For patients who have chronic lymphocytic leukemia, fighting off a serious infection can be difficult and often is just not possible. And a team of Mayo researchers is starting to find out why in a paper published recently in the journal Leukemia.
What is Chronic Lymphocytic Leukemia?
This disease is cancer of an immune cell called a B lymphocyte. These cells form in bone marrow and migrate out to patrol in the blood stream and lymphoid organs. But in chronic lymphocytic leukemia, the immune system is depleted, a state called immunodeficiency. Because of that, people with this type of leukemia are prone to serious infections and the diseases those may cause. They are also prone to developing other types of cancer.
And it’s those resulting problems that may ultimately contribute to death explains Kay Medina, Ph.D., a Mayo Clinic immunologist. Dr. Medina specializes in how immune cells develop from bone marrow stem cells.
In our bone marrow, stem cells convert to red blood cells, platelets or a variety of immune cells. Those are then sent into the blood stream where they do their job. Red blood cells replace cells that are worn out.
White blood cells patrol the byways of our circulation, chasing down everything from cellular debris to bacteria to virus particles. But not in patients with chronic lymphocytic leukemia.
Joining the Team
Research on chronic lymphocytic leukemia is going on in several labs at Mayo Clinic. Dr. Medina got involved after speaking with colleagues Wei Ding, M.B.B.S, Ph.D., and Neil Kay, M.D., both chronic lymphocytic leukemia physician researchers.
“Mayo has a strong tradition of encouraging physician/basic research collaborations to advance knowledge of disease mechanisms, development, and assessment of new treatment approaches,” says Dr. Medina.
The basic research helps us understand the cause of the disease, in this case the leukemia cell, but it also helps to understand what the disease does to other parts of the body, such as the lymph nodes, spleen, blood and bone marrow, she says.
“Bone marrow is the organ that replenishes all cells in the immune system but has not been evaluated for functional proficiency in CLL patients,” explains Dr. Medina.
Checking out the Cells and their Environment
Dr. Medina’s team, with funding from Mayo Clinic’s Center for Biomedical Discovery, decided to look at bone marrow stem cells and their ability to generate all blood cell types. Some of the immune deficiency may be the result of treatment, but untreated patients have the same problem. The chronic nature of the disease itself may also dampen immune activity. But Dr. Medina explains that the leukemia cells may promote an environment that suppresses immune function.
“Our research seeks to add to the discussion by identifying additional ways patients with CLL are unable to fight off tumors and other diseases,” says Dr. Medina.
In a paper published late last year, Dr. Medina and her team, including first author Bryce Manso who is a student in the Mayo Clinic Graduate School of Biomedical Sciences, examined bone marrow and blood samples from chronic lymphocytic leukemia patients and healthy controls to determine the frequency of bone marrow stem cells in each sample and how well they did their job.
The authors reported that, in general, samples from patients with chronic lymphocytic leukemia have fewer stem cells in their bone marrow, and those stem cells that remain work less well than stem cells from controls.
Stalled-Out Bone Marrow Stem Cells
As to why this happens, the authors found that it was linked to loosening controls for the on/off switches which regulate this process, proteins called transcription factors. These proteins regulate key functions in the cell, and are out of whack in samples from chronic lymphocytic leukemia patients. They may prevent bone marrow stem cells from pursuing a pathway for development; stalling-out their ability to differentiate, resulting in decreased production of important blood cells that provide the first line of defense against infectious agents.
But, Dr. Medina cautions, there is more to this story.
“This is an emerging area of research in that it’s both a unique explanation for the clinical problem of immune deficiency and it has been minimally studied,” says Dr. Medina. “Future studies are planned to look at specific transcription factors that control stem cell differentiation as well as how the presence of leukemic cells in the bone marrow alter blood cell development.” They will then relate this information to clinically relevant complications reported in chronic lymphocytic leukemia patients, she says.
Basic Research to Improve Patient Care
Dr. Medina, her team, and their clinical colleagues hope that by understanding how bone marrow function is impaired in chronic lymphocytic leukemia patients, they can develop unique strategies to boost bone marrow function or find alternate treatments that do not block or modify marrow function.
“Through this work we hope to find ways to reduce infections and the incidence of second cancers in chronic lymphocytic leukemia patients. Our research has the potential to improve quality of life as well as extend the lives of these patients” says Dr. Medina.
- Mayo Clinic Cancer Center
- Hematologic Malignancies Research Program
- Clinical trials at Mayo Clinic for chronic lymphocytic leukemia
- A Disease Registry for Patients With Chronic Lymphocytic Leukemia
- Mayo Clinic Connect: Blood Cancers & Disorders (online discussion, support, education)