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Introduction: Interferon regulatory factor 4 (IRF4) is a transcriptional factor with a key role in the modulation of inflammation and immune surveillance. The IRF4 gene is downregulated in Philadelphia-negative myeloproliferative neoplasms, and its expression is associated with prognosis and response to treatment. Methods: We evaluated the IRF4 expression kinetics during tyrosine kinase inhibitor (TKI) treatment in a cohort of 116 chronic myeloid leukemia (CML) patients to elucidate its role in the disease course. Results: A relationship between the IRF4 expression and the disease burden was observed at various disease stages. A correlation analysis between the International Scale (IS) and IRF4 values confirmed this close association. A significant increase is detected after 3 months of TKI treatment. Patients achieving an early molecular response (EMR) had higher IRF4 values at both diagnosis and after 3 months of therapy as compared to those failing the EMR target. Patients achieving treatment-free remission did not show IRF4 fluctuations during monitoring, while a decreased IRF4 expression emerged at the time of molecular relapse. Conclusion: Our data seem to confirm the relevance of IRF4 in the pathogenesis of CML, suggesting a pivotal role at the disease onset and a predictive value during the CML course. [ABSTRACT FROM AUTHOR]

BCR-ABL1 and JAK2 V617F coexistence in myeloproliferative neoplasms has been described as concomitant or sequential events. Despite this, we present a unique case of chronic myeloid leukemia (CML) not referable to either of the known scenarios. BCR-ABL1 molecular monitoring was performed by real-time quantitative PCR (RQ-PCR). At the time of molecular relapse, a targeted next-generation sequencing analysis with a customized panel of 26 genes commonly mutated in myeloid diseases was performed. To investigate the kinetics of the JAK2 variant and its association with the BCR-ABL1 rearrangement, RQ-PCR was performed at different time points during the patient's follow-up. While negative at CML diagnosis, the JAK2 mutation was first detected 9 years later (VAF: 7.2%). The mutational burden of JAK2 remained stable in multiple determinations, with minor fluctuations independent of BCR-ABL1 kinetics. At the last available time point, the patient was in deep molecular response (MR4), the JAK2 mutational burden was 7%, and no clinical-laboratory findings of Ph-MPN were detectable. In the presented case, the JAK2variantoccurring during the course of the disease seems to stay in the shadows of CML, just as a bystander. The impact of this event (that may be considered suggestive of clonal hematopoiesis of indeterminate potential) on the disease outcome, even if seemingly irrelevant, has still to be explored. [ABSTRACT FROM AUTHOR]

Interferon regulatory factor 4 (IRF4) is involved in the pathogenesis of various hematologic malignancies. Its expression has been related to the negative regulation of myeloid-derived suppressor cells (MDSCs) and the polarization of anti-inflammatory M2 macrophages, thereby altering immunosurveillance and inflammatory mechanisms. An abnormal inflammatory status in the bone marrow microenvironment of myeloproliferative neoplasms (MPNs) has recently been demonstrated; moreover, in chronic myeloid leukemia a downregulated expression of IRF4 has been found. In this context, we evaluated the IRF4 expression in 119 newly diagnosed consecutive Philadelphia negative MPNs (Ph- MPNs), showing a low expression among the MPNs phenotypes with a more significant decrease in primary myelofibrosis patients. Lower IRF4 levels were associated with JAK2 + and triple negatives cases carrying the worst prognosis. Furthermore, the IRF4 levels were related to leukemic transformation and a shorter leukemia-free survival; moreover, the risk of myelofibrosis transformation in polycythemia vera and essential thrombocythemia patients was more frequent in cases with lower IRF4 levels. Overall, our study demonstrates an IRF4 dysregulated expression in MPNs patients and its association with a worse prognosis. Further studies could validate these data, to improve our knowledge of the MPNs pathogenesis and confirm the IRF4 role as a new prognostic factor. [ABSTRACT FROM AUTHOR]

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm caused by the BCR-ABL1 fusion gene generation as a consequence of the t(9;22)(q34;q11) rearrangement. The identification of the BCR-ABL1 transcript was of critical importance for both CML diagnosis and minimal residual disease (MRD) monitoring. In this review, we report the recent advances in the CML MRD monitoring based on RNA, DNA and protein analysis. The detection of the BCR-ABL1 transcript by the quantitative reverse-transcriptase polymerase chain reaction is the gold standard method, but other systems based on digital PCR or on GeneXpert technology have been developed. In the last years, DNA-based assays showed high sensitivity and specificity, and flow cytometric approaches for the detection of the BCR–ABL1 fusion protein have also been tested. Recently, new MRD monitoring systems based on the detection of molecular markers other than the BCR-ABL1 fusion were proposed. These approaches, such as the identification of CD26+ leukemic stem cells, microRNAs and mitochondrial DNA mutations, just remain preliminary and need to be implemented. In the precision medicine era, the constant improvement of the CML MRD monitoring practice could allow clinicians to choose the best therapeutic algorithm and a more accurate selection of CML patients eligible for the tyrosine kinase inhibitors discontinuation. [ABSTRACT FROM AUTHOR]

The article presents a study which discusses use of droplet digital polymerase chain reaction (ddPCR) assay for quantification of calreticulin (CALR) mutant allelic burden in myeloproliferative neoplasms. Topics include CALR gene mutations in patients affected by thrombocythemia, evaluations by ddPCR experiments, and higher CALR allelic burden in primary myelofibrosis (PMF) patients.