WHAT IS CANCER? CANCER AS DISASTER

I answered this question in my blog for this course last semester here, so I won't redo the work.  The video I found below of cancerous cells metastisizing is a great visual representation of how cancerous cells replicate and eventually invade surrounding circulatory vessels and tissue. 

3D Animiation of Cancerous Cells Metastasizing 

 

Admittedly, I am having doubts about having chosen the disease cancer as my disaster for this course. I get the sense that I might repeat a lot of the information from my Spring 2010 "Apoptosis" blog. My "Apoptosis" blog focused on healthcare reform and cancer care, but it also covered many of the details of the disease--particularly my fascination with the term apoptosis. Apoptosis  is the term the Greeks used to describe petals or leaves dropping off from flowers or trees (OED).  Today it refers to the loosening of something from its origin.  In biology, the terms means the “death of individual cells” (OED).  I want to learn more about cancer at the cellular level, but I'm not sure if the scientific focus my blog might take for this course will be appropriate. In short, I am wavering about my disaster choice.

I am still interested in the term apoptosis, and I plan to explore it further if I stay with this disaster choice.  I am also interested in the term's association with the natural cycle of the death of a cell, in what scientists call a cell's suicide program or programmed cell death.  Cancer is caused by a defect in a cell's suicide program.  When the internal integrity of a cell is compromised, a healthy cell's natural response is to die in order to preserve life or for other specific purposes.  For example, cell death  in a growing embryo is responsible for the division of tissue that form our fingers and toes:

[C]ell death [] eliminates unnecessary cells. For example, during embryogenesis, the digits of our fingers and toes are sculpted by the death of cells in the intervening spaces. If these cells remained alive, our hands and feet would become webbed. Thus the timing and location of cell death, as well as cell growth and division, must be precisely controlled. (Molecular Cell Biology, "Cells Die by Suicide," NCBI, 2000)

Apoptosis specifically refers to the sequence of events that lead to the total obliteration of the cell:

The first visible sign of apoptosis is condensation of the nucleus and fragmentation of the DNA. The cell soon shrivels and is consumed by macrophages. A cell is directed to commit suicide when an essential factor is removed from the extracellular environment or when an internal signal is activated. Thus, the default state of the cell is to remain alive. (Molecular Cell Biology, "Cells Die by Suicide," NCBI, 2000)

When apoptosis fails, a cell continues to replicate without a purpose.  Normal cells are pre-programmed to reproduce between 50 to 60 times before dying, but cancer cells continue to double and re-double at at an alarming rate (1 to 2 to 4 to 8 to 16, etc.).  Cancer cells, unlike normal cells, do not "stop reproducing," do not "obey signals from other cells," do not "stick together," and do not "specialise, but stay immature" ("The Cancer Cell," Cancer Research UK).  Eventually these cells form into a tumour "that is made up of billions of copies of the original cancerous cell. Scientists describe cancer cells as being 'immortal'" ("The Cancer Cell," Cancer Research UK).  Depending on any number of factors the tumorous mass of cells may start to slough off into the surrounding tissue.

Cancerous cells may replicate indefinitely, and indeed be immortal, but cancer needs the host of the body.  Cancerous cells, like normal cells, need a blood supply.  As a tumor gets larger, the cells at its center get further away

from the blood vessels in the area where it is growing. So the centre of the tumour gets less and less of the oxygen and the other nutrients all cells need to survive.

In fact, scientists researching how tumours grow think that a cancer can't grow much bigger than a pin head before it needs to develop its own blood supply. Until it grows its own blood supply, the tumour cannot grow any bigger because the cells at the edge of the tumour will die due to lack of oxygen. ("How a cancer gets its blood supply," Cancer Research UK)

Later posts, if I stick with this topic, will explain research that focuses on blocking the blood supply to cancerous cells--among other recent innovations in cancer treatment.