Surface CD4 Expression Research Articles

Immune Modulatory Effects of Hypercholesterolemia: Can Atorvastatin Convert the Detrimental Effect of Hypercholesterolemia on the Immune System?

Many observations showed that hypercholesterolemia can disrupt immune response. Statin drugs that were used for the treatment of hypercholesterolemia patients can interfere in the regulation of the immune response and cytokine secretion. The primary aim of the current study was to investigate the immune response among treatment-naïve patients with hypercholesterolemia and healthy subjects. The secondary goal of the study was to determine whether atorvastatin can reverse the detrimental effect of hypercholesterolemia on the immune system. Peripheral blood mononuclear cells (PBMCs) were isolated from 50 patients afflicted with hypercholesterolemia who were treatment-naïve along with 50 sex/age-matched hypercholesterolemia patients receiving atorvastatin, and 50 sex/age-matched healthy subjects. Quantitative PCR and ELISA methods were used for gene and protein expression analysis of T helper 1 (Th1) and Th2 related cytokines. Additionally, the expression of the cluster of differentiation (CD) markers on T, B, and natural killer (NK) cells was measured by flow cytometry method. The results showed that hypercholesterolemia and atorvastatin down-regulated the expression of Th1-related cytokines and elevated the levels of Th2-related cytokines. The expression of cell surface markers, CD25 and CD69, was significantly decreased in the treatment-naïve, and atorvastatin groups. It seems that atorvastatin is not able to repair the deleterious effects of hypercholesterolemia on the immune system. Moreover, elevated levels of cholesterol along with the administration of atorvastatin tilt the Th1/Th2 balance in favor of Th2 and reduce T cell activation.

CD38, a Receptor with Multifunctional Activities: From Modulatory Functions on Regulatory Cell Subsets and Extracellular Vesicles, to a Target for Therapeutic Strategies.

CD38 is a multifunctional cell surface protein endowed with receptor/enzymatic functions. The protein is generally expressed at low/intermediate levels on hematological tissues and some solid tumors, scoring the highest levels on plasma cells (PC) and PC-derived neoplasia. CD38 was originally described as a receptor expressed by activated cells, mainly T lymphocytes, wherein it also regulates cell adhesion and cooperates in signal transduction mediated by major receptor complexes. Furthermore, CD38 metabolizes extracellular NAD+, generating ADPR and cyclic ADPR. This ecto-enzyme controls extra-cellular nucleotide homeostasis and intra-cellular calcium fluxes, stressing its relevance in multiple physiopathological conditions (infection, tumorigenesis and aging). In clinics, CD38 was adopted as a cell activation marker and in the diagnostic/staging of leukemias. Quantitative surface CD38 expression by multiple myeloma (MM) cells was the basic criterion used for therapeutic application of anti-CD38 monoclonal antibodies (mAbs). Anti-CD38 mAbs-mediated PC depletion in autoimmunity and organ transplants is currently under investigation. This review analyzes different aspects of CD38’s role in regulatory cell populations and how these effects are obtained. Characterizing CD38 functional properties may widen the extension of therapeutic applications for anti-CD38 mAbs. The availability of therapeutic mAbs with different effects on CD38 enzymatic functions may be rapidly translated to immunotherapeutic strategies of cell immune defense.

Modulation of CD81 By Epigenetic Drug Combination Sensitizes Acute Lymphoblastic Leukemia Via Decreased BTK Signaling

