SAMHD1 Limits the Efficacy of Forodesine in Leukemia by Protecting Cells against the Cytotoxicity of dGTP.

The anti-leukemia agent forodesine causes cytotoxic overload of intracellular deoxyguanosine triphosphate (dGTP) but is efficacious only in a subset of patients. We report that SAMHD1, a phosphohydrolase degrading deoxyribonucleoside triphosphate (dNTP), protects cells against the effects of dNTP imbalances. SAMHD1-deficient cells induce intrinsic apoptosis upon provision of deoxyribonucleosides, particularly deoxyguanosine (dG). Moreover, dG and forodesine act synergistically to kill cells lacking SAMHD1. Using mass cytometry, we find that these compounds kill SAMHD1-deficient malignant cells in patients with chronic lymphocytic leukemia (CLL). Normal cells and CLL cells from patients without SAMHD1 mutation are unaffected. We therefore propose to use forodesine as a precision medicine for leukemia, stratifying patients by SAMHD1 genotype or expression.

Human Wharton's jelly-derived mesenchymal stromal cells engineered to secrete Epstein-Barr virus interleukin-10 show enhanced immunosuppressive properties.

BACKGROUND AIMS: Mesenchymal stromal cells (MSCs) modulate the immune response and represent a potential treatment for inflammatory and autoimmune diseases. We hypothesized that this feature could be potentiated by co-administering anti-inflammatory cytokines. In this article, we asked whether engineering of Wharton Jelly-derived human MSCs (WJ-hMSCs) to express an anti-inflammatory cytokine increases cell immunomodulatory properties without altering their native features. METHODS: We used Epstein-Barr virus-derived interleukin-10 (vIL-10), which shares some immunosuppressive properties with human IL-10 but lacks immunostimulatory activity. Engineering was accomplished by transducing WJ-hMSCs with a self-inactivating feline immunodeficiency virus-derived vector co-expressing vIL-10 and herpes simplex virus type-1 thymidine kinase (TK). TK was added to allow future tracking of WJ-hMSC in vivo by positron electron tomography (PET). RESULTS: The results show that (i) expression of TK and/or vIL-10 does not change WJ-hMSC phenotypic and functional properties; (ii) vIL-10 is secreted, biologically active and enhances the immunosuppressing functions of WJ-hMSCs; (iii) v-IL10 and TK can be produced simultaneously by the same cells and do not interfere with each other. DISCUSSION: WJ-hMSCs engineered to secrete vIL-10 could be a powerful tool for adoptive cell therapy of immune-mediated diseases, and therefore, additional studies are warranted to confirm their efficacy in suitable animal disease models.

Gene editing of DNAH11 restores normal cilia motility in primary ciliary dyskinesia.

BACKGROUND: Primary ciliary dyskinesia (PCD) is a rare autosomal recessive genetic disorder characterised by dysfunction of motile cilia. Ciliary dysmotility causes poor mucociliary clearance and leads to impairment of pulmonary function and severe respiratory infections. PCD has no specific therapy. With the aim to permanently restore gene function and normalise ciliary motility, we used gene editing to replace mutated with wild-type sequence in defective cells. METHODS: The target gene was dynein heavy chain 11 (DNAH11), an essential component of ciliary structure. Airway ciliated cells were collected from two patients with PCD with DNAH11 nonsense mutations and altered ciliary beating and pattern. Repair of the genetic defect was performed ex vivo by site-specific recombination using transcription activator-like effector nucleases (TALENs). RESULTS: In an epithelial cell line engineered to contain the DNAH11 target site, TALENs cleaved over 80% of the mutated DNAH11 sequence and replaced the mutated sequence with wild-type sequence in about 50% of cells. In airway ciliated cells of patients with PCD, site-specific recombination and normalisation of ciliary beating and pattern occurred in 33% and 29% of cells, respectively. CONCLUSION: This study demonstrates that gene editing can rescue ciliary beating ex vivo, opening up new avenues for treating PCD.