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Mutant calreticulin (CALR) proteins resulting from a -1/+2 frameshifting mutation of the CALR exon 9 carry a novel C-terminal amino acid sequence and drive the development of myeloproliferative neoplasms (MPNs). Mutant CALRs were shown to interact with and activate the thrombopoietin receptor (TpoR/MPL) in the same cell. We report that mutant CALR proteins are secreted and can be found in patient plasma at levels up to 160 ng/mL, with a mean of 25.64 ng/mL. Plasma mutant CALR is found in complex with soluble transferrin receptor 1 (sTFR1) that acts as a carrier protein and increases mutant CALR half-life. Recombinant mutant CALR proteins bound and activated the TpoR in cell lines and primary megakaryocytic progenitors from patients with mutated CALR in which they drive thrombopoietin-independent colony formation. Importantly, the CALR-sTFR1 complex remains functional for TpoR activation. By bioluminescence resonance energy transfer assay, we show that mutant CALR proteins produced in 1 cell can specifically interact in trans with the TpoR on a target cell. In comparison with cells that only carry TpoR, cells that carry both TpoR and mutant CALR are hypersensitive to exogenous mutant CALR proteins and respond to levels of mutant CALR proteins similar to those in patient plasma. This is consistent with CALR-mutated cells that expose TpoR carrying immature N-linked sugars at the cell surface. Thus, secreted mutant CALR proteins will act more specifically on the MPN clone. In conclusion, a chaperone, CALR, can turn into a rogue cytokine through somatic mutation of its encoding gene., (© 2023 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Introduction: Myeloproliferative neoplasms (MPNs) include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Patients with MPNs are prone to develop arterial and venous thrombosis either at diagnosis or during follow-up; in particular splancnic vein is strongly associated with MPN. Conversely, presence of MPN is uncommon in patients with deep vein thrombosis of the lower extremities and with pulmonary embolism. Only few studies with conflicting results have evaluated the prevalence of an underlying MPN in patients with cerebral venous thrombosis (CVT), and limited evidence exists on the incidence of CVT in patients with established MPN., Methods: We assessed the frequency of MPNs in a series of 706 patients with cerebral vein thrombosis (CVT) and the frequency of CVT in a cohort of 2,143 MPNs patients., Results: Twenty-seven CVT patients (3.8%) were diagnosed with MPN: 9 before CVT (1.3%), 4 concomitantly (0.6%), and 14 after CVT (2.0%). Nine CVT cases (0.4%) were diagnosed in the MPN cohort, with a slightly higher frequency in PV (five of 735, 0.7%) than in ET (three of 964, 0.3%) and in PMF (one of 444, 0.2%)., Conclusion: Considering the analyses of these databases jointly, the results obtained suggest a weak association between CVT and MPNs and ultimately suggest that a thorough investigation looking for an underlying MPN may not be warranted in all the patients with CVT without overt myeloproliferative features., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

We studied mutations of MPL exon 10 in patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF), first investigating a cohort of 892 consecutive patients. MPL mutation scanning was performed on granulocyte genomic DNA by using a high-resolution melt assay, and the mutant allele burden was evaluated by using deep sequencing. Somatic mutations of MPL, all but one involving codon W515, were detected in 26/661 (4%) patients with ET, 10/187 (5%) with PMF, and 7/44 (16%) patients with post-ET myelofibrosis. Comparison of JAK2 (V617F)-mutated and MPL-mutated patients showed only minor phenotypic differences. In an extended group of 62 MPL-mutated patients, the granulocyte mutant allele burden ranged from 1% to 95% and was significantly higher in patients with PMF or post-ET myelofibrosis compared with those with ET. Patients with higher mutation burdens had evidence of acquired copy-neutral loss of heterozygosity (CN-LOH) of chromosome 1p in granulocytes, consistent with a transition from heterozygosity to homozygosity for the MPL mutation in clonal cells. A significant association was found between MPL-mutant allele burden greater than 50% and marrow fibrosis. These observations suggest that acquired CN-LOH of chromosome 1p involving the MPL location may represent a molecular mechanism of fibrotic transformation in MPL-mutated myeloproliferative neoplasms.

