Cancer Biology

First of all, what IS cancer? 

Cancer describes a group of diseases in which cells rapidly divide, grow out of control, and can spread to other areas in the body. Cancer development is spurred by changes in genes, called mutations, that lead to uncontrolled cell growth and other types of cellular dysfunction. 

DNA Mutations

A mutation is a change. 

During cell division (mitosis), the DNA within a cell is replicated,  transcribed (written), and translated to make DNA for new daughter cells. This is a complicated, multi-step operation in which a lot of mistakes can be made. When a mistake occurs during DNA replication, it is called a mutation. Mutations can also "pre-exist" in the body if they were inherited from a parent's genes, or they can occur as the result of exposure to carcinogens (cancer-causing substances). 

Fortunately, we have a built-in system of checks and balances to limit, prevent, and repair mutations, but mistakes can also occur within that system. When a mutation is not corrected, two things happen: 1) any resulting problems from that mutation can develop in the body (e.g. cells grow uncontrollably) and 2) the mutation is passed down to the next generation of daughter cells and the problems persist. ((A mutation is like a bug stuck on the screen of a photocopying machine. Once it's there, all of the copies moving forward will contain that "bug."))

Chris Gunter, PhD, Associate Investigator at the National Human Genome Research Institute notes, "Did you know that on any average day, the 37 trillion cells in your body will acquire trillions of point mutations? These changes come from random errors in copying DNA as the cell divides or from environmental exposures, like cigarette smoke or even sunshine. It sounds a little scary, but almost all of these changes are in parts of your genome where it does not really matter. Your cells have also evolved ways to deal with some point mutations and correct them back to your original genome. But the very rare point mutation in your somatic cells, which are the cells that won't be sperm or eggs, ultimately could lead to symptomatic disease."

A mutation can impact activities at the cellular level: it can turn genes on, off, up, or down (expression, regression, overexpression, or loss of expression) which can then lead to under- or overproduction of proteins or the production of proteins that don't function properly. Some mutations may cause a lot of problems and other mutations may cause no issue at all. When these mutations impact genes that protect us from cancer, like tumor suppressor genes that control out-of-control cell growth or DNA repair genes, then we have a problem. 

If we think of DNA as a blueprint for a house then a mutation would be a minor change to that blueprint. While that change might appear to be minor, it could be quite problematic. Let's say the original blueprint called for a solid wall to be built alongside the primary shower, but a change occurred that is now directing the general contractor to install electrical outlets along the same wall. We now have a fire hazard and an electrocution hazard where there should have been a simple wall. Small change. Big impact. 

Is cancer smart? 

Its IQ is certainly not what we're referring to here, but cancer cells are incredibly plastic, adaptive, and heterogenous. Cancer cells "taste" their environment, and then use that information to benefit their survival. If they taste something they don't like, they can ignore it, work around it, etc. And when they taste something they like, they can capitalize, gobble it up, and use it to their benefit. An example of this would be a tumor creating a perfect tumor microenvironment (TME) around themselves that not only provides everything the cancer cells need to grow and proliferate, but the TME also forms a protective "capsule" that is challenging for immune cells to penetrate. Think about how we, as people, adapt to different climates, for example. Over time, we learn what to do, not to do, how to dress, how to hydrate and eat, limitations of outdoor activities, etc. Cancer does the same thing. If it's cold, it'll grab a coat so it can stay and thrive without having to relocate.