More on the Microbiome and Cancer: This Time Good News

A few days ago I wrote about how cancer is associated with the depletion of the human biome and subsequent chronic low-grade inflammation.  The news is grim indeed.  But today, I am posting about something at least a little positive on the cancer front.  Very exciting research is showing that by manipulating the bacterial microbiome, cancer immunotherapies can be made markedly more effective.[i]

Immunotherapy, in this case, ACT (adoptive T cell therapy) is a new concept in cancer treatment and involves essentially manipulating a person’s own immune system to kill the cancer cells. Researchers at the University of Pennsylvania discovered that ACT’s effectiveness is significantly affected by differences in the gut bacteria.  The use of antibiotics also greatly affects response, as does fecal transplant.

In ACT, T cells (part of the immune system) are collected from a patient and then multiplied in a lab to increase the number of tumor-killing cells.  These are then given back to the patient.

The scientists used genetically identical mice from two different laboratories who thus, had different bacterial microbiomes.  One set of mice had markedly stronger anti-tumor effect from the ACT than the other.  The researchers then used antibiotics to kill certain types of gut bacteria (gram negative) and this greatly increased the efficacy of the ACT.  Amazingly, when fecal transplant was used to move the bacteria from the greater-response mice to the 2nd set of mice, this latter group showed the same stronger positive response.

“This means that the microbiota-dependent response to ACT was successfully transferred between mice, and that modulation with specific antibiotics can be used to increase ACT efficacy…confirming that this technique could be applied to control gut microbiome populations and improve ACT. Collectively, the findings demonstrate an important role played by the gut microbiota in the antitumor effectiveness of ACT.”

Completely coincidentally, as I was getting ready to write this post about these amazing results out of U.Penn, I came across another article in Nature [ii]about this exact topic:  how gut bacteria affect the immune system and thus, response to cancer treatments.  It describes multiple other remarkable studies done on this.  For example, one researcher collected stool samples from patients with melanoma before and after an immunotherapy treatment called checkpoint inhibition.  “Those with a richer diversity of bacteria in their stool had more T cells peppered throughout their tumors before treatment than the other group, and they also responded more often and better to the immunotherapy.”  She actually did fecal transplant from the two groups of patients into mice.  The rodents that received stool from the higher-response group had slower growth of melanoma tumors, substantiating the fact that it is the gut microbes that make the difference.

Multiple human trials are happening right now.

Says one researcher, “It’s still almost like magic—that bugs in the gut might actually help to treat cancer.”

What a breakthrough this may all soon be.  With all my heart, I hope so.




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