JAK2 V617F mouse drug sensitivity testing provides a validated preclinical platform for evaluating the efficacy of candidate therapeutics against myeloproliferative neoplasms (MPNs) driven by constitutive JAK-STAT signaling. Using genetically engineered JAK2 V617F mouse models, this service delivers quantitative pharmacodynamic, hematological, and histopathological readouts that support target validation, lead optimization, and IND-enabling studies. Our integrated workflow combines in vivo dosing, allele burden quantification, phospho-flow cytometry, and survival analysis to generate decision-grade data for oncology drug development programs.
Technical Overview
The JAK2 V617F mutation is a somatic gain-of-function point mutation in the pseudokinase domain of the Janus kinase 2 (JAK2) gene, resulting in a valine-to-phenylalanine substitution at codon 617. This mutation is detected in approximately 95% of patients with polycythemia vera (PV), 50–60% of patients with essential thrombocythemia (ET), and roughly half of patients with primary myelofibrosis (PMF). The mutation abrogates autoinhibitory regulation of JAK2, leading to constitutive activation of downstream JAK-STAT, MAPK/ERK, and PI3K/AKT signaling pathways, uncontrolled myeloproliferation, and progressive extramedullary hematopoiesis.
Drug sensitivity testing in JAK2 V617F mouse models evaluates how candidate compounds—such as JAK inhibitors, STAT inhibitors, hypomethylating agents, and combination regimens—modulate disease phenotypes in vivo. Both transgenic and knock-in JAK2 V617F mice, as well as bone marrow transplantation (BMT) models, faithfully recapitulate key human MPN features, including erythrocytosis, leukocytosis, splenomegaly, bone marrow hypercellularity, and reticulin fibrosis. These models therefore serve as the gold standard for preclinical efficacy assessment in MPN drug development.
- Mutation: JAK2 V617F (c.1849G>T, p.Val617Phe) with constitutive kinase activation
- Disease relevance: Polycythemia vera, essential thrombocythemia, primary myelofibrosis
- Model types: Conditional knock-in, transgenic overexpression, and syngeneic BMT models
- Key phenotypes: Elevated hematocrit and white blood cell counts, splenomegaly, myelofibrosis, reduced survival
- Reference inhibitors: Ruxolitinib, fedratinib, and pacritinib as positive assay controls
Testing Samples
Peripheral Blood
Serial blood samples are collected at defined time points throughout the dosing period for complete blood count (CBC) analysis, plasma cytokine quantification, and circulating allele burden measurement. The small sample volume requirement permits longitudinal monitoring within the same animals, reducing inter-animal variability and study costs.
Bone Marrow Cells
Femoral and tibial bone marrow is harvested at necropsy for flow cytometric immunophenotyping of hematopoietic stem and progenitor cell (HSPC) compartments, colony-forming unit (CFU) assays, and genomic DNA extraction for JAK2 V617F allele burden determination by qPCR or droplet digital PCR.
Spleen and Liver Tissues
Splenomegaly is a hallmark disease endpoint in JAK2 V617F mice and a highly sensitive pharmacodynamic marker. Spleens and livers are weighed, and portions are processed for histopathology, single-cell suspensions for phospho-flow analysis, and molecular assays to quantify extramedullary hematopoiesis and drug response.
Serum and Plasma
Circulating inflammatory cytokines, including IL-6, TNF-alpha, and additional STAT-dependent mediators, are profiled from plasma or serum using multiplex immunoassays. Cytokine suppression serves as an early pharmacodynamic indicator of JAK pathway inhibition.
Sorted Hematopoietic Populations
Lineage-negative Sca-1-positive c-Kit-positive (LSK) cells, myeloid progenitors, and mature lineage-positive fractions can be fluorescence-activated cell sorted (FACS) for compartment-specific analysis of allele burden, signaling inhibition, and drug penetration into disease-propagating stem cell pools.
Testing Items
Drug sensitivity testing in JAK2 V617F mice encompasses a comprehensive panel of efficacy, pharmacodynamic, and safety endpoints designed to characterize compound activity across multiple biological dimensions.
- Overall and disease-free survival analysis using Kaplan-Meier methodology with log-rank statistical testing
- Spleen and liver weight normalized to body weight as quantitative tumor burden endpoints
- Serial CBC profiling: hematocrit, hemoglobin, red blood cells, white blood cells, platelets, and differential counts
- JAK2 V617F allele burden quantification in blood, bone marrow, and spleen by qPCR or ddPCR
- Phospho-STAT3 and phospho-STAT5 levels in hematopoietic cells by phospho-flow cytometry or Western blot
- Ex vivo CFU assays assessing colony-forming capacity of myeloid, erythroid, and megakaryocytic progenitors
- Histopathology and reticulin fiber staining for myelofibrosis grading in bone marrow and spleen sections
- Plasma cytokine profiling by multiplex ELISA to quantify inflammatory pathway suppression
- Body weight, clinical observation, and clinical chemistry for tolerability and safety monitoring
- Optional pharmacokinetic sampling to confirm target exposure and support PK/PD modeling
Testing Methods
Study Design and In Vivo Dosing
Studies are typically initiated after disease onset is confirmed by elevated hematocrit or leukocytosis, generally 4–8 weeks after BMT or induction in genetic models. Animals are randomized into vehicle control, positive control (ruxolitinib 60 mg/kg BID or comparable), and test article groups, with 8–12 mice per group for adequate statistical power. Test compounds are administered orally, intraperitoneally, or intravenously according to sponsor-specified schedules over 2–6 week treatment periods, with dose levels informed by maximum tolerated dose studies.
