scholarly journals Therapeutic potential of JAK2 inhibitors

Hematology ◽  
2009 ◽  
Vol 2009 (1) ◽  
pp. 636-642 ◽  
Author(s):  
Srdan Verstovsek
Keyword(s):  
Therapeutic Potential ◽  
Myeloproliferative Neoplasms ◽  
Primary Myelofibrosis ◽  
Binding Pocket ◽  
Therapeutic Benefit ◽  
Wild Type ◽  
Competitive Inhibitors ◽  
Clinical Benefits ◽  
Kinase Mutation ◽  
Jak2 Inhibitors

AbstractThe discovery of an activating tyrosine kinase mutation JAK2V617F in myeloproliferative neoplasms (MPNs), polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) has resulted in the development of JAK2 inhibitors, of which several are being evaluated in phase I/II clinical studies. It is important to recognize that because the V617F mutation is localized in a region outside the adenosine triphosphate (ATP)-binding pocket of JAK2 enzyme, ATP-competitive inhibitors of JAK2 kinase (like the current JAK2 inhibitors in the clinic) are not likely to discriminate between wild-type and mutant JAK2 enzymes. Therefore, JAK2 inhibitors, by virtue of their near equipotent activity against wild-type JAK2 that is important for normal hematopoiesis, may have adverse myelosuppression as an expected side effect, if administered at doses that aim to completely inhibit the mutant JAK2 enzyme. While they may prove to be effective in controlling hyperproliferation of hematopoietic cells in PV and ET, they may not be able to eliminate mutant clones. On the other hand, JAK inhibitors may have great therapeutic benefit by controlling the disease for patients with MPNs who suffer from debilitating signs (eg, splenomegaly) or constitutional symptoms (which presumably result from high levels of circulating cytokines that signal through JAK enzymes). Indeed, the primary clinical benefits observed so far in MF patients have been significant reduction is splenomegaly, elimination of debilitating disease-related symptoms, and weight gain. Most importantly, patients with and without the JAK2V617F mutation appear to benefit to the same extent. In this review we summarize current clinical experience with JAK2 inhibitors in MPNs.

Therapeutic Advances in Myeloproliferative Neoplasms: The Role of New-Small Molecule Inhibitors

2012 ◽  
pp. 406-410 ◽  
Author(s):  
Srdan Verstovsek
Keyword(s):  
Molecular Mechanisms ◽  
Therapeutic Potential ◽  
Myeloproliferative Neoplasms ◽  
Janus Kinase ◽  
Treatment Focus ◽  
Rational Combination ◽  
Short And Long Term ◽  
Jak2 Inhibitors

Overview: The discovery that a somatic point mutation (JAK2V617F) in the Janus kinase 2 ( JAK2) is highly prevalent in patients with myeloproliferative neoplasms (MPNs) has been a crucial breakthrough in our understanding of the underlying molecular mechanisms of these diseases. Therefore, preclinical and clinical research in recent years has focused intensely on the development of new therapies targeted to JAK2. These efforts culminated in recent approval of ruxolitinib as the first official therapy for patients with intermediate- or high-risk myelofibrosis (MF). Therapy with JAK2 inhibitors substantially improves quality of life and reduces organomegaly in MF with or without JAKV617F mutation. Recent results suggest that patients with advanced MF may live longer when receiving therapy with ruxolitinib. However, JAK2 inhibitors do not eliminate the disease and new medications are needed to expand on the benefits seen with JAK2 inhibitors. Although many agents are still in the early stages of development, the wealth of publications and presentations has continued to support our growing understanding of the pathophysiology of MF as well as the potential short- and long-term outcomes of these new and diverse approaches to treatment. Focus of ongoing efforts is particularly on the improvements in anemia and fibrosis, as well as on rational combination trials of JAK2 inhibitors and other potentially active agents. Therapeutic potential and limitations of JAK2 inhibitors and other novel medications in clinical studies are reviewed.

