Nucleophosmin-1 and Ribosome-Associated Components Are Constitutively Overexpressed in NOTCH1 Mutated IGHV Unmutated CLL

Abstract Abstract 3880 Background: activating mutations of NOTCH1 have been identified in about 10% of chronic lymphocytic leukemia (CLL) cases at diagnosis, with a higher frequency in unmutated IGHV (IGHV-UM) CLL, chemorefractory CLL and CLL in advanced disease phases. In CLL, all NOTCH1 mutations disrupt the C-terminal PEST domain and cause an accumulation of an active NOTCH1 isoform. Notably, about 80% of NOTCH1 mutations are represented by a CT frameshift deletion at nucleotides 7544–7545 (c.7544–7545delCT). Clinically, the presence of NOTCH1 mutations is an independent predictor of overall survival in CLL and identifies a subset of patients with particularly unfavourable prognosis (Rossi et al, Blood, 119, 521, 2012). Aim: to identify peculiar molecular and biological features of NOTCH1 mutated CLL in the context of IGHV-UM CLL. Methods: the presence of the c.7544–7545delCT NOTCH1 frameshift deletion was investigated by an ad-hoc amplification refractory mutation system (ARMS) PCR set up to obtain an amplicon specific for the NOTCH1 mutated form and a second amplicon as control. The percentage of NOTCH1 DNA in the context of the CLL clone was determined by quantitative real-time PCR (QRT-PCR), calculating the ratio between the amount of the specific NOTCH1 mutated amplicon and the amount of the control amplicon, the latter representing the total amount of NOTCH1 DNA irrespective of its mutational status. Gene expression profile (GEP) was performed by a one-color labeling strategy using the 4×44K Agilent platform. The differential expression of specific genes/proteins was validated by QRT-PCR, western blotting and immunohistochemistry. A BrdU uptake assay was used to evaluate proliferation of CLL cells by CpG/IL2 stimulation. Results: in a cohort of 380 IGHV-UM CLL, the c.7544–7545delCT NOTCH1 mutation was found in 83/380 (21.8%) cases. QRT-PCR revealed a percentage of NOTCH1 mutated DNA ranging from 1 to 37%. CLL cases carrying the c.7544–7545delCT NOTCH1 mutation (NOTCH1-Mut) showed higher NOTCH1 protein expression than CLL cases lacking NOTCH1-Mut employing monoclonal antibodies either recognizing the trans-membrane (mean fold increase=3) or the intra-citoplasmic (mean fold increase=2.1) NOTCH1 domain. A GEP comparing RNA from purified CLL samples of 5 NOTCH1-Mut CLL and 5 CLL lacking NOTCH1-Mut was performed, selecting the 5 NOTCH1-Mut cases among those with the higher percentages of NOTCH1 mutated DNA (percentages of NOTCH1 mutated DNA ranging from 15 to 37%). This approach selected the nucleophosmin 1 gene (NPM1) and genes codifying for several ribosomal proteins (RPS6, RPS10, RPS17, RPS28, RPSA, RPL7A, RPL18) as significantly up regulated in NOTCH1-Mut CLL cases. A higher expression of the above mentioned genes in NOTCH1-Mut CLL was validated in a wider series of 34 cases (18 NOTCH1-Mut cases; NPM1, p=0.03; RPS6, p=0.045; RPS10, p=0.048; RPS17, p=0.048; RPS28, p=0.049; RPSA, p=0.048; RPL7A, p=0.039; RPL18, p=0.041, respectively). Western blot analysis in 8 cases (4 NOTCH1-Mut cases) confirmed a higher NPM1 expression in NOTCH1-Mut cases (range of fold increase from 1.6 to 5.2) also at protein level. Consistently, lymph nodes preparations from NOTCH1-Mut CLL cases revealed a strong NPM1 staining both in nucleoli and cytoplasms. Finally, when stimulated in-vitro with the CpG/IL2 combination, NOTCH1-mut IGHV-UM CLL cells proliferated, as detected by a BrdU uptake assay (>10 fold increase over control), and up-regulated NPM1 both at transcript (mean fold increase=2.02 after 18 hours of CpG exposure, p=0.001) and protein (fold increase of 1.34 after 6 hours of CpG exposure) levels. Conclusion: NPM1 was identified as constitutively overexpressed in NOTCH1-Mut IGHV-UM CLL together with several ribosome-associated components. These findings are suggestive for an increased activity of the ribosomal machinery in NOTCH1-Mut IGHV-UM CLL as part of the molecular processes leading to control of CLL cell growth and survival in this clinically unfavourable disease subset. Disclosures: No relevant conflicts of interest to declare.

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Transcriptional Mistargeting Of NFAT2 In CLL

Blood ◽

10.1182/blood.v122.21.4122.4122 ◽

2013 ◽

Vol 122 (21) ◽

pp. 4122-4122

Author(s):

Melanie Märklin ◽

Jonas S. Heitmann ◽

David Worbs ◽

Alexandra Poljak ◽

Claude Evouna ◽

...

Keyword(s):

