Assessment of intestinal status in MPLW515L mutant myeloproliferative neoplasms mice model.

The MPLW515L mutation is a prevalent genetic mutation in patients with myeloproliferative neoplasms (MPN), and utilizing this mutation in mice model can provide important insights into the disease. However, the relationship between intestinal homeostasis and MPN mice model remains elusive. In this study, we utilized a retroviral vector to transfect hematopoietic stem cells with the MPLW515L mutation, creating mutated MPN mice model to investigate their intestinal status. Our results revealed that the MPLW515L in MPN mice model aggravated inflammation in the intestines, decreased the levels of tight junction proteins and receptors for bacteria metabolites. Additionally, there was increased activation of the caspase1/IL-1ß signaling pathway and a significant reduction in phos-p38 levels in the intestinal tissue in MPN mice. The MPLW515L mutation also led to up-expression of anti-microbial genes in the intestinal tract. Though the mutation had no impact on the alpha diversity and dominant bacterial taxa, it did influence the rare bacterial taxa/sub-communities and consequently impacted intestinal homeostasis. Our findings demonstrate the significance of MPLW515L mice model for studying MPN disease and highlight the mutation's influence on intestinal homeostasis, including inflammation, activation of the IL-1ß signaling pathway, and the composition of gut microbial communities.

A customized mass array panel for BCR::ABL1 tyrosine kinase domain mutation screening in chronic myeloid leukemia.

Introduction: The therapeutic strategy and management of chronic myeloid leukemia (CML) have rapidly improved with the discovery of effective tyrosine kinase inhibitors (TKIs) to target BCR::ABL1 oncoprotein. However, nearly 30% of patients develop TKI resistance due to acquired mutations on the tyrosine kinase domain (TKD) of BCR::ABL1. Methods: We customized a mass array panel initially intended to detect and monitor the mutational burden of hotspot BCR::ABL1 TKD mutations accumulated in our database, including key mutations recently recommended by European LeukemiaNet. Additionally, we extended the feasibility of using the assay panel for the molecular classification of myeloproliferative neoplasms (MPNs) by incorporating primer sets specific for analyzing JAK2 V617F, MPL 515 K/L, and CALR types 1 and 2. Results: We found that the developed mass array panel was superior for detecting and monitoring clinically significant BCR::ABL1 TKD mutations, especially in cases with low mutational burden and harboring compound/polyclonal mutations, compared with direct sequencing. Moreover, our customized mass array panel detected common genetic alterations in MPNs, and the findings were consistent with those of other comparable assays available in our laboratory. Conclusions: Our customized mass array panel was practicably used as a routine robust assay for screening and monitoring BCR::ABL1 TKD mutations in patients with CML undergoing TKI treatment and feasible for analyzing common genetic mutations in MPNs.

Low JAK2 V617F Allele Burden in Ph-Negative Chronic Myeloproliferative Neoplasms Is Associated with Additional CALR or MPL Gene Mutations.

JAK2 (Janus kinase 2) V617F, CALR (Calreticulin) exon 9, and MPL (receptor for thrombopoietin) exon 10 mutations are associated with the vast majority of Ph-negative chronic myeloproliferative neoplasms (MPNs). These mutations affect sequential stages of proliferative signal transduction and therefore, after the emergence of one type of mutation, other types should not have any selective advantages for clonal expansion. However, simultaneous findings of these mutations have been reported by different investigators in up to 10% of MPN cases. Our study includes DNA samples from 1958 patients with clinical evidence of MPN, admitted to the National Research Center for Hematology for genetic analysis between 2016 and 2019. In 315 of 1402 cases (22.6%), CALR mutations were detected. In 23 of these 315 cases (7.3%), the JAK2 V617F mutation was found in addition to the CALR mutation. In 16 from 24 (69.6%) cases, with combined CALR and JAK2 mutations, V617F allele burden was lower than 1%. A combination of JAK2 V617F with MPL W515L/K was also observed in 1 out of 1348 cases, only. JAK2 allele burden in this case was also lower than 1%. Additional mutations may coexist over the low background of JAK2 V617F allele. Therefore, in cases of detecting MPNs with a low allelic load JAK2 V617F, it may be advisable to search for other molecular markers, primarily mutations in exon 9 of CALR. The load of the combined mutations measured at different time points may indicate that, at least in some cases, these mutations could be represented by different clones of malignant cells.

