Scavenger Receptor Type B1 Is Essential for High Density Lipoprotein Nanoparticle Induced B-Cell Lymphoma Cell Death

Abstract Introduction: We recently reported that biomimetic, synthetic high-density lipoprotein nanoparticles (HDL NP), similar to natural HDL in size, shape, charge, and composition potently induce apoptosis in human B cell lymphoma cell lines in vitro, and in vivo, without adversely affecting primary hepatocytes or macrophages (Yang et al. 2013. PNAS 110(7): 2511-6). We showed that HDL NPs bind to the high-affinity HDL receptor, scavenger receptor type B-1 (SR-B1), expressed by lymphoma cells, and may play a functional role in apoptosis of B cell lymphomas. Methods: We analyzed tissue microarrays (TMAs) from patients with non-Hodgkin's lymphoma (NHL) for SR-B1 expression. In silico analyses of gene microarray datasets from the publicly available database Oncomine were conducted to investigate SR-B1 expression in lymphoma at the mRNA level. The B cell lymphoma cell lines Ramos (Burkitt's lymphoma), SUDHL4 (diffuse large B cell lymphoma) and HF-1 (transformed follicular lymphoma) were used to investigate the requirement for SR-B1 in HDL NP induced cell death. A blocking antibody, and stably expressed shRNA targeting SR-B1 expression were used to inhibit HDL NP interactions with SR-B1. Results: SR-B1 was overexpressed in a subpopulation of NHL represented in available TMAs. At the mRNA level, SR-B1 was up-regulated in 20% of lymphoma data sets (6 of 30). These data further confirm SR-B1 as a potential target of therapeutic intervention in B cell lymphomas. Antibody blockade of SR-B1 in the SR-B1+ cell lines Ramos, SUDHL4, and HF-1 prevented HDL NP induced cell death in a dose dependent manner (Figure 1A). Stable knockdown of SR-B1 by shRNA in Ramos cells also protected against HDL NP induced cell death compared with wild type and scrambled shRNA controls (Figure 1B). HDL NP induced cholesterol efflux in Ramos, SUDHL4, and HF-1 cells was reduced by the SR-B1 blocking antibody, or SR-B1 knockdown, further supporting that the HDL NP binds SR-B1. Conclusion: SR-B1 is expressed in primary B cell lymphomas, and interference of HDL NP interaction with SR-B1, through antibody blockade or knockdown of SR-B1, abrogated HDL NP induced cell death in multiple B cell lymphoma cell lines. Taken together, our data demonstrate the requirement of SR-B1 in HDL NP induced lymphoma cell death, and provide a rationale to pursue HDL NPs as potent therapy for B cell lymphomas in cases that express SR-B1. Figure 1. Antibody blockade (A) and shRNA knockdown (B) of SR-B1 prevents HDL NP induce cell death. Figure 1. Antibody blockade (A) and shRNA knockdown (B) of SR-B1 prevents HDL NP induce cell death. Disclosures Gordon: Dr Leo I. Gordon: Patents & Royalties: Patent for gold nanoparticles pending; Northwestern University: Employment. Thaxton:Aurasense: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: High Density Lipoprotein Nanoparticles for Lymphoma.

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Biomimetic Synthetic High Density Lipoprotein Nanostructures Target the SR-B1 Receptor and Differentially Manipulate Cellular Cholesterol Flux in Lymphoma Cells: A Novel Treatment Paradigm

Blood ◽

10.1182/blood.v120.21.157.157 ◽

2012 ◽

Vol 120 (21) ◽

pp. 157-157 ◽

Cited By ~ 1

Author(s):

Shuo Yang ◽

Marina G Damiano ◽

Heng Zhang ◽

Sushant Tripathy ◽

Andrey Ugolkov ◽

...