GNF-2, An Allosteric BCR-ABL Inhibitor, Identifies a Novel Myristoylation-Mediated Mechanism Regulating the Ability of BCR-ABL to Activate HCK and IGF-1 Signaling.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 40-40 ◽  
Author(s):  
Ron Geyer ◽  
Teodora Zlateva ◽  
Asha Lakshmikuttyamma ◽  
David P. Sheridan ◽  
John F. DeCoteau
Keyword(s):  
Binding Sites ◽  
Cellular Localization ◽  
Kinase Activity ◽  
Conflicts Of Interest ◽  
Biological Effects ◽  
Binding Pocket ◽  
Negative Regulator ◽  
Wild Type ◽  
Abl Kinase ◽  
Competitive Inhibitors

Abstract Abstract 40 Pharmacologic inhibition of BCR-ABL, using clinically active ATP-competitive inhibitors imatinib, nilotinib, and dasatinib, has been used to investigate BCR-ABL kinase activated signaling pathways. However, these agents show cross reactivity with other kinases (e.g. Kit, PDGFR, SRC family members), and their multi-targeted nature complicates assigning biological effects to the inhibition of a specific kinase target. Allosteric kinase inhibitors modulate the catalytic activity of protein kinases by binding to a site distant from the active site and inducing a protein conformation that inhibits kinase activity. These agents show promise as clinical agents and may offer advantages over ATP-competitive inhibitors in studying the function of specific kinases because they exploit binding sites and regulatory mechanisms that are unique to a particular kinase. GNF-2, a mono-selective BCR-ABL inhibitor that targets wild-type BCR-ABL and many clinically relevant imatinib resistant mutants, was recently discovered and provided the first demonstration that c-ABL kinase activity could be modulated by an inhibitor that binds outside the ATP or substrate binding sites. GNF-2 binds to a myristoyl-binding pocket in the C-lobe of the c-ABL kinase domain but its mechanism of inhibiting specific BCR-ABL kinase targets remains unclear. We previously reported that BCR-ABL activates an autocrine IGF-1 pro-survival signaling pathway in CML blast crisis cells through HCK-mediated activation of STAT5b. As GNF-2 is known to inhibit STAT5b phosphorylation, and HCK myristolyation is known to regulate its cellular localization, we hypothesized that GNF-2 inhibits BCR-ABL activation of HCK by binding to the ABL myristoyl-binding pocket and blocking access to the HCK myristoyl moiety. In support of this hypothesis, we now show that GNF-2 inhibits HCK phosphorylation and IGF-1 activation, but not HCK binding to BCR-ABL. To confirm the importance of the HCK myristoyl moiety in HCK activation, we mutated the myristoyl attachment site at position 2 in HCK from glycine to alanine. The mutant G2A HCK still interacted with BCR-ABL in co-immunoprecipitation assays but showed significantly lower levels of phosphorylation compared to wild-type HCK. To confirm that the decrease in phosphorylation was not due to mislocalization of G2A HCK, we mutated the myristoylation binding pocket of BCR-ABL by changing glutamic acid at position 505 to lysine. Similar to G2A HCK, E505K BCR-ABL still interacted with HCK, but the phosphorylation levels of HCK were dramatically reduced. To confirm that the HCK myristoyl moiety directly interacted with the ABL myristoyl-binding pocket, we used fluorescent spectroscopy to measure the ability of a myristoylated peptide corresponding to the six N-terminal amino acids of HCK to displace GNF-2. The fluorescence of GNF-2 is enhanced when it associates with the myristoyl-binding pocket of ABL. Using this assay, we calculated the Kd of GNF-2 to be 180 nM. We then assayed the ability of myristolyated HCK peptide to displace GNF-2 from ABL. We calculated the IC50 of the myristolyated HCK peptide to be 25 μM when ABL was saturated with 300 nM GNF-2. Myristate showed an IC50 of 213 μM, which is ∼ 10-fold higher than the myristoylated peptide. No binding was detected between the non-myristoylated peptide and ABL. Together, our study highlights a novel acquired function resulting from the fusion of BCR to the N-terminus of ABL, which converts the myristoyl-binding pocket in ABL from a negative regulator of kinase activity to an HCK activation motif that activates downstream IGF-1 signaling. These results also reveal the mechanism of action of the mono-selective BCR-ABL inhibitor GNF-2 and highlight the ABL myristoyl-binding pocket as a therapeutic target for inhibiting BCR-ABL activity. Disclosures: No relevant conflicts of interest to declare.