MPL exon 10 mutations other than canonical MPL W515L/K mutations identified by in-house MPL exon 10 direct sequencing in essential thrombocythemia.

MPL exon 10 mutations are one of the driver mutations in essential thrombocythemia (ET) or myelofibrosis (MF). We have established an in-house MPL mutation analysis system, covering the entire region of MPL exon 10 by direct sequencing. Since 2009, MPL exon 10 mutation analysis has been performed for diagnosis of myeloproliferative neoplasms (MPN) without JAK2 V617F or CALR exon 9 mutations. So far, 11 cases of MPL exon 10 mutation have been found in 51 patients with suspected MPN. In patients with ET, we detected five non-canonical MPL mutations including one novel mutation, MPL R514_P518delinsK, and one canonical MPL W515L mutation. Notably, three ET patients without canonical MPL mutations had thrombotic events. Meanwhile, in primary or secondary MF, only canonical MPL W515L/K mutations were found. Further cases need to be examined to elucidate the full MPL mutation profile in MPN. However, our data indicate that analysis of the whole of MPL exon 10 is warranted for the diagnosis of MPL mutations, especially in ET, and that the use of Japanese commercial laboratory tests that only detect canonical MPL W515L/K mutations may miss a significant percentage of MPL exon 10 mutations, which could delay the administration of anti-thrombotic therapy.

The Role of New Technologies in Myeloproliferative Neoplasms.

The hallmark of BCR-ABL1-negative myeloproliferative neoplasms (MPNs) is the presence of a driver mutation in JAK2, CALR, or MPL gene. These genetic alterations represent a key feature, useful for diagnostic, prognostic and therapeutical approaches. Molecular biology tests are now widely available with different specificity and sensitivity. Recently, the allele burden quantification of driver mutations has become a useful tool, both for prognostication and efficacy evaluation of therapies. Moreover, other sub-clonal mutations have been reported in MPN patients, which are associated with poorer prognosis. ASXL1 mutation appears to be the worst amongst them. Both driver and sub-clonal mutations are now taken into consideration in new prognostic scoring systems and may be better investigated using next generation sequence (NGS) technology. In this review we summarize the value of NGS and its contribution in providing a comprehensive picture of mutational landscape to guide treatment decisions. Finally, discussing the role that NGS has in defining the potential risk of disease development, we forecast NGS as the standard molecular biology technique for evaluating these patients.

Prevalence of MPL (W515K/L) Mutations in Patients with Negative-JAK2 (V617F) Myeloproliferative Neoplasm in North-East of Iran.

BACKGROUND AND OBJECTIVE: Janus kinase 2 (JAK2) and Myeloproliferative Leukemia (MPL) mutations are confirmatory indicators for Myeloproliferative Neoplasm (MPN). The current study was performed to determine the frequency of MPL mutation in MPN patients without JAK2 mutation, in order to assign MPL mutation frequency in North-East of Iran. METHODS: Total of 105 negative JAK2 cases including 5 Myeloproliferative Disorders (MPD), 15 Polycytemia Vera (PV) and 15 Essential Thrombocytosis (ET) who referred to Qaem Medical Center were assigned to this study. ARMS-PCR was carried out for measuring MPL mutations. RESULTS: A significant difference was observed between MPL mutant and non-mutant groups from overview of MPL mutation (P=0.00001). From the total studied population, 14.28% were ET cases and 4.71% of them had splenomegaly. About 66.66% had thrombocytosis and 33.33% of all the individuals had leukocytosis according to WHO criteria, and 4.76% of non-MPL mutant individuals had splenomegaly (P=1).This mutation was reported in 4-6% of ET and PMF individuals. In this research, 4.76 % of studied individuals had MPL (W515L/K) mutation, which were diagnosed with ET. CONCLUSION: Generally, the presence of JAK2 and MPL mutations are the most important criteria for MPN diagnosis. The obtained frequency of MPL mutation was similar to previous studies. Despite the high frequency of JAK2 and Philadelphia abnormality, MPL mutation was rare in myeloprolifrative disorders. Further studies are suggested to investigate its prognostic effects for these diseases.

