Leukemias are cancers of the cells that give rise to white
blood cells. For example in myeloid leukemias the cells that normally would
become the blood cells neutrophils or macrophages start to make copies of
themselves but refuse to mature. What happens is that the body is flooding with
cells that on the one hand do not protect the patient from disease, and on the
other hand start to interfere with organ function. In lymphocytic leukemias the
cells that give rise to lymphocytes such as T and B cells, stop maturing.
Despite advances in our knowledge of the molecular basis for many leukemias, in
many situations the only definitive cure can be achieved through stem cell
transplantation. Traditionally this has been performed using bone marrow stem
cells from donors that are matched with recipients. The process of
transplantation involves initial destruction of the recipient bone marrow and
leukemic cells by administration of high doses of radiation and chemotherapy.
Subsequently donor bone marrow is given which contains high numbers of stem
cells. These donor stem cells eventually take over the function of making blood
and the recipient is cured of leukemia but has someone else’s stem cells inside
of them.
One of the major barriers to complete success of bone
marrow transplantation is that donors must be matched very strictly. If the
donor is not matched then the immune cells in the bone marrow start to attack
the recipient. This is called graft versus host disease, and is one of the most
devastating side effects of bone marrow transplantation, which in some cases is
lethal.
The current story from CNN describes a personal experience
of a lady, Diana Tirpak, who could not find a bone marrow donor. In general it
is rather difficult to find an unrelated matching donor. In minorities the
process is even more difficult. Tirpak, a retired school nurse in Hudson, Ohio
was so convinced that the search for a donor was futile that she helped her
husband buy a suit for her funeral. "I was bound and determined he was going to
look fine at the funeral," she said.
Fortunately advances in "alternative sources" of stem cells
have saved Tirpak’s life. While it is known that stem cells reside in the bone
marrow, another source that is only in recent times being appreciated is cord
blood. Originally cord blood transplantation was restricted to children since
the number of stem cells per cord is relatively small. However new advances in
transplantation, as well as introduction of "two cord" approaches have opened up
this procedure for adults.
Dr. Mary Laughlin, founder and medical director of the
Cleveland Cord Blood Center stated "Cord blood is rich in stem cells and easier
to match than adult bone marrow because the immune cells are not developed.
Also, patients can get the treatment in about three weeks — as opposed to six
to eight for bone marrow from an adult donor. That can be a critical time
interval for a patient who is in remission," she said, noting that doctors often
fear a patient’s relapse while awaiting the transplant.
To get a sense of how difficult it is to find bone marrow
donor matches, the National Bone Marrow Registry has more than 12 million donors
that meet the needs of only about 60 percent of Caucasians in the United
States. In contrast, only 5 to 15 percent of minorities have available donors.
Another example of the difficulties minorities face in
obtaining a suitable donor is the story of Nathan Mumford, who is
African-American and was diagnosed with leukemia shortly after finishing
college. "We went through that process, and nobody had a match. Siblings are
the best matches. My brother or my sister wasn’t a match. My friends, aunts,
uncles, cousins, nobody was a match. So, couldn’t go that route," Mumford said.
Luckily he too was eligible for a cord blood transplant. "That was an
opportunity," said Mumford, who survived Hodgkin’s disease as a child. "That was
a chance for me to live. I’m not a quitter. I’ve never been a quitter, so I
wasn’t going to quit."
In November of 2004 he was treated by cord blood
transplantation. Now his leukemia is cured and he claims he is in great shape.
I just feel amazing," he said. "I have a lot of energy, and I’m just excited
about it."
The use of cord blood transplants among unrelated donors
have risen from 1 percent in 2001 to 24 percent last year, Dr. Laughlin says.
It should be noted that the use of cord blood for leukemias
is different than its use for other conditions that do not need destruction of
the recipient’s bone marrow. For example in patients with heart failure there
is a need for stem cells that can either directly give rise to new heart cells,
or produce growth factors that activate stem cells in the heart. The use of
cord blood derived stem cells for heart failure has yielded some positive
results in animal studies and in several individual case reports as seen in this
video
http://www.youtube.com/watch?v=PcFQeRNuPDo .
