Combination Of Ibrutinib With ABT-199, a BCL-2 Pathway Inhibitor: Effective Therapeutic Strategy In a Novel Mantle Cell Lymphoma Cell Line Model

Abstract Background Mantle cell lymphoma (MCL) is an aggressive subtype of Non-Hodgkin Lymphoma associated with poor prognosis. Constitutive activation of B-cell receptor (BCR) signaling plays an essential role for the survival and proliferation of malignant B-cells. Targeting Bruton’s tyrosine kinase (BTK), a component of BCR signaling pathway, with ibrutinib is a promising strategy. As a single agent, complete and partial response rates of 21% and 47%, respectively, were observed in a phase 2 study for relapsed or refractory MCL. Simultaneous inhibition of multiple biologic pathways has the potential to result in a synergism. We combined ibrutinib with ABT-199, a BH3 mimetic that selectively targets the BCL-2 pathway, and tested their in vitroefficacy against MCL. Experimental design A novel MCL cell line, CCMCL1, and four other MCL cell lines (Jeko-1, Mino, JVM2, Rec-1) were used for flow cytometry-based apoptosis and cell cycle analyses to evaluate the combinational effect of ibrutinib with ABT-199 (ChemieTek. Indianpolis. IN). The interaction between drugs was examined with Calcusyn software and combination index values served to determine the combined effect as synergistic (<1), additive (=1), or antagonistic (>1). Immunoblotting was performed to investigate signaling pathways of MCL cells exposed to these agents. Results CCMCL1 was derived from primary leukemic MCL cells. Cells were initially directly injected via tail vein into an NSG mouse. Engrafted cells were then isolated at 10 weeks from spleen and placed into routine cell culture. Immunophenotyping showed CCMCL1 cells have similar characteristics as the primary patient MCL cells, which expressed CD5, CD19, CD20, FMC7 and monotypic kappa light chain. Immunohistochemical staining of engrafted mouse spleen tissue showed expression of cyclin D1 and SOX11. The karyotype is highly complex with an IGH@/CCND1 fusion by metaphase FISH. In addition to spleen, MCL cell infiltration was observed in mouse liver, bone marrow, blood, brain, lung, kidney and intestine. In vitro cultured CCMCL1 cells underwent apoptosis upon expose to ibrutinib and ABT-199 as single agents. Combination of these two drugs resulted in synergistic induction of apoptosis (Table 1). Synergism was also observed with Jeko-1, Mino, JVM-2 and Rec-1 cells. Immunoblotting showed CCMCL1 cells have constitutive expression of cyclin D1, SOX11, PAX5 and MCL1. Ibrutinib as a single agent induced a rapid down-regulation of SOX11 and MCL1, while combination of ibrutinib with ABT-199 further enhanced down regulation of SOX11, followed by down-regulation of PAX5 at a later time point. We are currently testing the in vivo efficacy of combining these two drugs in a CCMCL1 NSG mouse model. Conclusion Our CCMCL1/NSG mouse model is a new model for pre-clinical assessment of MCL treatment approaches. Combination of ibrutinib with ABT-199 has synergistic effect of apoptotic induction in CCMCL1 as well as four other MCL cell lines tested. Ibrutinib or ibruitnib/ABT-199 combination induced apoptosis of MCL is associated with down-regulation of SOX11 and PAX5. Simultaneous down regulation of MCL1 via ibrutinib and targeting of BCL2 may contribute to the in vitrosynergism observed. These data support further investigation of this novel therapeutic strategy. Disclosures: No relevant conflicts of interest to declare.

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BET bromodomain inhibitor birabresib in mantle cell lymphoma: in vivo activity and identification of novel combinations to overcome adaptive resistance

ESMO Open ◽

10.1136/esmoopen-2018-000387 ◽

2018 ◽

Vol 3 (6) ◽

pp. e000387 ◽

Cited By ~ 10

Author(s):

Chiara Tarantelli ◽

Elena Bernasconi ◽

Eugenio Gaudio ◽

Luciano Cascione ◽

Valentina Restelli ◽

...