scholarly journals The role of JAK2 inhibitors in MPNs 7 years after approval

Blood ◽  
2018 ◽  
Vol 131 (22) ◽  
pp. 2426-2435 ◽  
Author(s):  
Francesco Passamonti ◽  
Margherita Maffioli
Keyword(s):  
Myeloproliferative Neoplasms ◽  
Symptom Relief ◽  
Primary Myelofibrosis ◽  
Driver Mutations ◽  
Volume Response ◽  
Symptom Response ◽  
Definition Of ◽  
Jak2 Inhibitors

Abstract Myeloproliferative neoplasms (MPNs) include essential thrombocythemia, polycythemia vera (PV), and primary myelofibrosis (MF). Phenotype-driver mutations of JAK2, CALR, and MPL genes are present in MPNs and can be variably combined with additional mutations. Driver mutations entail a constitutive activation of the JAK2/STAT pathway, the key signaling cascade in MPNs. Among JAK2 inhibitors (JAKis), ruxolitinib (RUX) has been approved for the treatment of intermediate and high-risk MF and for PV inadequately controlled by or intolerant of hydroxyurea. Other JAKis, such as fedratinib and pacritinib, proved to be useful in MF. The primary end points in MF trials were spleen volume response (SVR) and symptom response, whereas in PV trials they were hematocrit control with or without spleen response. In advanced MF, RUX achieved a long lasting SVR of >35% in ∼60% of patients, establishing a new benchmark for MF treatment. RUX efficacy in early MF is also remarkable and toxicity is mild. In PV, RUX achieved hematocrit control in ∼60% of cases and SVR in 40%. Symptom relief was evident in both conditions. In the long-term, however, many MF patients lose their SVR. Indeed, the definition of RUX failure and the design of new trials in this setting are unmet needs. Decrease of hemoglobin/platelet levels and increased infection rates are the most common side effects of RUX, and nonmelanoma skin tumors need to be monitored while on treatment. In conclusion, the introduction of JAKis raises the bar of treatment goals in MF and PV.

scholarly journals Activated IL-6 signaling contributes to the pathogenesis of, and is a novel therapeutic target for, CALR-mutated MPNs

2021 ◽  
Vol 5 (8) ◽  
pp. 2184-2195
Author(s):  
Manjola Balliu ◽  
Laura Calabresi ◽  
Niccolò Bartalucci ◽  
Simone Romagnoli ◽  
Laura Maggi ◽  
...  
Keyword(s):  
Messenger Rna ◽  
Therapeutic Potential ◽  
Myeloproliferative Neoplasms ◽  
Supporting Cell ◽  
Loss Of Function ◽  
Wild Type ◽  
Colony Forming Unit ◽  
Thrombopoietin Receptor ◽  
Cd34 Cells

Abstract Calreticulin (CALR), an endoplasmic reticulum–associated chaperone, is frequently mutated in myeloproliferative neoplasms (MPNs). Mutated CALR promotes downstream JAK2/STAT5 signaling through interaction with, and activation of, the thrombopoietin receptor (MPL). Here, we provide evidence of a novel mechanism contributing to CALR-mutated MPNs, represented by abnormal activation of the interleukin 6 (IL-6)-signaling pathway. We found that UT7 and UT7/mpl cells, engineered by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) to express the CALR type 1–like (DEL) mutation, acquired cytokine independence and were primed to the megakaryocyte (Mk) lineage. Levels of IL-6 messenger RNA (mRNA), extracellular-released IL-6, membrane-associated glycoprotein 130 (gp130), and IL-6 receptor (IL-6R), phosphorylated JAK1 and STAT3 (p-JAK1 and p-STAT3), and IL-6 promoter region occupancy by STAT3 all resulted in increased CALR DEL cells in the absence of MPL stimulation. Wild-type, but not mutated, CALR physically interacted with gp130 and IL-6R, downregulating their expression on the cell membrane. Agents targeting gp130 (SC-144), IL-6R (tocilizumab [TCZ]), and cell-released IL-6 reduced proliferation of CALR DEL as well as CALR knockout cells, supporting a mutated CALR loss-of-function model. CD34+ cells from CALR-mutated patients showed increased levels of IL-6 mRNA and p-STAT3, and colony-forming unit–Mk growth was inhibited by either SC144 or TCZ, as well as an IL-6 antibody, supporting cell-autonomous activation of the IL-6 pathway. Targeting IL-6 signaling also reduced colony formation by CD34+ cells of JAK2V617F-mutated patients. The combination of TCZ and ruxolitinib was synergistic at very low nanomolar concentrations. Overall, our results suggest that target inhibition of IL-6 signaling may have therapeutic potential in CALR, and possibly JAK2V617F, mutated MPNs.

