Bacteria living in the digestive tract of humans can have a hand in influencing cancer treatment response, opening up a new avenue for researchers to focus on in the effort to improve how the disease is treated, reports a research team led by specialists from The University of Texas MD Anderson Cancer Center.

In a study published in the journal Science, the researchers showed that metastatic melanoma patients administered with an anti-PDI checkpoint blockade were able to control their disease longer when they have certain bacteria types in abundance or a highly diverse bacteria population in their guts.

"Our studies in patients and subsequent mouse research really drive home that our gut microbiomes modulate both systemic and anti-tumor immunity," said the study's leader, Jennifer Wargo, M.D., a Genomic Medicine and Surgical Oncology associate professor.

Wargo and colleagues believe their findings have the potential to pave the way for bigger breakthroughs because it's not at all difficult to change an individual's microbiome. According to Vancheswaran Gopalakrishnan, Ph.D., the study's lead co-first author, microbiome modification can be targeted using probiotics or antibiotics, exercise, diet, or fecal transplantation.

Microbiome Modification And Cancer Immunotherapy

To create a clinical trial combining checkpoint blockade and microbiome modulation, the researchers teamed up with the Parker Institute for Cancer Immunotherapy.

Immune checkpoint blockade drugs work to free up a patient's immune system so it can attack cancer cells, helping about 25 percent of patients with metastatic melanoma. However, drug response is not always the same, so research has been focused to extend how checkpoint blockades affect the body,

For the study, Wargo and her colleagues analyzed cheek swabs and fecal samples from patients undergoing anti-PDI treatment, which blocks PDI proteins in T-cells to halt the immune system. Specifically, the researchers conducted whole genome and 16S rRNA sequencing to identify composition, functional potential, and diversity in microbiomes developed out of the cheek swabs and fecal samples.

The Future Of Cancer Treatment?

According to their findings, there was no dramatic difference in progression or response in the cheek swabs but it was entirely a different story with the fecal samples, with additional analysis showing responding patients with high Clostridiales/Ruminococcaceae bacteria levels have T-cells that penetrate tumors better and have more T-cells in circulation to kill off abnormal cells.

The results are promising but the researchers warn that there remains a lot to be learned about how the microbiome affects cancer treatment, urging people to avoid self-medicating with probiotics or other means to boost levels of beneficial gut bacteria in the body.