Keyword(s):

B Cells ◽

High Density Lipoprotein ◽

B Cell ◽

Cell Lines ◽

Cell Lymphoma ◽

Density Lipoprotein ◽

B Cell Lymphoma ◽

High Density ◽

Lymphoma Cell ◽

Lymphoma Cells

Abstract Abstract 157 We report a nanoparticle-enabled therapeutic approach to B cell lymphoma using synthetic, high-density lipoprotein nanoparticles (HDL-NP). Like natural HDLs, biomimetic HDL-NPs target scavenger receptor type B-1 (SR-B1), a high-affinity HDL receptor expressed by lymphoma cells. Functionally, and unlike natural HDL, a gold nanoparticle template used to control HDL-NP synthesis enables differential manipulation of cellular cholesterol flux through SR-B1. Recent evidence in lymphoblasts and myeloblasts from patients with acute lymphocytic leukemia (ALL) and acute myeloid leukemia (AML) demonstrates enhanced uptake of cholesterol through high-density lipoprotein (HDL) carriers, which may result in increased cell proliferation. We therefore hypothesized that by targeting SR-B1, we could manipulate cholesterol flux in lymphoma cells thereby targeting cellular signaling pathways that would lead to cell death and offer an innovative approach to the treatment of lymphoma and other cancers. Methods: To accomplish this, we developed a biomimetic spherical nanoparticle (HDL-NP) with surface chemical properties similar to natural HDL, including the ability to sequester cholesterol. Biomimetic HDL-NPs are synthesized using a 5 nm diameter gold (Au) nanoparticle (NP) as a size- and shape-restrictive template on which to assemble the surface chemical components of natural HDLs, including phospholipids and the HDL-defining apolipoprotein A1 (Apo A1). Importantly, the core AuNP template occupies the real estate in natural cholesterol-rich HDLs reserved for esterified cholesterol, which inherently limits the ability of HDL-NPs to deliver cholesterol. We incubated the HDL-NPs with various lymphoma cell lines, and similarly tested the HDL-NPs in a xenograft model. Results: We first examined gene expression profiles of diffuse large B-cell lymphoma (DLBCL), Burkitt Lymphoma (BL) and normal B cells from patient samples in a database generated using Affymetrix U133plus 2.0 arrays in order to establish the prevalence of SR-B1 expression. We compared the expression of SR-B1 in BL cases (n=20), and DLBCL cases (n=40) that were further subdivided as activated B-cell (ABC)-like DLBCL (n=20), and germinal center (GC)-like DLBCL (n=20) to normal naive (n=3) and memory (n=3) B cells obtained from healthy donors. We found that SR-B1 was expressed at two to four-fold higher levels in the lymphomas (ABC and GC) compared with normal B cells. Next, we determined the expression of SR-B1 in lymphoma cell lines and normal peripheral lymphocytes by immunoblotting, and we found that SR-B1 is expressed in multiple B cell lymphoma cell lines, but not in Jurkat, a T-cell line, and is not expressed by normal human lymphocytes. Incubation of HDL-NP with Ramos, LY-3 and SUDHL-4 resulted in a dose-dependent decrease in cell viability and apoptosis (Figure 1) of the Ramos and SUDHL-4 cells, less so in LY-3 cells, and not in the Jurkat line. This required the nanoparticle construct and could not be duplicated by individual components of that construct, and was reversible with addition of acetylated low-density lipoprotein, indicating that the SR-B1 receptor was targeted. Xenograft experiments with SCID beige mice (C.B-Igh-1b/GbmsTac-Prkdcscid-Lystbg N7) bearing Ramos and Jurkat flank tumor xenografts confirmed the activity of the HDL-NP (Figure 2). Conclusion: We report a template-directed and bio-functional therapeutic nanostructure that could shift the paradigm for treating lymphoma and other cancers. A combination of SR-B1 binding and manipulation of cholesterol flux is responsible for selective induction of apoptosis in B cell lymphoma. Disclosures: Thaxton: Aurasense: Employment, Equity Ownership.

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High Density Lipoprotein-like Nanoparticles Synergize with Akt and Btk Inhibitors to Induce Cell Death in Diffuse Large B Cell Lymphomas

Blood ◽

10.1182/blood.v128.22.3022.3022 ◽

2016 ◽

Vol 128 (22) ◽

pp. 3022-3022

Author(s):

Jonathan Scott Rink ◽

Sol Misener ◽

Osman Cen ◽

Shuo Yang ◽

Leo I. Gordon ◽

...