B Cells ◽

Signaling Pathway ◽

Target Genes ◽

Nuclear Translocation ◽

Conflicts Of Interest ◽

Lymphocytic Leukemia ◽

Resting Cells ◽

Qrt Pcr ◽

Mutational Status ◽

Healthy Donors

Abstract Chronic Lymphocytic Leukemia (CLL) is a hematological malignancy of mature B cells and constitutes the most common leukemia in adults. It is characterized by a progressive accumulation of clonal B cells, which coexpress CD19, CD23 and CD5. The clinical course of CLL can be predicted by serveral prognostic markers like CD38, ZAP70 and cytogenetic abnormalities. While the treatment of CLL has significantly improved during recent years, it remains an essentially incurable disease and the molecular events that lead to its development are still largely elusive. NFAT is a family of highly phosphorylated transcription factors residing in the cytoplasm of resting cells. Upon dephosphorylation NFAT proteins translocate to the nucleus where they orchestrate developmental and activation programs in diverse cell types. NFAT is inactivated by a network of several kinases. Several recent studies have demonstrated that Ca2+/NFAT signaling is involved in the pathogenesis of a wide array of different tumor types including pancreatic adenocarcinoma, breast cancer and Non Hodgkin´s lymphoma. In this study we investigated the significance of the Ca2+/NFAT signaling pathway in B-CLL. For this purpose, we analyzed CLL cell lines (MEC-1, JVM-3) as well as primary blood samples from patients with CLL (n=30). The analyzed patient population exhibited a representative distribution of age, sex, Binet stage, WBC count, cytogenetics and IGVH mutational status. We detected a profound overexpression of NFAT2 mRNA as well as NFAT2 protein in all CLL samples. Using qRT-PCR we found that CD19+CD5+ CLL cells exhibited an at least three fold overexpression of NFAT2 as compared to CD19+ B cells isolated from healthy donors. In one case, NFAT2 expression in CLL cells was 200 times higher than in the corresponding controls. This profound overexpression of NFAT2 in CLL cells could be confirmed on the protein level using Western Blotting and Immunocytochemistry. We could further demonstrate that even under resting conditions significant amounts of NFAT2 protein had translocated to the nucleus in CLL cells, whereas virtually all NFAT2 was in the cytoplasm in healthy B cells. NFAT2 nuclear translocation could be inhibited using pretreatment with Cyclosporin A demonstrating that this process was still calcineurin-dependent in CLL cells. We could further show that nuclear NFAT2 in CLL cells was able to bind DNA using electrophoretic mobility shift assays (EMSA). To assess the transcriptional activity of NFAT2 in human CLL we determined the expression of the apoptosis regulators OX40L, osteopontin and PD-L2, which we previously identified as NFAT2 target genes in a gene expression analysis with CD19+CD5+ CLL cells from TCL1 transgenic mice with intact NFAT2 and NFAT2 deletion, respectively. Interestingly, qRT-PCR revealed a tremendous reduction of all three target genes in the analyzed CLL samples as compared to control B cells from healthy donors. This is particularly remarkable, since in the TCL1 mouse model we observed a similar reduction of the expression of these genes in CLL cells with NFAT2 ablation. In summary, these results provide strong evidence that the Ca2+/NFAT signaling axis is constitutively activated in CD19+CD5+ CLL cells. Our data suggest that the profound overexpression of NFAT2 in CLL cells leads to its targeting to aberrant genetic loci different from its phsiological target genes resulting in a consecutive knock out phenotype with respect to the expression of the apoptosis regulators OX40, osteopontin and PD-L2 in CLL. Further investigation is therefore warranted to decipher the therapeutic potential of modulating the Ca2+/Calcineurin/NFAT signaling pathway in this disease. Disclosures: No relevant conflicts of interest to declare.

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NOTCH1 Mutations Are Associated with High CD49d Expression in Chronic Lymphocytic Leukemia

Blood ◽

10.1182/blood.v124.21.1978.1978 ◽

2014 ◽

Vol 124 (21) ◽

pp. 1978-1978

Author(s):

Antonella Zucchetto ◽

Chiara Caldana ◽

Federico Pozzo ◽

Silvia Rasi ◽

Carmela Ciardullo ◽

...

Keyword(s):

Chronic Lymphocytic Leukemia ◽

Conflicts Of Interest ◽

Statistical Significance ◽

Fold Increase ◽

Lymphocytic Leukemia ◽

Wild Type ◽

Apoptosis Resistance ◽

Mutation Burden ◽

Trisomy 12 ◽

Notch1 Mutations

Abstract Mutations of NOTCH1 have emerged as one of the most frequent somatic alterations in chronic lymphocytic leukemia (CLL), affecting up to 10–15% of patients. These mutations (~80% are 7544-7545delCT frameshift deletions) generate a truncated protein that accumulates in the cell and activates the downstream NOTCH1 signaling which is implicated in apoptosis resistance and increased survival of CLL cells. CD49d (α4 integrin chain) is one of the most relevant negative prognosticator in CLL, expressed by ~40% of CLL cases, and associated with aggressive/accelerated clinical courses, whose key role in CLL cell microenvironmental interactions has been thoroughly investigated. Literature data indicate that NOTCH1 has a role in activating the integrin signaling in several cell models. Given the higher CD49d expression characterizing trisomy 12 CLL, a CLL subset in which the NOTCH1 pathway is more often activated by NOTCH1 mutations, this study was aimed at investigating the contribution of NOTCH1 in the regulation of CD49d expression in CLL. The 7544-7545delCT NOTCH1 mutations were investigated by ARMS-PCR in 1027 CLL cases, all characterized for CD49d expression and for the cytogenetic profiles by FISH. NOTCH1 mutated cases were 158/1027 (15%), with a higher prevalence (36.7% of NOTCH1 mutated cases) in the trisomy 12 cytogenetic group. Analysis of CD49d expression highlighted a very strong association between the presence of NOTCH1 mutations and CD49d expression (p<0.0001). In particular, high CD49d expression (>30% of positive cells) was found in 102/158 (64.5%) NOTCH1 mutated cases as compared to 285/869 (32.8%) NOTCH1 wild-type cases. Of note, excluding trisomy 12 CLL, again NOTCH1 mutated CLL (100/865, 11.6%) displayed a significantly higher frequency of CD49d+ cases (52%) as compared to NOTCH1 wild-type CLL (25.7%) (p<0.0001). We next analyzed the percentage of mutated NOTCH1 DNA in the context of the CLL clone by a quantitative real-time PCR (QRT-PCR) approach set up by us to quantify the delCT NOTCH1 mutation. Using the 10% cut-off value to discriminate between cases with high (high NOTCH1) and low (low NOTCH1) mutation burden, 90/138 (67.7%) and 43/138 (32.3%) CLL cases were classified as low NOTCH1 and high NOTCH1, respectively. A higher prevalence of CD49d+ cases was found in the high NOTCH1 group (79%) as compared to the low NOTCH1 group (58%) (p=0.03). Moreover, a significant association between CD49d expression and a high NOTCH1 mutation burden was observed also excluding trisomy 12 CLL, with 69% of CD49d+ cases in the high NOTCH1 group, compared to 41% of CD49d+cases in the low NOTCH1 group (p=0.03). The association between NOTCH1 mutations and CD49d expression was next confirmed by next-generation sequencing results using the flow cytometrically sorted (>99% purity) CD49d- and CD49d+ components from 8 CLL cases characterized by both CD49d bimodal expression, and the presence of 7544-7545delCT NOTCH1 mutations at the subclonal level. In 7/8 cases, the CD49d+ component showed a higher NOTCH1 mutation burden compared to the CD49d- component, this difference reaching statistical significance in 4/7 cases. Of note, a similar clustering of mutations could not be observed in the CD49d- and CD49d+ components of other CLL cases characterized by bimodal CD49d expression and subclonal mutations of SF3B1 (n=1), BIRC3 (n=2) or TP53 (n=2). To verify whether NOTCH1 accumulation, as occurring in NOTCH1 mutated CLL, may influence CD49d expression, MEC-1 cells were transfected with a vector containing either a NOTCH1 intracellular domain (NICD) with 7544-7545delCT or a NICD carrying a missense mutation (c.5304G>A) generating a stop codon at the beginning of the sequence, as control. The higher levels of both NOTCH1 transcript (fold increase over control=2.2) and protein (fold increase over control=1.3) characterizing mutated-NICD MEC-1 cells, was paralleled by higher levels of CD49d expression (mean fluorescence intensity=23.300 versus 12.400) in these cells. Altogether our data demonstrate a direct correlation between NOTCH1 mutations and CD49d expression also outside the trisomy 12 CLL group, and suggest that accumulation of NOTCH1 may be directly or indirectly responsible for the up-regulation of CD49d expression. Disclosures No relevant conflicts of interest to declare.