Keyword(s):

Mantle Cell Lymphoma ◽

Cell Lines ◽

Cell Lymphoma ◽

Antitumour Activity ◽

Single Agent ◽

Treatment Strategies ◽

Bet Inhibitor ◽

Mantle Cell

BackgroundThe outcome of patients affected by mantle cell lymphoma (MCL) has improved in recent years, but there is still a need for novel treatment strategies for these patients. Human cancers, including MCL, present recurrent alterations in genes that encode transcription machinery proteins and of proteins involved in regulating chromatin structure, providing the rationale to pharmacologically target epigenetic proteins. The Bromodomain and Extra Terminal domain (BET) family proteins act as transcriptional regulators of key signalling pathways including those sustaining cell viability. Birabresib (MK-8628/OTX015) has shown antitumour activity in different preclinical models and has been the first BET inhibitor to successfully undergo early clinical trials.Materials and methodsThe activity of birabresib as a single agent and in combination, as well as its mechanism of action was studied in MCL cell lines.ResultsBirabresib showed in vitro and in vivo activities, which appeared mediated via downregulation of MYC targets, cell cycle and NFKB pathway genes and were independent of direct downregulation of CCND1. Additionally, the combination of birabresib with other targeted agents (especially pomalidomide, or inhibitors of BTK, mTOR and ATR) was beneficial in MCL cell lines.ConclusionOur data provide the rationale to evaluate birabresib in patients affected by MCL.

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Therapeutic Activity of Lenalidomide in Mantle Cell Lymphoma and Indolent Non-Hodgkin’s Lymphomas

Advances in Hematology ◽

10.1155/2012/523842 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7 ◽

Cited By ~ 4

Author(s):

Marco Gunnellini ◽

Lorenzo Falchi

Keyword(s):

Mantle Cell Lymphoma ◽

Cell Lymphoma ◽

Single Agent ◽

Response Rates ◽

Prognostic Scores ◽

Cell Transplant ◽

Survival Times ◽

Phase Ii Studies ◽

Mantle Cell ◽

Hodgkin's Lymphomas

Mantle cell lymphoma (MCL) comprises 3–10% of NHL, with survival times ranging from 3 and 5 years. Indolent lymphomas represent approximately 30% of all NHLs with patient survival largely dependent on validated prognostic scores. High response rates are typically achieved in these patients with current first-line chemoimmunotherapy. However, most patients will eventually relapse and become chemorefractory with poor outcome. Alternative chemoimmunotherapy regimens are often used as salvage strategy and stem cell transplant remains an option for selected patients. However, novel approaches are urgently needed for patients no longer responding to conventional chemotherapy. Lenalidomide is an immunomodulatory drug with activity in multiple myeloma, myelodisplastic syndrome and chronic lymphoproliferative disorders. In phase II studies of indolent NHL and MCL lenalidomide has shown activity with encouraging response rates, both as a single agent and in combination with other drugs. Some of these responses may be durable. Optimal dose of lenalidomide has not been defined yet. The role of lenalidomide in the therapeutic armamentarium of patients with indolent NHL or MCL will be discussed in the present paper.

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Combined inhibition of Chk1 and Wee1 as a new therapeutic strategy for mantle cell lymphoma

Oncotarget ◽

10.18632/oncotarget.2583 ◽

2014 ◽

Vol 6 (5) ◽

pp. 3394-3408 ◽

Cited By ~ 40

Author(s):

Rosaria Chilà ◽

Alessandra Basana ◽

Monica Lupi ◽

Federica Guffanti ◽

Eugenio Gaudio ◽

...

