Frequencies, Laboratory Features, and Granulocyte Activation in Chinese Patients with CALR-Mutated Myeloproliferative Neoplasms

Immunophenotype of myeloid granulocytes in Chinese patients with BCR::ABL1-negative myeloproliferative neoplasms

Typical BCR::ABL1-negative myeloproliferative neoplasms (MPN) are mainly referred to as polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofbrosis (PMF). Granulocytes in MPN patients are involved in their inflammation and form an important part of the pathophysiology of MPN patients. It has been shown that the immunophenotype of granulocytes in MPN patients is altered. We used flow cytometry to explore the immunophenotype of MPN patients and correlate it with clinical parameters. The results showed that PMF patients and PV patients had higher CD15+CD11b+ granulocytes than ET patients and normal controls. When grouped by gene mutation, changes in the granulocyte immunophenotype of MPN patients were independent of the JAK2V617F and CALR mutations. There was no significant heterogeneity in immunophenotype between ET patients and Pre-PMF, and between Overt-PMF and Pre-PMF patients. Granulocytes from some MPN patients showed an abnormal CD13/CD16 phenotype with a significant increase in mature granulocytes on molecular and cytomorphological grounds, and this abnormal pattern occurred significantly more frequently in PMF patients than in ET patients. CD15-CD11b- was negatively correlated with WBC and Hb and positively correlated with DIPSS score, whereas high CD10+ granulocytes were significantly and negatively associated with prognostic system IPSS and DIPSS scores in PMF patients. In conclusion, this study demonstrates the landscape of bone marrow granulocyte immunophenotypes in MPN patients. MPN patients, especially those with PMF, have a significant granulocyte developmental overmaturation phenotype. CD10+ granulocytes may be involved in the prognosis of PMF patients.

Proteogenetic drug response profiling elucidates targetable vulnerabilities of myelofibrosis

Myelofibrosis is a hematopoietic stem cell disorder belonging to the myeloproliferative neoplasms. Myelofibrosis patients frequently carry driver mutations in either JAK2 or Calreticulin (CALR) and have limited therapeutic options. Here, we integrate ex vivo drug response and proteotype analyses across myelofibrosis patient cohorts to discover targetable vulnerabilities and associated therapeutic strategies. Drug sensitivities of mutated and progenitor cells were measured in patient blood using high-content imaging and single-cell deep learning-based analyses. Integration with matched molecular profiling revealed three targetable vulnerabilities. First, CALR mutations drive BET and HDAC inhibitor sensitivity, particularly in the absence of high Ras pathway protein levels. Second, an MCM complex-high proliferative signature corresponds to advanced disease and sensitivity to drugs targeting pro-survival signaling and DNA replication. Third, homozygous CALR mutations result in high endoplasmic reticulum (ER) stress, responding to ER stressors and unfolded protein response inhibition. Overall, our integrated analyses provide a molecularly motivated roadmap for individualized myelofibrosis patient treatment.

Novel Pathophysiological Mechanisms of Thrombosis in Myeloproliferative Neoplasms

PURPOSE OF REVIEW

Thrombosis remains a leading cause of morbidity and mortality in BCR/ABL negative myeloproliferative neoplasms (MPN). Circulating blood cells are both increased in quantity and qualitatively abnormal in MPN, resulting in an increased thrombotic risk. Herein, we review recently elucidated mechanisms of MPN thrombosis and discuss implications of drugs currently under investigation for MPN.

RECENT FINDINGS

Recent studies highlight that in JAK2^V617F granulocytes and platelets, thrombo-inflammatory genes are upregulated. Furthermore, in JAK2^V617F granulocytes, protein expression of integrin CD11b, tissue factor, and leukocyte alkaline phosphatase are all increased. Overall, myeloid cells, namely neutrophils, may contribute in several ways, such as through increased adhesion via β1 integrin binding to VCAM1, increased infiltration, and enhanced inducibility to extrude neutrophil extracellular traps. Non-myeloid inflammatory cells may also contribute via secretion of cytokines. With regard to red blood cells, number, rigidity, adhesion, and generation of microvesicles may lead to increased vascular resistance as well as increased cell-cell interactions that promote rolling and adhesion. Platelets may also contribute in a similar fashion. Lastly, the vasculature is also increasingly appreciated, as several studies have demonstrated increased endothelial expression of pro-coagulant and pro-adhesive proteins, such as von Willebrand factor or P-selectin in JAK2^V617F endothelial cells. With the advent of molecular diagnostics, MPN therapeutics are advancing beyond cytoreduction. Our increased understanding of pro-inflammatory and thrombotic pathophysiology in MPN provides a rational basis for evaluation of in-development MPN therapeutics to reduce thrombosis.

