NOTCH1 mutations are associated with high CD49d expression in chronic lymphocytic leukemia: link between the NOTCH1 and the NF-κB pathways.

In chronic lymphocytic leukemia (CLL), stabilizing mutations of NOTCH1, affecting up to 10-15% of cases, have been associated to poor prognosis, disease progression and refractoriness to chemotherapy. NOTCH1 mutations are significantly overrepresented in trisomy 12 CLL, a disease subset frequently expressing CD49d, the α4 chain of the very-late-activation-4 integrin, a well-known key regulator of microenviromental interactions, and negative prognosticator in CLL. In the present study, by analysing a wide cohort of 1180 CLL, we observed a very strong association between the presence of NOTCH1 mutations and the expression of CD49d (P<0.0001), occurring also outside the trisomy 12 CLL subset. Using both the MEC-1 CLL-like cells stably transfected with the NOTCH1 intracellular domain and primary CLL cells bearing a mutated or wild-type NOTCH1 gene configuration, we provide evidence that triggering of the NOTCH1 pathway resulted in a positive CD49d expression regulation, which was driven by a NOTCH1-dependent activation of nuclear factot-κB (NF-κB). Consistently, pharmacological inhibition of the NOTCH1 and/or of the NF-κB pathways resulted in impaired NF-κB nuclear translocation with consequent down-modulation of CD49d expression. Altogether, our data link for the first time NOTCH1 mutations to CD49d expression regulation through the involvement of the NF-κB pathway in CLL.

NOTCH1-mutated chronic lymphocytic leukemia cells are characterized by a MYC-related overexpression of nucleophosmin 1 and ribosome-associated components.

In chronic lymphocytic leukemia (CLL), the mechanisms controlling cell growth and proliferation in the presence of NOTCH1 mutations remain largely unexplored. By performing a gene expression profile of NOTCH1-mutated (NOTCH1-mut) versus NOTCH1 wild-type CLL, we identified a gene signature of NOTCH1-mut CLL characterized by the upregulation of genes related to ribosome biogenesis, such as nucleophosmin 1 (NPM1) and ribosomal proteins (RNPs). Activation of NOTCH1 signaling by ethylenediaminetetraacetic acid or by coculture with JAGGED1-expressing stromal cells increased NPM1 expression, and inhibition of NOTCH1 signaling by either NOTCH1-specific small interfering RNA (siRNA) or γ-secretase inhibitor reduced NPM1 expression. Bioinformatic analyses and in vitro activation/inhibition of NOTCH1 signaling suggested a role of MYC as a mediator of NOTCH1 effects over NPM1 and RNP expression in NOTCH1-mut CLL. Chromatin immunoprecipitation experiments performed on NOTCH1 intracellular domain (NICD)-transfected CLL-like cells showed the direct binding of NOTCH1 to the MYC promoter, and transfection with MYC-specific siRNA reduced NPM1 expression. In turn, NPM1 determined a proliferation advantage of CLL-like cells, as demonstrated by NPM1-specific siRNA transfection. In conclusion, NOTCH1 mutations in CLL are associated with the overexpression of MYC and MYC-related genes involved in protein biosynthesis including NPM1, which are allegedly responsible for cell growth and/or proliferation advantages of NOTCH1-mut CLL.

Venetoclax: Bcl-2 inhibition for the treatment of chronic lymphocytic leukemia.

Venetoclax (ABT-199) is a small-molecule selective oral inhibitor of the antiapoptotic protein Bcl-2 that promotes programmed cell death of chronic lymphocytic leukemia (CLL) cells regulating the release of proapoptotic factors, such as Smac/Diablo, apoptosis-inducing factor (AIF) and cytochrome c. In April 2016, the U.S. Food and Drug Administration (FDA) granted accelerated approval to venetoclax for patients diagnosed with CLL with 17p deletion, as detected by an FDA-approved test, who have received at least one prior therapy. This review will focus on the mechanism of action, preclinical studies and clinical development of venetoclax both as a monotherapy and in combination with other drugs for CLL in the current milieu of therapy dominated by novel tyrosine kinase inhibitors such as ibrutinib and idelalisib.

CD49d prevails over the novel recurrent mutations as independent prognosticator of overall survival in chronic lymphocytic leukemia.

