Colorectal Cancer and Cancer Stem Cell Theory

 

 
By Mustafa Zeybek, GCSOM, MBS 2019
Mentor: Darina Lazarova, PhD

Many of us have heard of various types of cancers, however, most of us are unfamiliar with what cancer really is and how these cancers arise. In our everyday lives we may be exposed to terms such as leukemia, lymphoma, carcinoma and so on without any idea what these words mean other than the fact that they are related to cancer. When we delve deeper, we see that cancer cells were once normal, but through mutations, they became abnormal. Our body is like a well-oiled machine and as we age or we are exposed to harmful substances this machine begins to malfunction. This is essentially the concept of cancer. Colorectal cancer is an important cancer of the colon and rectal area.

In the example of the machine, imagine that limits are set such as temperature or pressure to ensure that the machine runs smoothly. Once you surpass these limits, the machine begins to behave unconventionally. For example, parts may break, compartments may explode and one dysfunction in one area may spread and cause malfunctions in other areas. Similarly, our now mutated cells can lose their limits and replicate out of control, spreading and increasing in number. This is representative of characteristics of cancer cells.

Referring to the machine example, if we want another identical machine or even a more specific machine to increase efficiency, we may place an order from the factory to bring these new machines to us. However, if there is a mistake in the factory or in the processing of the order and we receive way too many machines than we wanted, we have to deal with the consequences such as making space to store these excess machines that we did not have normally. Comparatively, a factory is like our stem cells in our bodies that renew our supply of cells, whereas the mistake or error is like the cancer stem cells forming a tumor. The cancer stem cell (CSC) theory proposes that these CSCs are a small population of cells that have both the characteristics of cancer and stem cells.

Within a factory there are certain procedures and methods/steps of making machines that are usually followed. If there is a mistake somewhere along the line then this can get propagated and cause the errors that we discussed above. Correspondingly, these procedures are like the pathways within cells. They regulate how the cell responds to stimuli and what actions occur. Specifically, there are two pathways related to colorectal cancer called the Wnt and NFkB signaling pathways. They have been linked together and deregulation of them has been shown to lead to colorectal cancer.

Lastly, there are certain identifying markers on cell surfaces that allow for differentiation between different cell types. This is similar to having different signs on machines to identify them. There has been research that has identified surface markers CD166, CD133, and CD44 for colorectal cancer stem cells. These stem cells would be specific for the colon and they would characteristically possess these markers.