Keyword(s):

Mantle Cell Lymphoma ◽

Therapeutic Strategy ◽

Cell Lymphoma ◽

Mantle Cell

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Venetoclax as a single agent and in combination with PI3K‐MTOR1/2 kinase inhibitors against ibrutinib sensitive and resistant mantle cell lymphoma

British Journal of Haematology ◽

10.1111/bjh.15079 ◽

2018 ◽

Vol 184 (2) ◽

pp. 298-302 ◽

Cited By ~ 3

Author(s):

Huijuan Jiang ◽

Tint Lwin ◽

Xiaohong Zhao ◽

Yuan Ren ◽

Grace Li ◽

...

Keyword(s):

Mantle Cell Lymphoma ◽

Kinase Inhibitors ◽

Cell Lymphoma ◽

Single Agent ◽

Mantle Cell

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Induction of Apoptosis in Jeko-1 Mantle Cell Lymphoma Cell Line by Resveratrol: A Proteomic Analysis

Journal of Proteome Research ◽

10.1021/pr700712p ◽

2008 ◽

Vol 7 (7) ◽

pp. 2670-2680 ◽

Cited By ~ 17

Author(s):

Daniela Cecconi ◽

Alberto Zamò ◽

Alice Parisi ◽

Elena Bianchi ◽

Claudia Parolini ◽

...

Keyword(s):

Mantle Cell Lymphoma ◽

Cell Line ◽

Proteomic Analysis ◽

Cell Lymphoma ◽

Lymphoma Cell ◽

Lymphoma Cell Line ◽

Mantle Cell Lymphoma Cell ◽

Mantle Cell ◽

Induction Of Apoptosis

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Anti-Tumor Activity of Single-Agent CCI-779 for Relapsed Mantle Cell Lymphoma: A Phase II Trial in the North Central Cancer Treatment Group.

Blood ◽

10.1182/blood.v104.11.129.129 ◽

2004 ◽

Vol 104 (11) ◽

pp. 129-129 ◽

Cited By ~ 3

Author(s):

Thomas Witzig ◽

Susan Geyer ◽

Irene Ghobrial ◽

David Inwards ◽

Rafael Fonseca ◽

...

Keyword(s):

Cyclin D1 ◽

Mantle Cell Lymphoma ◽

Median Time ◽

Response Rate ◽

Cell Lymphoma ◽

Single Agent ◽

Pi3k Pathway ◽

Mantle Cell ◽

Grade 3 ◽

Anti Tumor Activity

Abstract Purpose: Mantle cell lymphoma (MCL) is characterized by a t(11;14) resulting in overexpression of cyclin D1, a member of the phosphatidylinosital 3 kinase (PI3K) pathway. This study tested whether CCI-779, which inhibits the PI3K pathway at the level of the mammalian target of rapamycin (mTOR) could produce tumor responses in patients (pts) with MCL. Patients and Methods: Eligible pts had biopsy-proven, cyclin D1 positive MCL and had relapsed or were refractory to therapy. Pts received CCI-779 250 mg IV every week as a single agent. Pts were re-staged after 1 cycle (4 doses) and every 3 cycles thereafter. Pts with a tumor response after 6 cycles were eligible to continue drug for a total of 12 cycles or 2 cycles after complete remission (CR) and then were observed. Results: Thirty-five pts were enrolled and evaluable for toxicity; 1 patient had MCL by histology but was cyclin D1 negative and ineligible for efficacy evaluation. The median age was 70 years (range, 38–89), 91% were stage 4, and 69% had ≥ 2 extranodal sites. Pts had received a median of 3 prior therapies (range, 1–11) and 54% were refractory to their last treatment. The overall response rate was 38% (13/34) with 1 CR (3%) and 12 PRs (35%), surpassing the pre-defined criteria for a promising agent. Responses tended to occur rapidly with median time to response of 1 month (range, 1–8). To date, 26 patients have progressed, with a median time-to-progression of 6.8 months (95% CI: 3.8 – 9.7). Median duration of response for the 13 responders was 5.7 months (95% CI: 5.2 – 13.2). Overall, 32 out of 35 patients who received treatment had grade 3 or 4 toxicity. The most common toxicities were hematologic with grade 3 (n=24) or grade 4 (n=4). Thrombocytopenia was the most frequent grade 3/4 toxicity (n=25) and the largest cause of dose-reductions, although counts typically recovered within one week. Only 4 patients could tolerate sustained 250 mg per week throughout their treatment (including one who went on to alternate treatment after 1 cycle) and the median dose/month was 175 mg. Conclusions: Single-agent CCI-779 has substantial anti-tumor activity in relapsed MCL. This study demonstrates that agents, which selectively target cellular pathways dysregulated in MCL cells can produce therapeutic benefit. The high response rate warrants further studies of this agent in MCL, but the high incidence of hematologic toxicity suggests that a lower dose should be explored. CCI-779 at 25mg is currently being evaluated in MCL through an NCCTG trial