CD49d, the alpha-chain of the integrin heterodimer α4ß1, was identified among the strongest predictors of overall survival (OS) in chronic lymphocytic leukemia (CLL), along with IGHV mutational status and deletion of the 17p chromosome involving TP53. In addition to TP53, the clinical relevance of NOTCH1, SF3B1 and BIRC3 gene mutations has been recently emphasized. By analyzing a cohort of 778 unselected CLL patients, we assessed the clinical relevance of CD49d as an OS predictor in subgroups defined by mutation/deletion of the TP53, NOTCH1, SF3B1 and BIRC3 genes. In this context, CD49d emerged as an independent predictor of OS in multivariate Cox analysis (Hazard ratio =1.88, P<0.0001). Consistently, high CD49d expression identified CLL subsets with inferior OS in the context of each category of a previously reported hierarchical risk stratification model. Moreover, by evaluating the relative importance of biological prognosticators by random survival forests, CD49d was selected among the top-ranked OS predictor (variable importance =0.0410), along with IGHV mutational status and TP53 abnormalities. These results confirmed CD49d as an independent negative OS prognosticator in CLL also in comprehensive models comprising the novel recurrent mutations. In this context, TP53 disruption and NOTCH1 mutations retained prognostic relevance, in keeping with their roles in CLL cell immuno-chemoresistance.

NOTCH1 mutations associate with low CD20 level in chronic lymphocytic leukemia: evidence for a NOTCH1 mutation-driven epigenetic dysregulation.

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.

Minimal residual disease negativity in elderly patients with acute myeloid leukemia may indicate different postremission strategies than in younger patients.

In the present analysis, we evaluated whether in elderly acute myeloid leukemia (AML) patients (>60 years), minimal residual disease (MRD) assessed by flow cytometry may have a role in guiding choice of postremission strategies. We analyzed 149 young and 61 elderly adults who achieved morphological CR after induction course of EORTC/GIMEMA protocols. Elderly patients reached a postconsolidation MRD negative status less frequently than younger ones (11 vs 28 %, p = 0.009). MRD negativity resulted in a longer 5-year disease-free survival (DFS) both in elderly (57 vs 13 %, p = 0.0197) and in younger patients (56 vs 31 %, p = 0.0017). Accordingly, 5-year cumulative incidence of relapse (CIR) of both elderly (83 vs 42 %, p = 0.045) and younger patients (59 vs 24 % p = NS) who were MRD positive doubled that of MRD negative ones. Nevertheless, CIR of MRD negative elderly patients was twofold higher than that of younger MRD negative ones (42 vs 24 %, p = NS). In conclusion, elderly patients in whom chemotherapy yields a MRD negative CR have duration of DFS and rate of CIR significantly better than those who remain MRD positive. Nonetheless, the high CIR rate observed in the elderly suggests that MRD negativity might have different therapeutic implications in this population than in the younger counterpart.

The CD49d/CD29 complex is physically and functionally associated with CD38 in B-cell chronic lymphocytic leukemia cells.

CD49d and CD38 are independent negative prognostic markers in chronic lymphocytic leukemia (CLL). Their associated expression marks a disease subset with a highly aggressive clinical course. Here, we demonstrate a constitutive physical association between the CD49d/CD29 integrin complex and CD38 in primary CLL cells and B-cell lines by (i) cocapping, (ii) coimmunoprecipitation and (iii) cell adhesion experiments using CD49d-specific substrates (vascular-cell adhesion molecule-1 or CS-1/H89 fibronectin fragments). The role of CD38 in CD49d-mediated cell adhesion was studied in CD49d(+)CD38(+) and CD49d(+)CD38(-) primary CLL cells, and confirmed using CD38 transfectants of the originally CD49d(+)CD38(-) CLL-derived cell line Mec-1. Results indicate that CD49d(+)CD38(+) cells adhered more efficiently onto CD49d-specific substrates than CD49d(+)CD38(-) cells (P < 0.001). Upon adhesion, CD49d(+)CD38(+) cells underwent distinctive changes in cell shape and morphology, with higher levels of phosphorylated Vav-1 than CD49d(+)CD38(-) cells (P = 0.0006) and a more complex distribution of F-actin to the adhesion sites. Lastly, adherent CD49d(+)CD38(+) cells were more resistant to serum-deprivation-induced (P < 0.001) and spontaneous (P = 0.03) apoptosis than the CD49d(+)CD38(-) counterpart. Altogether, our results point to a direct role for CD38 in enhancing CD49d-mediated adhesion processes in CLL, thus providing an explanation for the negative clinical impact exerted by these molecules when coexpressed in neoplastic cells.

