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The immune cells in the human body are an army that fights pathogens. Whether it is a virus, a bacterium, or a parasite, immune cells can effectively attack most invaders and protect us from disease.

In recent years, scientists have discovered a new application of immune cells—treating cancer. Cancer cells often carry a large number of breakthroughs that may be recognized by immune cells. In order to escape the attack of immune cells, these cancer cells have evolved a series of strategies to disguise themselves as good people.

But these tricks have been gradually seen by scientists. By inhibiting the PD-1/PD-L1 pathway, we can let immune T cells polish their eyes and attack cancer cells. In addition, we can also separate T cells from cancer patients, insert molecules that recognize cancer cells, and then return them to the patient to kill cancer cells.

These treatments using immune cells have achieved remarkable results and have rewritten many treatments for cancer. But scientists also pointed out that the current immunotherapy is concentrated on T cells, slightly monotonous. Be aware that there are many types of immune cells. It would be better if these immune cells can be developed into anti-cancer therapies.

Recently, a study published in Nature Biomedical Engineering, brings us the hope of the emergence of innovative immunotherapy. In this study, scientists have shown that macrophages have an amazing killing effect on cancer in preclinical models.

Macrophages are an important class of immune cells discovered in 1882 by the Russian zoologist Professor élie Metchnikoff. This opened the curtain of human research on the innate immune system, and also helped Professor élie Metchnikoff get the 1908 Nobel Prize in Physiology or Medicine.

As the name suggests, macrophages have a “good appetite” that can phagocytose cell debris, foreign germs, and other pathogens. Although some studies have shown that macrophages can “eat” cancer cells, why can’t they clean the cancer cells when the cancer is just sprouting, and eliminate the disease?

For more than 100 years, as people’s understanding of biology has deepened, we have gradually discovered the reason behind it: in our body, there is indeed a group of macrophages with anticancer activity called M1 macrophages. However, tumors can secrete macrophage colony-stimulating factor (MCSF), “buy” these M1 cells, and turn them into M2 macrophages that turing blind eyes to cancer cells.

What’s worse is that the tumor also expresses a protein called CD47. This protein is like a small sign that says “Don’t eat me”, confusing the macrophages that are not “bought” by cancer cells, letting them put down their weapons.

It is because of this dual mechanism that macrophages cannot effectively attack tumors.

Knowing the reason, direction to solve the problem may then be found. Scientists from the Brigham and Women’s Hospital at Harvard Medical School have designed a miraculous drug that inhibits both the MCSF pathway and the CD47 pathway. According to the design, after the former pathway is inhibited, the proportion of M1 cells that can attack the tumor in macrophages will increase; when the latter pathway is suppressed, the label of cancer cells “don’t eat me” will be torn off. In other words, with this simple drug, bottlenecks met by macrophages in the attack of cancer can be removed at once.

“Our technology can turn M2 cells into M1 cells by inhibiting the M2 signaling pathway,” said Professor Ashish Kulkarni, one of the leaders of the study: “If we can “teach” these macrophages and suppress the label of ‘don’t eat me’, we then can be able to break the balance between M1 cells and M2 cells, increase the proportion of the former, and inhibit tumor growth.”

In theory, this new drug is designed to be perfect. But what is the actual effect? The researchers tested it in animal models of breast cancer and skin cancer. The animals were divided into three groups, one receiving standard anticancer therapy, one receiving this innovative macrophage-targeted drug, and the other receiving no treatment as a control.

As scientists expected, mice that did not receive any treatment produced huge tumors on the 10th day of the experiment, while tumors in mice that received standard anticancer therapy showed a reduction in tumor volume.

Amazingly, therapy targeting macrophages almost completely inhibits tumor growth! In addition, the survival rate of mice has also increased.

“We even saw macrophages phagocytizing cancer cells,” said Professor Shiladitya Sengupta, one of the heads of the study.

This result has excited scientists, and they can’t wait to start the next research and development program. If the study can be repeated in humans, it will undoubtedly add a powerful new army to cancer immunotherapy.