Stem Cells for Leukemia

Battling cancer is tough enough, and unfortunately, the experience is familiar for more than just a few—in the United States alone, 19 million adults have ever been diagnosed with the disease, according to the Centers for Disease Control and Prevention (CDC).

Even when patients are given a clean bill of health, there is always a possibility that the cancer can come out of remission. However, for survivors of acute myeloid leukemia (AML), a cancer of the blood and bone marrow, there may be a new reason to hope.

Researchers at the RIKEN Research Center for Allergy and Immunology in Japan have uncovered a potential bio-inhibitor for the leukemia stem cells (LSCs) that survive chemotherapy and can cause an AML relapse. While leukemia is commonly considered a children’s cancer, AML is the most common form of leukemia in adults, with nearly 30,000 new cases reported in the U.S., Europe, and Japan in 2011.

AML is a very aggressive form of leukemia and has a relatively poor long-term prognoses. At five years, the survival rate is 40 to 45 percent for patients younger than 60 and less than 10 percent for older patients. 

“AML is difficult to cure because, even though initial treatments may be successful, many patients later succumb to AML relapse,” said study author Fumihiko Ishikawa, M.D., Ph.D., in an interview with Healthline. “We hope that by targeting AML stem cells, it is possible to prevent relapse in AML patients."

The Cure Is in the Stem Cells

Chances are you’ve heard about stem cells, whether casually scanning a medical journal or watching a recent sci-fi movie. The exciting thing about these cells is that they are, essentially, blank cells that have not yet begun to specialize. Each cell in your body is tailored, like a puzzle piece, so that it can function as, say, a heart muscle cell. But because a stem cell is a blank slate, its potential for use is enormous.

If doctors can encourage stem cells to grow into heart cells, or even a whole new heart, for example, someone in need of a heart transplant could be given a fresh organ grown from their own cells, which reduces the risk of organ rejection. Leukemia stem cells, or LSCs, however, are not quite so noble.

LSCs, unlike normal stem cells, contain a larger amount of a protein known as hematopoietic cell kinase (HCK). LSCs are resistant to treatment, especially in AML patients, and unfortunately, if they’re not destroyed during chemotherapy it is likely that within five years they will regenerate as cancerous cells.

Ishikawa and his team reported in 2010 that AML stem cells are particularly resistant to chemotherapy, due to the presence of HCK. After screening a large-scale chemical library, they uncovered a compound called RK-20449 that blocks HCK and eliminates chemotherapy-resistant LSCs. Researchers gave RK-20449 to a group of mice infected with an aggressive form of treatment-resistant LSCs and found that the chemical helped to prevent relapse and improve their survival rate.

“We found RK-20449 to be effective in eliminating human AML stem cells, which are thought to cause relapse in AML patients,” Ishikawa said. 

Current Treatments for AML

“In current standard of care for most AML, the patients are initially treated with what is called ‘induction chemotherapy,'” Ishikawa said. Patients receive a combination of drugs that is geared toward killing as many leukemia cells as possible. If the treatment is successful and the blood and bone marrow appear free of leukemia cells, the patient is considered to be in remission. 

Even in remission, the patient will receive additional rounds of chemotherapy to keep the leukemia from returning. Stem cell transplantation is then used in some patients to clear out any remaining AML cells and to help strengthen and protect their bone marrow cells.

Unfortunately, not all patients are candidates for this stem cell treatment. RIKEN researchers hope that in the future RK-20449 in drug form can be used to neutralize LSCs and prepare patients for stem cells treatments, Ishikawa said.

The Bottom Line

Ishikawa's research is still in its infancy, so AML patients won’t be given RK-20449 any time soon, but the potential is there for a new, more effective treatment.

“We hope that this study leads to more work that can take basic research findings from the bench to the bedside, to find effective treatments for leukemia and other cancers by targeting cancer stem cells,” Ishikawa said.

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