Emily Whitehead is a seven years old girl who was diagnosed with acute lymphoblastic leukemia (ALL) two years earlier. She received chemotherapy as a treatment but relapsed twice from it. Thanks to a revolutionary new treatment that apparently allowed her immune system to fight the cancer, she has now been in complete remission for seven months.
Leukemia is a cancer of white blood cells, also called blood cancer. There are four main types of leukemia including acute lymphocytic (or lymphoblastic) leukemia which touches 6000 people every year in the United States and is the most common form of leukemia in children. This disease is due to the growth of abnormal B lymphocytes causing dysfunctions in the immune system thus the patient is more sensible to infections.
There are numerous different approaches to treat this disease depending on many factors such as the patient’s age, health status and the particular characteristics of the leukemia. The major treatment is chemotherapy but some approaches such as radiation therapy, targeted therapy and biological therapy can also be used. In some cases, bone marrow transplant is also considered. The medical approach of leukemia treatment includes three stages which are Induction therapy, Consolidation therapy and Maintenance therapy. The patient is considered cured if there are no signs of leukemia in the first five years following the end of the treatment. If there is a relapse and some signs of leukemia are detected in the first year, the treatment may continue with more chemotherapy, a stem cell transplant or joining a clinical trial for new treatments which is what happened to Emily.
In an endless effort to find a new and more efficient way to cure leukemia, a team of researchers from the University of Pennsylvania tested a new approach: adoptive T cell therapy. The aim of this experiment is to inject the patient with T cells previously programmed to kill the malignant B cells therefore destroying the cells responsible for the leukemia. This approach had already been tested before as the Professor Carl H. June and his team have been working on this technique for many years. They tested it first in animals collecting very promising results. Moreover, the modified T cell treatment has been under study and tested in people for over a decade to evaluate the safety and effectiveness of this therapy in some clinical trials.
As leukemia is a cancer caused by malignant white blood cells (usually B cells) undergoing uncontrolled growth, the Philadelphia team developed a technique in which they collect millions of T cells from the infected patient and then reprogrammed them to target the cancer before reinjecting them into the patient.
HIV is part of a family of virus called lentivirus. These viruses are able to introduce their genetic material into the host cell’s DNA which makes them a very good carrier of genes. Professor June and its team used a harmless and derived form of the HIV virus to reprogram the collected T cells: they introduced in those cells, some genes allowing them to synthesize a new protein called “chimeric antigen receptor”. This new protein is, in theory, going to help T cells target and kill the cancer cells by recognizing and binding to them through this protein.
The newly engineered T cells are pumped back into the patient where they are going to grow and multiply to fight the disease . They can stay in the patient’s body for years even after the disease.
Emily was part of an early-stage clinical trial primarily aimed to determine the safety of the treatment more than its efficacy. In her case, the result was a complete remission after she had experienced two relapses from chemotherapy.
Although this treatment shows very good and promising results, it has yet to be perfected. In fact, this therapy presents some severe side effects such as a potentially fatal immune response known as “cytokine storm”. It is due to the fact that the engineered T cells also attack the healthy B cells. This is a very risky side effect for already weakened cancer patient as it exposes them to other potential diseases and infections.
Moreover, this is a very expensive treatment as it currently costs $20,000 and it doesn’t work for everyone. Scientists are quite uncertain about the reasons why but remain very enthusiastic regarding those findings: it was announced, in a scientific conference late 2012, that nine out of twelves patients in the trial including Emily have been successfully treated from their cancer.
The complete remission of Emily from her “incurable” cancer - with actual treatments on the market- is an amazing result and the Professor Carl June hopes that this new technique will be able to replace bone marrow transplants which constitutes nowadays the last resort to treat ALL.
However, this therapy is still highly expansive and experimental thus scientists have to find out the best way to use it.
Similar therapies are also being tested in other clinical trials around the world and some researchers are already investigating other ways to improve this adoptive T cell therapy with the objective to apply it to other types of cancer.
Although this treatment is still at an early stage and many improvements have yet to be done, there is a great chance that this treatment could work in less advanced leukemia as it was successful in “hopeless” cases. These results give us a good hope that one day it can be used on a wider scale to treat cancer patients.
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Lucie ALLARD, Gwladys BAALA, Julie BORDENAVE, Charlotte CATANIA, Eugénie LEMPEREUR. Estudiantes de 1º de Odontología. Curso 2016-2017