Ruxolitinib has been approved by FDA for the treatment of myeloproliferative neoplasms such as polycythemia vera and idiopathic myelofibrosis. Although ruxolitinib has been in the clinic for more than ten years, surprisingly, no JAK2 drug resistant mutations have been identified in patients. At the moment, it is not clear whether the absence of JAK2 mutations in MPN patients is due to a lack of JAK2 addiction or residues that mediate the drug resistance compromising the JAK2 function. To find out this, we established a Ba/F3 cell-based screening strategy to predict mutations in JAK2-V617F that cause resistance towards ruxolitinib. In this study, we have recovered seven residues in the kinase domain of JAK2 that affect ruxolitinib sensitivity. All these mutations confer cross-resistance across the panel of JAK2 kinase inhibitors except JAK2-L983F. JAK2-L983F reduces the sensitivity towards ruxolitinib. However, it is sensitive towards fedratinib indicating that our screen identifies the drug-specific resistance profiles. All the ruxolitinib resistant JAK2 variants displayed sensitivity towards Type II JAK2 inhibitor CHZ-868. Finally, our study also shows that HSP90 inhibitors are potent against ruxolitinib resistant variants through the JAK2 degradation and provides the rationale for clinical evaluation of potent HSP90 inhibitors in genetic resistance driven by JAK2 inhibitors.

Lindera obtusiloba Blume has several activities, such as anti-inflammatory, anti-allergic, anti-tumor, anti-wrinkle, and antioxidant activities. Interleukin-6 (IL-6) is a classic pro-inflammatory cytokine that is associated with various functions, such as proliferation, invasion, inflammatory responses and functions within antioxidant defence systems. In this study, we investigated IL-6-induced STAT3 activation of lignan compounds isolated from L. obtusiloba. The structures of the isolated compounds were elucidated via spectroscopic nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI-MS). As a result, seven lignans were identified from L. obtusiloba. All the isolated compounds (1-7) were evaluated for their IL-6-induced STAT3 inhibitory effects in Hep3B cells using a luciferase reporter assay. Of the isolates, compounds 1 and 5 showed inhibitory effects against IL-6-stimulated STAT3 activation. Furthermore, the mRNA expression levels of inflammation-related genes such as CRP, IL-1b, and SOCS3 were significantly reduced by exposure to compound 1 and 5. The protein levels of p-STAT3, p-JAK2 in IL-6 induced U266 cells were regulated in the presence of lignans derived from Lindera obtusiloba by western blot assay. Based on the results, this study of L. obtusiloba demonstrates that the species has promise as a bioactive candidate for the treatment of IL-6-induced STAT3-related disease.

Objectives: Essential thrombocythemia (ET) is a chronic myeloproliferative neoplasm characterized by elevated platelet counts and an increased risk of thrombotic events, including ischemic strokes. Methods: We conducted a retrospective analysis of data from consecutive ischemic stroke patients with ET between March 2014 and February 2023. Results: This case series describes the clinical presentation, radiological features, and management of five patients with ET-associated ischemic strokes, all harboring the JAK2 mutation. The diverse radiological findings suggest that both large and small vessel diseases may be influenced by the prothrombotic state induced by ET. A significant elevation in platelet count was observed to correlate with the emergence of new acute infarctions in some cases. Conclusions: The study highlights combined use of antiplatelet and cytoreductive therapy in preventing secondary stroke events in patients with ET and JAK2 mutations. The heterogeneity of stroke patterns in this population necessitates a comprehensive understanding of the underlying pathophysiological mechanisms and tailored therapeutic approaches.