Further evidence that the microbiome can improve melanoma cancer therapy

T stages of melanoma

Yesterday we discussed a paper that discussed how the microbiome impacted a melanoma cancer therapy.  In the same issue of Science another article was published where researchers from Chicago independently made a similar discovery - that the microbiome itself can impart an anti-tumor effect on melanoma.

The scientists were using a  common mouse model for melanoma between two different laboratories (Taconic Labs and Jackson Labs) when they noted that the cancer progressed much differently between the labs.  The Taconic mice had more aggressive cancer than the Jackson mice.  They hypothesized that one possible difference between the mice in the two labs were their microbiomes.  In fact, when the Taconic mice were given the Jackson mice's microbiomes, the Taconic mice's cancer grew more slowly.  The scientists then attempted to identify which bacteria were having the effect.  They compared the mice's microbiomes and discovered that Bifidobacteria were much more abundant in the Jackson mice.  Upon treating the Taconic mice with strains of Bifidobacterium longum and Bifidobacterium breve the Taconic mice's cancer grew more slowly.  Interestingly, the scientists discovered that the bacteria were likely increasing the activation of T-cells, because mice that had mutated T-cells did not have the microbiome-mediated anti-cancer effect.

This study points to an exciting role of the microbiome in mediating and activating the immune system to attack and destroy some cancers.  The researchers note that there are likely other microbiome bacteria that have this effect, but that they have only identified the Bifidobacteria.  Hopefully the scientists will be able to measure the effect in humans, and observe an association between patient outcome and the presence and absence of certain gut bacteria.

Clinical trial for probiotics in irritable bowel syndrome fails to show efficacy

Irritable bowel syndrome is the most common functional gastrointestinal disorder, affecting about 10-15% of people in the United States alone, according to the International Foundation for Functional Gastrointestinal Disorders website. Fortunately, as described by the IFFGD, IBS is a functional disorder, meaning that while it does affect quality of life, it does not affect life expectancy. Probiotics have been studied as treatment for IBS because, as we’ve seen in many other examples of probiotic use, it is safe and rarely has any negative effects on the consumer. Some trials have shown that probiotics help relieve the symptoms of IBS; however the conclusions are controversial due to study structure and participant numbers. For this reason, scientists in Seoul, South Korea recently published a study in the Journal of Clinical Biochemistry and Nutrition, which studied the effects of a multi-species probiotic mixture on IBS symptoms using a double-blind study with a large number of participants.

Eighty-one patients participated in the 4-week-long double-blind study, with 42 people receiving a multi-species probiotic (containing Lactobacilli, Bifidobacteria, and Streptococci) and 38 people receiving a placebo. Baseline fecal samples were collected before probiotic/placebo consumption, revealing no significant difference between the two groups of participants. After consumption, the probiotic group showed a significant increase in concentrations of the probiotic bacterial strains in fecal samples, but not significant increase of levels of Bacteroidetes and Firmicutes.

In terms of symptom relief, while the probiotic group reported a greater percentage of relief, it was not significantly greater than the placebo group. This could be a classic case of the placebo effect, which is a phenomenon in which a sham treatment can actually improve symptoms because the person receiving the placebo believes it will help them. The results of this study are not concrete because there was no significant difference in symptom improvement; however there were significant increases in probiotic strains in fecal samples of the probiotic group. This study could be a step in the right direction toward relieving IBS symptoms.

New research shows that Bifidobacteria transfer from mother to child

Both natural birth (as opposed to birth by C-section) and breastfeeding are topics that stir up a lot of conversation among mothers and the scientific community. For example, there is the question of whether breastfeeding rather than formula feeding has some specific benefit to an infant’s health. Well, what about the infant’s gut microbial health? A new article published by Applied and Environmental Microbiology takes a look at whether natural birth and breastfeeding coincides with an exchange of bacteria from mother to child.

Four mother and infant pairs were included in the study that was meant to discover whether the mother transfers any bacterial strains to the infant during vaginal birth and breastfeeding. In particular, the scientists were looking at the genus Bifidobacterium because this group has been known to be early colonizers of the infant gut. In addition, this genus has specific ways of digesting a human mother’s milk. Mother-infant pairs 2 and 4 exclusively breastfed, while pairs 1 and 3 supplemented with formula. Milk samples were collected from the mothers and fecal samples were collected from the mothers and children.

After sequencing the bacteria, B. adolescentis, B. angulatum, B. breve, B. dentitum, B. pseudolongum and B. thermacidophilum were found to be common between all of the mother and the infant fecal samples. The scientists then looked to see which bacteria were in both the mother’s milk and the infant’s fecal sample. The results suggest that the milk may be responsible for transferring B. adolescentis, B. angulatum, B. breve, B. longum and B. pseudolongum to the infant. Interestingly, there were also some bifidobacteria strains that were unique to the infant, suggesting that either they went undetected in the mother or that the infant was exposed to this bacteria from somewhere else.

After six months, samples were collected again in order to see how/if the sample compositions change. The scientists found that, especially in the infants, the abundance of bifidobacteria decreases. This is most likely due to changes in diet – less breastfeeding and more formula feeding – and perhaps environmental exposure. All in all, the results of this experiment shows that the infant microbiome might indeed be influenced by a vertical transfer of bacteria from mother to child. With more evidence of this as a possibility, science may begin looking into more complete analyses with larger study sizes.