To treat SCD, Sloan-Kettering scientists devised a novel engineering strategy combining RNA interference with globin gene transfer by creating a therapeutic transgene, consisting of the gamma-globin gene and small interfering RNA specific for beta S-globin, the globin mutant chain that causes sickle cell disease.
"An innovative and sophisticated approach was needed to genetically engineer hematopoietic stem cells using a practical and clinically applicable process. The transferred gene must not disrupt the cells' normal functions," explained Isabelle Riviere, PhD, Co-Director of the Gene Transfer and Somatic Cell Engineering Facility and a study co-author.
The new gene had two functions -- produce normal hemoglobin and suppress the generation of sickle shaped hemoglobin S. The therapeutic gene was engineered into a lentiviral vector and introduced into hematopoietic stem cells. After the cells received the treatment, they made normal hemoglobin.
"This proved our hypothesis that you can simultaneously add one function and delete another in the same cell and obtain synergistic genetic modifications within a single cell," said Selda Samakoglu, PhD, a member of Dr. Sadelain's laboratory and the study's first author. "In this case, we used the technique to correct sickle cell disease, but it should be broadly applicable to use therapeutically in stem cells or malignant cells."