Background We previously discovered that the epigenetic drug combination - azacitidine (aza, DNMTi) and panobinostat (pano, HDACi) can sensitize ALL cells to chemotherapy (Quagliano et al., Leuk Res, 44:101, 2017). This sensitization occurred through a decrease in cellular adhesion and a modulation of the cell surface expression of the tetraspanin protein CD81 (Quagliano et al., Blood, 132:3957, 2018). This study aims to elucidate the molecular mechanism by which CD81 surface modulation by pre-treatment with aza/pano leads to chemosensitization. Methods CD81 knockout Nalm6 (CD81KO) cells were generated by CRISPR/Cas9 mutagenesis. IHC was performed using anti-human mitochondria antibody on femurs harvested from NSG-SGM3 mice at 72 h post transplantation with WT or CD81KO cells. For adhesion assay, ALL cells stained with VPD450 were co-cultured with Saos-2 cells for 24 h. Unbound cells were washed, and bound cells were collected for flow cytometry analysis. CD19 surface expression was determined after 48 h treatment with aza/pano (500 nM/1.5 nM) using flow cytometry. For western blot analysis, aza/pano treated cells were transferred on to Saos-2 monolayers and treated with Ara-C (30 nM) for 16 h. Results CD81KO cells not only had decreased homing and engraftment visualized by reduced ALL cell presence in bone marrow (Fig. 1A), but also had 45% reduction in cellular adhesion to osteoblasts compared to WT Nalm6 cells (Fig. 1B), indicating that CD81 downregulation results in reduced bone marrow interactions. To investigate the signaling effects downstream of aza/pano-mediated CD81 modulation, we first tested if CD19 was affected due to its prominent role in the formation of the B-cell co-receptor and because CD19 requires CD81 for proper membrane trafficking (Cherukuri et al., J Immunol, 172:370, 2004). CD19 surface expression was reduced in aza/pano-treated cells and completely knocked out in CD81KO cells (Fig. 1C). CD19 is known to prolong and amplify the activation of Bruton's tyrosine kinase (BTK), so we also analyzed the phosphorylation of BTK in aza/pano-treated cells and found it to be reduced by 63% (Fig. 1D). This reduction in BTK phosphorylation may be responsible for the decrease in cell adhesion following treatment with aza/pano because prior studies observed reduced adhesion following BTK inhibition (Herman et al., Clin Cancer Res, 21:4642, 2015). Taken together, these data suggest that aza/pano induced reduction in cell adhesion was mediated by downregulation of CD81 and BTK dephosphorylation. We studied how the expression of p53 and its target BCL2 associated X protein (BAX), which are known to be induced by Ara-C, were affected following pre-treatment with aza/pano. Cells with Ara-C treatment alone or the aza/pano pre-treatment both had minor induction of p53 expression compared to control, while aza/pano pre-treated cells that received Ara-C had further increase in p53 protein (1.7-fold increase compared to Ara-C alone, Fig. 1E). Bax mRNA and protein were increased 4.2-fold in aza/pano-treated cells following Ara-C treatment compared to Ara-C alone. Increased Bax expression following Ara-C treatment in aza/pano pre-treated cells was accompanied by a 3.9-fold increase in cleavage of caspase-3 compared to cells treated with Ara-C alone, which in turn causes cleavage of Poly-ADP Ribose Polymerase (PARP) (Fig. 1E). Both p53 and Bax protein levels were higher in CD81KO cells than in WT cells (Fig. 1E), suggesting that aza/pano-mediated reduction of CD81 is involved in inducing the expression of p53. CD81KO cells that were treated with Ara-C also had further increase in p53 and Bax expression compared to Ara-C treated WT cells (Fig. 1E), consistent with an increased sensitivity to chemotherapy. To confirm the role of BTK inhibition in the induction of p53, Nalm6 cells were treated with the BTK inhibitor fenebrutinib for 24 h (10 nM). Following treatment, expression of p53 was induced and Bax expression was 2.6-fold higher in treated cells compared to untreated cells (Fig. 1E). Taken together, these data suggest that modulation of the surface expression of CD81 and the phosphorylation of BTK by aza/pano induces sensitization via upregulation of p53 and overexpression of Bax. Conclusion We identify a novel mechanism by which aza/pano treatment induces chemosensitization by reducing cell adhesion via modulating CD81 surface expression, reducing BTK phosphorylation, and inducing p53. Figure 1 Disclosures No relevant conflicts of interest to declare.

Targeting Nicotinamide Adenine Dinucleotide (NAD) Glycohydrase Activity of CD38 Exerts Anti-Myeloma Effect Accompanying Intracellular NAD Elevation

