Health

Hope from vaccines to prevent and treat cancer


AmericaNew cancer vaccines focus on stimulating the immune system, preventing and repelling malignant cells; or personalized to each patient.

For decades, scientists have been trying to harness the inherent power of the human immune system to fight cancer. They sought to disrupt the defenses that tumors use to repel the disease. Despite initial challenges and setbacks, researchers still believe that humanity is closer than ever to a cancer vaccine. While vaccines are still in the experimental stage, far from the threshold of approval, experts say they represent the future of cancer care.

“We’ve made a lot of progress in understanding how the immune system recognizes cancer. There are dozens of vaccine candidates under study,” said Vinod Balachandran, a surgeon at Memorial Sloan Kettering Cancer Center. around the world”.

New approaches include vaccine prevention and treatment. In particular, therapeutic vaccines can differentiate tumor cells from normal cells to stimulate an immune response against them. The researchers are also developing a list of immunotherapies to enhance the vaccine’s effectiveness.

Cancer cells arise from human cells, just like normal cells to hide. As a result, the immune system is often tolerant and unable to detect them. Cancer vaccines can activate the immune system, find the difference between diseased and healthy cells, recognize them as foreign and refuse to tolerate them.

According to scientists, It is important to distinguish between therapeutic vaccines, preventive vaccines and immunotherapy drugs.

Cancer prevention vaccines are mainly given to people with pre-malignant lesions such as colon polyps, to prevent them from progressing to cancer.

Olivera Finn, professor of immunology at the University of Pittsburgh, and colleagues were the first to identify tumor-specific antigens. This is a protein found only on cancer cells, not in healthy cells, can be used as a target for the immune system to attack.

This antigen, called MUC1, is found in colon, breast, prostate, lung and pancreatic cancer cells. MUC1-based vaccines have promoted a robust immune response in human clinical trials with premalignant colon polyps.

Experts believe vaccines can stop the growth of new polyps and keep existing ones from turning cancerous. Professor Finn said the vaccine reduced polyp recurrence rates by 38% in clinical trials.

“We and other research groups look at premalignant lesions and try to strengthen the immune system, stopping the progression from premalignant to malignancy,” Finn said.

A woman receives the HPV vaccine to prevent cervical cancer in Shanghai. Image: AP

Therapeutic vaccines are different from preventive vaccines. Used in people who already have cancer cells, to help prevent the disease from getting worse or coming back. They prompt the immune system to find and destroy cancer cells that contain certain tumor-specific antigens that healthy cells do not.

The vaccine provides certain molecules that act like this antigen to stimulate the immune system to create “killer” T cells, which kill cancer cells.

Keith Knutson, cancer vaccine specialist at the Mayo Clinic, said: “Therapeutic vaccines contain substances that stimulate the production of new immune cells that can fight tumors. We will inject an antigen (a protein fragment of cancer cells) to stimulate the production of T cells capable of attacking tumors.

This mechanism of action is similar to that of vaccines against viral diseases.

In some cases, vaccines are personalized, that is, prepared for a patient from his or her own tumor samples. This is called a neoantigen vaccine. Neoantigens arise from mutations unique to a person’s cancer cells.

Patrick Ott, Clinical Director of the Center for Melanoma at Dana-Farber Cancer Institute, has tested the vaccine on melanoma. “Targeting neoantigens is a completely novel approach,” he said. For example, in a recent small study, 4 out of 6 vaccinated patients had no tumor recurrence after 35 months. Other patients there were two tumors that grew, but then completely regressed when taking more immunotherapy drugs.”

Meanwhile, Dr. Balachandran is working on neoantigen vaccines for patients with pancreatic cancer, one of the deadliest cancers. He collaborated with scientists at BioNTech (the company that manufactures the Covid-19 vaccine with Pfizer) to research a personalized vaccine using mRNA technology. Preliminary results show that half of the patients in the clinical trial developed a strong immune response.

“The biggest advantage of neoantigen vaccines is that they can induce a powerful immune response, because they are tailored to each tumour. In addition, advances in mRNA technology could lead to rapid production of neoantigen vaccines. , removing a major obstacle in the past,” Berzofsky said.

During study, Scientists also face a number of challenges. Usually, tumors damage the immune system. Therapeutic drugs counteract these effects by unlocking the immune system so it can do its job effectively.

“Vaccines initially failed because they failed to stimulate the immune system. This system is limited by both the tumor and the cancer therapies. The tumors have managed to evade the immune system. However, now they are. Here, we know forms of immunosuppression, understanding what the immunosuppressive environment really is,” said Dr. Finn.

Although research is progressing rapidly, experts note that a cancer vaccine is many years away from the finish line. However, they predict that in the future, this will be the standard in cancer prevention and treatment.

“We’re creating the premise, laying the foundation. I believe that one day, doctors can determine the risk of each type of cancer for a patient and give a preventive vaccine,” Finn said.

Thuc Linh (Follow Washington Post)

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