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NOTCH1 Mutated IGHV Unmutated Chronic Lymphocytic Leukemia Cells Are Characterized By a Constitutive Overexpression of Nucleophosmin-1 and Ribosome-Associated Components

Blood ◽

10.1182/blood.v124.21.3308.3308 ◽

2014 ◽

Vol 124 (21) ◽

pp. 3308-3308

Author(s):

Federico Pozzo ◽

Tamara Bittolo ◽

Erika Tissino ◽

Francesca Maria Rossi ◽

Riccardo Bomben ◽

...

Keyword(s):

Flow Cytometry ◽

Chronic Lymphocytic Leukemia ◽

Protein Expression ◽

Ribosomal Proteins ◽

Fold Change ◽

Lymphocytic Leukemia ◽

Control Vector ◽

Protein Levels ◽

Qrt Pcr ◽

Notch1 Mutations

Abstract Background: stabilizing mutations of NOTCH1 have been identified in about 10% of chronic lymphocytic leukemia (CLL) cases at diagnosis, with a higher frequency in unmutated IGHV (IGHV-UM), immuno-chemorefractory or advanced disease phase CLL, and have been associated with particularly unfavourable prognosis (Rossi et al, Blood, 2012; Del Poeta et al, Br J Haematol, 2013; Stingelbauer et al, Blood, 2014). In CLL, all NOTCH1 mutations disrupt the C-terminal PEST domain (about 80% of which are a 7544-7545delCT frameshift deletion) and cause an accumulation of an active NOTCH1 isoform. Aim: to identify molecular/biological features of NOTCH1 mutated CLL. Methods: the presence of NOTCH1 mutations was investigated by ARMS-PCR or by direct sequencing. The percentage of NOTCH1 mutated DNA in the context of the CLL clone was determined by quantitative real-time PCR (QRT-PCR) and/or by next-generation-sequencing. Gene expression profile (GEP) was performed by a one-color labeling strategy using the 4x44K platform. Specific gene/protein validations were performed by QRT-PCR, western blotting, flow cytometry and immunofluorescence. Cell proliferation was evaluated by Cell Trace Violet assay. CLL-like cell line MEC-1 was transfected with a vector either with a NOTCH1 intracellular domain (NICD) with 7544-7545delCT or with a NICD carrying a missense mutation (c.5304G>A), generating a stop codon at the beginning of the sequence, as control. Results:i) in a cohort of 588 IGHV-UM CLL, 144/588 (24.5%) cases carried NOTCH1 mutations (NOTCH1-mut cases), with a percentage of NOTCH1 mutated DNA ranging from 1% to 37%. NOTCH1-mut cases (8 cases; 11%-37% of NOTCH1 mutated DNA) showed higher NOTCH1 protein expression than NOTCH1 wild type cases (NOTCH1-wt, 11 cases) employing monoclonal antibodies either recognizing the trans-membrane (mean fold-change=3.0) or the intracellular (mean fold-change=2.1) NOTCH1 domain. ii) A GEP comparing purified cells of 5 IGHV-UM NOTCH1-mut cases (15%-37% of NOTCH1 mutated DNA) and 5 IGHV-UM NOTCH1-wt cases selected nucleophosmin-1 (NPM1) and genes codifying for several ribosomal proteins (RPS6, RPS10, RPS17, RPS28, RPSA, RPL7A, RPL18) as significantly up regulated in NOTCH1-mut CLL. A higher expression of NPM1 and of the genes codifying for 4 ribosomal proteins in NOTCH1-mut cases was validated in a wider independent series of 34 cases by QRT-PCR (18 NOTCH1-mut cases).iii) Western blot in 19 cases (8 NOTCH1-mut cases) confirmed a higher NPM1 protein expression in NOTCH1-mut cases (1.3-5.2 range of fold-change) also at protein level. When intracellular distribution and fluorescent intensity of NPM1 immunostaining were evaluated, an additional cytoplasmic staining was visible in NOTCH1-mut cases, along with a clear nucleolar staining visible in both NOTCH1-mut and NOTCH1-wt cases. NPM1 protein expression was also determined by an intra-nuclear staining by flow cytometry. By using this approach, 2 NOTCH1-mut cases were sorted according to NPM1 expression; notably, the NPM1high subpopulation showed a higher NOTCH1 mutational load than the NPM1low subpopulation. iv) MEC-1 cells transfected with mutated NICD showed higher NOTCH1 transcript and protein levels than MEC-1 cells transfected with the control vector (increments over the control: NICD transcript =2.2, NICD protein =1.3). These NICD mutated MEC-1 cells were characterized by higher NPM1 transcript and protein levels than the MEC-1 cells transfected with the control vector (increments over the control: NPM1 transcript =2.0, NPM1 protein =1.5). By performing a cell-trace-violet proliferation assay, NICD mutated MEC-1 cells were characterized by higher proliferation rates than MEC-1 cells transfected with the control vector (p=0.018). Finally, when the transfected MEC-1 cells were treated with 0.5 microM etoposide for 48 hours, NICD mutated MEC-1 cells presented higher viability rates than the MEC-1 cells transfected with the control vector, as evaluated by Annexin V/7-AAD staining (percentage of viable cells: 70% vs. 50%). Conclusions: NPM1 was constitutively overexpressed in NOTCH1-mut IGHV-UM CLL together with several ribosome-associated components. An increased activity of the ribosomal machinery/DNA-repair mechanisms (Lindstrom MS. Biochem.Res.Int. 2011) in NOTCH1-mut CLL can confer proliferative advantages and resistance to chemotherapeutic agents. Disclosures No relevant conflicts of interest to declare.

