Researchers show that using a tumor’s own bacteria is a promising anticancer therapy

Ishikawa, Japan — Cancer remains one of the leading causes of death worldwide. Researchers are constantly looking for new therapies with improved anticancer activity, fewer side effects, and lower costs. In recent years, interest in bacterial agents as anticancer therapeutics has grown, due to the ability of some bacteria to selectively grow inside hypoxic tumors, i.e., these cells do not receive rich oxygen supply. But bacterial anticancer therapies tend to focus on the idea of bacteria as a drug carrier, and use advanced and expensive scientific techniques like genetic engineering, synthetic bioengineering, and nanotechnology. This makes it important to identify bacteria that are naturally effective and tumor-specific, thereby eliminating the need to employ advanced technologies to enhance their anticancer properties.

For years, scientists have known that some species of bacteria grow naturally inside tumors. So far, studies on these bacteria, called intratumoral bacteria, have focused on their role in cancer development or in their effects on other anticancer therapies, such as their ability to reduce adverse effects from chemotherapy etc. The use of intratumoral bacteria as anticancer therapeutics is an underexplored area of research.

Recently, a research team, led by Associate Professor Eijiro Miyako from the Japan Advanced Institute of Science and Technology (JAIST), revealed that intratumoral bacteria that are associated with natural purple photosynthetic bacteria show strong anticancer efficacy. Their findings have been published in Advanced Science.

Explaining their research, Dr. Miyako says, “We succeeded in isolating and identifying three types of bacteria from colon cancer tissues, Proteus mirabilis, which we have termed, A-gyo; photosynthetic Rhodopseudomonas palustris, which we have termed UN-gyo; and a complex bacteria that consists of both A-gyo and UN-gyo, which we call AUN. This consortium of bacteria, when injected into tumors, show a high antitumor effect.“

The researchers injected the three bacteria, A-gyo, UN-gyo, and AUN into various mouse models of cancer. They found that these intratumoral bacteria can thrive in hypoxic tumor environments and trigger the immune system to kill the tumor cells. Essentially, the association between A-gyo and photosynthetic UN-gyo in the form of AUN provokes strong anticancer responses in mouse models of colorectal cancer, metastatic lung cancer, and extensive drug-resistant breast cancer. In fact, mice that were treated with these bacteria showed significantly prolonged survival rates. The anticancer efficacy of these bacteria was found even in mouse models that were treated with a single dose.

Another result from the study is the significant near-infrared fluorescence of AUN in tumors, indicating its potential as a tumor-specific diagnosis probe. The researchers also performed a variety of tests and assays to demonstrate that AUN has little effect on living tissue, i.e., it is biocompatible.

“Conventionally employed advanced anticancer therapies are extremely expensive,” comments Dr. Miyako. “The anticancer bacteria assessed in this study can easily be grown in large quantities at low cost in simple, sustainable, low-carbon processes. This would be a huge boost to the accessibility of cancer treatment worldwide.“

This study is the first of its kind and blows the doors open for further research on the field of intratumoral bacteria as anticancer therapeutics.

###

Reference

About Japan Advanced Institute of Science and Technology, Japan

Founded in 1990 in Ishikawa prefecture, the Japan Advanced Institute of Science and Technology (JAIST) was the first independent national graduate school in Japan. Now, after 30 years of steady progress, JAIST has become one of Japan’s top-ranking universities. JAIST counts with multiple satellite campuses and strives to foster capable leaders with a state-of-the-art education system where diversity is key; about 40% of its alumni are international students. The university has a unique style of graduate education based on a carefully designed coursework-oriented curriculum to ensure that its students have a solid foundation on which to carry out cutting-edge research. JAIST also works closely both with local and overseas communities by promoting industry–academia collaborative research.  

About Associate Professor Eijiro Miyako from Japan Advanced Institute of Science and Technology, Japan

Dr. Miyako Eijiro is an Associate Professor at the Materials Chemistry Frontiers Research Area, Japan Advanced Institute of Science and Technology (JAIST). He has been a visiting scientist at Centre National de la Recherche Scientifique (CNRS) (France) and Nanyang Technological University (Singapore). He also served as the Senior Researcher at National Institute of Advanced Industrial Science and Technology (AIST), Japan. His research interests are in the areas of Bioengineering, Materials Chemistry, Nanotechnology, and Nanomedicine. He has also received research prizes and awards such as PCCP Prize in Royal Society of Chemistry and Research Encouragement Award in The Fullerenes, Nanotubes and Graphene Research Society.

Funding information

This research is supported by the Ministry of Education, Culture, Sports, Science and Technology Grant-in-Aid for Scientific Research A (23H00551), the Ministry of Education, Culture, Sports, Science and Technology Grant-in-Aid for Challenging Research (Pioneering) (22K18440), the Japan Science and Technology Agency (JST) Optimal Research Results Deployment Program (A-STEP) (JPMJTR22U1), the Fermentation Research Institute, and the Uehara Memorial Life Science Foundation. It was supported by the Transcendental Biomedical DX Research Center and the Student Function and Sensory Research Center.