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Truncations in CCND1 mRNA 3′ UTR Alters microRNA Regulation in Mantle Cell Lymphoma.

Blood ◽

10.1182/blood.v110.11.3184.3184 ◽

2007 ◽

Vol 110 (11) ◽

pp. 3184-3184

Author(s):

Robert W. Chen ◽

Lynne Bemis ◽

Carol Amato ◽

Birks Diane ◽

Myint Han ◽

...

Keyword(s):

Cell Cycle ◽

Protein Expression ◽

Mantle Cell Lymphoma ◽

Cell Line ◽

Cell Lymphoma ◽

Regulation Of Gene Expression ◽

Proliferative Potential ◽

Transcriptional Level ◽

Cell Cycle Regulator ◽

Mantle Cell

Abstract Mantle Cell Lymphoma (MCL) represents only 5–10% of all non-Hodgkins lymphomas, making it an uncommon but difficult form of lymphoma to treat. It has a poor prognosis among the B cell lymphomas with median survival of three years. The genetic hallmark of MCL is the t(11,14) translocation causing amplification of cyclin D1 (CCND1), a known cell cycle regulator which is overexpressed in many other cancers. MicroRNAs (miRNA) are a new class of abundant small RNAs that play important regulatory roles at the post transcriptional level. They act by binding to the 3′ untranslated region (UTR) of mRNAs and block either their translation or initiate their degradation. Recent reports have shown truncations in the CCND1 3′ UTR occur in MCL and indicate a worse prognosis. We hypothesized that truncations in 3′ UTR of CCND1 alter it’s regulation by microRNAs. Based on bioinformatics, we identified microRNA 16 with putative docking sites in the 3′UTR of CCND1. Mir-16 has been implicated as a cell cycle regulator. We identified 2 cell lines (Jeko-1 and Z138) with truncations in CCND1 3′ UTR and demonstrated increased CCND1 mRNA expression by qRT-PCR, increased protein expression by western blot, and higher proliferative potential by cell cycle. We prepared a reporter construct by ligating the full length 3′ UTR of CCND1 to GFP. We then co-transfected this construct with mimics of mir-16 into a cancer cell line and demonstrated downregulation of CCND1 protein expression by flow cytometry. In the MCL cell line Granta-519 with non-truncated CCND1, transfection with mimics of mir-16 deminstrated decreased expression of CCND1 mRNA. These studies suggest that the overexpression of CCDN1 In MCL may result from altered regulation of gene expression from loss of a miRNA regulatory site and may give new clues into the patho-biology of this disease and insights into possible new therapies.

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FTY720 Demonstrates Promising in-Vitro and in-Vivo Pre-Clinical Activity by Down-Modulation of Cyclin D1 and Pakt in Mantle Cell Lymphoma.

Blood ◽

10.1182/blood.v114.22.3728.3728 ◽

2009 ◽

Vol 114 (22) ◽

pp. 3728-3728

Author(s):

Lapo Alinari ◽

Qing Liu ◽

Ching-Shih Chen ◽

Fengting Yan ◽

James T Dalton ◽

...