The miR-17∼92 family regulates the response to Toll-like receptor 9 triggering of CLL cells with unmutated IGHV genes.

Chronic lymphocytic leukemia (CLL) cells from clinically aggressive cases have a greater capacity to respond to external microenvironmental stimuli, including those transduced through Toll-like-receptor-9 (TLR9). Concomitant microRNA and gene expression profiling in purified CLL cells (n=17) expressing either unmutated (UM) or mutated (M) IGHV genes selected microRNAs from the miR-17∼92 family as significantly upregulated and in part responsible for modifications in the gene expression profile of UM CLL cells stimulated with the TLR9 agonist CpG. Notably, the stable and sustained upregulation of miR-17∼92 microRNAs by CpG was preceded by a transient induction of the proto-oncogene MYC. The enforced expression of miR-17, a major member from this family, reduced the expression of the tumor suppressor genes E2F5, TP53INP1, TRIM8 and ZBTB4, and protected cells from serum-free-induced apoptosis (P ≤ 0.05). Consistently, transfection with miR-17∼92 family antagomiRs reduced Bromo-deoxy-uridine incorporation in CpG-stimulated UM CLL cells. Finally, miR-17 expression levels, evaluated in 83 CLL samples, were significantly higher in UM (P=0.03) and ZAP-70(high) (P=0.02) cases. Altogether, these data reveal a role for microRNAs of the miR-17∼92 family in regulating pro-survival and growth-promoting responses of CLL cells to TLR9 triggering. Overall, targeting of this pathway may represent a novel therapeutic option for management of aggressive CLL.

Circulating regulatory T cells in "clinical" monoclonal B-cell lymphocytosis.

Regulatory T-cells (Tregs) constitute a small subset of cells involved in antitumour immunity and are generally increased in patients with chronic lymphocytic leukemia (CLL). No data is available on Tregs in monoclonal B-cell lymphocytosis (MBL), a disease entity characterized by less than 5000/microL circulating clonal B-cells in absence of other features of lymphoproliferative disorders. We used multicolour flow cytometry to evaluate the number of circulating Tregs in 56 patients with "clinical" MBL, 74 patients with previously untreated CLL and 40 healthy subjects. MBL patients showed a lower absolute number of Tregs, compared to CLL patients, but slightly higher than controls. Moreover, the absolute cell number of Tregs directly correlated both with more advanced Rai/Binet clinical stages and peripheral blood B-cell lymphocytosis. Of note, the absolute number of Tregs was found lower in MBL patients than in CLL patients staged as 0/A Rai/Binet. The study showed that Treg increase gradually from normal subjects to "clinical" MBL patients and are significantly higher in CLL patients as compared to MBL patients. Moreover, a significant direct relationship was found between higher Treg values and a higher tumor burden expressed by B-lymphocytosis or more advanced clinical stages. In light of this data, MBL seems to be a preliminary phase preceding CLL. The progressive increase of Treg numbers might contribute both to the clinical evolution of MBL to overt CLL and to CLL progression.

Exposure of B cell chronic lymphocytic leukemia (B-CLL) cells to nutlin-3 induces a characteristic gene expression profile, which correlates with nutlin-3-mediated cytotoxicity.

By analyzing the cDNA obtained from 16 B-cell chronic lymphocytic leukemia (B-CLL) patient samples, we found that Nutlin-3, a small molecule inhibitor of MDM2/p53 interaction, induced a characteristic gene expression profile (GEP) signature in 13 out of 16 B-CLL samples. The lack of Nutlin-3-induced GEP signature in 3 out of 16 B-CLL samples was not due to p53 deletion and/or mutation, as demonstrated by FISH analysis and p53 sequencing. Of note, the 3 B-CLL samples in which Nutlin-3 did not elicit the GEP signature were also less susceptible to Nutlin-3-mediated cytotoxicity with respect to the remaining 13 B-CLL samples. However, the partial lack of response in these p53 wild-type B-CLL samples was not due to defects in the ability of Nutlin-3 to promote p53 induction, as confirmed by the rapid accumulation of p53 protein at Western blot analysis in response to Nutlin-3 in all samples examined. Upon exposure to Nutlin-3, the genes up-regulated with the highest score in the majority of B-CLL cells were all known p53-target genes, including genes involved in apoptotic pathways, such as FAS and BAX, as well as MDM2. Taken together, our data indicate that the ability of Nutlin-3 to induce a characteristic GEP signature correlates with its cytotoxic potential in p53 wild-type B-CLL cells. However, in some p53 wild-type B-CLL samples, the response to Nutlin-3 cannot be predicted on the basis of FISH analysis or p53 sequencing.

