Bacteria could promote cancer metastasis

Summary: Microbes and Cancer

A recent study shows that bacteria infecting cancer cells and their surrounding environment may alter the immune system of the host, and promote cancer progression leading to metastasis. This opens new avenues for cancer therapy, targeting the microbiota to hamper cancer growth.

Do bacteria play a role in cancer?

A paper by Susan Bullman, Galeano Niño, Wu, H., LaCourse, et al. (1) has explored the role played by bacteria in cancer growth, development and expansion.

They looked at two types of cancer of the digestive system, a type of oral cancer, and a colorectal cancer investigating the microbes found in the cancerous tissue, and the region that surrounds it.

They found that the distribution of bacteria within a tumor isn't random; it is a highly organized microbiota in different niches and provides de cancer that recruits a type of cell knwon as myeloid to induce inflammation and block the activity of cancer-killing T cells produced by the immune system. This allows tumoral growth.

The microbes also altered the tumor's epithelial cells allowing them to invade the surrounding tissue.

Research has found that 33 major types of cancer contain microbes infecting the tumors. Tumors contain malignant cells surrounded by a network of non-malignant cells and microbes, the microbes have a role in the cancer's development, resistance to the immune system, chemo drugs and, promote its metastasis.

The positive side of these findings is that it could open up new therapeutic options to treat cancer by killing the bacteria using antibiotics. Another interesting option is that it seems that each type of cancer have their own unique microbiome so blood tests to identify certain bacteria could help detect cancer at an early stage.

References and Further Reading

(1) Galeano Niño, J.L., Wu, H., LaCourse, K.D. et al. (2022). Effect of the intratumoral microbiota on spatial and cellular heterogeneity in cancer. Nature 611, 810–817 (2022). https://doi.org/10.1038/s41586-022-05435-0.