Keyword(s):

Cell Death ◽

B Cell ◽

Cell Lines ◽

Cell Lymphoma ◽

Density Lipoprotein ◽

B Cell Lymphoma ◽

Cell Receptor ◽

Cholesterol Homeostasis ◽

B Cell Lymphomas ◽

Bcr Signaling

Abstract Introduction: We previously reported that our bio-inspired, synthetic high-density lipoprotein-like nanoparticles (HDL NP) induced apoptosis in B cell lymphoma cells expressing scavenger receptor type B1 (SCARB1), the high-affinity receptor for cholesterol-rich HDLs. HDL NPs consist of a 5nm gold nanoparticle core surface functionalized with the HDL-defining apolipoprotein A1 and a phospholipid bilayer, and bind specifically to SCARB1, inducing the efflux of free cholesterol and inhibiting cholesteryl ester influx. SCARB1 is overexpressed in a subset of follicular and diffuse large B cell lymphomas (DLBCL), and resides in cholesterol-rich plasma membrane microdomains called lipid rafts, similar to the B cell receptor (BCR) and its associated signaling kinases. Upon binding to natural HDL, SCARB1 activates a number of pro-survival signaling kinases, including Akt and PI3K. Both Akt and PI3K are also involved in B cell receptor-mediated signaling in germinal center-derived (GC) DLBCL, through tonic BCR signaling, and activated B cell (ABC) DLBCL, through chronic active BCR signaling. Additionally, PI3K was recently shown to play a role in recruitment and activation of Btk, a crucial survival kinase downstream of the BCR. We hypothesized that small molecule inhibitors against pro-survival kinases, specifically Akt and Btk, will synergize with HDL NPs against B cell lymphomas. Methods: Burkitt's lymphoma (Ramos), GC DLBCL (SUDHL4) and ABC DLBCL (TMD8 and HBL-1) cell lines were treated with the Akt inhibitor GDC-0068 or the Btk inhibitor Ibrutinib, in the absence or presence of HDL NPs, and synergy was calculated using the Calcusyn software. Phos-flow was used to assay for changes in the phosphorylation status of Akt and Btk. Results: The Burkitt's lymphoma and GC DLBCL cell lines were more sensitive to HDL NP induced cell death compared to the ABC DLBCL cell lines (Ramos HDL NP IC50 = 1.5nM; SUDHL4 HDL NP IC50 = 2.1nM; TMD8 HDL NP IC50 = 31.4nM; HBL-1 HDL NP IC50 = 89nM). HDL NPs synergized with GDC-0068 in the Ramos, SUDHL4 and TMD8 cell lines (all combination indexes < 1). Correspondingly, HDL NPs dose-dependently decreased phosphorylation of Akt in Ramos and TMD8 cells. Ibrutinib synergized with the HDL NPs in all cell lines tested (all combination indexes < 1). In TMD8 cells, HDL NPs decreased p-Btk levels comparable to treatment with 10nM Ibrutinib. Addition of the PI3K inhibitor Pilaralisib (XL147) demonstrated mild synergy in the Ramos cell line, but not the SUDHL4, TMD8 or HBL-1 cell lines (all combination index values >1). Treatment of Ramos and SUDHL4 cells with an inhibitor of PTEN, a phosphatase responsible for acting in opposition to PI3K leading to inactivation of Akt, rescued the cells from HDL NP-induced cell death. TMD8 cells treated with the PTEN inhibitor demonstrated a smaller increase in survival when HDL NPs were applied, suggesting that PI3K may not play a major role in HDL NP-induced cell death in activated B cell DLBCLs. PTEN activity is influenced by the level of cholesterol and cholesteryl esters present in the cell, with increasing levels correlating with decreased PTEN activity. Cholesterol levels were higher in the ABC DLBCL cell lines compared to the other B cell lymphoma cell lines. HDL NPs significantly reduced the cholesterol content of Ramos cells, but not the TMD8 or HBL-1 cells, suggesting that the ability of the HDL NPs to alter cellular cholesterol homeostasis correlates with their ability to induce lymphoma cell death. Conclusion: HDL NPs demonstrated synergy with inhibitors to the pro-survival kinases Akt and Btk, suggesting that HDL NPs act to disrupt second messenger signaling pathways in lymphoma cells by directly altering signaling through SCARB1, modulating cellular cholesterol homeostasis, and/or through disruption of membrane raft organization. HDL NPs represent an innovative, targeted therapeutic, with great potential, to add to existing combination chemotherapy regimens. Disclosures Thaxton: Aurasense: Equity Ownership, Patents & Royalties: The patent for the HDL NPs has been licensed to Aurasense, a biotech company co-founded by C. Shad Thaxton..