Deregulation of the mitochondrial apoptotic machinery and development of molecular targeted drugs in acute myeloid leukemia.

Apoptosis plays a key role in the control of rapidly renewing tissues, such as the hematopoietic system and leukemia cells invariably have abnormalities in one or more apoptotic pathways, determining a survival advantage of these cells and the development of drug resistance. These defects are also frequently associated with a low rate of response to standard chemotherapy and with a poor survival in acute myeloid leukemia (AML). The major form of apoptosis proceeds through the mitochondrial pathway, with the mitochondrial outer membrane permeabilization, leading to the release of proteins normally found in the space between the inner and outer mitochondrial membranes (cytochrome C, AIF and others). Higher levels of anti-apoptosis proteins bcl-2, bcl-x(L), Mcl-1 block permeabilization of the membrane and are reported in AML patients presenting a poor outcome. On the contrary, activated pro-apoptotic bax or bad proteins allow this permeabilization and are correlated to a good prognosis in AML. Defects in the mitochondrial pathway induce multidrug-resistance and confer important prognostic information in AML. High ratios of bcl-2 to bax protein confer a poor prognosis with decreased rates of complete remission and overall survival. The prognostic information from the ratio of the proteins is greater than bcl-2 levels alone. Recently, we confirmed the impressive impact of the bax/bcl-2 ratio, determined by flow cytometry, on AML prognosis (complete remission and overall survival) in 255 AML patients. Bcl-2 down regulation might lower the apoptotic threshold of leukemic cells and, through this mechanism, favor response to chemotherapy. Phase II studies of oblimersen (antisense Bcl-2), cytarabine and daunorubicin or oblimersen plus gentuzumab, a cytotoxic antibody directed against CD33+ cells in relapsed AMLs, showed promising results. Defects in apoptosome proteins, such as APAF-1, are frequent in AML and treatment with 5-aza-2'-deoxycytidine, a specific inhibitor of DNA methylation, restored APAF-1 expression in leukemic cells. In conclusion, targeted therapies that are designed to induce apoptosis in leukemic cells, are the most promising anti-leukemia strategies. The elucidation of the apoptotic machinery and of its defects in AML lays the basis for developing new drugs able to trigger apoptosis and overcome therapy resistance.

Discriminant function analysis as decision support system for the diagnosis of acute leukemia with a minimal four color screening panel and multiparameter flow cytometry immunophenotyping.

Despite several recommendations for standardization of multiparameter flow cytometry (MFC) the number, specificity and combinations of reagents used by diagnostic laboratories for the diagnosis and classification of acute leukemias (AL) are still very diverse. Furthermore, the current diagnostic interpretation of flow cytometry readouts is influenced arbitrarily by individual experience and knowledge. We determined the potential value of a minimal four-color combination panel of 13 monoclonal antibodies (mAbs) with a CD45/sideward light scatter-gating strategy for a standardized MFC immunophenotyping of the clinically most relevant subgroups of AL. Bone marrow samples from 155 patients with acute myeloid leukemia (AML, n=79), B-cell precursor acute lymphoblastic leukemia (BCP-ALL, n=29), T-cell precursor acute lymphoblastic leukemia (T-ALL, n=12) and normal bone marrow donors (NBMD, n=35) were analyzed. A knowledge-based learning algorithm was generated by comparing the results of the minimal panel with the actual diagnosis, using discriminative function analysis. Correct classification of the test sample according to lineage, that is, BCP-ALL, T-ALL, AML and differentiation of NBMD was achieved in 97.2% of all cases with only six of the originally applied 13 mAbs of the panel. This provides evidence that discriminant function analysis can be utilized as a decision support system for interpretation of flow cytometry readouts.

The kinetics of reduction of minimal residual disease impacts on duration of response and survival of patients with acute myeloid leukemia.

