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The trajectory of B cell development goes through subsequent steps governed by complex genetic programs, strictly regulated by multiple transcription factors. Interferon regulatory factor 4 (IRF4) regulates key points from pre-B cell development and receptor editing to germinal center formation, class-switch recombination and plasma cell differentiation. The pleiotropic ability of IRF4 is mediated by its “kinetic control”, allowing different IRF4 expression levels to activate distinct genetic programs due to modulation of IRF4 DNA-binding affinity. IRF4 is implicated in B cell malignancies, acting both as tumor suppressor and as tumor oncogene in different types of precursors and mature B cell neoplasia. Here, we summarize the complexity of IRF4 functions related to different DNA-binding affinity, multiple IRF4-specific target DNA motif, and interactions with transcriptional partners. Moreover, we describe the unique role of IRF4 in acute leukemias and B cell mature neoplasia, focusing on pathogenetic implications and possible therapeutic strategies in multiple myeloma and chronic lymphocytic leukemia.

The colony-stimulating factor 3 receptor (CSF3R) plays an essential role in differentiation, growth, and survival of granulocytes. Driver mutations in CSF3R gene represent a diagnostic marker of chronic neutrophilic leukemia (CNL). Less commonly, these mutations are observed in other myeloid neoplasms but their pathogenetic and prognostic role is still unclear. Here, we analyzed a large cohort of myeloid neoplasms to evaluate the incidence of CSF3R mutations and co-mutational profile. Mutational analysis was performed using targeted NGS myeloid panel in a consecutive cohort of 360 patients with myeloid neoplasms. Mutations in CSF3R were identified in 20/360 (5.6%) cases. A CSF3R gene mutation was present in 13/179 AML cases (7.3%), in 2/27 (7.4%) CMML cases, in 1/94 (1.1%) MDS cases and in 4/60 (6.7%) other myeloid neoplasms. The frequencies of patients with CSF3R mutations lowered to 2.8% in all cases and 3.4% in AML, excluding cases with variants of uncertain significance (VUS). A total of 23 mutations of CSF3R gene were detected, half localized in the extracellular domain, 5 in the transmembrane region (type I) and 6 mutations in the cytoplasmic domain (type II). In AML, CSF3R mutations were more frequent in patients harboring CBF alterations (25.0%) and CEBPA mutations (11.8%). Two cases with AML harboring pathogenic CSF3R variants were primary refractory to induction therapy. CMML cases with T618I variant showed a myeloproliferative phenotype. Overall, our findings support the notion that CSF3R variants, particularly type I and II pathogenic mutations, may modulate the phenotypic features of leukemic cells in myeloid neoplasia.

Amyloid deposition within stenotic aortic valves (AVs) also appears frequent in the absence of cardiac amyloidosis, but its clinical and pathophysiological relevance has not been investigated. We will elucidate the rate of isolated AV amyloid deposition and its potential clinical and pathophysiological significance in aortic stenosis (AS). In 130 patients without systemic and/or cardiac amyloidosis, we collected the explanted AVs during cardiac surgery: 57 patients with calcific AS and 73 patients with AV insufficiency (41 with AV sclerosis and 32 without, who were used as controls). Amyloid deposition was found in 21 AS valves (37%), 4 sclerotic AVs (10%), and none of the controls. Patients with and without isolated AV amyloid deposition had similar clinical and echocardiographic characteristics and survival rates. Isolated AV amyloid deposition was associated with higher degrees of AV fibrosis (p = 0.0082) and calcification (p < 0.0001). Immunohistochemistry analysis suggested serum amyloid A1 (SAA1), in addition to transthyretin (TTR), as the protein possibly involved in AV amyloid deposition. Circulating SAA1 levels were within the normal range in all groups, and no difference was observed in AS patients with and without AV amyloid deposition. In vitro, AV interstitial cells (VICs) were stimulated with interleukin (IL)-1β which induced increased SAA1-mRNA both in the control VICs (+6.4 ± 0.5, p = 0.02) and the AS VICs (+7.6 ± 0.5, p = 0.008). In conclusion, isolated AV amyloid deposition is frequent in the context of AS, but it does not appear to have potential clinical relevance. Conversely, amyloid deposition within AV leaflets, probably promoted by local inflammation, could play a role in AS pathophysiology.