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Rapamycin relieves lentiviral vector transduction resistance in human and mouse hematopoietic stem cells

Cathy X. Wang, Blythe D. Sather, Xuefeng Wang, Jennifer Adair, Iram Khan, Swati Singh, Shanshan Lang, Amie Adams, Gabrielle Curinga, Hans-Peter Kiem, Carol H. Miao, David J. Rawlings, Bruce E. Torbett

Key points

  • Rapamycin significantly enhances lentiviral vector gene delivery to hematopoietic stem cells while preserving engraftment potential.

  • Rapamycin-mediated transduction enhancement is not accompanied by alterations in lentiviral integration site usage or chromosomal distribution.

Abstract

Transplantation of genetically modified hematopoietic stem cells (HSCs) is a promising therapeutic strategy for genetic diseases, HIV, and cancer. However, a barrier for clinical HSC gene therapy is the limited efficiency of gene delivery via lentiviral vectors (LV) into HSCs. We show here that rapamycin, an allosteric inhibitor of the mammalian target of rapamycin (mTOR) complexes, facilitates highly efficient lentiviral transduction of mouse and human HSCs and dramatically enhances marking frequency in long-term engrafting cells in mice. Mechanistically, rapamycin enhanced post-binding endocytic events, leading to increased levels of LV cytoplasmic entry, reverse transcription, and genomic integration. Despite increasing LV copy number, rapamycin did not significantly alter LV integration site profile or chromosomal distribution in mouse HSCs. Rapamycin also enhanced in situ transduction of mouse HSCs via direct intraosseous infusion. Collectively, rapamycin strongly augments LV transduction of HSCs in vitro and in vivo, and may prove useful for therapeutic gene delivery.

  • Submitted December 23, 2013.
  • Accepted May 12, 2014.