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Extensive Intraclonal Diversification in a Subgroup of Chronic Lymphocytic Leukemia Patients with Stereotyped IGHV4-34/IGKV2-30 B cell Receptors: Implications for Ongoing Interactions with Antigen.

Blood ◽

10.1182/blood.v114.22.2337.2337 ◽

2009 ◽

Vol 114 (22) ◽

pp. 2337-2337

Author(s):

Lesley-Ann Sutton ◽

Efterpi Kostareli ◽

Anastasia Hadzidimitriou ◽

Nikos Darzentas ◽

Athanasios Tsaftaris ◽

...

Keyword(s):

Chronic Lymphocytic Leukemia ◽

B Cell ◽

Heavy Chain ◽

Conflicts Of Interest ◽

Lymphocytic Leukemia ◽

B Cell Receptors ◽

Valuable Insight ◽

Cell Receptors ◽

Mutational Status ◽

The Impact

Abstract Abstract 2337 Poster Board II-314 Several studies indicate that the development of chronic lymphocytic leukemia (CLL) may be influenced by antigen (Ag) recognition through the clonotypic B cell receptors (BCRs). However, it is still unclear whether Ag involvement is restricted to the malignant transformation phase or whether the putative Ag(s) may continuously trigger the CLL clone. Valuable insight into these issues may be gleaned from the study of intraclonal diversification (ID) within the immunoglobulin (IG) genes through ongoing somatic hypermutation (SHM). Definitive data regarding ID within IG genes in CLL remains limited and conflicting. In the present study we systematically explored the presence of ID within IG genes of CLL, not only at cohort level but also in subgroups defined by BCR stereotypy and IG gene mutational status. We thus conducted a large-scale subcloning study of both IG heavy and light variable genes, in a total of 1496 and 1008 subcloned sequences from 71 and 56 CLL cases, respectively. The analysis was intentionally biased to cases expressing IGHV4-34/IGKV2-30 IGs (subset #4) and IGHV3-21/IGLV3-21 IGs (subset #2) that exhibit distinctive, subset-biased SHM patterns. PCR reactions were run using the high-fidelity Accuprime Pfx polymerase and at least 14 colonies/case were analyzed. All “non-ubiquitous” sequence changes from the germline were evaluated and recorded as follows: (i) unconfirmed mutation (UCM) - a mutation observed in only one subcloned sequence from the same sample (ii) confirmed mutation (CM) - a mutation observed more than once among subcloned sequences from the same sample. Analysis of heavy chain sequences revealed that 40% (28/71) of cases carried intraclonally diversified IGHV-D-J genes with CMs amongst subclones, whilst 32% (23/71) of cases carried only UCMs. The remaining 28% (20/71) of cases carried sets of identical IGHV-D-J subcloned sequences. Although most cases showed no or low levels of ID, an intense and, likely, functionally driven ID was evident in selected cases, especially those belonging to subset #4. The distinct ID in subset #4 was statistically significant when compared to all other groups defined by IGHV gene usage and mutation status, BCR stereotypy or heavy chain isotype. Subsequent analysis of the clonotypic light chains revealed that the impact of ID was generally low, with the outstanding exception again relating to subset #4. In fact, of 22 IGKV-J rearrangements exhibiting CMs, 11 (50%) utilized the IGKV2-30 gene and notably 10/11 (91%) of these were expressed by subset #4 cases. In such cases, the expressed IGKV2-30 gene was affected by an active and precisely targeted ID, analogous to their partner IGHV4-34 gene. These findings suggest that the SHM mechanism may continuously operate in certain subsets of CLL patients, particularly those cases expressing stereotyped IGHV4-34/IGKV2-30 BCRs typical of subset #4. In such cases, the observed ID patterns attest to the very precise targeting of the SHM process and may be considered as evidence for a “stereotyped response” to an active, ongoing interaction with Ag(s). Disclosures: No relevant conflicts of interest to declare.

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Analysis of Stereotyped IGHV Distribution In a Series of 1133 Chronic Lymphocytic Leukemia Patients: The Experience of a Multicenter Italian Study Group

Blood ◽

10.1182/blood.v116.21.2423.2423 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2423-2423

Author(s):

Francesco Maura ◽

Giovanna Cutrona ◽

Massimo Gentile ◽

Serena Matis ◽

Monica Colombo ◽

...