Mutation profile in Indian primary myelofibrosis patients and its clinical implications

Background:

Primary myelofibrosis (PMF) is a myeloproliferative neoplasm (MPN) characterized by abnormal proliferation of megakaryocytes, bone marrow fibrosis, and extramedullary hematopoiesis. We did mutation profile of 50 patients of PMF and tried to correlate it with initial clinical presentation of these patients.

Materials and Methods:

All new and follow up patients who were diagnosed as PMF based on WHO 2016 definition of PMF were included. Mutation profile of these patients including JAK2 V617F, JAK2 exon 12, CALR and MPL mutations was done and all clinical, demographic and laboratory details were recorded.

Results:

Total 50 patients were enrolled out of which 29 were males and 21 were females. Out of these patients, 32 (64%) were JAK2 positive, 13 (26%) were CALR positive, 1 (2%) were MPL positive and 4 (8%) were triple negative. As compared to JAK2+ve patients and triple negative group, CALR positive patients were younger, had lower total leucocyte count, larger spleen size, lower dynamic international prognostic scoring system (DIPSS) score and higher grade of fibrosis of marrow.

Conclusion:

This study depicts that incidence of JAK2 and CALR mutations in Indian PMF patients is fairly similar to that in rest of the world. CALR positive patients have better clinical parameters at presentation and have better prognosis as compared to JAK2 positive patients.

[Clinical significance of JAK2、CALR and MPL gene mutations in 1 648 Philadelphia chromosome negative myeloproliferative neoplasms patients from a single center]

目的

研究Ph染色体阴性的慢性骨髓增殖性肿瘤（MPN）患者JAK2、CALR及MPL基因突变情况，比较不同类型基因突变及突变阴性患者部分临床参数的差异。

方法

采用基因测序法分别检测1 648例Ph阴性MPN患者JAK2V617F、JAK2基因12号外显子、CALR基因9号外显子及MPL基因10号外显子突变情况。

结果

①JAK2V617F突变总检出率为82.8%（1 364/1 648），其中真性红细胞增多症（PV）为92.7%（471/508），原发性血小板增多症（ET）为78.1%（819/1 049），原发性骨髓纤维化（PMF）为81.3%（74/91）；JAK2基因12号外显子突变总检出率为0.5%（9/1 648），均为PV患者[1.7%（9/508）]；CALR基因突变总检出率为8.7%（143/1 648）,其中ET为12.6%（132/1 049），PMF为12.1%（11/91）；MPL基因突变总检出率为0.6%（10/1 648）,其中ET为0.9%（9/1 049），PMF为1.1%（1/91）。未发现两种及以上基因突变共存病例。②JAK2V617F突变组中位年龄[61（15~95）岁]高于JAK2 12号外显子突变组[49（33~62）岁]及突变阴性组[42（3~78）岁]（P值均<0.001），与CALR突变组[57（17~89）岁]、MPL突变组[59（22~71）岁]比较差异无统计学意义（P>0.05）。JAK2V617F突变阳性组白细胞计数、血红蛋白浓度均高于CALR突变阳性及阴性组（P<0.05），而与MPL突变阳性组比较仅表现为高白细胞计数（P=0.013）；CALR突变组血小板计数高于JAK2V617F突变组[966（400~2 069）×10⁹/L对800（198~3 730）×10⁹/L，P<0.001]。③共1 160例患者进行了有效染色体核型分析，CALR基因突变阳性、阴性患者异常核型检出率差异无统计学意义[9.8%（8/82）对7.4%（80/1 078），P=0.441]；JAK2V617F突变阳性、阴性患者异常核型检出率差异无统计学意义[7.7%（75/971）对6.9%（13/189），P=0.688]。CALR突变阳性组与JAK2V617F突变阳性组的异常核型检出率差异无统计学意义[9.8%（8/82）对7.7%（75/971），P=0.512]。7例JAK2基因12号外显子突变阳性及6例MPL基因突变阳性患者均未发现异常核型。

结论

基因检测使MPN的诊断及预后判断有了更可靠的依据，不同MPN亚型基因突变的发生频率、分布情况不同，不同基因突变导致独特的临床表型。