Acute leukaemia and the future of stem cell treatment for blood cancer
by Wideacademy - 10 January, 2018
- Blood cancer
- Stem Cell Transplant
- Graft Versus Host Disease
What is Acute Leukaemia?
Acute Leukaemia is a form of blood cancer which progresses especially quickly.
Leukaemia is identified by the overproduction of white blood cells, or leukocytes.
When the body produces more leukocytes than it should these white blood cells do not mature normally and so compromise, or totally impair, the immune system.
As a leukaemia sufferer’s body is flooded with leukocytes it is left unable to produce the right level of red blood cells and platelets.
A routine virus or bacteria may be fatal, as your body is unable to produce the healthy white blood cells which would have ordinarily fought it.
Even small injuries can cause death by internal bleeding which would otherwise have been prevented by platelets clotting together.
Symptoms of Acute Leukaemia can include:
- pale skin
- frequent infections
- unusual bleeding, such as of the gums or nose
There are several different types of leukaemia. Chronic leukaemia, in contrast to the acute form, is slower onset and is associated with better survival rates.
There are two main subtypes of acute leukaemia:
Acute Lymphoblastic leukaemia (ALL)
- starts in the early version of white blood cells in bone marrow which produce lymphocytes
- it can then spread quickly to other areas of the body, such as the lymph nodes, liver, spleen, brain and spinal cord
- also known as lymphoid or lymphoblastic leukaemias
Acute Myeloid Leukaemia (AML)
- starts from the early version of the cells which make white blood cells (called myeloid cells), but can also start from red blood cells or platelet-making cells (megakaryocytes)
- like ALL, it begins in the bone marrow but can quickly spread to other areas of the body
- also known as myelocytic, myelogenous or non-lymphocytic leukaemias
Biphenotypic Acute Leukaemia (BAL) is a rare mixture of both AML and ALL. Treatment is usually chosen according to its closer similarity to AML or ALL.
How can stem cells help?
Acute Leukaemia can be treated using a haemopoietic (or blood-forming) stem cell transplant.
The patient receives high dose chemotherapy before the stem cell transplant. This kills the cancer cells, but it will also kill the stem cells in the bone marrow.
The purpose of the stem cell transplant is to replace the cells lost during the chemotherapy.
Most often, these transplants will involve donor stem cells. This is called an allogeneic transplant. The cells must be a match, so are usually taken from your brother or sister, or someone else unrelated whose stem cells are similar.
Less commonly, your own stem cells might be used. In this case, the stem cells will be collected and frozen until after chemotherapy is completed — and then transfused back into your body. This is called an autologous transplant.
With both donor stem cells and autologous stem cells, the transplantation process is the same, and you receive them intravenously via a drip. The process only takes around an hour, but full recovery – allowing time for the haematopoietic stem cells to rebuild your immune system – can take several months. This recovery time must be in isolation, in a room with filtered air, to prevent any infections during the recovery phase.
Much of the research into stem cell therapy for acute leukaemia focuses on reducing the risk associated with the period between chemotherapy and recovery of your immune system. The recovery period lasts several months, during which there is a high risk of infection.
An effect called graft-versus-leukaemia is one solution for this that is currently undergoing research. It uses lower-dose chemotherapy alongside the injection of donor immune cells (lymphocytes).
The lower-dose chemotherapy means that the bone marrow does not need to be entirely replaced. Some of the bone marrow remains in the system and the idea is that any remaining leukaemia cells will be killed by the injected lymphocytes.
This technique can also be referred to as mini-allografts or reduced-intensity allografts.
The use of growth factors is also being tested. These are selected proteins which can enhance the production of the immune cells which fight infections, and can help to reduce the risk of infection as you recover.
Even using mini-allografts or growth factors, there continues to be a risk of graft-versus-host disease (GvHD) — when the donated stem cells attack the body, because they view it as foreign. Reducing the risk of this is another key focus for researchers.
Scientists are currently testing the use of regulatory T lymphocytes for this purpose. These have a role in regulating or suppressing the immune system, limiting the donor cells from attacking the patient’s own cells.
At more of an experimental stage are CAR T-cell based therapies. These are immunotherapies, or therapies targeted at building the immune system’s ability to fight off or destroy cancer cells.
CAR T-cell uses T-cells removed from the bloodstream and modified with an engineered gene (the ‘CAR’). They are then injected back into the patient, where the addition of the engineered gene helps them to be especially effective in fighting the leukaemia cells.
It is likely that in the future, stem cell therapy will be combined with immunotherapies in order to provide the most effective treatment for acute leukaemia.