Clinical outcome in patients with metastatic colorectal cancer harboring KRAS p.G13D mutation treated with cetuximab.

2011 ◽  
Vol 29 (4_suppl) ◽  
pp. 448-448 ◽  
Author(s):  
H. Bando ◽  
T. Yoshino ◽  
E. Shinozaki ◽  
S. Yuki ◽  
T. Nishina ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Metastatic Colorectal Cancer ◽  
Statistical Significance ◽  
Progression Free Survival ◽  
Therapeutic Benefit ◽  
Combination Regimen ◽  
Wild Type ◽  
Kras Status ◽  
Clinical Benefits ◽  
Colorectal Cancer Patients

448 Background: Metastatic colorectal cancer patients with KRAS codon 12 or 13 mutated tumors are presently excluded from treatment with cetuximab (Cmab). On the other hand, a few patients who have mutated KRAS status occasionally respond to Cmab. The tumors of those patients predominantly had codon 13 mutation, and all codon 13 responder have mutation of p.G13D. We now compared the efficacy of Cmab among patients with p.G13D- mutant, other KRAS mutant and KRAS wild-type colorectal cancer. Methods: The patients from 9 Japanese institutions were retrospectively collected and analyzed. All patients were refractory to fluoropyrimidine, oxaliplatin and irinotecan, and were treated with Cmab and irinotecan combination regimen. Response rate (RR), progression-free survival (PFS) and overall survival (OS) were calculated respectively according to KRAS status. Results: Ninety four patients were treated with combination therapy. Among 94 cases, 7 cases were p.G13D-mutant KRAS, 23 cases were other mutant KRAS and 63 cases were wild-type KRAS. Baseline characteristics by each subset were well-balanced. While one partial response (PR) and 4 stable diseases (SD) cases were found in 7 p.G13D-mutated cases, no PR was found in other KRAS mutated cases. Median PFS of the patients with p.G13D-mutant, other KRAS mutant and KRAS wild-type were 4.5 months (95%CI 1.7-), 2.3 months (95%CI 1.9-4.3), 4.6 months (95%CI 3.5-6.5) respectively. And median OS of the patients with p.G13D- mutant, other KRAS mutant and KRAS wild-type were 9.3months (95%CI 8.5- 11.8), 7.4 months (95%CI 4.5-9.4), 12.2 months (95%CI 8.7-19.8) respectively. Although statistical significance was not found between the two mutated groups, there are trends that the patients with p.G13D-mutant may have received better clinical benefits from Cmab than the patients with other KRAS mutant. Conclusions: Cmab may have therapeutic benefit in the patients with KRAS p.G13D-mutant colorectal cancer although further evaluation is warranted. No significant financial relationships to disclose.

Changing Concepts of Diagnostic Criteria of Myeloproliferative Disorders and the Molecular Etiology and Classification of Myeloproliferative Neoplasms: From Dameshek 1950 to Vainchenker 2005 and Beyond

2014 ◽  
Vol 133 (1) ◽  
pp. 36-51 ◽  
Author(s):  
Jan Jacques Michiels ◽  
Zwi Berneman ◽  
Wilfried Schroyens ◽  
Hendrik De Raeve
Keyword(s):  
Bone Marrow ◽  
Polycythemia Vera ◽  
Myeloproliferative Neoplasms ◽  
Primary Myelofibrosis ◽  
Myeloproliferative Disorders ◽  
Jak2v617f Mutation ◽  
Wild Type ◽  
Mutation Load ◽  
Molecular Etiology ◽  
Calr Mutations

