Do gut bugs change cancer therapy?

Contributing Columnist

It appears your gut bug population changes cancer therapy effectiveness.  A trial of immunotherapy on metastatic melanoma found those with greater variety of GI bacteria did far better than those with more limited populations.  If you had a lot of ruminococcus around, you were more likely to stay alive.


What Happened?

People with immunotherapy trials for melanoma at MD Anderson Cancer Center in Houston had their GI bacterial populations tracked into two groups – those who responded to treatment and those who did not, usuing  standard case-control technique.  The responders showed greater variety of bacteria, and rather different bacterial populations than those who did not.  In this case, diversity paid off.


What Was Cause, What Effect?

People with different gut bacteria have different diets and lifestyles.  If you eat lots of vegetables you not only have different kinds of bugs than if you choose meat with most meals, but you also get far more variety.  Yet many other factors  go into who gets what bacteria to populate your personal ecosystem, including where you travel, who you live with, how much physical activity you enjoy, not to mention how much booze you imbibe.

However, since different bacterial populations change propensity to illness, have shown major effects in autoimmune disease, stress and depression susceptibility, and are also used to treat illnesses like clostridium difficile, where antibiotic use allows a generally unimportant bacterium to kill tens of thousands ever year, chances are your gut bug populations helps determine what kinds of cancers and illnesses you’ll get.  There is a potent effect of diet on the incidence of many tumors. It won’t be shocking to learn your coresident bacteria help determine what kind you get.


Why Should Bacteria Matter?

There are somewhere between 40 trillion and 100 trillion bacteria in your gut. Trying to keep this restive population at bay is one of the reasons your gut lining gets shed in a day. Depending on little understood circumstances, the immunological challenge these bugs represent also changes how our immune system operates.  In terms of cancer therapy, they could 1. Modulate overall immune responses 2. Change absorption and penetration of drugs 3. Shift the conformational form and metabolize cancer drugs, among other effects. Having a whole ecosystem inside you changes your immunity and response to cancer.


How Can This Best Be Understood?

You might start by viewing the body as a giant information system, with innumberable sets of living, interacting data. Living things are themselves not just carriers of information, but information itself.  Importantly, gut bacteria don’t just make some of our vitamins, digest our foods, help us one day and fight us another.  They dwell in fraught competition for space and territory with tens of thousands of other bacterial species and subspecies.  Then come the other organisms living inside us, including bacteriophages – bacterial hunting viruses – rickettsia, mycoplasma, fungi, and untold numbers of non-bacteriophage viruses.  It’s a really complicated world down there. Our political divisions look simple by comparison.  And the interactions between these different components is not much understood beyond knowing they’re important to our own health.

One way to put it all together is to look at the question of biological intelligence – how all living things accrue and apply knowledge, mostly unconsciously. We are usually not aware of how many cancers we form on any given day – it may be hundreds – nor how our immune systems causes many cancers to self destruct, ingests some,  and walls off others.  Most of the drama happens off stage, with us only noticing what goes on when cancer cells grow into multiple clones or do something very recognizable, like produce hormones that change our blood pressure or cause us to bleed.


Bottom Line:

Cancer kills one in three Americans.  One of the most promising treatments now available is immunotherapy – helping to teach our own immune system how to kill the cancers it’s failed to keep at bay.  We’ve known for a long time such systems must work, as perhaps one in a thousand cancers will spontaneously remit.

Now it’s getting clear our own ecosystem – including our trillions of bacteria – have a role to play.  Yet it’s getting more probable that certain bacterial populations will make some treatments more effective.  We may be able to induce those populations by lifestyle manipulations, like what and when we ingest.

More interestingly, if bacterial and viral populations are part of cancer treatment, different patterns may prove helpful in preventing versus treating tumors.  A diet brimming with fruit and vegetables may be a great idea in preventing colon cancer, but may not be the way to go once you’ve got it.

Prevention and treatment are always contingent on just what kind of information system runs through us any given day.  And that changes – every moment of every day day.  Just another reason  to put information approaches to the fore when preventing and curing disease – whether it’s cancer or colds.

So different immigrant and domestic bacteria will need our help – if they’re to help us.

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