Myelofibrosis (MF) in 50% of cases is driven by an activating JAK2 mutation, mostly V617F. Ruxolinitib is approved for the treatment of MF. Responses to ruxolitinib in MF are of limited duration. Unexpectedly, treatment of JAK2-V617F expressing cells with ruxolitinib causes paradoxical hyperphosphorylation of JAK2 at activation loop Tyr1007/Tyr1008. The significance of ruxolitinib-induced JAK2 hyperphosphorylation is not well understood. We found that a ruxolitinib-resistant JAK2 variant (V617F + L983F) and a kinase dead mutant (JAK2-V617F + K882R) did not show paradoxical hyperphosphorylation after ruxolitinib treatment indicating that it is an intrinsic mechanism. Antibodies against pTyr1007/1008 failed to immunoprecipitate native JAK2-V617F in the presence of ruxolitinib, although JAK2-V617F was hyperphosphorylated at these sites, suggesting that in the presence of ruxolitinib the JAK2 activation loop is buried within the kinase domain. This stabilization of the activation loop conformation resulted in the protection of pTyr1007/1008 sites from phosphatases. Mutation of Arg975 and Lys999 to Ala reduced the phosphorylation at both Tyr1007/Tyr1008 residues, and notably, ruxolitinib treatment did not lead to JAK2 hyperphosphorylation. Importantly, hyperphosphorylated JAK2 after ruxolitinib dissociation displayed excess rebound activation of STAT5 target gene PIM kinase. Our results suggest a novel mode of kinase regulation by modulating kinase activity through conformational changes induced by ruxolitinib. Subject categories: JAK2-V617F, Ruxolitinib, JAK2 hyperphosphorylation, Phosphatases action, PIM kinases

Acute myeloid leukemia (AML) proliferation is significantly influenced by the interactions between leukemia blasts and the bone marrow (BM) microenvironment. Specifically, bone marrow mesenchymal stem cells (BMSCs) derived from AML patients (AML-MSCs) are known to support leukemia growth and facilitate disease progression. Studies have demonstrated that the transfer of mitochondria from MSCs to AML blasts not only aids in disease progression but also contributes to chemotherapy resistance. Furthermore, BM stromal cells can trigger a metabolic shift in malignant cells from mitochondrial respiration to glycolysis, which enhances both growth and chemo-resistance. This study focuses on identifying transcriptional and metabolic alterations in AML-MSCs to uncover potential targeted therapies for AML. We employed RNA sequencing and microarray analysis on MSCs cocultured with leukemic cells (MLL-AF9) and on MSCs isolated from both non-leukemic and MLL-AF9 leukemic mice. The Gene Set Enrichment Analysis (GSEA) indicated a significant downregulation of gene sets associated with oxidative phosphorylation and glycolysis in AML-MSCs. Furthermore, coculture of MSCs from wild-type mice (WT-MSCs) and a healthy donor individual (HD-MSCs) with AML cells demonstrated reduced oxidative phosphorylation and glycolysis. These metabolic changes were consistent in AML-MSCs derived from both leukemic mice and patients. Our results indicate that AML cells diminish the metabolic capacity of MSCs, specifically targeting oxidative phosphorylation and glycolysis. These findings suggest potential metabolic vulnerabilities that could be exploited to develop more effective therapeutic strategies for AML.

The complex and heterogeneous genomic landscape of multiple myeloma (MM) and many of its clinical and prognostic implications remains to be understood. In other cancers, such as breast cancer, using whole-exome sequencing (WES) and molecular signatures in clinical practice has revolutionized classification, prognostic prediction, and patient management. However, such integration is still in its early stages in MM. In this study, we analyzed WES data from 35 MM patients to identify potential mutational signatures and driver mutations correlated with clinical and cytogenetic characteristics. Our findings confirm the complex mutational spectrum and its impact on previously described ontogenetic and epigenetic pathways. They show TYW1 as a possible new potential driver gene and find no significant associations of mutational signatures with clinical findings. Further studies are needed to strengthen the role of mutational signatures in the clinical context of patients with MM to improve patient management.

Background: Acute myeloid leukemia (AML) is predominantly a disease of older patients with a poor long-term survival. Approval of the combination of venetoclax (VEN) with azacitidine (AZA) or decitabine (DAC) in the European Union in 2021 for the treatment of patients with newly diagnosed AML who are ineligible for induction chemotherapy has become the treatment backbone for older, medically non-fit AML patients. Based on in vitro priming of AML cells to all- trans retinoic acid (ATRA) by DAC, we had previously conducted a randomized phase II trial (DECIDER, AMLSG 14 − 09) in 200 elderly, non-fit AML patients on the effect of ATRA as add-on to DAC. Median overall survival (OS) was 8.2 months with ATRA versus 5.1 months without ATRA (hazard ratio, 0.65; 95% CI, 0.48 to 0.89; P = 0.006). Notably, ATRA did not add toxicity, the combination was active also in patients with adverse genetics, and prolonged time to treatment resistance. Investigating a triple combination of DAC, VEN and ATRA was a logical next step. This randomized double-blind phase III trial compares the efficacy of ATRA versus placebo as add-on to the backbone treatment (DAC and VEN) with respect to OS, objective best response, quality of life and safety. The accompanying translational research will contribute to identify molecular markers for drug efficacy and better tailoring epigenetic therapy. Methods: DECIDER-2 (AMLSG 32 − 21) is a prospective, randomized, double-blind, placebo-controlled, parallel group, multicenter trial. The primary study objective is to compare the efficacy of ATRA versus placebo as add-on to the backbone treatment (DAC and VEN) in terms of OS. The target population is adult AML patients unfit for standard induction chemotherapy. Patients are randomized (1:1) to receive backbone treatment in combination with either ATRA or placebo. Four interim safety analyses were planned with the involvement of the Data Monitoring Committee. Discussion: This trial investigates whether the in vitro cooperativity of DAC, VEN, and ATRA prolongs OS in unfit AML patients compared to placebo, offering a novel, low-toxicity triplet combination with a promising risk-benefit ratio. Clinical trial number: EU CT number: 2020-005495-36/2023-507461-26-00 (registered 18.11.2020); German clinical trials registry number: DRKS00023646 (registered 23.08.2022).

Sickle cell disease (SCD) with hemoglobin‐ (Hb‐) SC genotype is often considered a milder SCD variant, yet life‐threatening complications can occur. A 26‐year‐old man with HbSC disease presented with an infection triggered vaso‐occlusive crisis (VOC), acute chest syndrome (ACS), severe thrombocytopenia, Coombs‐negative hemolysis with schistocytes, acute kidney injury, and markedly elevated lactate dehydrogenase (LDH) in the setting of Klebsiella pneumoniae sepsis. The resulting severe thrombotic microangiopathy‐ (TMA‐) like phenotype initially raised concern for thrombotic thrombocytopenic purpura (TTP). However, ADAMTS13 activity was not significantly reduced, arguing against classical TTP. The episode was interpreted as a TTP‐like syndrome, whereas fat embolism syndrome (FES) remained an important differential diagnosis. The patient received red‐cell exchange, plasma exchange, caplacizumab, antibiotics, and dialysis, followed by hematologic and renal recovery. Months later, he developed a non‐aneurysmal infratentorial subarachnoid hemorrhage (SAH) with obstructive hydrocephalus requiring external ventricular drainage (EVD) and posterior fossa decompression, resulting in severe persistent neurological disability. The case, therefore, highlights the severity of HbSC disease and the challenge of urgent treatment decisions under substantial diagnostic uncertainty when a TMA‐like presentation overlaps with other severe SCD complications such as FES.