Introduction. The development of novel agents has improved the outcomes of multiple myeloma (MM) patients. Especially, daratumumab, an anti-CD38 monoclonal antibody which exerts therapeutic effect against MM cells through direct cell damage, antibody dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC), has shown its high efficacy in clinical practice. CD38 is a transmembrane glycoprotein highly expressed in plasma cells. CD38 is also a major nicotinamide adenine dinucleotide (NAD) glycohydrase in mammalian tissues, which regulate cellular levels of NAD. However, the role of CD38 as a NAD glycohydrase (NADase) in survival of MM cells is not well understood. In the present study, we conducted CD38 enzyme activity inhibition on MM cells using a small molecule compound 78c, a specific inhibitor for NADase enzymatic activity of CD38, in order to study the role of CD38 NADase activity in MM cell survival and to examine whether CD38 enzyme inhibition could be a new therapeutic strategy of MM. Materials and methods. MM cell lines (NCI-H929, KMS-12BM, KMS-12PE, U266) were treated with CD38 NADase inhibitor, 78c, in vitro. Viability of MM cell lines and patient-derived MM cells were analyzed by flow cytometry after 7AAD staining. MM cell lines possessing CD38 positive and negative fraction were sorted according to the CD38 expression using CD38 Micro-Beads. CD38 low MM cell lines were treated with All-trans retinoic acid(ATRA)to increase surface CD38 expression. Intracellular NAD and NADH concentrations in MM cells were analyzed using NAD / NADH assay kit. Detection of apoptosis in MM cell lines were examined by Annexin V and PI staining followed by flow cytometry analysis. Caspase inhibitor, Z-VAD-FMK, was used in combination with 78c to study the mechanism of 78c induced MM cell death. Results. 78c induced cell death in MM cell lines at low concentrations (IC50 10-20 μM). Addition of 78c to patient derived bone marrow cells showed cytotoxicity to MM cells, while toxicity to non-MM cells were limited. CD38 positive fraction of MM cell lines had better sensitivity to 78c compared to CD38 negative fraction. CD38 induction by ATRA in CD38 low MM cell lines showed increased sensitivity to 78c. These results proved that 78c efficacy correlates with surface CD38 expression. Comparison of intracellular NAD and NADH concentrations between CD38 positive and negative fractions of MM cell lines demonstrated a significant increase of NAD in the CD38 negative fraction compared to their positive counterparts, indicating that CD38 is indeed controlling the intracellular NAD concentration. Marked increase of NAD / NADH ratio was observed in 78c treated MM cell lines compared to control, proving that CD38 NADase inhibition affects intracellular NAD concentration in MM cells (Fig. 1). 78c treatment of MM cell lines significantly reduced the number of viable cells in the Annexin- / PI- region, however, addition of Z-VAD-FMK did not lead to recovery of viable cell numbers, indicating non-apototic cell death induction by CD38 NADase inhibition. Conclusions. CD38 is the major NADase in mammalian tissues, and involved in catabolism of NAD. CD38 NADase inhibitor, 78c, inhibited the growth of MM cells at low concentrations. 78c induced cell death was found to be highly specific to MM cells and its cytotoxic effect was associated with surface CD38 expression of MM cells. Increased amount of NAD in MM cells by 78c treatment suggests that NAD elevation is associated with MM cell death induced by CD38 NADase inhibition. Since, daratumumab has limited effect against CD38 NADase activity, modulation of intracellular NAD levels by CD38 NADase inhibition could provide a novel therapeutic strategy for MM (Fig. 2). Disclosures Matsuoka: Kyowa Kirin Co., Ltd.: Research Funding; Bristol-Myers Squibb Corp.: Research Funding; Chugai Pharmaceutical Co., Ltd.: Honoraria.

High Surface Expression of CD49d (VLA-4) and CD79b Correlates with Acalabrutinib Resistance in Patients with Chronic Lymphocytic Leukemia (CLL)

High Surface Expression of CD49d (VLA-4) and CD79b Correlates with Acalabrutinib Resistance in Patients with Chronic Lymphocytic Leukemia (CLL)

Comparative Assessment of Surface CD19 and CD20 Expression on B-Cell Lymphomas from Clinical Biopsies: Implications for Targeted Therapies

