Image: Breast cancer cells. Credit: Wikimedia.
Billions of bacteria, viruses, and yeasts live in and on our bodies. We often need them. For example, bacteria help us digest our food and work with our immune system to fight pathogens.
Intestinal bacteria have been studied extensively, including in the context of cancer. For example, it can affect the effectiveness of immunotherapy and chemotherapy. But bacteria also live outside our intestines and are found, for example, in tumors.
How they get to the tumor and what exactly they do there is largely unknown, making it unclear how important they are to the disease and its treatments. Since many patients eventually die from metastases, and many treatments aim to combat this, the research groups of Emil Voest and Lodwij Wessels from the Netherlands Cancer Institute examined these metastases. They analyzed the DNA code found in the tissues of more than 4,000 malignant tumors from 26 types of cancer.
Based on this huge amount of information (400 terabytes), they compiled a detailed catalog of the bacteria they found in the metastases. This showed that the type of bacteria found in the metastasis was strongly related to the location of the body, the conditions there, and the type of cancer.
The researchers also looked at how bacteria interact with cancer cells and their environment, and found that some bacteria could be associated with a worse response to treatment. For example, patients with lung cancer who had Fusobacterium bacteria found in their metastases responded worse to immunotherapy than their peers without those bacteria.
Through their study, the researchers hope to provide a better understanding of how bacteria help or hinder cancer and its treatments and how they can use this to the benefit of patients. For example, they are considering new forms of treatments that target bacteria that help tumors.