The Polycythemia Vera Study Group (PVSG) and WHO classifications distinguished the Philadelphia (Ph1) chromosome-positive chronic myeloid leukemia from the Ph1-negative myeloproliferative neoplasms (MPN) essential thrombocythemia (ET), polycythemia vera (PV) and primary myelofibrosis (MF) or primary megakaryocytic granulocytic myeloproliferation (PMGM). Half of PVSG/WHO-defined ET patients show low serum erythropoietin levels and carry the JAK2V617F mutation, indicating prodromal PV. The positive predictive value of a JAK2V617F PCR test is 95% for the diagnosis of PV, and about 50% for ET and MF. The WHO-defined JAK2V617F-positive ET comprises three ET phenotypes at clinical and bone marrow level when the integrated WHO and European Clinical, Molecular and Pathological (ECMP) criteria are applied: normocellular ET (WHO-ET), hypercellular ET due to increased erythropoiesis (prodromal PV) and hypercellular ET associated with megakaryocytic granulocytic myeloproliferation (EMGM). Four main molecular types of clonal MPN can be distinguished: JAK2V617F-positive ET and PV; JAK2 wild-type ET carrying the MPL515; mutations in the calreticulin (CALR) gene in JAK2/MPL wild-type ET and MF, and a small proportion of JAK2/MPL/CALR wild-type ET and MF patients. The JAK2V617F mutation load is low in heterozygous normocellular WHO-ET. The JAK2V617F mutation load in hetero-/homozygous PV and EMGM is clearly related to MPN disease burden in terms of splenomegaly, constitutional symptoms and fibrosis. The JAK2 wild-type ET carrying the MPL515 mutation is featured by clustered small and giant megakaryocytes with hyperlobulated stag-horn-like nuclei, in a normocellular bone marrow (WHO-ET), and lacks features of PV. JAK2/MPL wild-type, CALR mutated hypercellular ET associated with PMGM is featured by dense clustered large immature dysmorphic megakaryocytes and bulky (cloud-like) hyperchromatic nuclei, which are never seen in WHO-ECMP-defined JAK2V617F mutated ET, EMGM and PV, and neither in JAK2 wild-type ET carrying the MPL515 mutation. Two thirds of JAK2/MPL wild-type ET and MF patients carry one of the CALR mutations as the cause of the third distinct MPN entity. WHO-ECMP criteria are recommended to diagnose, classify and stage the broad spectrum of MPN of various molecular etiologies.

scholarly journals Small-molecule inhibitors in myeloproliferative neoplasms: are we aiming for the right targets?

Hematology ◽  
2012 ◽  
Vol 2012 (1) ◽  
pp. 553-560 ◽  
Author(s):  
Stefan N. Constantinescu ◽  
William Vainchenker
Keyword(s):  
Myeloproliferative Neoplasms ◽  
Binding Pocket ◽  
Kinase Domain ◽  
Wild Type ◽  
Time Treatment ◽  
Future Success ◽  
Epigenetic Regulators ◽  
The Right ◽  
First Time ◽  
Major Target

Abstract The ATP-binding pocket of the kinase domain of JAK2 is the major target of the present treatment of myeloproliferative neoplasms. Several inhibitors of JAK2 that are ATP competitive have been developed, but they do not discriminate between wild-type and mutant JAK2. These inhibitors have been used in myelofibrosis and, for the first time, treatment induced a reduction in spleen size and in constitutional symptoms. However, no dramatic effects on BM fibrosis, allele burden, or peripheral blast numbers were observed. These data indicate that other avenues should be explored that would either target mutant molecules (JAKs or receptors) more specifically and spare wild-type JAK2 or that would address other pathways that contribute to the malignant proliferation. Future success in treating myeloproliferative neoplasms will depend on advances of the understanding of JAK-STAT signaling and also on a better understanding of the disease pathogenesis, especially the role that mutants in spliceosome factors and epigenetic regulators play in the phenotype of the disease and the precise mechanism of fibrosis development.

Kinase Domain Mutations in JAK2V617F Confer Resistance to the Novel JAK2 Inhibitor Ruxolitinib

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 125-125
Author(s):  
Anagha Deshpande ◽  
Mamatha M. Reddy ◽  
Georg Schade ◽  
Arghya Ray ◽  
Tirumala K. Chowdary ◽  
...  
Keyword(s):  
Hydrophobic Interactions ◽  
Myeloproliferative Neoplasms ◽  
Point Mutations ◽  
Fold Increase ◽  
Binding Pocket ◽  
Kinase Domain ◽  
Drug Binding ◽  
Cross Resistance ◽  
Clinical Resistance ◽  
Jak2 Inhibitors