Background: CD19 and CD20 are B-cell lineage-specific antigens expressed on the cell surface of most B-cell lymphomas. While CD20 is acquired during late stages of B-cell lymphogenesis and is then lost upon differentiation into plasma cells, CD19 expression covers the entire spectrum of early B-cell genesis and maturation. CD20-targeting agents have been broadly integrated into the therapeutic armamentarium for B-cell lymphomas. More recently, CD19-targeting agents have emerged as promising alternatives with demonstrated therapeutic value. Given the imminent availability of both CD19 and CD20 targeted therapies, and potential for combinational approaches, we studied the surface expression of these antigens at the single-cell level on lymphoma cells and benign background lymphoid subsets from biopsy specimens. Methods: Flow cytometric analysis (seven-color) was performed on biopsy specimens from 47 patients with newly diagnosed B-cell lymphomas, including diffuse large B-cell lymphoma (n=15), follicular lymphoma (n=15), marginal zone lymphoma (n=9), mantle cell lymphoma (n=9), Burkitt lymphoma (n=2), and unclassifiable low-grade B-cell lymphoma (n=2). Small lymphocytic lymphoma was intentionally excluded, given its well-described loss of CD20 expression. Biopsies from eight additional patients with persistent/recurrent B-cell lymphomas after anti-CD20 therapy (greater than 6 months after last dose) were also evaluated. Thresholds for CD19 or CD20 antigen positivity were defined for each case, based on the 95th percentile fluorescence intensity of the respective marker on tumor-infiltrating T-cells (internal negative control). In addition, CD19 or CD20 fluorescence intensities of tumor cells were normalized to background benign B-cells (internal positive control) using the median fluorescence ratio (MFR). Results: Both CD19 and CD20 were highly expressed on CD20 treatment naïve tumor cells, with a slightly higher median percentage of positive tumor cells for CD19 (98%) compared with CD20 (93%) (p=0.003), and one case lacking CD20 expression. When compared with background benign B-cells, CD20 was frequently overexpressed on tumor cells (mean MFR=1.8), while CD19 expression was overall similar to background benign B-cells (mean MFR=0.9) (p=0.001). As the surface density of CD20 on benign B-cells is reportedly higher than CD19 (~100,000 vs ~20,000 molecules per cell, respectively), these findings are consistent with a higher density of surface CD20 than CD19 on most B-cell lymphomas. However, CD20 expression was more heterogeneous (within individual patient samples and across patients), with a higher median percentage of CD20-negative tumor events (median=0.5%, range=0-98%) compared with CD19-negative events (median=0%, range=0-28%) (p=0.003). Interestingly, expression of CD19 within the CD20-negative tumor subsets was largely preserved (mean % CD19-positive events=97.86%, min=40%). In addition, percentages of CD19/CD20 double-negative tumor events were very small (median=0%, range=0-4.9%), and only detectable in 15 cases (32%). Of eight additional cases studied post-anti-CD20 immunotherapy (6-84 months after last dose), the percentage of antigen-positive events by tumor cells was largely preserved for both CD19 (median=99.6%, range=93.5-100%) and CD20 (median=95.7%, range=55.6-100%), similar to the pre-therapy cohort. Conclusions: CD19 and CD20 are both highly and consistently expressed in B-cell lymphomas. While CD20 has a higher average density of surface molecules per tumor cell, CD19 expression is more homogenous and is preserved in small CD20-negative tumor subsets and after anti-CD20 targeted therapy. These findings support the clinical evaluation of anti-CD19 immunotherapies and combinational therapies targeting both surface antigens. Disclosures Horna: MorphoSys AG: Research Funding. Nowakowski:Selvita: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Research Funding; Bayer: Consultancy, Research Funding; Curis: Research Funding; F. Hoffmann-La Roche Ltd: Research Funding; Genentech, Inc.: Research Funding; MorphoSys: Consultancy, Research Funding; NanoString: Research Funding. Endell:MorphoSys AG: Employment, Patents & Royalties. Boxhammer:MorphoSys AG: Employment, Patents & Royalties.

Ifitm3 Is Essential for PI(3,4,5)P3-Dependent B-Cell Activation and Leukemogenesis