Keyword(s):

Chronic Lymphocytic Leukemia ◽

Heavy Chain ◽

Conflicts Of Interest ◽

Pairwise Alignment ◽

Immunoglobulin Heavy Chain ◽

Lymphocytic Leukemia ◽

Study Group ◽

Data Set ◽

Italian Study ◽

Mutational Status

Abstract Abstract 2423 Chronic lymphocytic leukemia (CLL) is characterized by an extremely variable clinical course. Mutational status of the immunoglobulin heavy-chain variable (IGHV) region defines two disease subsets with different prognosis. A fraction of CLL cases carries highly homologous B-cell receptors (BCR), i.e. characterized by non-random combinations of immunoglobulin heavy-chain variable (IGHV) genes and heavy-chain complementarity determining region-3 (HCDR3). We performed sequence analysis to characterize IGHV regions in a panel of 1133 CLL patients investigated by a multicenter Italian study group. A total of 1148 rearrangements were identified; the analysis of stereotyped subsets was performed based on previously reported criteria (Messmer et al, J Exp Med 2004; Stamatopuolos et al, Blood 2007). Specifically, we compared all our sequences with those found in three different publicly available data sets (Stamatopoulos et al, Blood 2007; Murray et al, Blood 2008 and Rossi et al, 2009 Clin Cancer Res). In addition, a pairwise alignment within all sequences was performed in order to discover novel potential subsets (HCDR3 identity > 60%). Based on the 2% cut-off used to discriminate between Mutated (M) and Unmutated (UM) cases, 777 sequences (67.59%) were classified as M, while 371 sequences (32.3%) as UM. The most represented IGHV genes within mutated cases were IGHV4-34 (104/118) and IGHV3-23 (85/96), whereas IGHV1-69 (97/112) was the most frequently used in the UM group. Interestingly, the IGHV3-21 gene, reported to be frequently expressed in CLL patients from Northern Europe, was present in only a small fraction of cases (24; 2.07%), confirming a previous finding reported by Ghia et al (Blood 2005) in a smaller panel. In our series, stereotyped HCDR3 sequences were found in 407/1148 (35.45%) patients, 177 of whom were M and 230 were UM cases. Overall, we observed that stereotyped sequences were significantly associated with UM IGHV status (Fisher's exact test, P<0.0001). Among the 407 stereotyped HCDR3 sequences, 345 belong to the clusters reported by Murray et al and 14 to those described by Rossi et al., 2009 Clin Cancer Res. The most frequent stereotyped subsets identified in our panel were #1 (35 cases), #7 (28 cases), #4 (24 cases), #3 and #9 (16 cases), #28 (13 cases), and #2 (12 cases), together with subsets #5, #8, #10, #12, #13, #16 and #22 (all ranging from 6 to 9 cases). Finally, we were able to identify by auto-matching analysis 48 sequences potentially specific for 23 novel putative stereotype subsets. In our series we identified 407/1148 (35.45%) stereotyped HCDR3 sequences. The percentage was higher than that reported by Stamatopoulos et al and Murray et al. This discrepancy may partially be due to the different approach used in our analysis, namely the matching to a general data set including all published stereotyped subsets instead of the auto-matching performed by those Authors. We demonstrated a significant association between IGHV status and stereotyped sequences and confirmed the finding that #1 is the most frequent subset identified so far. Finally, we were able to identify a series of 23 novel putative subsets that will require further confirmation. Disclosures: No relevant conflicts of interest to declare.

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Circulating CLL Cells Expressing CD49d Display a Phospho-Proteomic Profile Consistent with a Constitutive Receptor Engagement by Blood-Borne Ligands

Blood ◽

10.1182/blood.v120.21.930.930 ◽

2012 ◽

Vol 120 (21) ◽

pp. 930-930

Author(s):

Dania Benedetti ◽

Erika Tissino ◽

Daniela Marconi ◽

Michele Dal Bo ◽

Riccardo Bomben ◽

...

Keyword(s):

Cell Growth ◽

Tyrosine Kinase ◽

Translational Control ◽

Conflicts Of Interest ◽

Control Cell ◽

Adaptor Protein ◽

Fold Increase ◽

Lymphocytic Leukemia ◽

Strong Increase ◽

Lim Kinase

Abstract Abstract 930 Chronic lymphocytic leukemia (CLL) cell growth and survival occur in defined microenvironment niches controlled by several receptor/ligand interactions including those mediated by the α4β1 integrin. This integrin, in particular, is known to interact with both the extracellular matrix component fibronectin, via the non-RGD CS-1 fragments, and the bone marrow/stromal components, via the vascular-cell adhesion molecule-1 (VCAM-1). The α4 integrin chain (a.k.a. CD49d) has been previously shown to be associated with poor prognosis in CLL by marking a subset of CLL patients characterized by a more aggressive clinical course both in term of disease progression and overall survival. Despite the great deal of studies investigating CLL cell microenvironmental interactions in tissue sites, little is known regarding the constitutive engagement of adhesion receptors in circulating CLL cells, and the role in this context of plasma/plasma components. To address this issue, the proteomic profiles of circulating leukemic cells from 80 CLL cases expressing or not CD49d were explored using a reverse phase protein microarray (RPMA) approach quantitatively analysing 77 proteins (61 phosphoproteins) known to be involved in translational control, cell growth, apoptosis, B cell receptor and cytoskeletal signaling. Comparison of the signaling activation portrait between 40 CD49d pos and 40 CD49d neg CLL cases highlighted the over-expression in CD49d pos CLL of proteins involved in the regulation of integrin-mediated cytoskeletal dynamics, such as phospho-p21-activated kinase (PAK1 Ser199-204/PAK2 Ser192-197; p=0.0005), phospho-LIM kinase (LIMK1 Thr508/LIMK2 Thr505; p=0.00001) and the adaptor protein CrkII Tyr221 (p=0.039). Moreover, CD49d pos CLL cells were characterized by a high correlation between proteins involved in integrin-mediated signal trasduction, including the focal-adhesion kinase (FAK Tyr576-Ser577), the tyrosine kinase Src Tyr527 and the adaptor protein CrkL Tyr207. Since PAK and LIMK represent key players in the modulation of the structure and the activity of actin cytoskeleton, we focused on these proteins for validation experiments. The constitutive pPAK and pLIMK overexpression in the CD49d pos CLL group was confirmed by western blot analysis comparing purified CLL cells from 3 CD49d pos versus 3 CD49d neg cases (mean fold increase >100 for both proteins). The results obtained suggest that integrin signalling is constitutively active in CD49d-expressing circulating CLL cells, pointing to a constitutive receptor engagement by CD49d ligands allegedly present in plasma. To test whether plasma constituents could modulate integrin-signaling proteins, CLL cells from 5 cases, expressing or not CD49d, were challenged with autologous plasma (1:3 dilution) for 30 seconds, 1 and 3 minutes. The presence of plasma induced a strong increase of PAK and LIMK phosphorylation intensities in CD49d pos CLL cells, starting at 30 seconds upon stimulation (mean fold increase >10 as compared to control for both proteins), and increasing after 1 and 3 minutes (mean fold increase >40 and >50 for both the proteins, respectively). Conversely, plasma stimulation did not induce pPAK and pLIMK expression modulation in CD49d neg CLL cells. Of note, pretreatment of CD49d-expressing CLL cells with the anti-CD49d HP1/2 blocking antibody, resulted in lower up-regulation of pPAK and pLIMK with an overall 60% inhibition for both the proteins (p=0.01), confirming the involvement of CD49d triggering in the observed activated signaling. Given the above results, we investigated plasma from 24 CLL patients, expressing CD49d at different levels, for the presence of the CD49d ligand fibronectin using an ELISA detection kit. All samples tested showed more than 1 mg/ml fibronectin concentration, without differences between CD49d-expressing and CD49d neg CLL cases. Altogether these results sustain the hypothesis of an active role of plasma/plasma components in the activation of CD49d-mediated integrin pathway, thus favoring the delivery of chemoresistance/pro-survival signals even in the context of circulating CLL cells. Our results may be of interest in the perspective of novel therapies (e.g. Bruton tyrosine kinase inhibitors) known to provoke a massive egress of neoplastic cells from tissue sites into the blood stream. Disclosures: No relevant conflicts of interest to declare.

