Immunotherapy for cancer enables a patient’s own body to fight cancer. Every type of cancer is different, and every patient is unique. Could cancer treatment be specifically tailored to one person? Adoptive cell therapy or cellular immunotherapy does just that, using a patient’s T cells to fight their specific cancer.
What Is Immunotherapy for Cancer?
In the past, doctors have treated cancer by surgically removing a tumor and using chemicals or radiation to kill cancerous cells. These treatments have saved many lives, but they aren’t perfect. Although they are meant to attack cancerous cells, they can also attack healthy cells and make the patient sick. They can bring awful side effects, and they don’t always destroy every single cancerous cell.
Immunotherapy uses a patient’s own immune system to fight cancer. There are several different drugs and techniques that can kick the body’s natural defenses into high gear. Some types of immunotherapy are emerging in clinical trials, while others are already FDA approved and being used to treat patients.
This is part of a growing field called precision medicine, in which cancer treatment is targeted through individualized health care, according to Johns Hopkins Medicine. Immunotherapy isn’t a one-size-fits-all solution. Various types are being studied for nearly every type of cancer. So far, it has successfully treated at least 15 types of cancer, such as skin, lung, kidney and bladder cancers. Solid cancers are more challenging to treat through immunotherapy, but research continues.
Cellular immunotherapy uses immune cells like a microscopic army to battle cancerous cells. Our bodies already have cancer-fighting cells, and immunotherapy can make more of these “soldiers” and give them the ability to attack the specific cancer.
Medical practitioners extract the patient’s immune cells, alter them in a laboratory and then put them back into the body to fight the cancer.
T cells are the adaptive immune system’s primary killers of infected and diseased cells, according to Cancer.gov. Killer T cells, called cytotoxic T cells, can target cancer by recognizing a specific threat in the immune proteins, called antigens, on the surface of a cancerous cell. This is an incredible natural defense system, but it’s not enough to battle such a formidable enemy as cancer.
There are several challenges with T cells. Before they go into attack mode, they have to be activated. Then, they need to have the endurance to finish the job. Cancer.gov explains that sometimes they can be “exhausted” and lose their ability to kill. Plus, they need to exist in high enough quantities to fight cancer. Not all patients have T cells that can recognize cancer and activate. Some patients have killer T cells, but they don’t have enough of them. Cellular immunotherapy helps to fill in these gaps.
Types of Cell Immunotherapy Treatment
TIL: Tumor-Infiltrating Lymphocyte
This technique uses white blood cells, called lymphocytes, that have penetrated the stroma (the connective tissue) of a tumor, according to the American Association for Cancer Research (AACR). The therapy takes these tumor-infiltrating lymphocytes (TILs), which have already started to attack a tumor, and multiplies and activates them. Care providers harvest TILs from the patient’s tumor biopsy and send them to a laboratory. Next, a scientist analyzes the cells to isolate the ones that secrete proteins called cytokines, which signals that they know how to recognize and target the specific cancer. The lab can then add more proteins to help TILs find and destroy the cancerous cells. This technique can be effective for colorectal, skin, kidney and ovarian cancers.
CAR T: Chimeric Antigen Receptor Therapy
CAR T cell therapy is a similar type of adoptive cell therapy that uses a patient’s own modified T cells to fight cancer. According to the Association of Healthcare Journalists, in CAR therapy, T cells are harvested from peripheral blood cells to be genetically altered. In the lab, scientists equip these cells with a cell receptor that can recognize the specific cell-surface protein on cancerous cells. This type of immunotherapy is FDA approved for treating certain non-Hodgkin lymphomas and leukemia in people under the age of 25.
TCR: T Cell Receptor
According to the Cancer Research Institute, some patients don’t have T cells that recognize their tumors. In this case, there is a therapy that involves engineered T cell receptors (TCRs). The patient’s T cells are activated and expanded, plus they are given a new T cell receptor that can target specific antigens. This technique is personalized and precise.
NK: Natural Killer
Natural killer (NK) cell therapy is aptly named; instead of using T cells, this therapy incorporates other immune cells. According to TheScientist, unlike the previously mentioned adaptive cellular therapies that recognize threats by their antigens, NK cells are part of the innate immune response. They are broader than T cells and don’t need to be engineered in order to recognize tumors, but they can also be equipped with synthetic receptors. This is a newer therapy that could be safer, cheaper and faster than other treatments. In clinical trials, both the engineered and natural forms of NK treatment have been effective with fewer side effects than other cellular therapies, although the drawbacks are that they don’t last long in the body, and they don’t proliferate.
Outlook for Immunotherapy
Like traditional cancer therapies, cellular immunotherapy can have side effects. While the aim is to trigger the immune system to attack cancer cells, this can overstimulate the immune system. This could cause fever, skin rashes, inflammation, or endocrine disorders.
So far, immunotherapy hasn’t been proven to be effective for all cancer types, especially solid tumors. Another challenge is the cost and manufacturing, which is naturally slow and difficult due to the personalization. Despite these remaining challenges, immunotherapy for cancer is an extremely promising and active area of medical research. In the last five years, nearly 40,000 papers on this topic were recorded by the National Library of Medicine.
“It’s somewhat ironic that the very mutations that cause a certain cancer may turn out to be its Achilles’ heel and enable immunotherapy treatment,” Steven Rosenberg, MD, PhD, chief of surgery at the National Cancer Institute, Rosenberg told AACR.
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