Background: The interferon-inducible transmembrane protein Ifitm3 (also known as Fragilis) plays an important role in primordial germ cell specification and functions as critical antiviral effector preventing fusion of virion-containing vesicles with endosomal membranes. Results: Here, we identified Ifitm3 as a biomarker of poor clinical outcome in patients with various B-cell malignancies. We found that higher IFITM3 mRNA levels at the time of diagnosis represents a strong predictor of poor clinical outcome for children (COG P9906; P=0.011; n=207) and adults (ECOG E2993; P=0.017; n=55) with B-ALL. Interestingly, IFITM3 is a transcriptional target and strongly repressed by IKZF1 (Ikaros) a potent tumor suppressor in B-ALL and high IFITM3 mRNA levels represents a biomarker for patients with IKZF1-deletion. To study the function of Ifitm3 in a model for human pre-B ALL, pre-B cells from Ifitm3-/- mice were transformed with BCR-ABL1 or oncogenic NRASG12D. Strikingly, deletion of Ifitm3 resulted in destabilization of lipid rafts, loss of CD19 surface expression and loss of PI3K signaling. Ifitm3-/- leukemia cells could not sustain oncogenic signaling from BCR-ABL1 or oncogenic NRASG12D and failed to initiate fatal leukemia in transplant recipient mice. These changes were paralleled by G0/1 cell cycle arrest (P<0.001), loss of colony formation capacity (P=0.0004) and increased propensity to apoptosis. In mechanistic studies, we identified N-terminal phosphorylation at endocytic motif (20YEML23) by Src-kinases induced Ifitm3 cell surface accumulation during normal activation or oncogenic transformation of B-cells. In a lipid-binding assay in vitro, recombinant IFITM3 directly bound to PI(3,4,5)P3 but not any other phospholipids. In the cell membrane, therefore, IFITM3 functioned as a scaffold for PI(3,4,5)P3 and was essential for Src-kinase and PI3K signaling, as well as lipid raft formation and surface expression of multiple raft-associated receptors. Conversely, inducible overexpression of IKZF1 transcriptionally silenced IFITM3, resulting in loss of IFITM3 expression, reduction of lipid rafts and impairment of Src-kinase signaling. In the absence of Ifitm3, resting B-cell populations developed normally. However, consistent with defective Src-kinase and PI3K signaling, Ifitm3-/- B-cells failed to form germinal centers and to give rise to antigen-specific humoral immune responses. Likewise, Ifitm3-/- B-cell precursors were resistant to malignant transformation and lacked the ability to initiate BCR-ABL1- and NRASG12D-driven leukemia. Conversely, an Ifitm3-phosphomimetic of Src-kinase phosphorylation induced constitutive cell membrane localization, triggered oncogenic Src-PI3K signaling and initiated overt leukemia in pre-malignant B-cells. Conclusions: We conclude that Src-kinase-mediated phosphorylation of Ifitm3 induces a dynamic switch from antiviral effector functions in endosomes to lipid raft signaling at the cell membrane. While membrane-bound Ifitm3 is critical for normal B-cell receptor signaling and antigen-specific B-cell responses, its role as signal amplifier can be leveraged by multiple oncogenes for malignant B-cell transformation. Figure Disclosures Nix: UCSF: Patents & Royalties. Chen:Genovel Biotech Corp: Other: scientific founder and Chairman. Wiita:UCSF: Patents & Royalties; Indapta Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Protocol Intelligence: Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

Initial Findings of the Phase 1 Trial of PBCAR0191, a CD19 Targeted Allogeneic CAR-T Cell Therapy