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Vegf and bFGF Single-Nucleotide Polymorphisms In Chronic Lymphocytic Leukemia: Impact On Susceptibility

Blood ◽

10.1182/blood.v122.21.5287.5287 ◽

2013 ◽

Vol 122 (21) ◽

pp. 5287-5287

Author(s):

Sandra Ballester ◽

Begoña Pineda ◽

Eduardo Tormo ◽

Blanca Navarro ◽

Ariadna Perez ◽

...

Keyword(s):

Chronic Lymphocytic Leukemia ◽

Conflicts Of Interest ◽

Expression Patterns ◽

Lymphocytic Leukemia ◽

P Value ◽

Nucleotide Polymorphisms ◽

Exact Test ◽

Cd38 Expression ◽

Mutational Status ◽

The Individual

Abstract Background B-cell chronic lymphocytic leukemia (B-CLL) is a heterogeneous disease with a highly variable clinical outcome. Recent studies have identified a number of different molecular prognostic markers (including mutational status of the IgVH gene, ZAP70 and CD38 expression) that allow to discriminate patients in prognostic subgroups. However, different expression patterns of angiogenic factors as VEGF, VEGFR1 and bFGF have been related with B-CLL susceptibility and treatment requirements. We have analyzed the polymorphisms: -710 C/T in VEGFR1, rs1109324, rs1547651, rs3025039 (936C/T) and rs833052 in VEGF and rs1449683 (223 C/T) in bFGF in order to determine the possible association with susceptibility in B-CLL. Methods Peripheral blood samples from 230 B-CLL patients and 476 healthy controls were genotyped using probes TaqMan SNP Genotyping Assays. Samples were providing from the Hospital Clinic of Valencia. Four SNPs in the VEGF gene, one SNP in the bFGF gene and one SNP in the VEGFR1 gene were evaluated. Statistical analysis was performed using SNPStats program (Catalan Institute of Oncology) and Fisher's exact test was applied to evaluate the significance. Results We have observed an increased frequency of the T allele in the rs1449683 SNP [OR 1.62 (95% CI: 0.98-2.66) p-value =0.063] and in the rs1547651 SNP [OR 0.72 (95% CI: 0.51-1.03), p-value=0.072] in our B-LLC patients when compared to control subjects. Moreover we observed that T allele carriers of rs3025039 (VEGF) have a significant protective effect concerning this disease [OR 0.59 (95% CI: 0.39-0.89) p-value=0.009]. Conclusion Our data indicate an increased frequency of the T allele in polymorphisms rs1449683 (bFGF) and rs1547651 (VEGF) in the group of patients, which possibly account for the individual susceptibility to develop B-CLL. On the other hand the data provided suggest that the T allele of VEGF rs3025039 is likely important genetic marker of susceptibility to B-CLL. Further studies regarding the role of pro-angiogenic markers in B-CLL would be beneficial to help elucidate pathogenic pathways in this disease. Disclosures: No relevant conflicts of interest to declare.

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Revisiting Hypogammaglobulinemia in Chronic Lymphocytic Leukemia: A Combined Clinicobiological Approach

Blood ◽

10.1182/blood.v124.21.5633.5633 ◽

2014 ◽

Vol 124 (21) ◽

pp. 5633-5633 ◽

Cited By ~ 3

Author(s):

Panagiotis Baliakas ◽

Aliki Xochelli ◽

Eva Minga ◽

Anastasia Hadzidimitriou ◽

Vassiliki Douka ◽

...

