According to the National Cancer Institute, more than 600,000 people in the United States will die of cancer in 2025. It is the second leading cause of death in the country, after heart disease, as reported by the Centers for Disease Control and Prevention. A diagnosis is devastating to the patient, family, and friends, but a recent breakthrough may prove promising.

A team of scientists at Columbia University has found a new way to fight cancer by using bacteria as couriers to deliver cancer-killing viruses directly into tumors. CAPPSID, short for Coordinated Activity of Prokaryote and Picornavirus for Safe Intracellular Delivery, could help solve one of the biggest challenges in cancer therapy: how to get treatments past the body’s immune system.

For years, researchers have been studying oncolytic viruses, which are designed to infect and destroy cancer cells. The idea is to get the virus inside a tumor where it can then multiply rapidly and burst the cancer cell. But there’s a catch. As soon as the virus enters the bloodstream, the immune system usually attacks it. If a patient has had the virus before or has been vaccinated against it, the immune system is even faster at wiping it out. That means the treatment rarely makes it to the tumor.

The Columbia team came up with a clever workaround, as revealed in a study published by Nature Biomedical Engineering. They tucked the virus inside a bacterium. The bacterium, a modified strain of Salmonella, naturally seeks out tumors, which provide the low-oxygen, nutrient-rich environment in which bacteria thrive. This method is like a Trojan horse that sneaks the virus into the tumor, where it can go to work.

“Viruses alone often fail to reach enough tumor cells, while bacteria alone typically remain trapped inside the tumor core. Together, they achieve what neither could do alone,” Brighter Side of News explained.

“This is the first time we’ve shown bacteria and viruses can be engineered to work together against cancer,” said Tal Danino, associate professor of biomedical engineering at Columbia and senior author of the study. “The bacteria are really good at finding tumors, and the viruses are very good at killing cancer cells. When you combine them, you get the best of both worlds.”

“This approach is exciting because it overcomes a barrier that has held back viral cancer therapies for years,” said Nicholas Arpaia, a co-author of the study. “Our immune system is designed to fight off viruses, but here we’ve found a way to hide them until they reach the tumor.”

The potential is huge. By combining two very different organisms – bacteria and viruses – the Columbia researchers have opened the door to a whole new class of cancer treatments. As Danino put it, “We’re showing that multi-organism therapies might be the future of cancer care.”

“Their system works by programming Salmonella typhimurium, a bacterium known for homing in on tumors, to carry Senecavirus A, an oncolytic virus,” Brighter Side noted. “Together, they form a cooperative team with one mission: infiltrate tumors and destroy them from the inside.”

According to the study, different bacteria target different tissues, “microbiomes and even intra- versus extracellular spaces.” Staphylococcus epidermidis thrives on skin; Mycoplasma pneumoniae prefers the lungs; Listeria monocytogenes lives inside cells; and Salmonella typhimurium targets tumors.

Currently, there have been no human trials, and researchers want to broaden their tests to other cancer types. But the progress so far looks promising.