Background: Adoptive engineered autologous cellular immunotherapy has had a significant impact on the lives of some patients with advanced hematologic malignancies. However, the use of these therapies on a larger proportion of patients has been limited by variability of the final cell product, feasibility concerns, cost, and toxicity. Off-the-shelf allogeneic (allo) products offer the opportunity to address some of these concerns. Allo products have their own theoretical limitations, including the potential for graft-versus-host disease (GvHD) causing additional toxicity and host-versus-graft rejection limiting efficacy. PBCAR0191, an anti-CD19 allogeneic CAR T cell, was designed to limit the risk of GvHD by specifically inserting a CD19 specific CAR into the TRAC (T cell receptor alpha constant) locus in cells harvested from healthy donors. Those cells are then expanded, a CD3 elimination step is performed, followed by another expansion, and then PBCAR0191 is vialed and frozen for shipment then thawing, dilution, and infusion at the treatment site. To reduce the risk of PBCAR0191 rejection and increase the chances of cell expansion, lymphodepletion prior to dosing is required. This phase 1 3+3 dose escalation study is designed to identify an optimal dose of PBCAR0191 for efficacy evaluation. Methods: In each of 3 dose levels (3 x 105, 1 x 106, and 3 x 106 CAR-T+ cells/kg), up to 6 patients may be enrolled in each of 2 cohorts (Non-Hodgkin Lymphoma (NHL) and Acute Lymphoblastic Leukemia (ALL)). Eligibility requirements include adequate organ function, confirmed diagnosis to fit one of the cohorts, evaluable disease, at least 2 prior standard treatment regimens, no immunodeficiencies, no CNS disease, no active infections or other major medical issues requiring intervention, and no active GvHD. Eligible patients may have received allogeneic stem cell transplant or another CAR-T therapy. Lymphodepletion was administered on day -5 to day -3 using fludarabine 30mg/m2/day and cyclophosphamide 500mg/m2/day. Cells were administered on day 0. Correlative serum and PBMC samples were taken, while patients remained on study, on days 0, 1, 3, 7, 10, 14, 28, 42, 60 and every 30 days until 180 and then every 90 days until day 360. Assessment of response compared to baseline was performed on day 14 (optional for NHL only), and days 28, 60, 90, 180, 270, and 360, until progression. Results: Three patients with advanced NHL were enrolled and treated in DL1 between April 25, 2019 and May 24, 2019. Two males (one MCL, one DLBCL) and 1 female (DLBCL) ages 34 - 64 (median 64) years were treated. Two screen failures occurred, both patients with ALL, due to non-compliance (1) and loss of CD19 surface expression (1). One patient enrolled post disease progression after treatment with Axicabtagene ciloleucel. No significant toxicity was observed, including no serious adverse events and no dose-limiting toxicities with all patients having a minimum follow-up of 28 days (median 60 days). Two of the three patients experienced objective tumor response by Lugano criteria, at day 14 and day 28, respectively. Both patients progressed due to new lesions (on day 28 and day 60, respectively). The third patient has not met the definition of response, but has had evidence of central necrosis, decreased tumor size, and decreased PET-avidity at day 28, in the context of post-infusion tumor site pain and mild CRS symptoms. Peripheral blood analysis for CAR-T expansion has identified preliminary evidence of cell expansion with a low absolute numbers quantified, likely due to the low dose level at which treatment was initiated. Peripheral blood serum analysis for IFN-gamma, IL-6, and IL-15 indicate preliminary evidence of cell expansion, though not definitive. Conclusions: Further enrollment of patients into DL2 is ongoing. Data from DL2 entered by early October will be included in a presentation in the meeting. Findings to date indicate preliminary evidence of short-lived cell-mediated anti-tumor effect and preliminary evidence of cell expansion in vivo, which will be evaluated more fully at DL2 and DL3. Disclosures Jacobson: Bayer: Consultancy, Other: Travel Expenses; Humanigen: Consultancy, Other: Travel Expenses; Kite, a Gilead Company: Consultancy, Honoraria, Other: Travel Expenses, Research Funding; Novartis: Consultancy, Honoraria, Other: Travel Expenses; Precision Biosciences: Consultancy, Other: Travel Expenses; Pfizer: Consultancy, Research Funding; Celgene: Consultancy, Other: Travel Expenses. Herrera:Adaptive Biotechnologies: Consultancy; Gilead Sciences: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; AstraZeneca: Research Funding; Merck: Consultancy, Research Funding; Genentech, Inc.: Consultancy, Research Funding; Pharmacyclics: Research Funding; Immune Design: Research Funding; Kite Pharma: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding. Budde:F. Hoffmann-La Roche Ltd: Consultancy. DeAngelo:Amgen, Autolus, Celgene, Forty-seven, Incyte, Jazzs, Pfizer, Shire, Takeda: Consultancy; Novartis: Consultancy, Research Funding; Glycomimetics: Research Funding; Abbvie: Research Funding; Blueprint: Consultancy, Research Funding. Heery:Precision BioSciences: Employment. Stein:Amgen: Consultancy, Speakers Bureau; Stemline: Speakers Bureau; Celgene: Speakers Bureau. Jain:Kite/Gilead: Consultancy. Shah:Celgene/Juno: Honoraria; Kite/Gilead: Honoraria; Incyte: Research Funding; Jazz Pharmaceuticals: Research Funding; Pharmacyclics: Honoraria; Adaptive Biotechnologies: Honoraria; Spectrum/Astrotech: Honoraria; Novartis: Honoraria; AstraZeneca: Honoraria.

