the left upper corner.
Cell growth is the process of making more cells by cell division.
A healthy cell is stimulated to grow only when a growth signal from outside of the cell binds to a receptor on the surface of the cell.
The signal is passed through the cell and ultimately regulates genes in the nucleus whose products are required for cell division.
The next process is cell suicide. Cell growth must be balanced with cell death. A specialized type of cell suicide (apoptosis) is a precise process whereby components of the cell are degraded and packaged for neat and tidy disposal.
Cell suicide is regulated by external death signals and receptors (similar to cell growth) or by internal signals such as cell stress via the mitochondria.
The signal serves to turn on specific proteins called caspases that act as molecular scissors and play a role in degrading the cell.
- Angiogenesis is the formation of new blood vessels from pre-existing vessels.
Angiogenesis is regulated by both positive and negative factors, produced and released by cells.
Blood vessels are required to supply oxygen and nutrients to cells and also act as an avenue of transport for some cells.
The fourth process is Metastasis. Metastasis is the spread of cancer cells from one site to another via blood or lymphatic vessels.
In general, most healthy cells remain within one place (skin cells stay in the skin and lung cells stay in the lung) although of course there are exceptions such as blood cells and immune cells.
Metastasis is regulated by proteins that act as cellular hooks, linking cells to other cells and surfaces and also by proteins that enable motility.
Lastly, DNA repair indirectly affects total cell number and cell migration. As shown in this diagram, DNA repair occurs in the nucleus. It is a process that fixes DNA damage caused by carcinogens in order to avoid mutation. In this way, it acts as a safeguard to ensure cell functions are unaltered.
If mutations do occur in genes involved in these 5 processes just described: cell growth, cell suicide, angiogenesis, metastasis or DNA repair, then cancer may be a consequence.
It is our knowledge about these processes and the genes affected in cancer that is enabling us to develop new improved cancer therapies and have extended our hope for the future.
Introduction to the Biology of Cancer Podcast (6mins 2 secs)
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