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Medical Forum / Diseases and Disorders / Prostate Cancer / January 2006

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Ping Ed Friedman... Question about effect of soy consumption on PCa

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Dennis D - 13 Jan 2006 04:48 GMT
Ed,

I have read over your paper, and am still trying to understand and
digest it.  I know in previous posts here, you described your theory
that while soy consumption  helps prevent PCa, once it has started,
eating soy, ironically, promotes the growth of PCa because of a
resulting decrease in PCa cell apoptosis.  This flys in the
face of a widely accepted gospel.  Many men with PCa believe that
eating soy will benefit them, not harm them.  Moreover, how do you
explain studies to date that demonstrate that soy consumption slows
the rate of PSA rise in men with PCa.  Below, I have summarized one
such study as well as a study on PCa cells in mice. Also, anecdotally,
I know of men with PCa who attest to experiencing drops in their PSA
levels after eating soy.  How do you account for this ?

In a study by Hussan, et.al., groups of men with PCa (41 total) and
rising PSA  (one group (I) was newly diagnosed and untreated, a second
group(II) had received local therapy, and a third group (III) was
receiving hormone therapy)  consumed 100 mg soy isoflavone (Novasoy)
twice daily for an average of 5.5 months.  There was a decrease in the
rate of the rise of serum PSA in the whole group (P = 0.01) with rates
of rise decreasing from 14 to 6% in group II (P = 0.21) and from 31 to
9% in group III (P = 0.05) following the soy isoflavone intervention.
(2003)

http://oncologynutrition.org/public/research_updates/show_all.php?res_id=282
.................

Studies performed by researchers at the UC Davis Cancer Center showed
that genistein, a chemical found in soy, slowed prostate cancer growth
in mice and caused  prostate cancer cells to die.  (2001)

http://www.sciencedaily.com/releases/2001/06/010604072646.htm  

Thank you for addressing this important issue.  I sit nervously with a
glass of soy milk in my hand.  Should I drink it?  I had RP in 2003.

Dennis
Ed Friedman - 13 Jan 2006 18:06 GMT
> Ed,
>
[quoted text clipped - 34 lines]
>
> Dennis

Dennis,

You are quite correct.  All hormones, and hormone analogs such as
genistein, do things that are good and bad at the same time with regards
to prostate cancer.  When I made my statements before, I was basing it
just on how genistein interacts with hormone receptors.  Since then, I
have learned that research shows that much of genistein's anti-cancer
effect has nothing to do with the estrogen-receptors.

Therefore, at this point my view is that soy is ordinarily benificial
(although it is always possible to construct a series of mutations to
make it harmful) against prostate cancer.  However, for men receiving
high doses of 5AR2 inhibitors, soy can definitely increase bcl-2
production and thus increase the rate of cancer growth (as was observed
by Dr. Leibowitz and it explains the excess high Gleason scores in the
PCPT).  The interesting question is if you ingest large amounts of soy
and are taking 5AR2 inhibitors plus high doses of T, will the increased
amount of apoptotic proteins generated by the high T offset any bcl-2
increase due to the soy?

Ed Friedman

Ed Friedman
ron - 13 Jan 2006 18:35 GMT
Ed Friedman wrote...snip...
> When I made my statements before, I was basing it
> just on how genistein interacts with hormone receptors.  Since then, I
[quoted text clipped - 4 lines]
> (although it is always possible to construct a series of mutations to
> make it harmful) against prostate cancer.

Ed...Is this statement made for both initial and recurrent PCa?

> However, for men receiving high doses of 5AR2 inhibitors, soy can definitely increase
> bcl-2 production and thus increase the rate of cancer growth (as was observed
> by Dr. Leibowitz and it explains the excess high Gleason scores in the PCPT).

Are you aware of the published papers that have explained the PCPT
high-Gleason artifact through sampling error?..Ron
Ed Friedman - 13 Jan 2006 21:21 GMT
> Ed Friedman wrote...snip...
>
[quoted text clipped - 8 lines]
>
> Ed...Is this statement made for both initial and recurrent PCa?

Yes, although I still have some doubts about massive amounts of soy. If
bcl-2 works via thresholds and the specific genetic mutations for
somebody's PCa puts it close to the level of a threshold that is really
bad, then adding the soy could put the bcl-2 over that threshold.

>>However, for men receiving high doses of 5AR2 inhibitors, soy can definitely increase
>>bcl-2 production and thus increase the rate of cancer growth (as was observed
>>by Dr. Leibowitz and it explains the excess high Gleason scores in the PCPT).
>
> Are you aware of the published papers that have explained the PCPT
> high-Gleason artifact through sampling error?..Ron

I am not aware of papers explaining PCPT results as sampling error.  I
am aware of explanations that use the fact that F changes morphology to
explain it, and an explanation that ER-beta isn't active enough (and
suggesting soy to up the activity).  I'd be interested in those references.

Ed Friedman
ron - 13 Jan 2006 23:18 GMT
Ed Friedman wrote...snip...
> >>However, for men receiving high doses of 5AR2 inhibitors, soy can definitely increase
> >>bcl-2 production and thus increase the rate of cancer growth (as was observed
> >>by Dr. Leibowitz and it explains the excess high Gleason scores in the PCPT).

ron wrote:
> > Are you aware of the published papers that have explained the PCPT
> > high-Gleason artifact through sampling error?..Ron

Ed responded
> I am not aware of papers explaining PCPT results as sampling error.  I
> am aware of explanations that use the fact that F changes morphology to
> explain it, and an explanation that ER-beta isn't active enough (and
> suggesting soy to up the activity).  I'd be interested in those references.

The morphology issue is still being debated and tested, it is not yet
resolved.  Here is a reference that describes the sampling artifact
effect...Ron

J Urol. 2006 Feb;175(2):505-9; Evidence for a biopsy derived grade
artifact among larger prostate glands; Kulkarni GS, Al-Azab R, Lockwood
G, Toi A, Evans A, Trachtenberg J, Jewett MA, Finelli A, Fleshner NE.
Ed Friedman - 26 Jan 2006 21:18 GMT
> The morphology issue is still being debated and tested, it is not yet
> resolved.  Here is a reference that describes the sampling artifact
[quoted text clipped - 3 lines]
> artifact among larger prostate glands; Kulkarni GS, Al-Azab R, Lockwood
> G, Toi A, Evans A, Trachtenberg J, Jewett MA, Finelli A, Fleshner NE.

Ron,

I just read that article - thanks for the reference.  I always find your
posts intellectually challenging.

The article is interesting, but not convincing.  If they are correct,
then they predict that the pathology reports will differ markedly with
the biopsy reports, and I assume that somebody would have published
about this already if that were the case.

Also, one of the main arguments they use is that if F caused high grade
Gleason scores, then they should increase in time, whereas if it is all
an artifact, then the number should be stable over time - just as it was
observed.  However, they don't even consider F + diet (e.g. soy), which
would also be stable over time, assuming diets are not changing that
much.  Also, if the diet is not responsible, then you have to come up
with an explanation as to why other researchers aren't replicating Dr.
Leibowitz's results.

Ed Friedman
 
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