Sadly cancer is everywhere around us, taking millions of lives each year. We are warned about cancer every day and we are urged to check for tumors. Although we are given a lot of education about the prevention of cancer we are not told what a malignant tumor exactly is. What has changed in our cells to cause cancer?
Cells react to certain signals that regulate the cell cycle (=cell replication/dividing/mitosis). A lot of the processes involved in this cycle regulate the inhibition (=to stop) of the division of cells. When these inhibitions stop working, tumor cells are usually the result. An example of a growth inhibitor is anchorage dependency, this means that all cells need a surface they can grow on. This is to prevent many loose cells that just float about in the body, growing in places where they should not. There is also density-dependent-inhibition, which if there is space left on the surface that the cells are growing on, they will automatically try to fill that space by dividing. If there is no room for a cell to grow, then it’s not allowed to divide to avoid stressing other cells. In the cell cycle there are also a certain molecules that need to be present before a cell is allowed to divide. Examples of these are hormones and steroids.
Cancer cells lack all these biological “brakes”. A logical hypothesis is that cancer cells either make these growth factors themselves, or that these factors are no longer needed to start the pathway (=cascade of chemical reaction that lead to a response) that eventually leads to mitosis (=cell replication/dividing). These cells also don’t have the pathways that are needed to halt mitosis when pressure by other cells is detected, or the pathways that sense that there is no surface to grow onto. This gives the loose tumor cells that can flow through the body and grow into tumors.
Benign or malignant?
Usually the abnormal cell that has formed from a normal cell gets destroyed by the immune system. When it avoids its destruction it will transform into a tumor. When these tumor cells stay at the site where they originally formed they are called benign. However, when they start moving around the body they will be called invasive tumors or in other words a malignant tumor. This last process, called metastasis, is what eventually becomes a problem as this can destroy organs by pressure because of the growth of the tumor.
Usually cells would divide 20-50 times before they stop dividing and die, but cancer cells sometimes have the ability to “regenerate” caps of DNA that protect the chromosomes during replication. This is done by the protein called “telomerase reverse transcriptase (TERT)”. Usually this protein is only active in sperm and egg cells, but the cancer cells that activate this protein are in essence immortal.
The treatment for these run-away tumors is simply to poison the body, to throw enough toxins into the system to kill rapidly growing cells, but not enough to be fatal to the patient. An example of this is chemotherapy, which I will probably explain in a later blog post.
Concluding, cancer cells are cells that no longer have the brakes that stop growth and stop the cells dividing. When these cells stay at the same place they are called benign, and if they move they are called malignant. Some cancer cells are able to divide endlessly and are in essence “immortal”.
Campbell, Reece et al. (2008). Biology – Eighth Edition 242-243
Pictures retrieved 11/6/2012;
“Cancer cell under attack “
“Cancer biology logo”
Extra Links for people interested
The Neglected Cancer by The Inquirer http://www.philly.com/philly/health/20121105_The_neglected_cancer.html
Breast Cancer research
NCBI Pubmed’s entry about cancer, from causes, risk factors to treatments.
Dutch cancer research