Keyword(s):

Cell Cycle ◽

Cyclin D1 ◽

Mantle Cell Lymphoma ◽

Cell Line ◽

Cell Lymphoma ◽

Tumor Burden ◽

Time Dependent ◽

Control Group ◽

Mantle Cell

Abstract Abstract 3728 Poster Board III-664 Over-expression of Cyclin D1 and constitutive phosphorylation of Akt has been implicated in the pathogenesis of mantle cell lymphoma (MCL). Here we describe FTY720 (fingolimod), an immunosuppressive agent currently being explored in phase III studies in renal transplantation and multiple sclerosis patients, to mediate time- and dose-dependent cell death in primary MCL cells (6 patients) and MCL cell lines, Jeko and Mino. FTY720-induced apoptosis was associated with reactive oxygen species (ROS) generation, Bax up-regulation but not associated with caspase 3 activation in MCL. FTY720 treatment resulted in time-dependent down-modulation of Cyclin D1 and phospho Akt (p-Akt) protein level, two critical disease-relevant molecules in the pathogenesis of MCL. Consistent with the modulation of Cyclin D1, FTY720-induced cell cycle arrest with accumulation of cells in G0/G1 and G2/M phases of the cell cycle with concomitant decrease in S phase entry. Importantly, FTY720 treatment was also associated with a time-dependent phospho Erk (p-Erk) induction in Mino and Jeko cells. To determine the in vivo efficacy of FTY720, we developed a preclinical, in vivo xenograft model of human MCL where MCL cell lines (Jeko, Mino and SP53) were engrafted into severe combined immune deficient (SCID) mice. Cell dose titration trials identified 4 × 107 Mino or Jeko cells injected intravenously via tail vein to result in consistent engraftment and fatal tumor burden in all mice. All mice engrafted with 4 × 107 Jeko cells developed a disseminated disease within 3 weeks and had a median survival of 28 days (compared to 43 days for Mino and 51 days for SP53). Because the Jeko cell line was established from the peripheral blood of a patient with blastic variant MCL and demonstrated a more resistant phenotype to several immuno-chemoterapeutic compounds, this cell line was chosen to create a more stringent in vivo preclinical model. SCID mice were treated with the monoclonal antibody TMβ1 to deplete murine NK cells, engrafted with 4 × 107 Jeko cells and observed daily for signs of tumor burden. Ten mice/group were treated starting at day 15 post-engraftment with intraperitoneal injection of 100 μl of saline or FTY720 (5 mg/kg resuspended in 100 μl of saline), every day, for two weeks. The median survival for FTY720-treated mice (N=10) was 38 days (95% CI:30-39) compared to 26.5 days (95% CI: 26-27 days) for the control group mice (N=10). The results from the log-rank test indicated an overall statistical significant difference in survival functions between the FTY720 treatment and the control group (p=0.001). These results provide the first evidence for a potential use of FTY720 in targeting key pathways that are operable in the pathogenesis of MCL and warrant the further investigation of FTY720 in combination with other agents in clinical trials treating patients with MCL. Disclosures: No relevant conflicts of interest to declare.

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Herpes Zoster (HZ) Complicating Bortezomib Therapy of Relapsed/Refractory Indolent B-Cell and Mantle Cell Lymphoma: An Analysis of Two Phase II Trials.

Blood ◽

10.1182/blood.v116.21.2818.2818 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2818-2818

Author(s):

Vicki A. Morrison ◽

Richard I Fisher ◽

Andre Goy ◽

Sven de Vos ◽

Steven H. Bernstein ◽

...