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B-Cell Lymphoma With Rapidly Decreasing High-Density Lipoprotein Cholesterol: A Case Report

Journal of Medical Cases ◽

10.4021/jmc1525w ◽

2013 ◽

Author(s):

Sagun

Keyword(s):

Case Report ◽

High Density Lipoprotein ◽

B Cell ◽

High Density Lipoprotein Cholesterol ◽

Cell Lymphoma ◽

Density Lipoprotein ◽

B Cell Lymphoma ◽

High Density ◽

Lipoprotein Cholesterol

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Vav-1 expression correlates with NFκB activation and CD40-mediated cell death in diffuse large B-cell lymphoma cell lines

Hematological Oncology ◽

10.1002/hon.935 ◽

2010 ◽

pp. n/a-n/a ◽

Cited By ~ 2

Author(s):

Annette Hollmann ◽

Raquel Aloyz ◽

Kristi Baker ◽

Stephan Dirnhofer ◽

Trevor Owens ◽

...

Keyword(s):

Cell Death ◽

B Cell ◽

Cell Lines ◽

Cell Lymphoma ◽

B Cell Lymphoma ◽

Lymphoma Cell ◽

Large B Cell Lymphoma ◽

Large B Cell

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Inhibiting the Nuclear Exporter XPO1 and the Antiapoptotic Factor BCL2 Is Synergistic in XPO1 Mutant and Wildtype Lymphoma

Blood ◽

10.1182/blood-2020-134807 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 17-18

Author(s):

Frank Owusu-Ansah ◽

Jumana Afaghani ◽

Stanley Lee ◽

Justin Taylor

Keyword(s):