Abstract Abstract 125 The JAK2V617F kinase mutation is frequently associated with myeloproliferative neoplasms (MPNs) and thought to be instrumental for the overproduction of myeloid lineage cells. Ruxolitinib (INCB018424) and several additional small molecule drugs targeting JAK2 are currently in clinical development for treatment in these diseases. We performed a high-throughput in vitro screen to identify point mutations in JAK2V617F that would cause resistance to ruxolitinib. Seven libraries of mutagenized JAK2V617F cDNA were screened to specifically identify mutations in the predicted drug-binding region that would lower sensitivity towards ruxolitinib, using a cell-based assay. We found 5 different non-synonymous point mutations that conferred drug resistance, including Y931C, G935R, R938L, I960V and E985K. Cells containing mutations had a 9 to 33-fold higher EC50 for ruxolitinib. Results were analyzed by evaluating the three-dimensional structure of ruxolitinib bound to the ATP binding pocket of the monomer JAK2 kinase domain, using a docking algorithm. The inhibitor is held in the pocket by polar contacts and extensive hydrophobic interactions with several residues that line the binding pocket. A880, L855, V863 and M929 interact with the inhibitor on one side, and V911 and L983 provide hydrophobic interactions on the other side. The pyrazol ring of ruxolitinib appears to have a π-π interaction with the Y931 ring. Most mutations that were identified in our screen are either residues that interact with ruxolitinib or are in proximity to the binding pocket and hence are likely to indirectly alter inhibitor binding. The structural analysis indicates that there are additional residues in the kinase domain that may be critical for optimal binding of ruxolitinib and point mutations at these sites may also alter the affinity of the drug. Our analysis further suggests that ruxolitinib and other JAK2 inhibitors may bind in a similar way to the kinase domain. Consequently, these identified mutations conferred cross-resistance to all JAK2 kinase inhibitors tested in cell growth assays, including AZD1480 (5.6 to >7-fold higher EC50), TG101348 (2.2 to 2.8-fold increase in EC50), lestaurtinib (CEP-701) (2.6 to 3.3-fold increase in EC50) and CYT-387 (5.1 to 7.4-fold increase in EC50). Surprisingly, introduction of the ‘gatekeeper' mutation (M929I) in JAK2V617F affected only ruxolitinib sensitivity (4-fold increase in EC50). In addition, the E985K and Y931C mutations reduced the sensitivity to ruxolitinib and offered a growth advantage to cells during treatment, compared to native JAK2V617F expressing cells. These results suggest that the development of point mutations in JAK2 could result in clinical resistance to a wide variety of JAK2 inhibitors currently in clinical trials in patients with myeloproliferative neoplasms. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Dual targeting of JAK2 and ERK interferes with the myeloproliferative neoplasm clone and enhances therapeutic efficacy

Leukemia ◽  
2021 ◽  
Author(s):  
Sime Brkic ◽  
Simona Stivala ◽  
Alice Santopolo ◽  
Jakub Szybinski ◽  
Sarah Jungius ◽  
...  
Keyword(s):  
Therapeutic Efficacy ◽  
Mapk Pathway ◽  
Myeloproliferative Neoplasms ◽  
Myeloproliferative Neoplasm ◽  
Term Treatment ◽  
Wild Type ◽  
Jak2 Inhibitor ◽  
Dual Targeting ◽  
Clinical Benefits ◽  
Jak2 Inhibition

AbstractMyeloproliferative neoplasms (MPN) show dysregulated JAK2 signaling. JAK2 inhibitors provide clinical benefits, but compensatory activation of MAPK pathway signaling impedes efficacy. We hypothesized that dual targeting of JAK2 and ERK1/2 could enhance clone control and therapeutic efficacy. We employed genetic and pharmacologic targeting of ERK1/2 in Jak2V617F MPN mice, cells and patient clinical isolates. Competitive transplantations of Jak2V617F vs. wild-type bone marrow (BM) showed that ERK1/2 deficiency in hematopoiesis mitigated MPN features and reduced the Jak2V617F clone in blood and hematopoietic progenitor compartments. ERK1/2 ablation combined with JAK2 inhibition suppressed MAPK transcriptional programs, normalized cytoses and promoted clone control suggesting dual JAK2/ERK1/2 targeting as enhanced corrective approach. Combined pharmacologic JAK2/ERK1/2 inhibition with ruxolitinib and ERK inhibitors reduced proliferation of Jak2V617F cells and corrected erythrocytosis and splenomegaly of Jak2V617F MPN mice. Longer-term treatment was able to induce clone reductions. BM fibrosis was significantly decreased in MPLW515L-driven MPN to an extent not seen with JAK2 inhibitor monotherapy. Colony formation from JAK2V617F patients’ CD34+ blood and BM was dose-dependently inhibited by combined JAK2/ERK1/2 inhibition in PV, ET, and MF subsets. Overall, we observed that dual targeting of JAK2 and ERK1/2 was able to enhance therapeutic efficacy suggesting a novel treatment approach for MPN.