Keyword(s):

B Cell ◽

Mantle Cell Lymphoma ◽

Board Of Directors ◽

Cell Lymphoma ◽

Single Agent ◽

Phase Ii Trials ◽

Two Phase ◽

Advisory Committees ◽

Mantle Cell ◽

Purine Analog

Abstract Abstract 2818 Background: The use of bortezomib-based therapy is known to be associated with an increased risk of HZ in patients (pts) with multiple myeloma, who have disease-related inherent immune defects. A 13% incidence of HZ occurrence in pts with relapsed/refractory MM who received single agent bortezomib has been previously reported (J Clin Oncol 2008; 26:4784-4790). However, the occurrence of HZ in bortezomib-treated pts with non-Hodgkin lymphoma (NHL) has not been previously examined. Methods: We reviewed clinical data from two phase II trials in which bortezomib therapy was administered to pts with relapsed/refractory mantle cell NHL or indolent B-cell NHL. The occurrence of HZ complicating their treatment course was delineated, and an analysis for potential predisposing risk factors was undertaken. Results: A total of 236 relapsed/refractory pts, median age 65 years (yrs), enrolled on these trials was examined. Mantle cell NHL pts (n=155) received single-agent bortezomib, 1.3 mg/m2, days (D) 1, 4, 8, 11, 21-D cycles; those with indolent B-cell NHL (n=81) received either bortezomib, 1.3 mg/m2, D 1, 4, 8, 11, 21-D cycles, plus rituximab, 375 mg/m2, D 1, 8, 15 (cycle 1) and D 1 (cycle 2) (n=41), or bortezomib, 1.6 mg/m2, D 1, 8, 15, 22, 35-D cycles, and rituximab, 375 mg/m2, D 1, 8, 15, 22 (cycle 1) (n=40). HZ occurred in 24 pts (10.2%) overall, with a comparable incidence in both disease subgroups. Median time to HZ occurrence was 39 (range, 11–206) days (< 2 cycles). Overall, 11% of pts had had a prior episode of HZ. Baseline demographic and clinical variables were examined, including age, gender, disease stage, baseline absolute neutrophil and lymphocyte counts, hemoglobin, lactate dehydrogenase, prior HZ, and number and types of prior therapies, to determine if any may predict for subsequent development of HZ. With regard to age, 71% of pts with HZ were age ≥65 yrs, compared to 48% without HZ (p=0.03). 63% of pts with HZ had received ≥2 lines of prior therapy, compared to 47% in those without HZ (p=0.15). 4% of pts with HZ had undergone prior stem cell transplantation, compared to 13% of pts without HZ. Of the pts with HZ, 25% had received prior purine analog therapy, compared to 9% of pts without HZ. The other baseline variables had no impact on the occurrence of HZ. In the 77 pts who responded to bortezomib protocol therapy (complete/partial responses), the incidence of HZ was 14%, compared to an 8% incidence of HZ in the 159 non-responders (p=0.15). Conclusions: HZ may complicate the course of relapsed/refractory indolent or mantle cell NHL pts receiving bortezomib-based therapies, with an incidence similar to the myeloma population. Pts who are elderly, more heavily-pretreated, or have received prior purine analog therapy may be at greater risk of this complication, and should be strongly considered for antiviral prophylaxis during such therapy. Disclosures: Morrison: Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Genentech: Speakers Bureau; Pfizer: Speakers Bureau. Off Label Use: Discussion of Velcade in NHL subtypes other than mantle cell lymphoma is included. Fisher:Allos Therapeutics: Consultancy; CytoKinetics: Consultancy; GSK: Consultancy; MundiPharma: Consultancy; Seattle Genetics: Consultancy; Millennium Pharmaceuticals, Inc,: Consultancy. Goy:Millennium, Celgene, GSK and Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Bernstein:Millennium Pharmaceuticals, Inc: Consultancy, Honoraria, Speakers Bureau. Boral:Millennium Pharmaceuticals, Inc.: Employment; Takeda Pharmaceuticals: Equity Ownership. Neuwirth:Millennium Pharmaceuticals, Inc.: Employment.

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Whole Transcriptome Sequencing Reveals Recurrent NOTCH1 Mutations in Mantle Cell Lymphoma

Blood ◽

10.1182/blood.v118.21.436.436 ◽

2011 ◽

Vol 118 (21) ◽

pp. 436-436 ◽

Cited By ~ 3

Author(s):

Robert Kridel ◽

Barbara Meissner ◽

Sanja Rogic ◽

Merrill Boyle ◽

Adele Telenius ◽

...

