The purpose of this study was to compare the expression and function of NOTCH1 in chronic lymphocytic leukemia (CLL) patients harboring a wild-type (WT) or mutated NOTCH1 gene. NOTCH1 mRNA and surface protein expression levels were independent of the NOTCH1 gene mutational status, consistent with the requirement for NOTCH1 signaling in this leukemia. However, compared with NOTCH1-WT CLL, mutated cases displayed biochemical and transcriptional evidence of an intense activation of the NOTCH1 pathway. In vivo, expression and activation of NOTCH1 was highest in CLL cells from the lymph nodes as confirmed by immunohistochemistry. In vitro, the NOTCH1 pathway was rapidly downregulated, suggesting that signaling relies upon micro-environmental interactions even in NOTCH1-mutated cases. Accordingly, co-culture of Jagged1(+) (the NOTCH1 ligand) nurse-like cells with autologous CLL cells sustained NOTCH1 activity over time and mediated CLL survival and resistance against pro-apoptotic stimuli, both abrogated when NOTCH1 signaling was pharmacologically switched off. Together, these results show that NOTCH1 mutations have stabilizing effects on the NOTCH1 pathway in CLL. Furthermore, micro-environmental interactions appear critical in activating the NOTCH1 pathway both in WT and mutated patients. Finally, NOTCH1 signals may create conditions that favor drug resistance, thus making NOTCH1 a potential molecular target in CLL.

In chronic lymphocytic leukemia (CLL), NOTCH1 mutations have been associated with clinical resistance to the anti-CD20 rituximab, although the mechanisms behind this peculiar behavior remain to be clarified. In a wide CLL series (n=692), we demonstrated that CLL cells from NOTCH1-mutated cases (87/692) were characterized by lower CD20 expression and lower relative lysis induced by anti-CD20 exposure in vitro. Consistently, CD20 expression by CLL cells was upregulated in vitro by γ-secretase inhibitors or NOTCH1-specific small interfering RNA and the stable transfection of a mutated (c.7541-7542delCT) NOTCH1 intracellular domain (NICD-mut) into CLL-like cells resulted in a strong downregulation of both CD20 protein and transcript. By using these NICD-mut transfectants, we investigated protein interactions of RBPJ, a transcription factor acting either as activator or repressor of NOTCH1 pathway when respectively bound to NICD or histone deacetylases (HDACs). Compared with controls, NICD-mut transfectants had RBPJ preferentially complexed to NICD and showed higher levels of HDACs interacting with the promoter of the CD20 gene. Finally, treatment with the HDAC inhibitor valproic acid upregulated CD20 in both NICD-mut transfectants and primary CLL cells. In conclusion, NOTCH1 mutations are associated with low CD20 levels in CLL and are responsible for a dysregulation of HDAC-mediated epigenetic repression of CD20 expression.

Even if NOTCH1 is commonly mutated in chronic lymphocytic leukemia (CLL), its functional impact in the disease remains unclear. Using CRISPR/Cas9-generated Mec-1 cell line models, we show that NOTCH1 regulates growth and homing of CLL cells by dictating expression levels of the tumor suppressor gene DUSP22. Specifically, NOTCH1 affects the methylation of DUSP22 promoter by modulating a nuclear complex, which tunes the activity of DNA methyltransferase 3A (DNMT3A). These effects are enhanced by PEST-domain mutations, which stabilize the molecule and prolong signaling. CLL patients with a NOTCH1-mutated clone showed low levels of DUSP22 and active chemotaxis to CCL19. Lastly, in xenograft models, NOTCH1-mutated cells displayed a unique homing behavior, localizing preferentially to the spleen and brain. These findings connect NOTCH1, DUSP22, and CCL19-driven chemotaxis within a single functional network, suggesting that modulation of the homing process may provide a relevant contribution to the unfavorable prognosis associated with NOTCH1 mutations in CLL.