B Cell ◽

Cell Lines ◽

Cell Lymphoma ◽

Ex Vivo ◽

Mutant Cell ◽

B Cell Lymphoma ◽

Lymphoma Cell ◽

B Cell Lymphomas ◽

Increased Sensitivity ◽

Refractory Lymphoma

We have recently shown that XPO1 mutations are drivers of lymphomagenesis and occur across B-cell lymphomas, specifically in chronic lymphocytic leukemia (CLL), classical Hodgkin lymphoma and primary mediastinal B-cell lymphoma. The co-occurrence of other oncogenic events cooperating with XPO1 provides an opportunity for combined targeted therapy. Increased expression of the anti-apoptotic factor BCL2 has long been known to be a critical part of the pathophysiology of B-cell lymphomas. Recently, the oral BCL2 inhibitor, venetoclax, was approved in CLL and is currently being evaluated in clinical trials for other B-cell lymphomas. Selinexor is a potent, oral XPO1 inhibitor that was recently approved in multiple myeloma and diffuse large B-cell lymphoma. XPO1 inhibition exerts its antineoplastic effects by blocking key lymphomagenic pathways, such as NFκB, and decreasing the anti-apoptotic protein survivin. We therefore hypothesized that combining selinexor and venetoclax would have potential synergy and provide an oral precision combination therapy for relapsed, refractory lymphoma. We first set out to determine whether XPO1 mutant lymphoma cell lines showed differential response to either selinexor or venetoclax monotherapy. Five lymphoma cell lines; 3 diffuse large B-cell lymphoma (SU-DHL-6, SU-DHL-16, FARAGE) and 2 classical Hodgkin lymphoma (L428 and SUP-HD1), were subjected to next-generation sequencing (NGS) to assess for the presence or absence of XPO1 mutations. SUDHL-16 and SUP-HD1 were heterozygous for the XPO1 E571K hotspot mutation while SUDHL-6, FARAGE and SUP-HD1 were wildtype at the XPO1 locus. These 5 cell lines were used to assess sensitivity to Selinexor and/or Venetoclax. The CellTiter Glo assay was used to assess cell viability after 72 hours of treatment. Assays were performed in triplicate on 96-well plates that were read using a Spectramax plate reader. The XPO1 mutant cells showed increased sensitivity to selinexor (XPO1 mutant IC50 = 16-35nM; XPO1 WT IC50 = 41-231nM) as previously seen in conditional knockin mouse models of XPO1 mutant CLL (Figure A). Additionally, the XPO1 mutant cell lines showed increased sensitivity to single-agent venetoclax (XPO1 mutant IC50 = 2-13nM; XPO1 WT IC50 = 5-2853nM), an observation that has not previously been made (Figure B). Next, we tested the synergy of the combination of selinexor and venetoclax in the XPO1 mutant and wildtype cell lines. Increasing concentrations of the individual drugs were applied to each individual cell line in a 6x6 matrix. The cell viability percentage for each concentration was then entered into a synergy finder (www. synergyfinder.fimm.fi). The Bliss Independence model was used to calculate synergy of the Selinexor-Venetoclax combinations. As hypothesized, the combination of selinexor and venetoclax indeed showed synergy in both the wildtype and mutant XPO1 cell lines. Furthermore, the XPO1 mutant cell lines showed a higher degree of synergy compared to the wildtype cells (Figure C). Finally, a remarkable patient allowed us to test this combination ex vivo. This patient with CLL had undergone multiple therapies including chemoimmunotherapy, ibrutinib and venetoclax monotherapies. This patient had a founder XPO1 E571K mutation and also had acquired a BTK C481S ibrutinib resistance mutation and MYC amplification. These cells were unique in that they were easily able to be tested in ex-vivo culture to test sensitivity to different therapies. When tested with chemotherapy or ibrutinib they were completely resistant, and even with venetoclax they were fairly resistant; however, they remained sensitive to XPO1 inhibition with Selinexor. Selinexor and venetoclax showed remarkable synergy measured by a BLISS delta score of 18.78 (Figure D). In conclusion, inhibiting the nuclear exporter XPO1 and the anti-apoptotic factor BCL2 is synergistic in both XPO1 wildtype and mutant lymphoma. XPO1 mutant lymphomas show increased sensitivity to both selinexor and venetoclax. Additionally, selinexor and venetoclax showed a higher degree of synergism in XPO1 mutant lymphoma cell lines and were highly synergistic in primary XPO1 mutant CLL patient cells ex vivo. This combination is highly promising as an all oral alternative for relapsed, refractory lymphoma. Next steps include preclinical testing in mouse models in vivo using XPO1 mutant and wildtype mice crossed with mice overexpressing BCL2. Figure Disclosures No relevant conflicts of interest to declare.

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Prosurvival and Chemoprotective Effects of Tumor-Associated Macrophages Reversed By Anti-CSF-1R Monoclonal Antibody in B-Cell Lymphomas

Blood ◽

10.1182/blood.v124.21.498.498 ◽

2014 ◽

Vol 124 (21) ◽

pp. 498-498

Author(s):

Anupama Gopisetty ◽

Myriam Foglietta ◽

Min Zhang ◽

Zhiqiang Wang ◽

Nathan Fowler ◽

...

