A surprising new study from Israel finds that malignant colorectal cancer cells can be eliminated with eosinophils — white blood cells that originate in bone marrow and may once have killed off intestinal parasites, but which today are responsible for chronic asthma and allergies.
The research, published in Cancer Immunology Research on January 21, was led by Prof. Ariel Munitz of the Tel Aviv University Sackler School of Medicine department of microbiology and clinical immunology and conducted by his doctoral student Hadar Reichman, in collaboration with colleagues in Tel Aviv Medical Center’s gastroenterology department.
“Eosinophils are white blood cells that secrete powerfully destructive proteins,” Munitz said. “They may have played an evolutionary role in combating parasites. But now that most people, particularly in the West, enjoy good hygiene and few parasites, the eosinophils have become destructive agents, causing allergies and asthma.
“Our new research theorized that since eosinophils are capable of killing parasites and can cause damage in the lungs of asthma patients, they might play a role in cancer treatment and would be able to kill tumor cells.”
The largest eosinophil reservoir is situated in the digestive system, so the researchers initially decided to test their theories on colorectal cancer. In the first stage of research, they selected samples from tumors of 275 patients to determine the number of eosinophils in a tumor as compared with the stage and severity of the disease.
“We found that the higher the number of eosinophils in the tumor, the less severe the disease, which represents a clear correlation,” said Munitz. “We identified that the cancerous environment attracts these cells, which infiltrate the tumors and flourish there for a long time.”
Potent anti-tumor activities
The researchers subsequently tested their hypotheses in various mouse models of colorectal cancer. They discovered that eosinophils displayed potent anti-tumor activities and could directly kill tumor cells.
“We also found that when eosinophils were activated by a protein called IFN-gamma, they induced an even greater tumor-killing response,” Munitz explained.
“Following various extensive analyses, we concluded that eosinophils have unique and distinct activities in comparison with other cells present in the tumor. For example, eosinophils can kill tumors independently of known tumor-fighting cytotoxic T cells.”
He believes eosinophils could be used in treating cancer if their robust anti-tumor response somehow could be unleashed pharmaceutically, or by combining treatments to harness the potent forces of both eosinophils and cytotoxic T cells.
“We have discovered a new target for immunotherapy for cancer patients — the eosinophils,” concluded Munitz. “We hope that our research will serve as a foundation for drug development in a number of different approaches.”
The study was supported by the Israel Cancer Research Foundation, the Israel Cancer Association and the Israel Science Foundation.