Keyword(s):

Clinical Stage ◽

Normal Serum ◽

Lymphocytic Leukemia ◽

Cd38 Expression ◽

Serum Immunoglobulins ◽

Cytogenetic Aberrations ◽

Mutational Status ◽

Ighv Gene ◽

Immunoglobulin Subclasses ◽

Notch1 Mutations

Abstract Chronic lymphocytic leukemia (CLL) is characterized by progressive hypogammaglobulinemia that can affect one or more immunoglobulin subclasses. Although many underlying mechanisms have been suggested, the pathogenesis of this phenomenon remains to be elucidated. In the present study, we revisit hypogammaglobulinemia in CLL through a combined clinicobiological approach aiming at identifying associations with particular disease profiles that would offer pathogenetic insight and guidance for further research. The study group included 412 CLL patients with available information about serum immunoglobulins either at diagnosis (n=380) or before treatment initiation (n=32). Patient characteristics were as follows: median age: 65 years; males/females: 266/146; Binet stage A: 272/335, unmutated IGHV genes (U-CLL): 140/412 cases (34%); CD38 expression: 59/330 cases (18%); clonotypic IG of the MD or G isotype: 250 and 43 cases, respectively; isolated del(13q): 64/136 (47%); trisomy 12: 18/183 (10%); del(11q): 18/186 (10%); del(17p): 11/189 (6%); NOTCH1 del7544-45/p.P2514Rfs*4: 8/219 (4%). With a median follow up of 5 years, 152/329 cases (46%) received treatment. Decreased immunoglobulin serum levels in at least one subclass were identified in 220/412 patients (53%), as follows: (i) decreased IgM, 172/412 cases (41%); (ii) decreased IgG, 78/412 cases (19%); (iii) decreased IgA, 100/412 cases (24%). In 36/412 cases (9%), a decrease in all serum immunoglobulin subclasses was noted. No statistically significant differences were identified between patients with normal serum immunoglobulin levels versus those with hypogammaglobulinemia regarding age, gender, disease burden at diagnosis, IGHV gene mutational status, CD38 expression, cytogenetic aberrations, NOTCH1 mutations and the incidence of a second malignancy. However patients with hypogammaglobulinemia exhibited increased need for treatment compared to patients with normal serum immunoglobulins (91/175 vs 61/154 respectively, p=0.025). Among cases with hypogammaglobulinemia, 90 (41%) and 26 (12%) exhibited isolated IgM and IgA subclass deficiency, respectively; isolated IgG decrease, was relatively rare (10/220 cases, 4%). Interestingly, when comparing isolated IgA versus other subclass deficiencies, statistically significant associations were identified with (i) advanced clinical stage (Binet B/C, Rai III/IV) (p=0.002); (ii) female gender (p=0.041); and, (iii) NOTCH1 mutations (p=0.004). A propos of the latter, it is noteworthy that in 5/8 (63%) mutant NOTCH1 cases with hypogammaglobulinemia, the affected subclass was IgA. Within our cohort, we identified cases belonging to one of three different, well characterized subsets with stereotyped B-cell receptor immunoglobulin (BcR IG), namely: (1) subset #1 (clan I IGHV genes/IGKV1(D)-39): U-CLL, clinically aggressive, n=12; (2) subset #2 (IGHV3-21/IGLV3-21), mixed IGHV mutational status, noted clinical aggressiveness, n=5; and, (3) subset #4, mutated IGHV4-34/IGKV2-30 BcR IG, clinically indolent, n=12. Notably, all subset #2 cases showed low levels of at least one serum subclass, while in 4/5 and 3/5 cases, two or all three immunoglobulin subclasses were affected. Although numbers are small, the incidence of hypogammaglobulinemia in subset #2 was significantly (p<0.05) higher compared to either subset #1 or subset #4). Univariate analysis revealed clinical stage, CD38 expression and IGHV mutational status as statistically important parameters (p<0.05) for both time-to-first–treatment (TTFT) and overall survival (OS); in contrast, hypogammaglobulinemia had no impact either on on TTFT or OS. In multivariate analysis, clinical stage and IGHV gene mutational status retained independent significance. In conclusion, abnormalities of serum immunoglobulins are detected in CLL patients with heterogeneous clinicobiological profiles, including different disease burden (clinical stage), cytogenetic aberrations and IGHV gene mutational status. However, certain observations reported herein, in particular the high incidence of hypogammaglobulinemia in subset #2 and the association of NOTCH1 mutations with IgA subclass deficiency, are noteworthy and indicate the need for research towards unraveling causal mechanisms among the observed interwined events. Disclosures No relevant conflicts of interest to declare.

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Serum IgM Activates BCR Signaling Pathways and Increases Survival of Chronic Lymphocytic Leukemia B Cells

Blood ◽

10.1182/blood.v126.23.4131.4131 ◽

2015 ◽

Vol 126 (23) ◽

pp. 4131-4131

Author(s):

Stefania Gobessi ◽

Binu K Sasi ◽

Luca Laurenti ◽

Dimitar G Efremov

Keyword(s):

B Cells ◽

Chronic Lymphocytic Leukemia ◽

Signaling Pathways ◽

Target Genes ◽

Conflicts Of Interest ◽

Direct Interaction ◽

Leukemic Cell ◽

Fold Increase ◽

Lymphocytic Leukemia ◽

Bcr Signaling

Abstract Serum IgM would be expected to bind chronic lymphocytic leukemia B cells through two different mechanisms. The first mechanism is via interactions between the immunoglobulin heavy chain CDR3 of the leukemic B cell receptors (BCRs) and internal epitopes located in the FR2 and FR3 regions of serum IgM molecules, analogous to the recently identified cell-autonomous BCR-BCR interaction. The latter interaction represents a general feature of human CLL BCRs and was recently shown to be positively selected during leukemia development in the Eμ-TCL1 transgenic murine model. The second mechanism is by binding of serum IgM to the recently identified Fc receptor for IgM (FcμR), which is overexpressed on CLL B cells. In the present study we investigated the consequences of the interaction between serum IgM and CLL cells. Incubation of CLL cells with Alexa488-conjugated human IgM resulted in strong cell surface labeling, confirming that IgM binds to CLL cells. Binding was substantially inhibited by preculture of CLL cells with Fcμ, suggesting that IgM interacts with CLL B cells primarily through the FcμR. To investigate whether IgM also binds to the leukemic BCRs, we analyzed activation of downstream BCR signaling pathways and expression of a well-defined set of BCR-target genes (Herishanu Y et al, Blood. 2011;117:563-74) in CLL cells cultured in the presence or absence of purified IgM. After three hours in culture with polyclonal or monoclonal human IgM, 5 of the 7 investigated BCR target genes (OAS3, RGS1, GFI1, CCND2 and KLF4) showed a 2- to 9-fold increase with respect to unstimulated CLL cells, whereas the remaining two genes (EGR1 and EGR2) were not induced. The induced BCR target genes were also upregulated to an equal or even greater extent by Fcμ, suggesting that these effects are primarily or exclusively caused by binding of IgM to the FcμR. Analysis of downstream signaling events, such as SYK and ERK phosphorylation, also showed similar induction by IgM and Fcμ. However, intracellular Ca2+ flux was induced to a substantially greater extent with IgM, suggesting that certain effects are mediated by a direct interaction between serum IgM and the leukemic cell BCRs. Since co-ligation of the FcμR was recently shown to enhance the survival of anti-IgM-stimulated murine B lymphocytes (Ouchida R et al, J Immunol. 2015;194:3096-101), we investigated the consequences of IgM binding on CLL cell survival. CLL cells from 18 patients were cultured with or without purified human IgM for 72 hours and then analyzed by Annexin V/PI staining. A modest but significant increase in the percentage of viable CLL cells was observed in the presence of IgM (percentage of viable CLL cells without IgM: 40.5±17.8; with IgM: 43.8±18.4; P =0.016), which was replicated in a smaller series of samples cultured with Fcμ (n=12, percentage of viable CLL cells without Fcμ: 41.1±17.8; with Fcμ: 49.5±15.6; P =0.019). Altogether, these data suggest that binding of serum IgM results in activation of prosurvival pathways in CLL cells and that this effect is most likely mediated by co-triggering the FcμR and BCR. Disclosures No relevant conflicts of interest to declare.

