Bacteria, a vast and often beneficial presence on and within our bodies, have recently been found to shield cancer cells by certain species. This intriguing discovery could pave the way for novel approaches in cancer treatment.

In a groundbreaking study published in Nature, researchers led by Dr. Kristin Arp have discovered a significant role that bacteria play in the development and progression of oral and intestinal tumors.

According to the study, if patients with melanoma have a more diverse population, or an abundance, of "good" bacteria in their guts, they respond better to immunotherapy. This could potentially open up new avenues for cancer treatment.

Bacteria have been found to be unevenly distributed in tumors, with certain areas containing more bacteria than others. Cancer cells in these bacteria-rich regions have a greater capacity to proliferate and migrate.

The 16S ribosomal DNA (rDNA) analysis was used to identify and characterize bacteria in tumor samples, with Fusobacterium being the most prevalent. When Bullman implanted a patient's tumor containing Fusobacterium into mice and gave them antibiotics, it not only killed the bacteria but also decreased the tumor size, indicating that Fusobacterium is associated with the growth and survival of the cancer.

Existing drugs can be reevaluated for their efficacy as both anticancer drugs and antimicrobial drugs, specifically targeting tumor-dwelling bacteria. The study found that 15 percent of the screened bioactive compounds that can kill F. nucleatum and other microbes also had potential as cancer chemotherapy drugs.

The human body contains almost as many, if not more, microbial cells as human cells. Bacteria make up most of the microbiome in the human body and are found in the gut, on the skin, in the respiratory and urogenital tracts, and in mammary glands.

Intriguingly, the study also found that bacterial infection trapped neutrophils at the center of infected cancer spheroids, helping cancer cells escape the T cells. Parts of tumors with more bacteria had fewer blood vessels, lower levels of T cells, and higher levels of myeloid cells, suggesting that these bacteria are contributing to an immunosuppressed environment within the tumor.

Areas of tumors with more bacteria were generally more immunosuppressed than bacteria-free areas. This finding adds to the growing body of evidence that bacteria are not just passive bystanders in the tumor microenvironment, but active participants in cancer development and progression.

The presence of certain bacteria in a patient's gut has also been found to boost the success of immunotherapy. This opens up the possibility of using probiotics or antibiotics to modulate the gut microbiome and improve the efficacy of immunotherapy.

The new study "pretty conclusively shows that not only there are microbes within tumors, but they can actually be within cancer cells themselves, and even within immune cells," according to the researchers. This finding could potentially revolutionize our understanding of cancer and lead to the development of new, targeted therapies.

An accompanying study published in the journal Cell Reports finds that some anticancer drugs, such as 5-fluorouracil, may be effective because they also kill the bacteria which help the tumor develop. This suggests that the role of bacteria in cancer may be more complex than previously thought, with bacteria potentially playing both positive and negative roles in cancer development.

The team of Bullman and Johnston focused on oral and colorectal cancer tumors to investigate the role of bacteria in cancer development. The study published in Nature investigating the role of bacteria in the development and progression of oral and intestinal tumors is a significant step forward in our understanding of cancer and could potentially lead to the development of new, targeted therapies.

Bacteria, a vast and often beneficial presence on and within our bodies, have recently been found to shield cancer cells by certain species. This intriguing discovery could pave the way for novel approaches in cancer treatment.