I need a good technical answer. I know it is not completely known why, and I know that there are many different genes involved, but can somebody give me a clear answer?
Answer:
I'll give a shot at this one.Normal cells have a limited number of times which they can divide. This is dictated by the length of their telomeres which acts as a counter. Most normal human cells can divide about 40-60 times in a lifetime. Cancer cells have achieved immortality by being able to regenerate telomeres. This allows them to continue to divide passed that point. That is the basic concept as to why cancer continues to grow. This is an area of much research for treatment possibilities.If you are asking why cancer can survive thru treatment, this is a more complex question. I will try to cover some of the reasons.One or more of the mutations of cancer cells involves tumor suppressor genes. These genes may repair damage to DNA or cause the cell to commit suicide (apoptosis) to prevent propagation of genetic errors. Since there are defective tumor suppressor genes, cancer cells are more suspectible to accumulating further gene mutations each generation (genetic instability).That's why histological grade (how abnormal or differentiated the cell looks) is important in prognosis and usually directly correlates tot he aggressiveness of a cancer. Do not confuse this with stage which is a measure of the physical progress of cancer spreading.These mutations are often for the evolutionary benefit of the cancer cell. Common mutations allow them to
1. use p-gycloproteins to pump out chemotherapy drugs.
2. change their surface antigen signature (preventing recognization by antibodies)
3. employ other defense mechanisms against the immune system
4. repair DNA damage caused by chemotherapy and radiation (but not DNA damage that is part of the cancer)However, cancer cells like any other cell may die from lack of blood supply. Necrosis (dead tissue) may be caused by cancer cells which have outgrown their blood supply. This is an area of much current research for treatment (anti-angiogenesis) and some drugs are already available which capitalize on this approach (Avastin, Erbitux, Tarceva, Iressa, etc.)I hope this clears things up for you without being too technical.
hopefully they can die... with Chemo
if administered in time, with the correct diagnosis
and hereditary factors
Cancer cells do die just like normal cells, but unlike normal cells in which the rate of death is in equilibrium with the rate of growth, in cancer, this is shifted such that growth is dramatically more than death, and so cancer grows uncontrolled.Different cancers have different reasons for this imbalance, i.e. different sets of genes are involved, but in general, this is usually a result of mutations in either proto-oncogenes or tumor-suppressor genes. Proto-oncogenes are genes that when mutated, cause increased rate of growth; tumor-suppressor genes are genes that when altered, fail to cause proper senescence (aging) or apoptosis (death) of the cancer cells.This is in fact a very simplistic view of cancer. In actuality, there are likely multiple process and many levels of defects or pathways working at the same time in the same cell.
As you may know cancer is the result of the normal cell cycle that takes place in our bodies to replenish cells that die or need replacing, goes out of control. In so far as normal cells follow a natural cycle of development and multiplying and stop multiplying as they are controlled by certain genes to start and stop the growth cycle, as the body requires. If these controlling genes are mutated or damage in some way the cell growth cycle goes out of control, resulting in the development of excess cells and a build up. (Cancer).
Various treatments such as chemotherapy and radiotherapy kill off and stop these fast growing cells. Research into gene therapy and gene silencing technology may one control those genes that contribute to these out of control cells developing.If you would like to read more about this process, the following site may be of interest.
Something as big as cancer is really hard to describe how it works, however, if you are interested in watching an hour long program produced by NOVA and shown on PBS on Feb 21st, 2001 click on this link:http://www.pbs.org/wgbh/nova/cancer/prog...Trust me, after watching this, you should basically know how cancer cells work. I've watched it so many times and it all make sense to me. This Doctor might just have find a way to effectively treat cancer without chemo.Go for it, trust me, watching this will make your day.
Have fun
Subscribe to:
Post Comments (Atom)
No comments:
Post a Comment