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Immunophenotypic Profile and Recurrent Somatic Mutations in 131 Chronic Lymphocytic Leukemia Patients: Low Expression of CD25 in NOTCH1-Mutated Cases

Blood ◽

10.1182/blood.v128.22.3201.3201 ◽

2016 ◽

Vol 128 (22) ◽

pp. 3201-3201

Author(s):

Miriam Castillo ◽

Ana María Hurtado ◽

Tzu Hua Chen-Liang ◽

Julia Muñoz-Ballester ◽

Bartlomiej P Przychodzen ◽

...

Keyword(s):

Chronic Lymphocytic Leukemia ◽

Somatic Mutations ◽

Lymphoblastic Leukemia ◽

Lymphocytic Leukemia ◽

Limited Information ◽

Male Predominance ◽

Mutational Status ◽

The Impact ◽

Notch1 Mutations ◽

Low Expression

Abstract Background: We and others have reported on the impact of recurrent somatic mutations not only in the multistep pathogenetic process, but also in the clinical heterogeneity of chronic lymphocytic leukemia (CLL) patients. Immunophenotyping, as part of the diagnostic workout, is used for assessing clonality, as a differential diagnosis tool, and to examine the expression of molecules associated with a worse prognosis. Recently, NOTCH1 mutations have been linked to low CD20 levels in CLL and with a relative resistance to anti-CD20 immunotherapy in vitro. But to date, there is limited information on the correlation between cell surface marker expression and the presence of somatic mutations in CLL. The aim of this study was to evaluate potential associations between an extended phenotypic panel and the mutational status of 13 recurrently mutated genes in CLL detected by deep sequencing. Patients and Methods: To this end, we performed targeted NGS sequencing of blood samples, collected at diagnosis, from 131 CLL patients. Every patient underwent, at baseline, a flow cytometry characterization with a panel including (sIg)λ, (sIg)κ, CD19, CD5, CD11b, CD81, CD10, CD79b, CD29, CD38, FMC7, CD22, CD45, CD103, CD11c, CD25, ZAP70, CD11a, and CD24. We designed a TruSeq Custom Amplicon panel (Illumina, Inc. San Diego, CA, USA) containing 13 genes and covering 28.099 bases. The average amplicon size was 238 base pairs and ~ 99.1% of the regions were covered on both strands. Paired-end sequencing (2x250 bp) was performed with MiSeq v2.2 chemistry, and a mean depth of 998 reads/base within the regions of interest was obtained. Raw data were analyzed with IlluminaonJboard Real Time Analysis (RTA v.2.4.60.8) software and MiSeq Reporter. Results: With a median age of 68 y.o. (range, 33-95) and a slight male predominance, the median follow up time of our cohort was 43 months (24-104). We found that 47/131 (35%) patients harbored at least one mutation, with NOTCH1 (n = 13, 10%), ATM (n = 10, %), TP53 (n = 8, %), and SF3B1 (n = 8, 5.5%), as the most frequently mutated genes. Those patients with a NOTCH1 mutation showed a lower CD25 expression (25 mean fluorescence intensity units (MFIu)) than those without a mutation (45 MFIu), p=0.001. In addition, a higher expression of CD5 (265 vs. 219 MFIu, p= 0.02), of the monoclonal light chain (90.5 vs. 58.6 MFIu, p=0.03), and a higher percentage of CD38+ cells in the CD19+CD5+ compartment (37% vs. 19%, p=0.006) were significantly associated with the presence of, at least, one somatic mutation. We could not validate the recently reported association between the presence of NOTCH1 mutations and a low expression of CD20. In our cohort, the MFI expression in NOTCH1 mutated and non-mutated patients was 176 and 135 units, respectively (p=0.2) In the multivariate Cox analysis, the presence of a somatic variant in TP53 and a higher percentage of positive CD38 cells in the tumour population showed both a worse overall survival and shorter time to first treatment. The independence of these two variables was also supported by not finding a significative difference percentage of CD38 positive cells between TP53 mutated and non mutated cases (p=0.5). Conclusions: The associations described herein suggest potential pathogenic pathways in CLL, in particular the CD25-NOTCH1 axis, with a significative inferior expression of CD25 when activating NOTCH1 mutations are present. The relationship found between these two variables, with an inversed direction to that found in physiological conditions, has also been shown in the setting of NOTCH1-mutated acute lymphoblastic leukemia, emerging as a potential targetable pathway in this subset of CLL patients. Disclosures Maciejewski: Apellis Pharmaceuticals Inc: Membership on an entity's Board of Directors or advisory committees; Alexion Pharmaceuticals Inc: Consultancy, Honoraria, Speakers Bureau; Celgene: Consultancy, Honoraria, Speakers Bureau.

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