Researchers develop a new platform that recreates cancer in a dish to quickly determine the best bacterial treatment

A bacterium capable of sensing and responding intelligently to diseases, cancer infections, has become a promising area of ​​synthetic biology. Rapid advances in genetic engineering tools have allowed researchers to "program" cells to perform a variety of sophisticated tasks. For example, a gene network can be wired together to form a genetic circuit in which cells can be manipulated to sense the environment and modulate their behavior or produce molecules in response.

Recent research has shown that many bacteria selectively colonize tumors in vivo, prompting scientists to design them as programmable vehicles, biological "robots," in other words, to deliver anti-cancer treatments. Researchers are also developing new "smart" drugs by programming bacteria to fight against other diseases, such as gastrointestinal diseases and infections. The key to advancing these "living medicines" is to identify the best therapeutic candidates.

However, while current synthetic biology tools can create a huge number of programmed cells, researchers' dependence on animal testing has greatly limited the number of therapies that can be tested and their speed. In fact, the ability to rapidly develop new treatments for humans far exceeds the number of tests performed on animals, creating a major bottleneck for clinical translation.

Researchers at Columbia Engineering are reporting today in PNAS that they have come up with a system allowing them to study tens to hundreds of bacteria programmed into mini-tissues in a box, which can reduce the study time by several months to several days. For proof of concept, they focused on testing anti-tumor bacteria programmed with the help of mini-tumors called tumor spheroids. The speed and high throughput of their technology, which they call BSCC for "co-cultivation of bacterial spheroids", allow for stable growth of bacteria in tumor spheroids, allowing for long-term study. The method can also be used for other species of bacteria and cell types. The team, led by Tal Danino, badistant professor in biomedical engineering, says this study, to their knowledge, is the first to quickly identify and characterize bacterial therapies in vitro and will be a useful tool for many researchers in the field.

"We are very pleased with the effectiveness of BSCC and believe that it will really accelerate the bacterial treatment of engineering for clinical purposes," Danino said. "By combining automation and robotics technologies, BSCC can test an extensive library of therapies to discover effective treatments.Since BSCC is so widely applicable, we can modify the system to test human specimens as well." As with other diseases, we personalize medical treatments by creating cancer of the patient in a dish and quickly identify the best treatment for each individual. "

The researchers knew that if many bacteria can grow inside a tumor because of the decrease in their immune system, the bacteria are killed on the outside of the tumor, where the system immune is active. Inspired by this mechanism, they searched for an antibacterial agent capable of mimicking the "killer" effect of bacteria outside the spheroids.

They developed a protocol for the use of gentamicin, an antibiotic, for the growth of bacteria inside spheroids similar to body tumors. Using BSCC, they then rapidly tested a broad range of programmed anti-cancer bacterial therapies consisting of various types of bacteria, genetic circuits and therapeutic payloads.

"We used 3-D multicellular spheroids because they summarized conditions in the human body, such as oxygen and nutrient gradients – they can not be made in single-cell cell culture. 2D ", says Tetsuhiro Harimoto, lead author of the journal who is a PhD student in Danino's laboratory. "In addition, the 3D spheroid provides bacteria enough space to live in its nucleus, in the same way that bacteria colonize tumors of the body, which we can not do in 2D monolayer culture." it is simple to make a large number of 3D spheroids and adapt them for high throughput screening. "

The team used the BSCC high-throughput system to rapidly characterize pools of programmed bacteria and then quickly determine the best candidate for therapeutic use. They discovered an effective therapy against colon cancer, using a new bacterial toxin, the theta toxin, badociated with an optimal genetic circuit of drug delivery in the attenuated Salmonella Typhimurium bacteria. They have also discovered new combinations of bacterial therapies that can further improve the effectiveness of cancer control.

The researchers compared their BSCC results to those found in animal models and found similar behavior of bacteria in these models. They have also discovered that their best candidate, the theta toxin, is more powerful than the therapies created in the past, demonstrating the power of high throughput screening of BSCC.

Danino's group has focused on cancer treatment in this study, but he hopes to expand BSCC to characterize bacterial-based therapeutic agents for various diseases, including gastrointestinal diseases and infections. Their ultimate goal is to use these new bacterial therapies in clinics around the world.