Wiskott-Aldrich syndrome (WAS) is characterized by microthrombocytopenia, immunodeficiency, autoimmunity, and susceptibility to malignancies. In our hematopoietic stem cell gene therapy (GT) trial using a γ-retroviral vector, 9 of 10 patients showed sustained engraftment and correction of WAS protein (WASP) expression in lymphoid and myeloid cells and platelets. GT resulted in partial or complete resolution of immunodeficiency, autoimmunity, and bleeding diathesis. Analysis of retroviral insertion sites revealed >140,000 unambiguous integration sites and a polyclonal pattern of hematopoiesis in all patients early after GT. Seven patients developed acute leukemia [one acute myeloid leukemia (AML), four T cell acute lymphoblastic leukemia (T-ALL), and two primary T-ALL with secondary AML associated with a dominant clone with vector integration at the LMO2 (six T-ALL), MDS1 (two AML), or MN1 (one AML) locus]. Cytogenetic analysis revealed additional genetic alterations such as chromosomal translocations. This study shows that hematopoietic stem cell GT for WAS is feasible and effective, but the use of γ-retroviral vectors is associated with a substantial risk of leukemogenesis.

We identify SMARCD2 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily D, member 2), also known as BAF60b (BRG1/Brahma-associated factor 60b), as a critical regulator of myeloid differentiation in humans, mice, and zebrafish. Studying patients from three unrelated pedigrees characterized by neutropenia, specific granule deficiency, myelodysplasia with excess of blast cells, and various developmental aberrations, we identified three homozygous loss-of-function mutations in SMARCD2. Using mice and zebrafish as model systems, we showed that SMARCD2 controls early steps in the differentiation of myeloid–erythroid progenitor cells. In vitro, SMARCD2 interacts with the transcription factor CEBPε and controls expression of neutrophil proteins stored in specific granules. Defective expression of SMARCD2 leads to transcriptional and chromatin changes in acute myeloid leukemia (AML) human promyelocytic cells. In summary, SMARCD2 is a key factor controlling myelopoiesis and is a potential tumor suppressor in leukemia.

Here we show that MYSM1 deficiency is associated with developmental aberrations, progressive BMF with myelodysplastic features, and increased susceptibility to genotoxic stress. HSCT represents a curative therapy for patients with MYSM1 deficiency.

During the initiation of tumor associated angiogenesis endothelial cells migrate, adhere to extracellular matrix and form cell-cell contacts. Humoral factors of malignant cells conduct this process. We investigated whether cell surface expression of the carbohydrate blood group determinant Lewis(y) (CD174) and its precursor structure H2 (CD173) on endothelial cells is influenced by soluble factors of tumor cells. Using a bone marrow derived endothelial cell line we observed an enhanced expression of CD173/CD174 and transcription of FUT1, the key enzyme for their synthesis, after treatment with tumor necrosis factor-alpha (TNF-alpha) or conditioned supernatants of the leukemia cell line KG1a. CD173/CD174 are concentrated on pseudopodial extensions responsible for initial contacts between endothelial cells. Endothelial migration induced by TNF-alpha could be diminished by antibodies to CD174 as well as by siRNA induced downmodulation of FUT1 transcription. Endothelial FUT1-siRNA-transfectants displayed impaired in vitro angiogenesis when cultivated on extracellular matrix and in spheroid assays. In vivo upregulation of CD174 expression was observed immunocytologically in capillaries of tumor-infiltrated tissue. Together, our observations point to a tumor induced transcription of endothelial FUT1 and consequently an enhanced expression of CD174 which is involved in migration and early cell-cell contacts during tumor associated angiogenesis.