UNLABELLED: We assessed by multiparametric flow cytometry the levels of minimal residual disease (MRD) in 100 adult patients with acute myelogenous leukemia (AML) achieving complete remission after intensive chemotherapy. The aim of the study was to determine the optimal threshold, in terms of residual leukemic cells, and the time point of choice, that is, post-induction (post-Ind) or post-consolidation (post-Cons), able to better predict outcome. By applying the maximally selected log-rank statistics, the threshold discriminating MRD- from MRD+ cases was set at 3.5 x 10(-4) residual leukemic cells, a level that allowed the identification of distinct subgroups of patients, both at post-Ind and post-Cons time points. Post-Cons MRD- patients had a superior outcome in terms of relapse rate, overall survival (OS) and relapse-free survival (RFS) (P<0.001, for all comparisons), regardless of the MRD status after induction. In particular, patients entering MRD negativity only after consolidation showed the same outcome as those achieving early negativity after induction. Multivariate analysis, including karyotype, age, MDR1 phenotype, post-Ind and post-Cons MRD levels, indicated that the post-Cons MRD status independently affected relapse rate, OS and RFS (P<0.001, for all comparisons). IN CONCLUSION: (1) the threshold of 3.5 x 10(-4) is valid in discriminating risk categories in adult AML and (2) post-Cons MRD assessment is critical to predict disease outcome.

Graft failure due to hemolytic uremic syndrome recurrence.

The hemolytic uremic syndrome (HUS) is a severe disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. We herein report our experience with a 43-year-old female patient who underwent a second cadaveric kidney transplantation in February 2005, for adult-onset HUS. The first renal transplantation, which was performed in 1996, required removal after 3 weeks for probable recurrence of HUS. The immunosuppressive regimen for the second transplant included basiliximab, tacrolimus, mycophenolate mofetil, and steroids. On postoperative day (POD) 7, she received steroid treatment for an acute rejection episode with improved renal function. On POD 19 due to worsening renal function, a graft biopsy showed HUS recurrence, thus we instituted hemodialysis and then plasmapheresis treatments. At two months after transplantation, the patient continued under plasmapheresis treatment due to clinical evidence of HUS. On POD 80, cytomegalovirus infection was diagnosed and intravenous gancyclovir treatment started for 3 weeks. After 110 days from transplant, a deterioration in renal function was evident: the graft was swollen and painful with Doppler ultrasound showing patency of both the renal artery and vein but, low blood flow. After 2 weeks of hemodialysis, the patient underwent transplantectomy. In adult-onset HUS the recurrence rate reduces graft survival, particularly among patients undergoing second transplantation.

Long-term observation of patients with anti-neutrophil cytoplasmic antibody-associated vasculitis treated with rituximab.

OBJECTIVE: Rituximab, a chimeric anti-CD20 monoclonal antibody, has been shown to be quite effective in the treatment of immune disorders resulting from autoantibodies. We prospectively studied the long-term effects of rituximab in 10 patients with anti-neutrophil cytoplasmic antibody (ANCA)-positive vasculitis refractory to conventional therapy (n=3) or in second or subsequent relapse (n=7). METHODS: The median age of patients was 53 yrs (range 38-70 yrs). Eight were classified as Wegener's granulomatosis, and two as microscopic polyangiitis. Clinical activity was assessed using the Birmingham Vasculitis Activity Score modification for Wegener's granulomatosis. Treatment consisted of intravenous infusions of rituximab given at the dose of 375 mg/m2 weekly for four consecutive weeks. RESULTS: All patients experienced a rapid clinical improvement following the administration of rituximab, with nine complete responses and one partial response at 6 months. With a median follow-up of 33.5 months (range 26-45 months), three patients have thus far relapsed. Retreatment with the monoclonal antibody at the same dose and schedule resulted in a new sustained response in all these patients. Rituximab therapy resulted in prolonged B-cell depletion. The ANCA titres decreased significantly in all patients, with eight out of 10 becoming ANCA-negative and three remaining ANCA-negative even after B-cell recovery. Infusion-related side effects were observed in one patient, but were of mild intensity and did not require discontinuation of treatment. CONCLUSIONS: Rituximab is an effective and well-tolerated treatment for patients with ANCA-associated vasculitis and should be strongly considered in severely affected patients who do not respond to standard therapy or in those in whom cytotoxic therapy bears a high risk of morbidity.