Cell Adhesion of ALL to Stromal Cells May Mediate CAR T-Cell Resistance: A Novel Escape Mechanism for Immunotherapy

Backgroud: Despite advances in therapy and improved survival, relapsed and refractory B-cell precursor acute lymphoblastic leukemia (r/r BCP-ALL) in pediatric and adult patients still remains a problem. Chimeric antigen receptor T cells against CD19 (CD19 CAR T) show promising results in patients with r/r BCP-ALL. However, relapse of the disease still occurs with appreciable frequency even with this novel therapy. As a significant number of relapses post-CAR T lack surface CD19 expression, further CD19-directed therapy is not an option for these cases. Hypothesis: Sometimes despite CAR T engraftment and establishment of B-cell aplasia, relapse still occurs. We hypothesized that, similarly to cell adhesion mediated chemotherapeutic drug resistance (CAM-DR), cell adhesion mediated CAR T-cell resistance (CAM-CART-R) can contribute to relapse of ALL. Results: To test our hypothesis, primary ALL cells were treated with CD19 CAR T cells either with murine calvaria-derived bone marrow stromal cells, OP9, or cultured only with media in short term cultures. We observed B-ALL cells treated with CD19 CAR T on OP9 has 10-20% higher viability compared to B-ALL and CD19 CAR T co-culture in medium alone, supporting the notion of CAM-CART-R. We also determined that soluble factors in OP9 primed medium may contribute to CAM-CART-R. However, the direct stromal contact mediated significant protection again CAR T induced apoptosis of B-ALL cells. To determine the molecular mechanisms underlying the survival promoting effects of stromal cells on CD19-, these cells were starved in serum-free media for 4hours and then treated with PI3Kδ inhibitor CAL-101 or DMSO and co-cultured with OP9 cells for 1 hour. We found that p-Akt is upregulated by stromal contact in CD19-negative B-ALL cells post-CAR T therapy and that PI3Kδ inhibition using can downregulate p-Akt in CD19-negative B-ALL patients. Critically, we investigated whether CD19 CAR T cells were functional under these conditions. For this purpose, we determined if stromal contact of ALL cells or stromal contact of CAR T cells changes the intracellular cytokine milieu of CD19 CAR T cells and found that intracellular IL-6, TNF- α and IFN-γ were reduced upon stromal contact supporting our hypothesis of a role of stromal cells in CAM-CART-R. We also determined that immune checkpoints molecules on T cells are unaffected by OP9 cells. Despite the reduction of cytokine level in T cells upon co-culture with B-ALL cells on OP9, PD-1, TIM-3 and LAG3 expression on CD19 CAR T cells after 2 days of co-culture was not altered as determined by flow cytometry. Resistance of ALL cells to CD19 CART cells was not mediated through checkpoint inhibition, since the PD-1/PD-L1 inhibitor Nivolumab failed to enhance ALL killing. Phenotypic profiling of thirteen cases of primary ALL relapse post-CD19 CAR T cell therapy showed high expression of adhesion molecules including integrin α4. Phenotypic analysis also revealed high expression of integrins is retained in primary ALL cells after CD19 knockout in one case. To explore possible solutions to overcome CAM-CART-R, we examined a strategy of blocking specifically integrin α4. We have previously shown that blocking integrin α4 can de-adhere CD19-negative B-ALL relapse post-CAR T cell therapy from their respective counter-ligands in vitro and that these cells can benefit from integrin blocking therapy in vivo. We have now confirmed this in NSG mice injected with CD19-negative B-ALL cells from a patient with post-CAR T cell relapse. Mice were treated intraperitoneally (n=6/group) with total immunoglobulin (Ig) control or humanized anti-human integrin α4 antibody Natalizumab (NZM). As a result, Natalizumab monotherapy significantly prolonged survival of leukemic mice compared to control Ig group (66 days (Ig) vs 85 days (NZM) p<0.005). Further combination treatments with chemotherapy are in progress. Conclusion: In summary, our data indicate that similarly to CAM-DR, CAM-CART-R can occur resulting in relapse of ALL. Targeting adhesion molecules may be a new approach to treat or prevent relapse following CD19 CAR T cell therapy for . Disclosures Ahmed: CellMedica: Other: Royalties; Celgene: Other: Royalties; Adaptimmune: Membership on an entity's Board of Directors or advisory committees. Babak:Simurx. Inc: Other: Founder . Pulsipher:Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Other: Education for employees; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Amgen: Other: Lecture; Bellicum: Consultancy; Miltenyi: Research Funding; Medac: Honoraria. Wayne:AbbVie: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding; Servier: Consultancy; Spectrum Pharmaceuticals: Consultancy, Research Funding. Abdel-Azim:Adaptive: Research Funding.

