Oral Vaccine Shows Promise in Boosting Immunotherapy for Colorectal Cancer

A new oral vaccine strategy, developed by researchers at Stony Brook University, is demonstrating potential to enhance the effectiveness of immunotherapy in treating colorectal cancer (CRC). The vaccine utilizes a modified strain of Listeria monocytogenes to stimulate immune responses directly within the gut, offering a targeted approach to combat this deadly disease.

The Challenge of Colorectal Cancer and Immunotherapy

Colorectal cancer remains a significant global health challenge, projected to result in over 150,000 new diagnoses and more than 55,000 deaths in the US alone in 2026 [1]. While immunotherapy has revolutionized cancer treatment, most colorectal cancers do not respond to currently approved immune checkpoint inhibitors (ICIs) [4].

Harnessing the Power of Listeria monocytogenes

Listeria monocytogenes has been investigated as a cancer vaccine vector due to its ability to elicit both innate and adaptive immune responses, and its capacity to activate CD8 T cells [4]. Previous attempts focused on intravenous delivery, but the Stony Brook team has pioneered an oral delivery method.

A Targeted Oral Approach

The researchers engineered a highly attenuated strain of Listeria by deleting key virulence genes, preventing illness while maintaining the ability to access the intestinal immune system [1]. This modified bacterium, delivered via inoculated bread in murine models, induced a robust CD8 T cell response comparable to that of the fully virulent form [2]. Importantly, the vaccine remained localized to the intestinal tissues, without causing weight loss or spreading to other organs [2].

Enhanced Efficacy with Immune Checkpoint Inhibitors

While the vaccine alone showed some ability to curtail local tumor growth, its true potential emerged when combined with ICIs [1]. This combination therapy led to profound tumor control in preclinical models, suggesting the vaccine can effectively “turn on” the immune system in tumors previously resistant to standard immunotherapy [4]. The research demonstrated the accumulation of tumor-specific CD8 T cells in the tumor environment, providing immediate and long-lasting protection [1].

Future Implications

“such a strategy could significantly improve the prognosis for patients with advanced or metastatic colorectal cancer who have limited therapeutic options otherwise,” said Brian Sheridan, PhD, associate professor at the Renaissance School of Medicine at Stony Brook University [1]. This method could also pave the way for a new generation of cancer vaccines capable of both preventing disease onset and enhancing the efficacy of existing immunotherapies [1].

The study received support from the Department of Defense, the National Institutes of Health’s National Institute of Allergy and Infectious Diseases (NIAID), the Research Foundation for the State University of New York, and charitable foundations [1].