The inflammatory phenotype of neck adipose tissue (NAT) might reflect its involvement in the pathogenesis of carotid atherosclerosis. We investigated inflammatory gene expression in the subcutaneous and the perivascular (pericarotid) adipose tissue from patients with carotid stenosis (CS) undergoing endarterectomy and a control group of patients without significant carotid atherosclerosis undergoing thyroid surgery. Only male patients were included (n = 13 in each study group). Clinical and biochemical data along with serum leptin, adiponectin, and monocyte chemoattractant protein 1 (MCP-1) were collected. Adipose tissue samples were obtained from both the subcutaneous and pericarotid compartments. Real-time polymerase chain reaction was used to measure gene expression of macrophage markers and adipokines. The CS group had higher subcutaneous and pericarotid visfatin gene expression and higher pericarotid expression of MCP-1 and CD68 genes. The ratio between pericarotid CD206 and CD68 gene expression was similar between study groups. Adiponectin gene expression in both NAT compartments did not differ between groups, but it was negatively associated with body weight. These observations suggest that NAT, and especially the pericarotid compartment, express enhanced inflammatory properties in patients with CS, but the proportion of anti-inflammatory macrophages in advanced atherosclerosis seems to be maintained.

Association of monocyte CCR2 expression with obesity and insulin resistance in postmenopausal women Abstract Purpose: Monocytes actively participate in in ammatory mechanisms that contribute to the development of adipose tissue dysfunction and atherogenesis. e aim of this study was to evaluate the association of monocyte CCR2 chemokine receptor expression and intracellular oxidative burst with the metabolic and in ammatory factors related to body weight.Methods: e study was performed in 67 postmenopausal women with normal, overweight and obese body mass index. Monocyte CCR2 surface expression and intracellular oxidative burst activity (determined using 2' , 7'-dichloro uorescin diacetate) were analyzed by ow cytometry. Serum levels of HMW adoponectin, monocyte chemoattractant protein-1 (MCP-1), insulin, glucose, lipids and C-reactive protein were determined.Results: Subjects with homeostasis model assessment-estimated insulin resistance (HOMA-IR) above the median had signi cantly higher proportion of CCR2+ monocytes and higher mean uorescence intensity (MFI) of CCR2 and oxidative burst. e proportion of CCR2+ monocytes and CCR2 MFI were correlated with body weight, body mass index, fat mass, insulin and HOMA-IR. Oxidative burst also correlated with anthropometric measures, fat mass and expression of CCR2. No correlations were found between these markers of monocyte activation and HMW adiponectin or monocyte chemoattractant protein-1. e absolute number of monocytes was associated with insulin and this association remained signi cant a er adjusting for C-reactive protein. In the multiple regression model the monocyte number was determined to be an independent predictor of insulin level.Conclusion: ese results provide support for signi cant associations of monocyte number and markers involved in monocyte activation with obesity and insulin resistance.

Human CD38, an ecto-enzyme and a receptor, performs as an independent negative prognostic marker for patients with chronic lymphocytic leukemia (CLL), a hematological malignancy characterized by the accumulation of a population of mature B lymphocytes expressing CD5. Patients with a CD38⁺ CLL clone display a more aggressive form of the disease with earlier treatment requirements and ultimately shorter overall survival than patients with a CD38⁻ clone. Several lines of evidence indicate that CD38 is not only a diagnostic marker but also a key element in the molecular network regulating disease maintenance and progression. First, CD38 is a receptor that induces proliferation and increases survival of CLL cells. Second, CD38 signals facilitate access of CLL cells to growth-favorable districts. This is achieved by enhancing i) chemotaxis towards CXCL12, ii) integrin-mediated adhesion and iii) matrix metalloprotease synthesis and secretion. Third, blocking monoclonal antibodies targeting CD38 impair CLL homing to spleen and bone marrow in xenograft models. These functions appear to be modulated by frontal interactions with CD31 as well as by lateral associations on the CLL membrane to form a large supramolecular complex similar to the invadosomes of epithelial cells. Our understanding has evolved from considering CD38 as a marker of unfavorable prognosis to recognizing its function as a disease modifier. Studies in the next few years will likely determine whether the molecule can also serve as a target for new therapies, using monoclonal antibodies, inhibitors of the enzymatic activity or both.