Tyrosine 625 plays a key role and cooperates with tyrosine 630 in MPL W515L-induced signaling and myeloproliferative neoplasms.

BACKGROUND: Myeloproliferative neoplasms (MPN) are a group of blood cancers that boost normal blood cell production in the bone marrow. Abnormal mutations in stem cells were found accompanying with the occurrence of MPN. It has been shown that MPL mutations (MPL W515L or MPL W515K) were involved in patients with MPN. Since tyrosine residues 625 and 630 mediate normal MPL signaling, whether them affect MPL W515L-induced myeloproliferative neoplasms (MPNs) is unknown. RESULTS: In this study, we further tested their functions in MPL W515L-induced myeloproliferative neoplasms (MPNs) by substituting either or both of them with phenylalanine in MPL W515L (termed as MPL515/625, MPL515/630 and MPL515/625/630, respectively). In vitro, MPL515/630 but not MPL515/625 or MPL515/625/630 retained the ability to induce TPO-independent proliferation and increase colony-forming unit megakaryocytes (CFU-Mk). Accordingly, differential activation of the downstream signaling by four mutants was observed and constitutively active STAT5 or AKT instead of STAT3 partially compensated MPL515/625/630 function. Further support this, STAT5-deficiency impaired MPL W515L-induced CFU-Mk expansion. In vivo, MPL515/630 but not MPL515/625 or MPL515/625/630 induced typical features of MPNs with high WBC and platelet counts, splenomegaly, hepatomegaly and hypercellularity in the bone marrow. Surprisingly, MPL515/625 also caused hypercellularity of bone marrow and splenomegaly without any other significant features. We also observed differential effects of the four mutants on progenitors, myeloid cells and megakaryocytes. CONCLUSIONS: Our studies have revealed distinct features of tyrosine sites 625 and 630 in mediating MPL W515L-induced megakaryocyte hyperproliferation and MPNs. Our study also suggests that MPL cytosolic phosphorylated Y625 and flanking amino acids could become targets for pharmacologic inhibition in MPNs.

The mutation profile of JAK2, MPL and CALR in Mexican patients with Philadelphia chromosome-negative myeloproliferative neoplasms.

CONTEXT AND OBJECTIVE: By using molecular markers, it is possible to gain information on both the classification and etiopathogenesis of chronic myeloproliferative neoplasias (MPN). METHODS: In a group of 27 Mexican mestizo patients with MPNs, we studied seven molecular markers: the BCR/ABL1 fusion gene, the JAK2 V617F mutation, the JAK2 exon 12 mutations, the MPL W515L mutation, the MPL W515K mutation, and the calreticulin (CALR) exon 9 deletion or insertion. Patients with the BCR/ABL1 fusion gene were excluded. We studied 14 patients with essential thrombocythemia (ET), eight with polycythemia vera (PV), four with primary myelofibrosis (MF), and one with undifferentiated MPN. RESULTS: We found twelve individuals with the JAK2 V617F mutation; five of them had been clinically classified as PV, five as ET, and one as MF. One patient with the MPL W515L was identified with a clinical picture of ET. Five patients with the CALR mutation were identified, four ET and one MF. No individuals with either the MPL W515K mutation or the JAK2 exon 12 mutations were identified. The most consistent relationship was that between PV and the JAK2 V617F mutation (p=.01). CONCLUSIONS: Despite its small size, the study shows much less prevalence of JAK2 mutation in PV, ET and MF, which does not match international data.

