Recently I’ve been talking with my students about cancer in my cell biology class. I was amazed at how little the class understood about general mechanisms of cancer. The majority of the students are sophmores and have just started to scratch the surface of biology but I was still rather taken back by their lack of knowledge.
Last week I began asking people around town what they knew of cancer and got a pretty mixed bag of responses. Some people had no clue about cancer and some were very well versed, I assume that a lot of this variation is dependent on how proximal cancer has affected your life. Despite some very good answers I feel that there needs to be more awareness about what cancer is because it affects such a large portion of the population. So today I will start part 1 of my Cancer Basics series. This is intended for the lay audience and won’t be ground breaking other than to clearly summarize some of the most important aspects of cancer.
What is Cancer?
A cancer is a group of cells which shows uncontrolled growth. Throughout the body cells must be replaced as they age, break down, or are damaged. The replacement of old cells by new ones is a highly regulated process throughout all systems depending on internal checks from the cell as well as external factors which are communicated by surrounding cells. Before a cell is able to divide all of the internal and external signals must correspond to pass certain checkpoints of division. Imagine a long hallway with three locked doors along the way, you must have the correct keys to pass through each door before you reach your destination. A cell that has broken free from the regulation cycle (essentially obtaining a masterkey) can now divide at whatever pace it decides no matter the messages coming from those around it. This is how tumors develop in the body. There are benign tumors in the body that grow unchecked but that are not cancerous because they are not invasive and do not spread to other locations in the body (invasion and metastasis will be covered in another post).
How does a cell break from the growth cycle?
Almost all cancers are believed to be caused by an alteration in the genetic material of the cell. Your DNA encodes for all proteins in the body, including those that participate in the maintenance of the growth cycle. An alteration in these genes can allow the cell to ignore the normal cues and administer its own reproductive clock. It is worth it to be noted that not all mutations in these proteins will cause cancer, there are mechanisms which the body uses to destroy those cells that are not dividing correctly (showing why cancer is so complex, it evades multiple cellular systems to survive).
The alterations which cause cancer can be induced by carcinogens such as tobacco smoke, radiation or chemicals. Recently viruses have been in the news for causing cancer such as the HPV virus giving rise to cervical cancer. It is not hard to imagine viruses (invade hosts DNA) giving rise to cancer (specific alterations in DNA). Cancer can also arise through errors in the replication of DNA or it can be inherited.
So that’s it for part 1 of my Cancer Basics series…part 2 will be up in the next few days.