The future of cancer care may involve a vaccine tailored to each patient’s tumor. Researchers in Japan have developed an experimental mRNA-based vaccine that targets gastric cancer metastases to the peritoneum, achieving complete tumor eradication in mice when combined with existing immunotherapy.
The study, led by Professor Kazuhiro Kakimi at Kindai University and published in Gastric Cancer on July 31, 2025, highlights a promising path toward personalized cancer treatment using the same lipid nanoparticle delivery platform as COVID-19 mRNA vaccines.
Why Peritoneal Metastases Are So Difficult to Treat
Gastric cancer, the fifth most common cancer worldwide, remains a leading cause of cancer-related death. Peritoneal metastasis—where tumor cells spread to the lining of the abdominal cavity—is the most common form of recurrence after surgery and is associated with a median survival of only four to six months. Current first-line treatments, such as anti-PD-1 therapy combined with chemotherapy, often fail in these patients. Immunotherapy, which works by harnessing the immune system to fight cancer, has shown limited success against this form of disease spread.
How the mRNA Vaccine Works
The Kindai University team created a vaccine containing messenger RNA (mRNA) that encodes three tumor-specific neoantigens (neoAgs) previously identified in a mouse gastric cancer cell line. These mRNA molecules were encapsulated in lipid nanoparticles (LNPs) for delivery. Once injected, the vaccine triggered the immune system to produce high numbers of cytotoxic T cells programmed to recognize and attack cancer cells displaying those specific neoAgs.
Two doses of the mRNA-LNP vaccine induced stronger immune responses than a dendritic cell-based vaccine. In mice with subcutaneous tumors, the vaccine alone eradicated cancer in all treated animals. Combining the vaccine with anti-PD-1 therapy—a checkpoint inhibitor targeting the PD-1 protein—sustained tumor-fighting T cells and prevented relapse. In models of peritoneal metastasis, the combination therapy reduced or eliminated tumor spread.
The Role of “Progenitor-Exhausted” T Cells
Tumor-reactive T cells often lose effectiveness over time, a process known as exhaustion. The researchers found that while anti-PD-1 therapy increased short-lived “intermediate exhausted” T cells, it did not boost the progenitor-exhausted (Texprog) cells that replenish them. The mRNA vaccine expanded these Texprog cells, and when combined with anti-PD-1, both populations increased, producing a durable antitumor effect. This targeted approach reflects the principles behind targeted cancer therapies, which focus treatment on specific molecular features of cancer cells.
“NeoAgs, derived from individual genetic alterations in each cancer patient, serve as unique immunological targets on tumor cells and represent the key to personalized immunotherapy,” said Prof. Kakimi.
Challenges and the Road Ahead
Despite the promising results, a major hurdle remains: identifying which neoantigens in each patient’s tumor will be recognized and attacked by T cells in the body. The process currently relies on complex prediction algorithms that are still being refined. Multiple pharmaceutical companies, including Moderna and BioNTech, are running clinical trials with neoAg-based mRNA vaccines in other cancers, often paired with checkpoint inhibitors.
Why This Matters for Personalized Medicine
Unlike conventional tumor-associated antigens, neoAgs arise from patient-specific mutations and are not found in normal tissue. This makes them ideal for highly targeted therapies that avoid damaging healthy cells. The Kindai University results suggest that combining such vaccines with checkpoint blockade could overcome one of the toughest barriers in gastric cancer treatment—peritoneal metastasis. If similar outcomes can be achieved in human trials, patients with otherwise untreatable tumor spread might one day receive a custom-built mRNA shot designed from the genetic code of their own cancer. This concept is central to precision medicine, which tailors treatment to the unique genetic and molecular profile of each patient.
Journal: Gastric Cancer
DOI: 10.1007/s10120-025-01640-8
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