The JAK2 Kinase Inhibitor LS104 Induces Growth-Arrest and Apoptosis in JAK2V617F Positive Cells.
Bibliographic record
Abstract
Abstract The JAK2V617F-mutation (V617F) is a novel, highly prevalent molecular marker in Ph-negative myeloproliferative disease (MPD). In vitro, the V617F mutation confers cytokine independent growth of Ba/F3 cells expressing erythropoietin receptor (EpoR) and constitutive activation of the JAK2 kinase and of the JAK-STAT pathway. In a murine bone-marrow transplant model the V617F-mutation alone is sufficient to induce a polycythemia vera-like phenotype. Therefore, mutant JAK2 kinase is a promising target for kinase inhibitor development. In this report, we characterize the small molecule LS104 (previously CR4; Grunberger et al., Blood 2003) as a novel non-ATP-competitive JAK2V617F kinase inhibitor. Ba/F3 cells stably transfected with EpoR and either the V617F-mutant (Ba/F3-EpoR-VF) or wildtype JAK2 (Ba/F3-EpoR-WT) were treated with LS104. Apoptosis assays as well as immunoblotting of JAK2 and of downstream signalling pathways were performed. The effects of LS104 on kinase activity were determined in an in vitro JAK2 kinase assay. A combination of LS104 with JAK-inhibitor I, which acts via the ATP-binding site, was tested in apoptosis assays. Finally, growth of endogenous erythroid colonies (EECs) obtained from patients with V617F-positive MPD was tested upon addition of LS104. LS104 selectively and dose dependently induced apoptosis in Ba/F3-EpoR-VF cells as compared to Ba/F3-EpoR-WT control cells. By immunoblotting we found inhibition of JAK2 autophosphorylation and of downstream targets as STAT5, AKT and ERK upon treatment with LS104. Activation of these targets by JAK2 was confirmed in experiments using JAK2 siRNA. The IC50 for JAK2 in an in vitro kinase assay using LS104 was <5μM, and this effect was not reversible using increased ATP-doses. Combination treatment of Ba/F3-EpoR-VF cells using LS104 plus JAK-inhibitor I lead to significantly increased apoptosis as compared to each substance alone. Furthermore, we observed 89% inhibition of in vitro formation of EECs at 10μM LS104 whereas growth of CFU-GM obtained from normal controls was virtually unaffected. Taken together, our data show that LS104 specifically inhibits JAK2 kinase activity and JAK2 downstream signals and thereby induces apoptosis in V617F-positive cells. Our data suggest, that LS104 either irreversibly binds to the ATP-binding site or acts as a substrate kinase inhibitor and may be combined with ATP-competitive JAK2 inhibitors to enhance treatment efficacy. Growth of EECs from patients with MPD is shown to be significantly suppressed by LS104. Based on these data, a phase I/II clinical trial of LS104 for patients with JAK2V617F-positive MPD has been initiated recently.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".