The Behavior of Cytogenetic/Molecular Markers Associated with JAK2 Mutation Status Before and After Primary Myelofibrosis Progression Supports the Hypothesis of the Leukemic Clone's Independence From the JAK2 Mutation

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 5058-5058
Author(s):  
Francesco Albano ◽  
Antonella Zagaria ◽  
Luisa Anelli ◽  
Nicoletta Coccaro ◽  
Giuseppina Tota ◽  
...  
Keyword(s):  
Conflicts Of Interest ◽  
Myeloproliferative Neoplasms ◽  
Chronic Phase ◽  
Primary Myelofibrosis ◽  
Jak2v617f Mutation ◽  
Wild Type ◽  
Jak2 Mutation ◽  
Cytogenetic Abnormalities ◽  
Qrt Pcr ◽  
Leukemic Clone

Abstract Abstract 5058 Leukemic transformation has been reported in 15–30% of primary myelofibrosis (PMF). However, very little is known about the molecular bases responsible for acute myeloid leukemia (AML) transformation. JAK2 status analysis of paired chronic myeloproliferative neoplasms (MPN) and AML samples showed that during AML transformation the JAK2 mutation could be lost. Two probable models have been proposed to explain the MPN evolution to AML: a) JAK2-mutated AML usually arose from PMF or myelofibrotic transformation of ET/PV as a consequence of genetic instability conferred by the presence of JAK2 mutations; b) JAK2 wild-type AML generally developed in patients with chronic-phase ET or PV, frequently as a consequence of a clone selection driven by the therapy (Thoennissen NH et al. Blood 2010, 115:2882; Beer PA et al., Blood 2010, 115:2891; Spivak JL, Blood 2010, 115:2727). In this report we describe two PMF cases with the JAK2V617F mutation associated with molecular/cytogenetic abnormalities who developed JAK2-wild type AML characterized by a leukemic clone bearing a new cytogenetic aberration. At the PMF diagnosis, Case #1 showed a normal karyotype 46, XY[20] and resulted JAK2V617F positive. Molecular analyses performed at the time of AML transformation revealed the presence of a JAK2V617F negative clone bearing a novel t(12;18)(p13;q12) rearrangement. As the t(12;18) breakpoints were located centromerically to SETBP1 (18q12. 3), quantitative real-time PCR (qRT-PCR) experiments were made, showing SETBP1 overexpression. To investigate the occurrence of SETBP1 dysregulation and the presence of t(12;18) at PMF onset, qRT-PCR and Fluorescence in situ hybridization were performed, revealing gene overexpression and absence of the chromosomal translocation, respectively. At PMF onset, Case #2 harbored a novel t(3;5)(q27. 1;q31. 1) in addition to the JAK2V617F mutation. At the time of AML evolution, disappearance of the t(3;5)(q27. 1;q31. 1) and leukemic clone expansion of t(3;3)(q21. 3;q26. 2) was associated with disappearance of the JAK2V617F mutation. In contrast to literature data showing that JAK2 mutation loss is commonly associated with AML transformation after PV and ET, our findings suggest that evolution to JAK2-wild type AML could also occur in JAK2V617F PMF patients. The presence of different cytogenetic abnormalities associated with PMF and AML allowed us to follow the sequence of molecular events that lead to JAK2V617F disappearance, indicating that MPN and AML are clonally unrelated and probably generated by the transformation of different stem cell levels. Moreover, the well-documented clonal heterogeneity landscape in our cases demonstrated that the genomic instability responsible for AML transformation already existed at PMF onset and was not generated either by JAK2V617F mutation expression or by the therapy. Disclosures: No relevant conflicts of interest to declare.

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