mutation screening for patients at risk of myeloid malignancy.

There is increasing recognition of the risk of developing therapy-related myeloid malignancy, including after cellular therapy. While retrospective studies have implicated pre-existing mutated hematopoietic clones as a common causative mechanism, no prospective screening to identify those patients at greatest risk is currently possible. We demonstrate that ultradeep DNA-sequencing prior to therapy may be used for discovery of mutations that are subsequently associated with malignancy.

Increased incidence of hematologic malignancies in SCD after HCT in adults with graft failure and mixed chimerism.

Lawal et al report on a 45-fold increase in secondary hematologic malignancy in 120 patients following hematopoietic stem cell transplantation (HSCT) for sickle cell disease (SCD), comparable to what has been reported following gene therapy. Notably, the cohort is enriched for older patients and for haploidentical transplant recipients with mixed chimerism following HSCT. These data further support the idea that pre-existing premalignant myeloid clones undergo clonal selection in the setting of nonmyeloablative HSCT and contribute to secondary malignancy.

The Notch Ligand Jagged1 Regulates the Osteoblastic Lineage by Maintaining the Osteoprogenitor Pool.

Notch signaling is critical for osteoblastic differentiation; however, the specific contribution of individual Notch ligands is unknown. Parathyroid hormone (PTH) regulates the Notch ligand Jagged1 in osteoblastic cells. To determine if osteolineage Jagged1 contributes to bone homeostasis, selective deletion of Jagged1 in osteolineage cells was achieved through the presence of Prx1 promoter-driven Cre recombinase expression, targeting mesenchymal stem cells (MSCs) and their progeny (PJag1 mice).

The niche as a target for hematopoietic manipulation and regeneration.

Hematopoietic stem cells (HSCs), rare primitive cells capable of reconstituting all blood cell lineages, are the only stem cells currently routinely used for therapeutic purposes. Clinical experience has shown that HSC number is an important limiting factor in treatment success. Strategies to expand HSCs are of great clinical appeal, as they would improve therapeutic use of these cells in stem cell transplantation and in conditions of bone marrow failure.