Keyword(s):

B Cell ◽

Cell Line ◽

Tumor Cells ◽

Cell Lines ◽

Cell Lymphoma ◽

B Cell Lymphoma ◽

Lymphoma Cell ◽

B Cell Lymphomas ◽

Lymphoma Cells ◽

Tumor Survival

Abstract The results of gene expression profiling (GEP) and immunohistochemical studies indicate that survival is worsened by macrophages (MΦ) in the tumor microenvironment of various B-cell lymphomas including follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL). Tumor-associated macrophages (TAMs) are known to be different from other types of MΦ, but the effects of TAMs that worsen prognosis in B-cell lymphoma are essentially unknown, as are the mechanisms of these effects. Here, we determined the phenotype and effects of TAMs on tumor survival, proliferation, and drug resistance in B-cell lymphomas and evaluated strategies to reverse their effects. As compared to peripheral blood monocytes (Mo) from normal donors (ND), Mo from FL patients were differentiated less into M1 MΦ (defined as CD68+CD163loCD206loCD86hi) by culture with CSF-1 for 5 days followed by IFN-g + LPS for 2 days more. In contrast, Mo from FL patients and ND were differentiated similarly into M2 MΦ (defined as CD68+CD163hiCD206hiCD86lo) by culture with CSF-1 followed by IL-4. Consistent with this, MΦ gene signatures from FL tumors were more similar to previously-described signatures of M2 rather than M1 MΦ (Martinez et al, J Immunol, 2006, 177(10):7303-11). In co-culture, primary FL tumor cells and lymphoma cell lines (including RL, a transformed FL cell line; Granta 519, a mantle cell lymphoma (MCL) cell line; and Raji, a Burkitt lymphoma cell line) induced differentiation of Mo into MΦ. Differentiation could be prevented by CS4 monoclonal antibody (mAb), a fully human IgG1 anti-human CSF-1R mAb (ImClone/Eli Lilly), but not isotype control Ab. Elevated levels of CSF-1 in culture supernatants after addition of CS4 mAb and real-time PCR of tumor cells suggested secretion of CSF-1 by lymphoma cells. Spontaneous apoptosis of primary FL and MCL tumor cells, determined by Annexin V and propidium iodide staining, was significantly reduced by co-culture with ND Mo (p<0.01), whether pre-differentiated into MΦ with CSF-1 or not, but this protection could be reversed by CS4 mAb. Mo and/or pre-differentiated MΦ protected primary FL and MCL tumor cells from cytotoxic effects of doxorubicin and/or bendamustine (p<0.01), but CS4 mAb reversed this effect. To assess effects of MΦ on proliferation, lymphoma cell lines (RL, Granta 519, and Raji) were CFSE-labeled prior to co-culture with Mo and doxorubicin, and proliferation assessed by CFSE dilution by flow cytometry in the presence or absence of CS4 or isotype control mAbs. MΦ promoted proliferation of all three cell lines, but this effect could be reversed by CS4 mAb. To further understand the mechanism by which MΦ promote tumor survival and growth, we performed phosflow analysis and found increased phosphorylation of STAT3 in co-cultured lymphoma cells. Consistent with this, we observed a correlation between an 11-gene STAT3 activation signature, described by Huang et al in DLBCL tumors (J Clin Oncol, 2013, 52.8414), and a MΦ gene signature in whole genome GEP studies of 191 FL tumors (Pearson correlation co-efficient=0.396, p<0.001). In conclusion, our results suggest that Mo from FL patients are predisposed to differentiate into an M2-like MΦ state. The interaction between lymphoma cells and Mo/MΦ is reciprocal: a change in Mo (MΦ differentiation) induced by interaction with lymphoma tumor cells leads to a change in the tumor cells (promotion of survival, proliferation, and chemoresistance). More importantly, our results demonstrate that targeting TAMs using CS4, an anti-CSF-1R mAb, can be an effective strategy to overcome the adverse effects of TAMs and reverse chemoresistance. Further studies are needed to determine whether STAT3 activation contributes to the protumor effects of TAMs. This may provide novel insights into the molecular mechanisms related to TAMs and lymphoma cells and offers additional targets for therapeutic development. In the long term, strategies targeting TAMs is especially appealing, as they should be able to be combined with existing therapies including chemotherapy, other immunotherapy, and targeted therapy, potentially improving their efficacy without increasing toxicity for FL, DLBCL, and other B-cell malignancies. Disclosures No relevant conflicts of interest to declare.

