More on Helminths and the Prevention of Cancer

Last October, I wrote about a study that looked at the effects on cancer of the immune modulation afforded by helminths (intestinal worms), which are the main component of the mammalian macrobiome.  That paper provided a very positive initial review of the mechanisms by which helminths may exert their anti-cancer effect, but obviously, a massive amount of data and studies needed to be done before any conclusions could be drawn.

Previous research has shown that there is a correlation between the lack of a strong Th2 immune response and the development of cancer.  Nowadays, the Th2 family of cytokines (chemical messengers) is associated with allergy (an inappropriate inflammatory response to benign environmental stimuli), but in fact, from an evolutionary stand point, these chemicals are there to keep our helminths in check.  (Some are good, some are bad, and too many of even the benign ones are not good.  Our bodies needed to develop a mechanism of action to deal with their presence in a way as to ensure our survival.) As I have written about before many times (here, as just one example), all mammals on the plant evolved with a macrobiome – our native animal life – as well as the much better known microbiome.  However, in the last 50 to 75 years or so, those of us living in the industrialized world (and our domesticated pets) have effectively been de-wormed.  As the Th2 cytokines also include those which are regulatory, which moderate inflammation, we are now perpetually low in regulatory chemicals and prone to out-of-control inflammation.  Some scientists have now come to believe that the loss of our helminths is one of the biggest factors in our current epidemic of inflammatory diseases, ranging from allergies to autoimmunity to autism to cancer.  Unlike a swift (i.e. acute) “allergic” response, helminths provide a strong and continual stimulation to the Th2 system, which as I said, over months and years, modulates inflammation. De-worming humans is akin to going into a rainforest and removing all the insects.  We abruptly killed off an entire species from our ecosystem.  And humans, like all ecosystems, were in a delicate balance…that we have destroyed.

In May, a new animal study came out looking at the effects of a helminth, H. Nana (which is native to rodents) on cancer. [i] The scientists broke the mice up into 4 groups:

1. The first group was given DMSO cutaneously (through the skin)
2. The 2^nd group were given only the H.nana
3. The 3^rd group was given another chemical, DMBA, again cutaneously. DMBA is known to induce tumor growth.
4. The 4^th group was given both the helminth, H. Nana, and the cutaneous DMBA.

The chemicals given  the mice did indeed induce tumor growth, and the tumor load, as well as blood levels of various  immune components were assessed by the researchers.

The results showed that the group that had first been colonized by the H.Nana had “…a reduced amount of tumors with smaller size…”  More than that, they found that they had significantly lower levels of proinflammatory immune cells in their blood.  They concluded that the reduction in tumor growth may be due to the increase in certain kinds of immune cells (eosinophils and neutrophils) that they found in the animals.  It is unlikely to be from anything secreted by the H.Nana because the protective effect lastedeven after the mice had eliminated the helminth.

One item of particular interest to me:

As my regular readers know, interleukin-10 (IL-10) is one of the predominant regulatory cytokines that is very much responsible for modulating the inflammatory response and balancing the immune system.  It is also thought to perhaps be associated with cancer, as lowering the inflammatory response may prevent the body from fighting cancer cells effectively.  (That is, an increase in IL-10 for people who already have cancer may be a bad idea.  This thinking , however, is still very controversial as IL-10’s relationship to cancer, should it exist, is poorly understood.)  What these researchers found though is pretty amazing.  The highest levels of IL-10 were found in the mice who were only given the carcinogenic DMBA, and this actually replicated the findings of previous studies!  Those who also had the helminths on board actually had a “significant reduction” in IL-10 levels, even though helminths are usually a potent stimulator of its production.  What does this suggest? It appears that helminths not only do not actually suppress immune response, but instead, seem to modulate it so that it is appropriate for the given situation.  Therefore, in the face of a carcinogen, the helminths stimulate the immune system in such a way as to help it fight cancer – and thus, the reduction in tumor growth seen in this group.  In fact, the tumors induced by DMBA typically start as benign and progress toward carcinoma (cancer).  However,  the few tumors that did grow in the mice with helminths on board did not progress toward malignancy.

That is a major WOW.

According to a 2017 article out of the University of Adelaide, in Australia (which, by the way, has the highest rates of cancer in the world)[ii]:  “…the 10 countries with the lowest opportunities for natural selection (among the “better” countries of the world) are: Iceland, Singapore, Japan, Switzerland, Sweden, Luxembourg, Germany, Italy, Cyprus, and Andorra….The 10 countries with highest opportunities for natural selection (among the “worse off” countries of the world): Burkina Faso, Chad, Central African Republic, Afghanistan, Somalia, Sierra Leone, Democratic Republic of the Congo, Guinea-Bissau, Burundi, and Cameroon.”[iii]

Their explanation , which of course is very likely a part of the picture, is that because we live longer in the industrialized world – ie. we don’t die from acute infections like malaria and the like, have better medical care, and so forth – we get cancer more often.  But it also strikes me that what they call the “worse off” countries are also those where helminth colonization is still the norm.

As I say to you  all the time – there are no simple answers.  The cancer question is undoubtedly going to turn out to be one of those cases where many factors,  from the two I just named, to our food, our chemical exposure, etc. are all a part of the picture.

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[i] Ramos-Martinez, E, et. al. The immune response to Hymenolepis nana in mice decreases tumorigenesis induced by 7,12 dimethylbenz-anthracene.  Cytokine. 2019. 123:154743.  doi.org/10.1016/j.cyto.2019.154743

[ii] https://www.wcrf.org/dietandcancer/cancer-trends/data-cancer-frequency-country

[iii] https://www.sciencedaily.com/releases/2017/10/171011100708.htm