Frequency and Clinicohematologic Characteristics of MPL W515 Mutations in Patients with Myeloproliferative Neoplasms

BACKGROUND: Recently, myeloproliferative leukemia (MPL) W515 mutations have been reported to be molecular markers for myeloproliferative neoplasms (MPNs). We studied the association between MPL W515 mutations and the clinico-hematological features of patients with MPNs. METHODS: Our study included 154 consecutive patients diagnosed with MPNs (31 had polycythemia vera [PV]; 106, essential thrombocythemia [ET]; and 17, primary myelofibrosis [PMF]). MPL W515 mutations were detected by real-time PCR and direct sequencing methods. RESULTS: The MPL W515L mutation was found in 4 patients and the MPL W515A mutation was detected in 1 patient. These 5 patients were diagnosed with JAK2 V617F-negative ET, and they accounted for 12.5% of patients with JAK2 V617F-negative ET. The patients with MPL W515-positive ET showed significantly lower hemoglobin levels and WBC counts than did patients with MPL W515-negative ET or JAK2 V617F-positive ET. CONCLUSIONS: MPL W515 mutation is a useful diagnostic marker for JAK2 V617F-negative MPNs and it is associated with specific hematologic characteristics such as lower hemoglobin levels and WBC counts.

MPL W515L/K Mutations in Chronic Myeloproliferative Neoplasms.

OBJECTIVE: The MPL gene encodes the thrombopoietin receptor. Recently MPL mutations (MPL W515L or MPL W515K) were described in patients with essential thrombocythemia (ET) and primary (idiopathic) myelofibrosis (PMF). The prevalence and the clinical importance of these mutations are not clear. In the present study, we aimed to investigate the frequency and clinical significance of MPL W515L/K mutations in our patients with ET and PMF. MATERIALS AND METHODS: A total of 77 patients (66 were diagnosed with ET and 11 with PMF) and 42 healthy controls were included in the study. Using peripheral blood samples, the presence of MPL W515L/K mutations and JAK-2 V617F mutation were analyzed by real-time polymerase chain reaction. RESULTS: In our study, MPL W515L/K or JAK-2 V617F mutations were not observed in healthy controls. JAK-2 V617F mutation was present in 35 patients, of whom 29 had ET (43.9%, 29/66) and 6 had PMF (54.5%, 6/11). In the patient group, MPL W515L/K mutations were found in only 2 PMF cases, and these cases were negative for JAK-2 V617F mutation. The prevalence of MPL W515L/K mutations in the patient group was 2.6%, and the prevalence of MPL W515L/K mutations among the cases negative for the JAK-2 V617F mutation was found to be 4.8%. The 2 cases with MPL W515L/K mutations had long follow-up times (124 months and 71 months, respectively), had no thrombotic or hemorrhagic complications, and had no additional cytogenetic anomalies. CONCLUSION: MPL W515L/K mutations may be helpful for identifying clonal disease in MPN patients with no established Ph chromosome or JAK-2 V617F mutation. CONFLICT OF INTEREST: None declared.

JAK2 V617F, MPL W515L and JAK2 Exon 12 Mutations in Chinese Patients with Primary Myelofibrosis.

OBJECTIVE: JAK2 V617F, MPL W515L and JAK2 exon 12 mutations are novel acquired mutations that induce constitutive cytokine-independent activation of the JAK-STAT pathway in myeloproliferative disorders (MPD). The discovery of these mutations provides novel mechanism for activation of signal transduction in hematopoietic malignancies. This research was to investigate their prevalence in Chinese patients with primary myelofibrosis (PMF). METHODS: We introduced allele-specific PCR (AS-PCR) combined with sequence analysis to simultaneously screen JAK2 V617F, MPL W515L and JAK2 exon 12 mutations in 30 patients with PMF. RESULTS: Fifteen PMF patients (50.0%) carried JAK2 V617F mutation, and only two JAK2 V617F-negative patients (6.7%) harbored MPL W515L mutation. None had JAK2 exon 12 mutations. Furthermore, these three mutations were not detected in 50 healthy controls. CONCLUSION: MPL W515L and JAK2 V617F mutations existed in PMF patients but JAK2 exon 12 mutations not. JAK2 V617F and MPL W515L and mutations might contribute to the primary molecular pathogenesis in patients with PMF.