Leukemia patients have found new hope, thanks to a breakthrough treatment technique that is quite possibly the most exciting development clinical research has seen in its war on cancer. It is called “Adoptive T-Cell Therapy” and unlike chemotherapy, it is not based on administering a toxic drug to the patient that kills rapidly dividing cancer cells (as well as healthy cells as a side-effect). Instead, it involves a genetic engineering technique, which empowers the patient’s own immune system to kill the cancer cells inside of them.
In developing the technique over the past 10 years, researchers at Memorial Sloan Kettering Cancer Center in New York City have focused on a common type of leukemia called B-Cell Acute Lymphoblastic Leukemia (or B-ALL). B-cells are a sub-type of white blood cell in the immune system that are responsible for the production of antibodies. B-ALL is a form of leukemia characterized by the presence of cancerous B-cells. There are about 6,100 new cases of B-ALL per year in the United States with about 1,400 patients dying of the disease each year. B-ALL is a difficult disease to treat using traditional chemotherapy as the patients often become resistant to the treatment and eventually relapse.
T-cells are a sub-type of white blood cell in the immune system responsible for fighting viral infections by recognizing and killing the foreign virus particles which cause diseases such as the flu or common cold. Under normal circumstances, T-cells are unable to recognize and kill cancer cells by the same mechanism. But thanks to years of hard work in leukemia research, that has now changed. Adoptive T-Cell Therapy is a new breakthrough treatment that empowers T-cells of the patient’s own immune system to recognize and kill cancerous B-cells by much the same mechanism they would use against viruses.
The cancerous B-cells which occur in B-ALL patients bear an antigen on their surface called CD-19. Under normal circumstances, the T-cells are unable to recognize and kill the cancerous B-cells but Adoptive T-Cell Therapy changes this. Through genetic engineering, the patient’s own T-cells are engineered to express a protein on their surface called Chimeric Antigen Receptor (or CAR). Once the T-cells have CAR on their surface, they become able to recognize the CD-19 protein which in turn empowers them to find and kill cancerous B-cells.
In their latest trial, the research team at Memorial Sloan Kettering administered Adoptive T-cell Therapy to 16 relapsed adult patients who were terminally ill with B-ALL (average age 50). Traditional chemotherapy was no longer working for these patients. They were infused with their own T-cells engineered to express CAR in a trial whose results were published in Science Translational Medicine on February 19, 2014. The result was that 14 of the 16 adult patients (87.5 percent) achieved complete remission with no detectable cancerous B-cells left in their bodies. Without Adoptive T-cell Therapy, only 30 percent of such patients would be expected to benefit from further rounds of traditional chemotherapy.
Bone marrow transplants are inherently necessary for full recovery by patients suffering from leukemia and other blood cancers. In order to qualify for a bone marrow transplant, a patient generally must first achieve complete remission which is attainable with Adoptive T-cell Therapy. At this time, a bone marrow transplant following successful Adoptive T-cell Therapy seems to be the next step in the treatment process.
Adoptive T-cell Therapy is a breakthrough treatment that could mark the beginning of a new age in cancer treatment. This was not an isolated instance of successful treatment using the technique as other US hospitals have shown similar remission rates in their trials. Researchers have also studied the technique in other types of cancer. The University of Pennsylvania, for instance, is doing so with patients with Chronic Lymphocytic Leukemia, another type of leukemia that affects mostly older patients. According to Dr. Renier Brentjens, researcher and medical oncologist at Memorial Sloan Kettering Cancer Center, learning to apply the technique to other types of cancers is their next research objective. Successfully doing so would empower patients to kill a variety of cancers using their own immune systems.
By Nicholas Maletskas, B.Sc.