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Numerous pathogenic CALR exon 9 mutations have been identified in myeloproliferative neoplasms (MPN), with type 1 (52bp deletion; CALRDEL) and type 2 (5bp insertion; CALRINS) being the most prevalent. Despite the universal pathobiology of MPN driven by various CALR mutants, it is unclear why different CALR mutations result in diverse clinical phenotypes. Through RNA sequencing followed by validation at the protein and mRNA levels, we found that S100A8 was specifically enriched in CALRDEL but not in CALRINS MPN-model cells. The expression of S100a8 could be regulated by STAT3 based on luciferase reporter assay complemented with inhibitor treatment. Pyrosequencing demonstrated relative hypomethylation in two CpG sites within the potential pSTAT3-targeting S100a8 promoter region in CALRDEL cells as compared to CALRINS cells, suggesting that distinct epigenetic alteration could factor into the divergent S100A8 levels in these cells. The functional analysis confirmed that S100A8 non-redundantly contributed to accelerated cellular proliferation and reduced apoptosis in CALRDEL cells. Clinical validation showed significantly enhanced S100A8 expression in CALRDEL-mutated MPN patients compared to CALRINS-mutated cases, and thrombocytosis was less prominent in those with S100A8 upregulation. This study provides indispensable insights into how different CALR mutations discrepantly drive the expression of specific genes that contributes to unique phenotypes in MPN.

Studies in Caucasians have shown that values of hematological indices could be affected by a wide variety of factors. However, parallel work in other ethnical populations, particularly from the Asia-Pacific region, is lacking. Therefore, we designed this study to explore the association between clinical/laboratory parameters and hemogram levels. Adult individuals who came to our hospital for health exams were screened. Information on demographics and laboratory profiles was obtained. We analyzed the impacts of these parameters on the variation of hemogram. Overall, 26,497 adults were included in the current analysis after excluding those with abnormal hemogram. Multivariate regression analysis showed increasing age and male gender negatively affected the number of platelets, whereas a higher serum apolipoprotein B level was associated with an elevated platelet count. Gender and serum albumin level were the major determinants of variation in hemoglobin level. A modestly increased white cell count was seen in men as well as individuals with elevated apolipoprotein B levels, but it was inversely correlated with changes in age and serum albumin levels. Conversely, some variables, although statistically significantly associated with the hematological indices, only provided a trivial explanation for the heterogeneity observed. We further established predictive models for the approximate estimation of hematological indices in healthy adults. Our data indicate that age, gender, and serum levels of apolipoprotein B and albumin affect hematological indices in various ways. We also demonstrate that variation in hemogram could be successfully predicted by a number of clinical and laboratory parameters.

Patients with myeloproliferative neoplasms (MPNs) are characterized by systemic inflammation. With the indolent nature of the diseases, second cancers (SCs) have emerged as a challenging issue in afflicted patients. Epidemiological studies have confirmed the excessive risk of SCs in MPNs, but little is known about their molecular basis. To explore further, we used whole exome sequencing to explore the genetic changes in the granulocytes of 26 paired MPN patients with or without SC. We noticed that MPN–SC patients harbor genomic variants of distinct genes, among which a unique pattern of co-occurrence or mutual exclusiveness could be identified. We also found that mutated genes in MPN–SC samples were enriched in immune-related pathways and inflammatory networks, an observation further supported by their increased plasma levels of TGF-β and IL-23. Noteworthily, variants of KRT6A, a gene capable of mediating tumor-associate macrophage activity, were more commonly detected in MPN–SC patients. Analysis through OncodriveCLUST disclosed that KRT6A replaces JAK2V617F as the more prominent disease driver in MPN–SC, whereas a major mutation in this gene (KRT6A c.745T>C) in our patients is linked to human carcinoma and predicted to be pathogenic in COSMIC database. Overall, we demonstrate that inflammation could be indispensable in MPN–SC pathogenesis.

Numerous pathogenic CALR exon 9 mutations have been identified in myeloproliferative neoplasms (MPN), with type 1 (52bp deletion; CALR[sup.DEL]) and type 2 (5bp insertion; CALR[sup.INS]) being the most prevalent. Despite the universal pathobiology of MPN driven by various CALR mutants, it is unclear why different CALR mutations result in diverse clinical phenotypes. Through RNA sequencing followed by validation at the protein and mRNA levels, we found that S100A8 was specifically enriched in CALR[sup.DEL] but not in CALR[sup.INS] MPN-model cells. The expression of S100a8 could be regulated by STAT3 based on luciferase reporter assay complemented with inhibitor treatment. Pyrosequencing demonstrated relative hypomethylation in two CpG sites within the potential pSTAT3-targeting S100a8 promoter region in CALR[sup.DEL] cells as compared to CALR[sup.INS] cells, suggesting that distinct epigenetic alteration could factor into the divergent S100A8 levels in these cells. The functional analysis confirmed that S100A8 non-redundantly contributed to accelerated cellular proliferation and reduced apoptosis in CALR[sup.DEL] cells. Clinical validation showed significantly enhanced S100A8 expression in CALR[sup.DEL]-mutated MPN patients compared to CALR[sup.INS]-mutated cases, and thrombocytosis was less prominent in those with S100A8 upregulation. This study provides indispensable insights into how different CALR mutations discrepantly drive the expression of specific genes that contributes to unique phenotypes in MPN.