Keyword(s):

Overall Survival ◽

Mantle Cell Lymphoma ◽

Cell Line ◽

Cell Lines ◽

Research Funding ◽

Cell Lymphoma ◽

The Other ◽

Mantle Cell ◽

Whole Transcriptome ◽

Notch1 Mutations

Abstract Abstract 436 Background: Mantle cell lymphoma (MCL) is an aggressive subtype of non-Hodgkin's lymphoma that is characterized by the hallmark t(11;14)(q13;q32) translocation, as well as a high number of secondary chromosomal alterations. Further, a small number of genes such as TP53, ATM and CCND1 have been reported to be recurrently mutated in MCL, but do not fully explain the biology and do not adequately account for the wide spectrum of clinical manifestations, response to treatment and prognosis. The aim of this study was to discover new somatic mutations that could contribute to our understanding of the pathogenesis of MCL. Methods: In our discovery cohort, we sequenced the transcriptomes of 18 clinical samples (11 diagnostic and 7 progression biopsies) and 2 mantle cell lymphoma-derived cell lines (Mino and Jeko-1). For this purpose, whole transcriptome shotgun sequencing was performed on RNA extracted from fresh frozen tissue. We assembled an extension cohort of 103 diagnostic patient samples and 4 additional cell lines (Rec-1, Z-138, Maver-1, JVM-2), and performed Sanger sequencing of NOTCH1 exons 26, 27 and 34 on genomic DNA. We further exposed the 6 cell lines to 1 μM of the γ-secretase inhibitor XXI (compound E) for 7 days and measured cellular proliferation with an EdU incorporation assay. Survival analysis was carried out in the 113 patients with diagnostic biopsies and available outcome data. Results: NOTCH1 mutations were found in 14 out of 121 patient samples (11.6%) and in 2 out of 6 cell lines, Mino and Rec-1 (33.3%). The majority of these mutations (12 out of 14) lie in exon 34 that encodes the PEST domain of NOTCH1 and consist of either small frameshift-causing indels (10 cases) or nonsense mutations (2 cases). These mutations are predicted to cause truncations of the C-terminal PEST domain. To gain further insight into functional relevance, we treated 6 cell lines with compound E, an inhibitor of the γ-secretase complex that plays a critical role in the release of the intracellular domain of NOTCH1 after ligand-induced activation. In Rec-1, that harbours a NOTCH1 mutation, we observed a significant decrease in proliferation (mean percentage of cells in culture incorporating EdU decreasing from 47.5% to 1.4%, p<.001). No effect of compound E was observed in Mino, the other cell line with a NOTCH1 mutation, nor in the 4 cell lines that are wild type for NOTCH1. Outcome correlation analysis showed that NOTCH1 mutations are associated with poor overall survival (1.56 versus 3.86 years respectively, p=.001), but not with significantly shortened progression-free survival (0.88 versus 1.73 years respectively, p=.07). Discussion: We have identified recurrent mutations in NOTCH1 in a subset of patients with MCL (11.6%). The frequency and the pattern of mutations are strikingly similar to what has recently been reported in chronic lymphocytic leukemia, the other major CD5 positive B-cell malignancy (Nature, 2011 Jun 5, 475:101–105 and J Exp Med, 2011 Jul 4, 208:1389–1401). NOTCH1 mutations are associated with adverse prognosis as evidenced by shortened overall survival. This latter finding, however, should ideally be validated in a larger and uniformly treated cohort. Finally, the sensitivity of the Rec-1 cell line to compound E suggests that NOTCH1 mutations could serve as the target for tailored therapy in mantle cell lymphoma. Disclosures: Sehn: Roche/Genentech: Consultancy, Honoraria, Research Funding. Connors:Roche: Research Funding.

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