BACKGROUND . NOTCH1 PEST domain mutations were among the first to be identified using whole exome sequencing and their prevalence and prognostic power for CLL patients has since been extensively studied. Nevertheless, the functional contribution of NOTCH1 and the impact of its mutations in CLL remain poorly understood. This is mainly due to the intrinsic limits in using primary CLL cells and to the rapid inactivation of the NOTCH1 pathway in vitro. AIM. The aim of the study was to highlight the NOTCH1-dependent mechanisms contributing to CLL pathogenesis and progression and the effects of PEST mutations in this disease context. RESULTS. By using the CRISPR/Cas9 technology, we first generated a cellular model either lacking NOTCH1 (Mec-1/KO) or expressing it in its wild-type or mutated forms. RNA-seq analysis of the transcriptome of Mec-1/WT and /KO cells, highlighted signaling and migration as the most prominently down-regulated pathways in KO cells. These findings were confirmed by showing that Mec-1/KO cells migrated significantly less towards CCL19 than their WT counterparts, as the result of the down-modulation of CCR7, the CCL19 receptor. Mechanistically, Mec-1/KO were characterized by increased expression of the tumor suppressor gene DUSP22, a phosphatase that negatively regulates MAPK and STAT3 signaling, in turn responsible for CCR7 gene transcription. Up-regulation of DUSP22 in Mec-1/KO was caused by decreased methylation of the gene promoter, as shown using a methylation specific PCR. Re-expression of the NOTCH1 Intracellular Domain (NICD) rescued the phenotype, increasing methylation of the DUSP22 promoter, which in turn led to decreased gene and protein expression. Mec-1 cells with reconstituted NICD expression showed increased STAT3 phosphorylation, CCR7 expression and, ultimately, migrated more actively in response to CCL19. Importantly, reconstitution with an NICD carrying the PEST domain mutation most commonly found in patients (ΔCT_7541-7542), significantly enhanced all these events, including DUSP22methylation, STAT3 phosphorylation, CCR7 expression, generating cells with the highest chemotactic responses to CCL19. NOTCH1 directly participates to the epigenetic regulation of DUSP22, by conditioning the activity of the DNA methyltransferase 3A (DNMT3A) on the gene promoter. By binding RBPJk, the NICD displaces HDAC1 from the repressor complex and initiates NOTCH1-dependent signaling. Consequently, free HDAC1 binds to and stabilizes DNMT3A, promoting its activity on DUSP22promoter. These results were first corroborated in a large cohort of CLL (n=113) carrying mutations in NOTCH1 PEST domain (ΔCT_7541-7542)at the clonal (>12%) or subclonal (≤12%) level. The clonally mutated subset showed significant downregulation of DUSP22expression and gene promoter hypermethylation compared to subclonal samples. Consistently, the clonal subset displayed higher constitutive STAT3 phosphorylation, expressed higher levels of CCR7 and migrated more efficiently to CCL19 than subclonally mutated CLL. The second confirmation was obtained by studying a Mec-1 variant with PEST domain mutation (Mec-1/PEST), generated using the CRISPR/Cas9 system. Like primary cells, Mec-1/PEST needed the ligand to initiate signaling. As predicted, the mutant NICD was more stable and more transcriptionally active. Consistently, these cells had the lowest DUSP22 levels and the highest CCR7 expression. When Mec-1/PEST were xenografted in immunocompromised mice, activation of the NOTCH1 pathway was more pronounced than that of Mec-1/WT cells. In keeping with their minimal expression of DUSP22, Mec-1/PEST cells were characterized by markedly increased metastatic properties, with extensive colonization of the liver, the spleen, and the brain, at variance with the other cell variants. CONCLUSIONS . Considered together, these results show that PEST mutations increase NICD stability, in turn affecting a complex nuclear balance. The final outcome for the CLL cell is decreased expression of the tumor suppressor gene DUSP22 and increased chemotaxis towards CCL19. As this chemokine regulates homing to secondary organs, conceivably NOTCH1 mutations might favor CLL recirculation to lymph node and spleen, where the local environment triggers proliferation and protects from apoptosis, two conditions that are associated with a more aggressive disease and an unfavorable prognosis. Disclosures Coscia: Karyopharm: Research Funding; Janssen: Honoraria; Mundipharma: Honoraria; Gilead: Honoraria; ROCHE: Honoraria, Other: Advisory board. Furman:Pharmacyclics, LLC, an AbbVie Company: Consultancy, Honoraria, Speakers Bureau. Gaidano:Roche: Consultancy, Honoraria, Speakers Bureau; Gilead: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Morphosys: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria.

