On Mon15 March 2004 Tim Tyler wrote:

CNCabej  wrote or quoted:

> Cancer is generally considered to be an abnormal growth of cells caused by
> mutations in DNA induced by carcinogenic substances, viral oncogenes, 
> ionizing radiations etc. Although evidence has been insufficient, and 
> it has also been argued that often this relationship was not seen, the 
> mutational theory of cancer is the explanation we find in every 
> textbook. A recent experiment raises doubts about the validity of the 
> dogma. Investigators show that mutation in the Ha-ras-1 gene is 
> sometime found in normal mammary gland and is absent in cancerous cells.

T.T.
"[...] it was also absent in *some* tumors" is what they wrote.

I.e. this particular mutation was probably not the sole causal factor.


N.C.

I believe that a closer look would help you agree with the investigators that
"this particular mutation" "is neither necessary
norsufficient for tumor
initiation".

N.C.
> I am not predicting (although I am not excluding) that this will start 
> a chain reaction of experiments designed to prove the EPIGENETIC origin 
> of cancer, but it should make us rethink what is real (production of 
> proteins) and what is fictious (determination of morphology, etiology 
> of diseases, etc.) on the role of genes in biology.


T.T.
I'm not sure I understand.
Isn't cancer thought to be caused by (among other things) radiation.


N.C.
What makes you taking for granted that radiation causes cancer by inducing
DNA mutations? The experiment  proves that a cancerogen  malignifies epithelial
cells without changing their DNA and probably without direct contact with the
carcinogen.
 
T.T.
It seems to me that radiation qualifies as "EPIGENETIC" in origin.

N.C.
Although you are not talking about the experiment under discussion, I don't
believe this is the most rational way of thinking about the role of radiation.
Would you try this one: Radiation is a physical carcinogen and mutagen at the
same time. Whether its carcinogen effect derives from its mutagen effect on the
DNA is still an open question (but again I  doubt whether you might call it
""GENETIC" by origin") . 
Now, returning to the experiment of Maffini et al., it has been thought that
mutations in the Ha-ras-1 gene cause cancer in the mammary gland. That
experiment in the unambiguous interpretation of the authors proves that that
mutation "is neither necessary nor sufficient for tumor initiation".

T.T.
I certainly can't see anything very revolutionary in the study you cite.

N.C.
Neither do I. Such results are predictable and
expected from my point of view.

T.T.
I don't see how it raises any doubts at all about the validity of the 
conventional explanations for cancer.

N.C.
If  the "conventional explanation for cancer" for you, as for most people,
implies that cancer is an abnormal growth of abnormal cells caused by mutations
in DNA, the experiment show that it is not the case with the cancer of the
mammary gland.

Thank you.
__________
 |im |yler  http://timtyler.org/  tim{at}tt1lock.org  Remove lock to reply.
---
þ RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info{at}bbsworld.com

---
 * RIMEGate(tm)V10.2áÿ* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 3/16/04 11:50:32 AM