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Novel Alkylating Agent, Ureidomustine Exhibit Pre-Clinical Efficacy in B-Cell Lymphoma with Minimal Dose-Limiting Myelotoxicity

Blood ◽

10.1182/blood.v126.23.1556.1556 ◽

2015 ◽

Vol 126 (23) ◽

pp. 1556-1556 ◽

Cited By ~ 1

Author(s):

Eloisi Caldas Lopes ◽

Shieh Jae-Hung ◽

Srikanth Ambati ◽

Su Tsann-Long ◽

Fabian Correa ◽

...

Keyword(s):

B Cell ◽

Cell Lines ◽

Cell Lymphoma ◽

B Cell Lymphoma ◽

S Phase ◽

Water Soluble ◽

Lymphoma Cell ◽

Therapeutic Window ◽

B Cell Lymphomas ◽

Normal Human

Abstract Many patients with B-cell lymphomas, including mantle cell lymphoma (MCL) and diffuse large B-cell lymphoma (DLBCL), are not cured by conventional chemo-immunotherapy. One reason for this is because these drugs, while effective, are limited by their narrow therapeutic window and significant toxicities. B-cell lymphomas are highly dependent on DNA damage checkpoints, and hence are biologically responsive to drugs that trigger these checkpoints. Hence, In order to identify superior DNA damaging anti-lymphoma drugs we evaluated a series of novel, third generation, DNA-directed alkylating agents that have DNA specific binding domains chemically linked via urea, carbamate or hydrazinecarboxamide to N-mustard pharmacophores. The chemically favorable water-soluble ureidomustine (BO-1055) was evaluated for activity against 23 human lymphoma cell lines including MCL, DLBCL (GCB and ABC subtype) and a spontaneous murine B-cell lymphoma. Fifty % of these MCL and DLBCL cell lines exhibited BO-1055 IC50 values in the nanomolar range including even markedly chemo-resistant cell lines as OCI-Ly10 (IC50 0.117μM ±0.21). In marked contrast, against normal human tissues (lung fibroblast IMR90, kidney fibroblast CV1, mesenchymal stromal, bronchial epithelium, myofibroblast, bone marrow-derived endothelium) and hematopoietic cells (cord blood CD34+ cells, colony-forming assay for hematopoietic progenitors) and in cobblestone area-forming assay for hematopoietic stem cells, BO-1055 IC50s were > 10μM. Hence BO-1055 has a significant therapeutic window (50-100-fold) between its toxicity against B-cell lymphomas compared to normal human cells. We evaluated BO-1055 cardiotoxicity in the HL-1 cardiomyocyte line and observed a 227-fold less cytotoxicity compared to Doxorubicin. Drug combination studies with BO-1055 and an Hsp90 inhibitor (PU-H71), an Hsp70 inhibitor (TT46), doxorubicin and bortezomib (Velcade) demonstrated synergistic effects based on Compusyn analysis with very low combination indices in 50% of lymphoma cell lines. The synergistic effect was not observed in normal cells. Notably, BO-1055 caused downregulation of the critical lymphoma oncoproteins MYC and BCL6, but not Bcl2. BCL6 normally suppresses the ATR-driven S-phase checkpoint. Accordingly treatment with BO-1055 resulted in accumulation of cells in S-phase and up-regulation of proteins involved in DNA repair and intra-S-phase checkpoints [MRE11, p-P95/NBS1 (ser343), RAD50, p-ATR (ser428)]. Finally, xenograft experiments in NSG mice bearing MCL JEKO1 GFP/luciferase+ tumors treated with BO-1055 (30mg/kg) 3x/week showed complete tumor remission after 2 weeks of treatment as monitored by luminescent imaging. In summary, BO-1055 is emerging as a potent therapeutic agent for B-cell lymphomas, with little toxicity against normal tissues and hence potentially wider therapeutic window than current lymphoma drugs. Disclosures Caldas Lopes: BOtique Biopharm: Employment.

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