Scientists have learned to "hack" bacteria, transforming them into a weapon against cancer.

This paves the way for the development of a new class of anticancer vaccines that utilize the natural properties of bacteria to target tumors. Such microbial cancer vaccines can be tailored to affect the primary tumor and metastases of a specific individual and may even prevent disease recurrence in the future.

In studies using mouse models of colorectal cancer and melanoma, the bacterial vaccine enhanced the immune system by suppressing the growth of primary and metastatic tumors, and in many cases, even destroying them. Importantly, it did not affect healthy parts of the body.

The bacterial vaccine proved to be significantly more effective than peptide-based therapeutic cancer vaccines previously used in numerous clinical trials.

“A key advantage of our system is its unique ability to coordinately restructure and activate all components of the immune system, eliciting a productive antitumor immune response. We believe this is why the system performs so well in solid tumor models, which are particularly resistant to other forms of immunotherapy,” says Andrew Redenti, a graduate student at Columbia University's College of Physicians and Surgeons who assisted in the study.

Bacterial vaccines can be customized for each type of tumor. “Every tumor is unique, as tumor cells carry specific genetic mutations that distinguish them from normal healthy cells. By programming bacteria to prompt the immune system to target these cancer-specific mutations, we can develop a more effective therapy that encourages the patient’s own immune system to detect and destroy cancer cells,” explains Nicholas Arpaia, Ph.D., an assistant professor in the Department of Microbiology and Immunology at Columbia University's College of Physicians and Surgeons, who led the research.

“By themselves, these characteristics do not provide bacteria with enough power to stimulate an immune response capable of destroying the tumor, but they serve as a solid starting point for creating a new area of cancer therapy,” the researchers state.

The foundation of this new system is a probiotic strain of Escherichia coli. Scientists have made numerous genetic modifications to precisely control how the bacteria interact with and educate the immune system, ensuring reliable tumor destruction.

Due to the nature of the bacterial system and additional genetic modifications made by the researchers, these bacterial cancer treatments also counteract the immunosuppressive mechanisms that tumors use to evade the immune system.

As a safety measure, the genetic modifications also block the inherent ability of bacteria to evade immune attacks directed against them. This means that the engineered bacteria are easily recognized and destroyed by the immune system and are quickly expelled from the body if they do not locate a tumor.

The first step in creating such microbial vaccines for humans will involve determining the sequence of the patient's tumor and identifying its unique neoantigens using bioinformatics methods.

Upon introduction into a patient with a tumor, the bacteria will migrate to the neoplasms, settle there, and consistently produce and deliver their beneficial "medications." After the bacterial vaccine is activated, the immune system will be compelled to eliminate cancer cells that have spread throughout the body and prevent further metastasis development.