Hematological and Flow Cytometric Analysis
CBC parameters are measured on automated veterinary hematology analyzers using EDTA-anticoagulated blood. Multi-color flow cytometry panels enumerate HSPC compartments (Lin, Sca-1, c-Kit, CD34, CD150, CD48), myeloid cells (Gr-1, CD11b), and erythroid precursors (Ter119, CD71), enabling quantitative assessment of differentiation blockage or restoration by drug treatment.
Molecular and Biochemical Assays
JAK2 V617F allele burden is quantified using allele-specific TaqMan qPCR assays validated against standard curves with known mutant-to-wild-type ratios, or by droplet digital PCR for enhanced sensitivity below 0.1% variant allele frequency. Western blotting, phospho-flow cytometry, and multiplex cytokine platforms quantify pathway inhibition, while immunohistochemistry evaluates tissue-level pharmacodynamic biomarkers.
Histopathology and Fibrosis Scoring
Formalin-fixed, paraffin-embedded bone marrow, spleen, and liver sections are stained with hematoxylin and eosin for morphology and Gomori silver or reticulin stains for fibrosis grading using the European consensus scoring system adapted for murine MPN models. Blinded pathological evaluation by board-certified veterinary pathologists ensures objective fibrosis and extramedullary hematopoiesis assessment.
Statistical Analysis
Group comparisons employ ANOVA with post hoc multiple comparison tests for continuous endpoints and two-way repeated measures ANOVA for longitudinal data. Survival curves are compared using log-rank tests. All analyses are performed with appropriate statistical software, and final reports include graphical data presentation, individual animal data tables, and GLP-compliant documentation when required.
Applications
JAK2 V617F mouse drug sensitivity testing supports multiple stages of oncology drug development, from early target validation through late-stage preclinical development.
- Efficacy evaluation of next-generation JAK inhibitors, allosteric inhibitors, and type-II kinase inhibitors
- Combination therapy assessment, including JAK inhibitors paired with hypomethylating agents, BCL-2 inhibitors, or epigenetic modulators
- Mechanism-of-action studies using phospho-STAT pathway biomarkers and pharmacodynamic time-course analysis
- Comparative benchmarking of test compounds against approved JAK inhibitors such as ruxolitinib
- Anti-fibrotic efficacy assessment in advanced myelofibrosis models with established reticulin fibrosis
- Leukemic transformation studies evaluating disease progression and clonal evolution under treatment pressure
- Pharmacodynamic biomarker qualification for translation into clinical trial patient stratification
- IND-enabling package data generation supporting regulatory submission for first-in-human studies
FAQ
What JAK2 V617F mouse models are available for testing?
We support conditional knock-in mice expressing JAK2 V617F at physiological levels, transgenic models with hematopoietic-specific expression, and rapid-throughput bone marrow transplantation models. The BMT model is preferred for 4–6 week efficacy studies, whereas knock-in models are better suited for long-term survival and fibrosis progression studies.
How long does a typical drug sensitivity study take?
A standard BMT-based efficacy study, including disease establishment, a 2–4 week dosing period, and comprehensive endpoint analysis, is typically completed within 8–12 weeks. Long-term survival and myelofibrosis studies may extend to 4–6 months depending on the disease stage evaluated.
What distinguishes a sensitive from a resistant response in this model?
Sensitive responses are defined by significant reduction in splenomegaly (greater than 30% spleen weight reduction), normalization of elevated hematocrit and leukocyte counts, suppression of phospho-STAT5 signaling, and reduction in JAK2 V617F allele burden. Partial responses may improve spleen size and cytokines without meaningful allele burden reduction, a pattern consistent with approved JAK inhibitors.
Can human JAK2 inhibitors be tested as positive controls?
Yes. Ruxolitinib is routinely included as a benchmark positive control at validated dose levels to confirm model responsiveness and enable head-to-head comparison of test compounds with standard-of-care therapy.
What deliverables are provided in the final report?
Final reports include the study protocol, randomization records, in-life observations, serial CBC data, spleen and liver weights with histological images, flow cytometry datasets, allele burden results, cytokine profiles, survival analysis, and comprehensive statistical interpretation with publication-quality figures.