Gene therapy of MPL deficiency: challenging balance between leukemia and pancytopenia.
Signaling of the thrombopoietin (THPO) receptor MPL is critical for the maintenance of hematopoietic stem cells (HSCs) and megakaryocytic differentiation. Inherited loss-of-function mutations of MPL cause severe thrombocytopenia and aplastic anemia, a syndrome called congenital amegakaryocytic thrombocytopenia (CAMT). With the aim to assess the toxicity of retroviral expression of Mpl as a basis for further development of a gene therapy for this disorder, we expressed Mpl in a murine bone marrow transplantation (BMT) model. Treated mice developed a profound yet transient elevation of multilineage hematopoiesis, which showed morphologic features of a chronic myeloproliferative disorder (CMPD) with progressive pancytopenia. Ten percent of mice (3/27) developed erythroleukemia, associated with insertional activation of Sfpi1 and Fli1. The majority of transplanted mice developed a progressive pancytopenia with histopathological features of a myelodysplastic syndrome (MDS)-like disorder. To avoid these adverse reactions, improved retroviral vectors were designed that mediate reduced and more physiological Mpl expression. Self-inactivating gamma-retroviral vectors were constructed that expressed Mpl from the phosphoglycerate kinase (PGK) or the murine Mpl promoter. Mice that received BM cells expressing Mpl from the Mpl promoter were free of any previously observed adverse reactions.
Department of Experimental Hematology, Hannover Medical School, Hannover, Germany.
Daniel C
DC
Wicke
Johann
J
Meyer
Guntram
G
Buesche
Dirk
D
Heckl
Hans
H
Kreipe
Zhixiong
Z
Li
Karl H
KH
Welte
Matthias
M
Ballmaier
Christopher
C
Baum
Ute
U
Modlich
D000818:Animals; D015139:Blotting, Southern; D015153:Blotting, Western; D024202:Electrophoretic Mobility Shift Assay; D004797:Enzyme-Linked Immunosorbent Assay; D015316:Genetic Therapy / Q000009:adverse effects* / Q000379:methods*; D007938:Leukemia / Q000209:etiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010198:Pancytopenia / Q000209:etiology*; D010735:Phosphoglycerate Kinase / Q000235:genetics / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics; D053628:Receptors, Thrombopoietin / Q000235:genetics / Q000378:metabolism*; D012190:Retroviridae / Q000235:genetics / Q000502:physiology*
D053628:Receptors, Thrombopoietin; D010735:Phosphoglycerate Kinase