Background: Myeloproliferative neoplasms (MPNs) include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). Somatic mutations in exon 10 of the MPL (myeloproliferative leukemia virus oncogene) gene, mainly substitutions encoding W515 variants, have recently been described in a minority of patients with ET or PMF. We optimized analytically sensitive methods for detecting and genotyping MPL variants., Methods: We used DNA previously isolated from circulating granulocytes of 60 patients with MPN that had previously been analyzed by high-resolution melting (HRM), direct sequencing, and the TaqMan allelic-discrimination assay. We developed conditions for enriching tumor mutant alleles with COLD-PCR (coamplification at lower denaturation temperature PCR) and coupled it with direct sequencing. Assays were designed for identifying MPL W515 substitutions with full COLD-PCR protocols. In parallel, we used innovative microarray substrates to develop assays for evaluating the mutant burden in granulocyte cells., Results: Mutations that were present at very low levels in patients who had previously been scored as having an MPL variant by HRM and as wild type by direct sequencing were successfully identified in granulocyte DNA. Notably, the microarray approach displayed analytical sensitivities of 0.1% to 5% mutant allele, depending on the particular mutation. This analytical sensitivity is similar to that obtained with COLD-PCR. The assay requires no enrichment strategy and allows both the characterization of each variant allele and the evaluation of its proportion in every patient., Conclusions: These procedures, which are transferable to clinical diagnostic laboratories, can be used for detecting very low proportions of minority mutant alleles that cannot be identified by other, conventional methods., (© 2012 American Association for Clinical Chemistry)

JAK2 (V617F) is associated with a genetic predisposition to its acquisition,as it is preferentially found in subjects with a common constitutional JAK2 haplotype known as 46/1 or GGCC. A recent study suggests that a genetic predisposition to acquisition of MPL mutation may exist in sporadic patients, since an association was found with the JAK2 46/1 haplotype. We genotyped 509 patients with myeloproliferative neoplasms (MPN), 7% of which carrying a somatic mutation of MPL Exon 10. We found that the JAK2 GGCC haplotype was closely associated with JAK2 (V617F) (OR 1.84, P < 0.001) but not with MPL mutations (OR 0.98), suggesting a different genetic background for these molecular lesions.

Myeloproliferative neoplasms (MPN) include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). These disorders may undergo phenotypic shifts, and may specifically evolve into secondary myelofibrosis (MF) or acute myeloid leukemia (AML). We studied genomic changes associated with these transformations in 29 patients who had serial samples collected in different phases of disease. Genomic DNA from granulocytes, i.e., the myeloproliferative genome, was processed and hybridized to genome-wide human SNP 6.0 arrays. Most patients in chronic phase had chromosomal regions with uniparental disomy (UPD) and/or copy number changes. Disease progression to secondary MF or AML was associated with the acquisition of additional chromosomal aberrations in granulocytes (P = 0.002). A close relationship was observed between aberrations of chromosome 9p (UPD and/or gain) and progression from PV to post-PV MF (P = 0.002). The acquisition of one or more aberrations involving chromosome 5, 7, or 17p was specifically associated with progression to AML (OR 5.9, 95% CI 1.2-27.7, P = 0.006), and significantly affected overall survival (HR 18, 95% CI 1.9-164, P = 0.01). These observations indicate that disease progression from chronic-phase MPN to secondary MF or AML is associated with specific chromosomal aberrations that can be detected by means of high-resolution SNP array analysis of granulocyte DNA., (Copyright © 2011 Wiley-Liss, Inc.)

Until few years ago, HIV infection was an absolute contraindication to consider organ transplants. Since HAART introduction, patient survival increased dramatically, but high mortality due to liver and kidney diseases became evident. For these reasons, this group of patients is now reconsidered for organ transplantation. In 2008, the Argentine Society of Transplants (SAT) and the Argentine Infectious Diseases Society (SADI), encouraged by the increasing published experience on kidney and liver transplants in this population, decided to form a Working Group, to prepare an update on this issue and elaborate practical recommendations for the better management of these patients. The first meeting was held on December 4th 2008. The most important conclusion was that HIV infection did not contraindicate a solid organ transplant. Later on, taking into account the accumulated experience and the available literature, the current document was prepared. HIV infected patients must fulfill certain clinical, immunological, virological and psychosocial criteria to be considered for solid organ transplants. HIV infected recipients of kidney and liver transplants currently show similar short and middle term survival to non HIV infected patients. There is not yet enough data on intrathoracic transplants in these patients in order to include them on a waiting list for these organs-transplants. Interactions between immunosupressors and antiretroviral drugs (specially protease inhibitors) are very important, and require a strict monitoring of immunosupressor levels.