
Gut Microbes Can Shape Responses to Cancer Immunotherapy - daegloe
https://www.scientificamerican.com/article/gut-microbes-can-shape-responses-to-cancer-immunotherapy/
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boyd
Here are the links to the study (missing from the Scientific American article
but in the original):

\- _Gut microbiome modulates response to anti–PD-1 immunotherapy in melanoma
patients_
[http://science.sciencemag.org/content/early/2017/11/01/scien...](http://science.sciencemag.org/content/early/2017/11/01/science.aan4236.full)

\- _Gut microbiome influences efficacy of PD-1–based immunotherapy against
epithelial tumors_
[http://science.sciencemag.org/content/early/2017/11/01/scien...](http://science.sciencemag.org/content/early/2017/11/01/science.aan3706.full)

Here is some earlier (cited) work in mice that very strongly showed an effect
between this therapy and the mouse gut microbiome ( _Commensal Bifidobacterium
promotes antitumor immunity and facilitates anti–PD-L1 efficacy_ ):
[http://science.sciencemag.org/content/early/2015/11/04/scien...](http://science.sciencemag.org/content/early/2015/11/04/science.aac4255.full).
Really interesting to see these finding preliminarily reproduced in a clinical
setting.

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AlexCoventry
Do you have the DOIs for the supplementary materials available?

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feelix
Does anyone have any theories as to how this may work, assuming that it's not
a case of correlation does not equal causation?

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josephst18
Theory/ educated guess: these therapies try to antagonize the PD1 receptor,
which is found on immune cells (specifically, T cells); in a healthy
individual, the binding of PD-1L to PD-1 provides a "don't kill me" signal so
that the body's own cells are not destroyed by the immune system.

The problem with this is that cancers frequently develop mutations and
overexpress PD-1L which prevents the immune system from properly targeting
them for destruction. These anti-PD1/ anti-PD1L try to counteract this
overexpression, allowing the immune system's T cells to destroy the cancer.

However, targeting the cancer requires a functional immune system; this is
where the gut microbiome comes in. It's a sort of "home gym" for the immune
system--having a diverse range of bacteria helps keep the immune system
strong; gnotobiotic mice (mice bred and raised in completely germ-free
environment without any gut microbes) have significantly weakened immune
systems.

So theory is that the gut microbiome acts as a "home gym" where the immune
system can "train". Anything that reduces gut microbiome (such as antibiotics)
will also reduce this "training" and leave the immune system less able to
apply its training to fighting off cancer cells.

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arca_vorago
I was privileged to get to sysadmin for a pioneer microbiologist-geneticist
whose passion was the microbiome. Not long before I left, I started seeing
indicators that the the microbiome(s) in us and that we encounter and how they
interact is vastly more important than we have realized. From this biofilms
have made advances, etc. With sequencing getting so much cheaper, the research
opportunities are just sitting around waiting, and are the kind that offer
real and tangible results.

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vvdcect
What are the types of food that one could take to improve or help our gut
microbes?

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CuriouslyC
Beans are the best, as they have the highest percentage of fermentable fiber
in the form of raffinose. Pectin in apples, pears and citrus, the beta-glucan
in oats and barley, and inulin in alliums, chicory and jerusalem artichoke are
all good as well.

To get the most benefit, pair your fiber source with a probiotic food. Good
examples are unpasteurized sauerkraut, kimchi, yogurt, kefir, etc.

