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Wingy 08-05-2008 08:15 PM

Odd mechanism for cancer
 
On another discussion board (not a science board), a member posted the following explanation for the mechanism underlying cancer. I have been trying to convince him that there are a few, um, problems with this mechanism. (He insists, for example, that "interon" is the correct spelling for "intron" even though what he describes isn't even an intron!)

I would like to gather some other opinions, lest I am way off base here, about this proposed mechanism. Here are my questions:

1. Is there any such thing as an "interon"?

2. Have any human operons actually been identified, other than through genomic analysis (i.e., prospective operon sequences)?

3. If so, does this explanation bear any resemblance to what we mean when we say "operon?"

4. What is your evaluation of the passage as a whole?

Thanks for any input you can provide...

Here is the passage in question:

Quote:

On a scientific basis, cancer is defined as abnormal cell growth. To understand it, it is necessary first to understand the development of a fetus. As cell division begins through mitosis and the original egg splits into 2, then 4, then 8, then 16 etc. to 64 cells all of these cells can develop into any tissue - bone, muscle, nerve, etc.. When the embryo goes beyond this stage in division, the cells differentiate into the various tissues. Now, the chemical change that takes place - to use an analogy - is like flipping a switch. In this case, a biochemical switch. Once this switch is turned off, each cell in the embryo is going to continue to divide but they will each become a particular tissue. These are often termed the "operon" and the "interon", the operon being the switch and the interon being the chemical (tRNA, m-RNA) that disappears and causes the switch to shut off.

Now, it is hypothesized that a cancerous cell begins when the interon, or a chemical/substance biochemically similar, is reintroduced into the cell and reactivates the switch. So, the cell begins to divide again (uncontrolled, abnormal cell growth) but doesn't have the genetic materials necessary to become its own embryo, just a vascularized mass (it taps into your blood vessels). Most cancers develop as a tumor (pre-vascularized tumors are easier to remove and generally are benign) but some don't (like leukemia). Beyond abnormal cell growth, cancers are also invasive (they affect cells around them) and they may metastasis (travel through the blood to another spot and begin a new tumor). Tumors that have metastasised, or have the potential to, are termed malignant.

Where does the interon come from and what is it? It can differ from person to person - which it is believed accounts for why some people get cancer from, say, cigarettes or pthalates and others don't. There are various environmental, chemical, and genetic routes that can cause, explain or "predict" the susceptability of a person to certain cancers. It is almost analogous to allergies - my allergy is not your allergy although many people may be allergic to the same thing (which causes a higher incidence of cancer from a substance) or the substance may cause a high degree cross segmented cancer (known Carcinogenic chemicals such as Carbon tetrachloride or chlorinated solvents - though the actual incidence of cancer from even these chemicals is much lower than predicted).

admin 08-06-2008 07:03 AM

Re: Odd mechanism for cancer
 
Hello, i agree thats not a great explanation of cancer. A lot has changed since the ideas of mutations and DNA damage, with cancer stem cells etc.

However the basic premise is that a cancer cell is a cell which has undergone transformation to a degree that it may follow some or all of the points below:

1) has lost the original function of the original cell
2) has become less differentiated (to a more undifferentiated or embryonic stage) - some cancer cells express embryonic markers on their cell surface.

3) has lost apoptotic or cell death mechanisms. This allows cancer cells to survive even though they have damaged DNA, or altered chromosomes

4) increased ability to outgrow boundaries of the tissue / organ (this is due to the cancer cells lack of responsiveness to regulatory factors)

5) increased survival and division of the cancer cell in the host environment

6) increased ability of the cell to degrade ECM and migrate (in non-benign ie metastatic cancers)

Basically a cancer cell is a cell that:

A) does not obey apoptotic or DNA damage rules usually
B) does not listen to the other cells / tissues / organs in the body which regulate normal cells
C) can move and take over areas / kill cells / grow in places where it should not.

Essentially they are a rebellious cell that came about due to certain conditions either environmental insults and/or inborn errors. There are numerous theories of cancer development from the simple:

HNPCC hypothesis (stepwise knockout of dna damage and p53 proteins) to the more advanced stem cell hypothesis / complex cancer types.

admin 08-06-2008 07:15 AM

Re: Odd mechanism for cancer
 
Oh one clever professor once told me that cancer cells are super-survivors in that they are like Darwins theory of evolution.

If you stress a population (such as cell populations) some will cope (grow) better than others and some of these cells will be cells that have adaptive advantages ie mutations or other advantages in methylation or replication status. The more normal cells will be replaced / over taken by the differentiated (cancer like cells). Keep stressing those cells and they will become cancer.
ie If you keep stressing cells, you will eventually select for cancerous cells!

my question: Is radiotherapy selecting for cancerous cells?


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