No abstract

SummaryCells of the osteoblast lineage affect homing, 1, 2 number of long term repopulating hematopoietic stem cells (HSCs) 3, 4, HSC mobilization and lineage determination and B lymphopoiesis 5-8. More recently osteoblasts were implicated in pre-leukemic conditions in mice 9, 10. Yet, it has not been shown that a single genetic event taking place in osteoblasts can induce leukemogenesis. We show here that in mice, an activating mutation of β-catenin in osteoblasts alters the differentiation potential of myeloid and lymphoid progenitors leading to development of acute myeloid leukemia (AML) with common chromosomal aberrations and cell autonomous progression. Activated β-catenin stimulates expression of the Notch ligand Jagged-1 in osteoblasts. Subsequent activation of Notch signaling in HSC progenitors induces the malignant changes. Demonstrating the pathogenetic role of the Notch pathway, genetic or pharmacological inhibition of Notch signaling ameliorates AML. Nuclear accumulation and increased β-catenin signaling in osteoblasts was also identified in 38% of patients with MDS/AML. These patients showed increased Notch signaling in hematopoietic cells. These findings demonstrate that genetic alterations in osteoblasts can induce AML, identify molecular signals leading to this transformation and suggest a potential novel pharmacotherapeutic approach to AML.

Given advanced age, comorbidities, and immune dysfunction, CLL patients may be at particularly high risk of infection and poor outcomes related to coronavirus disease-19 (COVID-19). Robust analysis of outcomes for CLL patients, particularly examining effects of baseline characteristics and CLL-directed therapy, is critical to optimally manage CLL patients through this evolving pandemic. CLL patients diagnosed with symptomatic COVID-19 across 43 international centers (n=198) were included. Hospital admission occurred in 90%. Median age at COVID-19 diagnosis was 70.5 years. Median CIRS score was 8 (range 4-32). Thirty-nine percent were treatment-naïve ("watch and wait") while 61% had received ≥1 CLL-directed therapy (median 2, range 1-8). Ninety patients (45%) were receiving active CLL therapy at COVID-19 diagnosis, most commonly BTK inhibitors (BTKi; n=68/90, 76%). At a median follow-up of 16 days, the overall case fatality rate (CFR) was 33%, though 25% remain admitted. "Watch and wait" and treated cohorts had similar rates of admission (89% vs. 90%), ICU admission (35% vs. 36%), intubation (33% vs. 25%), and mortality (37% vs. 32%). CLL-directed treatment with BTKi at COVID-19 diagnosis did not impact survival (CFR 34% vs. 35%), though BTKi was held during COVID-19 course for most patients. These data suggest that the subgroup of CLL patients admitted with COVID-19, regardless of disease phase or treatment status, are at high risk of death. Future epidemiologic studies are needed to assess SARS-CoV-2 infection risk, these data should be validated independently, and randomized studies of BTKi in COVID-19 are needed to provide definitive evidence of benefit.

Chronic myeloid leukemia (CML) is defined by the presence of Philadelphia chromosome (Ph), resulting from a reciprocal translocation between chromosomes 9 and 22 [t(9;22] that gives rise to a BCR-ABL1 fusion gene. CML occurs in 3 different phases (chronic, accelerated, and blast phase) and is usually diagnosed in the chronic phase. Tyrosine kinase inhibitor (TKI) therapy is a highly effective first-line treatment option for all patients with newly diagnosed chronic phase CML (CP-CML). The selection TKI therapy should be based on the risk score, toxicity profile of TKI, patient's age, ability to tolerate therapy, and the presence of comorbid conditions. This manuscript discusses the recommendations outlined in the NCCN Guidelines for the diagnosis and management of patients with CP-CML.

Hypophosphatemia, with associated changes in bone and mineral metabolism, develops in a proportion of patients taking imatinib for either chronic myelogenous leukemia or gastrointestinal stromal tumors. The drug may inhibit bone remodeling (formation and resorption), even in patients with normal serum phosphate levels.