3607 Background: In B-cell chronic lymphocytic leukemia (B-CLL) there is a well documented intraclonal and interclonal variability of B-CLL cells in different lymphoid compartments with respect to the expression of a number of surface and intracellular molecules (for example CD38 and ZAP-70). This variability in part may reflect a number of interactions of malignant B-CLL clone with supporting microenviroment including cells (T-cells, nurse-like cells, etc.), cytokines, chemokines and stroma. One of the key interactions of B-CLL clone is with T-cells, through CD154/CD40 system. It is important pathway modulating survival, drug resistance and immunity. It is known that CD154 is transiently expressed on CD4+ T cells, as well as that CD154 can be coexpressed on B-CLL cells with CD40 in a subpopulation of B-CLL patients. Its expression on B-CLL cells can be induced by gene therapy and lenalidomide, being in part responsible for their therapeutic effects. Aim of this study was to determine the level of expression of CD154 and CD40 in vivo on B-CLL cells and T lymphocytes and to evaluate intra and interclonal differences due to different microenvironment, i.e. peripheral blood, bone marrow and lymph nodes. Methods: peripheral blood, (PB), bone marrow (BM) and lymph node (LN) samples were taken by conventional techniques (venepuncture and fine needle aspiration) on the same day. The expression level of CD154 and CD40 molecules on CD19+CD5+ B-CLL cells and CD19-CD5+ T cells was analyzed by flow cytometry. Results were expressed as mean fluorescence intensity (MFI) and analyzed by paired tests. Results: samples taken from 21 typical B-CLL patients with median age of 72 years were analyzed. There were 9 males and 12 females. Mean beta-2 microglobuin was 4.3mg/l, mean Total Tumor Mass size was 8.9 and mean Tumor Distribution pattern was 0.75. There were 2, 14 and 5 patients in Rai stage 0, I+II and III+IV, respectively. There were 6 previously treated patients (but off therapy 3 months before sampling). The expression level of CD154 was absent/low on T-cells and in 14/21 patients on B-CLL cells. However in 7/21 patients B-CLL cells had higher CD154 expression (“CD154 positive” patients). There was no detectible difference in CD154 expression on T cells between compartments, while on B-CLL cells there was highest expression in lymph nodes and lowest in peripheral blood (p<0.01). CD40 expression on B-CLL cells was significantly higher than CD154, i.e. all cases were positive, and there was no significant difference between lymphoid compartments. There was no significant difference between CD154 positive and negative patients in measured disease parameters. Conclusions: our results show that CD154 expression on T-cells is absent/low and not significantly different between lymphoid compartments regardless of different microenvironment milieu. CD40 expression on B-CLL cells is high and comparable through compartments. In subset of patients there is CD154 positivity on B-CLL cells and shows strong association with lymphoid compartments possibly indicating microenviroment influence on CD154/CD40 system in B-CLL in vivo. These results warrant further studies to indentify the role of CD154 expression on B-CLL cells in pathologic process and its regulation and may eventually uncover novel or modulate existing innovative therapeutic approaches (like gene therapy or immunomodulatory agents like lenalidomide). Disclosures: No relevant conflicts of interest to declare.