Today's Interesting Pathology Fact!
October 4th, 2018
Ever wonder why malignant tumors grow much faster than benign ones? Well today, we get to find out why! There are many factors that cause tumor cells to differ but for the most part, we'll keep the lesson brief (we could easily spend hundreds of hours going over the basics of cellular function; but let's keep it short, shall we?).
First of all, we must acknowledge the difference in growth rates. Benign tumors have a very slow growth rate. As a result, they are easier to treat since the risk of spreading (or metastasizing) is fairly low. Malignant tumors have different rates of growth depending on the type of cancer, but cancers that are at higher stages tend be aggressive as they grow quickly. These tumors spread all over the body and invade the cells of other organs, which causes our body to function at a lower capacity than we'd like it to. Due to our defenses being down, malignant tumors are able to spread more easily and thus keep growing.
As for the reason why these cancerous cells continue to grow uncontrollably, we can blame the cells themselves. Cells usually have a checkpoint they must reach before continuing with cellular division (mitosis) and their life cycle. They're separated into the G1, G2, and M checkpoint. Right now, we'll focus only on G1 and G2.
Before passing the G1 checkpoint, the cells checks itself to see if growth is needed. It'll also assess the size of cell, whether it has enough resources to grow, and if the DNA of the cells is damaged or not. If it passes the stage, then cell division begins (and is irreversible at this point). If this stage is not passed, then the cell does not divide.
At the G2 checkpoint, things get a little dicey if the cell doesn't do its job. Here, the DNA is the main focus and it's where it's checked for damage in detail. If the DNA was damaged in any way during the replication process, then the cell must fix the problem. Should the DNA be irreparable, then programmed cell death (apoptosis) must occur. By having the cells essentially kill themselves off, they prevent cancer from taking place. However, sometimes this mechanism doesn't work due to the proteins that make apoptosis happen being damaged themselves. At this point, it is very critical for this checkpoint to work properly. When it doesn't, cancer happens. The damaged cells grow (despite being flawed) uncontrollably and invade the body, resulting in a chronic, debilitating disease.
Researchers are trying to find ways to combat cancer growth, starting with the complications that arise during the cell's life cycle checkpoints. If you'd like to find out what achievements have been made already, check out these articles below. Thanks for reading!
From the National Center for Biotechnology website:
Reece, Jane, et al. Campbell Biology. 11th ed., Pearson, 2016. pp. 234-238.