Stories about: thalassemia

Zeroing in on the fetal-to-adult hemoglobin switch and a new way to combat sickle cell disease

Normal red blood cell vs. sickle-shaped blood cell, which is found in sickle cell disease
Normal red blood cell vs. sickle-shaped blood cell.

It’s been known for more than 40 years that in rare individuals, lingering production of the fetal form of hemoglobin — the oxygen-transporting protein found in red blood cells — can reduce the severity of certain inherited blood disorders, most notably sickle cell disease and thalassemia. Typically, however, a protein called BCL11A switches off fetal hemoglobin production past infancy, but exactly how this happens has not been well understood until now.

In a new paper in Cell, researchers at Dana-Farber/Boston Children’s Cancer and Blood Disorders Center have revealed how BCL11A controls the switch in the body’s production of fetal hemoglobin to adult hemoglobin. It does so by binding to a DNA sequence — made up of the bases T-G-A-C-C-A — that lies just in front of the fetal hemoglobin genes.

Another approach to curing sickle cell disease is already being evaluated in a new clinical trial at Dana-Farber/Boston Children’s. The novel gene therapy restores fetal hemoglobin production by genetically suppressing BCL11A, which prevents it from blocking fetal hemoglobin production. Learn more.

“Genetically modifying this TGACCA segment could be another possible strategy to cure sickle cell disease by blocking BCL11A’s ability to bind to this DNA site and switch off fetal hemoglobin production,” says Stuart Orkin, MD, senior author on the study.

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Getting iron out after putting blood in: Transfusions and iron overload

Frequent transfusions can leave the body overloaded with iron. Ellis Neufeld is helping find new ways of scrubbing that extra iron from the blood. (Research Indicates/Flickr)

In some children the body’s machinery for making red blood cells just doesn’t work right. Conditions like Diamond Blackfan anemia or thalassemia can leave the body anemic, struggling to keep up with its own demands for oxygen. And the misshapen red blood cells of sickle cell disease can get stuck in small blood vessels and cause anemia, organ damage and great pain.

Right now, the most effective way to care for these blood disorders is with blood transfusions. But unlike trauma or surgery, a single transfusion doesn’t solve the problem for people with life-long anemias or sickle cell. Most people with thalassemia, for example, have transfusions every month for their entire life.

“After about 20 transfusions, you reach a point where the body is overloaded with iron from all of the extra hemoglobin that’s been introduced into it,” says Ellis Neufeld, MD, PhD, director of the Thalassemia Program at Dana-Farber/Children’s Hospital Cancer Center (a partnership of Boston Children’s Hospital and Dana-Farber Cancer Institute). “The body has no way to actively remove iron on its own, so the iron starts to build up.” Over time, this can damage the liver, heart, pancreas and other major organs.

Over the last 40 years, a lot of work at DF/CHCC and elsewhere has gone into what’s called chelation therapy: drug-based treatments that scrub the blood of excess iron. Right now there are three chelating drugs in broad use: deferoxamine, deferasirox and deferiprone. They work well for many patients, but have their disadvantages.

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Sickle cell: New looks at a neglected disease

sickle cell disease red blood cells
(OpenStax College/Wikimedia Commons)

Sickle-cell anemia was the first disease to have its genetic cause identified, in the 1950s — a milestone in human genetics. Yet today, there’s just one FDA-approved drug, hydroxyurea, developed 20 years ago at Children’s. Though it’s a mainstay of treatment, reducing the frequency of severe pain, acute chest syndrome and the need for blood transfusions, it can cause toxicity, and about half of patients aren’t helped by it. Only a hematopoietic stem-cell transplant is curative.

Research on sickle-cell disease has generally been underfunded compared with other genetic diseases like cystic fibrosis that aren’t as common. But Children’s has been exploring new treatment approaches for decades, and two exciting possibilities have emerged.

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