First Analysis of the UKALL14 Phase 3 Randomised Trial to Determine If the Addition of Rituximab to Standard Induction Chemotherapy Improves EFS in Adults with Precursor B-ALL (CRUK/09/006)

First Analysis of the UKALL14 Phase 3 Randomised Trial to Determine If the Addition of Rituximab to Standard Induction Chemotherapy Improves EFS in Adults with Precursor B-ALL (CRUK/09/006)

Ofatumumab Plus Hypercvad/MA Induction Leads to High Rates of Minimal Residual Disease (MRD) Negativity in Patients with Newly Diagnosed Mantle Cell Lymphoma, Results of a Phase 2 Study

Background: Minimal residual disease (MRD) status is an independent prognostic marker for response duration in patients with mantle cell lymphoma (MCL). Rituximab-based therapy led to a molecular remission (MR) in 48% young MCL patients treated with intense chemo-immunotherapy. More recently, 4 courses of R-DHAP were reported to yield a 66% MRD negativity rate prior to high dose chemotherapy and autologous stem cell transplant (HDC-ASCT). Ofatumumab is a humanized type 1 anti-CD20 mAb that binds to a unique, more membrane-proximal epitope on the CD20 antigen. Pre-clinical studies have demonstrated that ofatumumab (O) is more active than rituximab in eliciting complement-mediated cytotoxicity (CMC) in MCL cell lines, primary tumor cells and murine lymphoma xenograft models. Hence, we evaluated the safety and efficacy of combining ofatumumab with HyperCVAD/MA (O-HyperCVAD) in newly diagnosed MCL (NCT01527149). Study design: This was a single-arm, open-label, multi-center (2 centers), prospective, phase 2 clinical trial. Thirty-seven transplant-eligible patients with newly diagnosed MCL were enrolled. Ofatumumab (1000mg) was given every 3 weeks on day 1, followed by standard doses of alternating HyperCVAD and MA starting on day 3. A total of 6 cycles were given at 3-week intervals followed by HDC-ASCT. Maintenance rituximab 375 mg/m2 every 2 months for 3 years post-ASCT was added after protocol amendment following publication of the LyMa study. Primary objectives were to determine the overall response rate (ORR) and CR rate (CRR) at the end of therapy. Secondary objectives included MRD negativity, progression free survival (PFS), overall survival (OS), feasibility of successful mobilization of autologous stem cells and safety assessment. MRD assessment was performed in peripheral blood (PB) and bone marrow (BM) using high sensitivity multiparametric flowcytometry at baseline, after 2 cycles, after 4 cycles, pre-ASCT, post-ASCT and 6 months post-ASCT. Exploratory endpoints included correlation of MRD with survival, correlation of surface CD20 levels with response and to compare differences in ORR according to Cheson and modified Cheson (MC) criteria. Results: Median age was 60yrs; 73% of patients were male, 92% had an ECOG PS 0-1, majority (81%) had stage 4 disease with 86% having bone marrow involvement; 22% had low risk, 43% had intermediate risk and 35% had high risk MIPI score; 11% had blastoid and 11% had pleiomorphic variants of MCL; 25% harbored p53 deletion. MRD was assessed in 28 of 37 patients; 9 patients from partner site were excluded due to time lag in sample delivery for flowcytometry. MRD positivity was noted in 75% patients in PB and 71.4% patients in BM at baseline. Subsequent samples showed an MRD negativity rate of 82.1% and 64.3% after 2 cycles and 76% and 96% pre-ASCT in PB and BM respectively. Post-ASCT, MRD in BM and PB was found negative in 58% and 90%, respectively. Attainment of early MRD negativity (after 2 cycles) was associated with improved PFS (p=0.04) and OS (p=0.03). Since majority of patients were MRD negative pre-ASCT, we could not demonstrate correlation between pre-ASCT MRD and survival outcomes. The ORR and CRR were 95% and 62% by Cheson and 97% and 84% respectively by modified Cheson criteria. At the end of induction therapy, ORR was 86% and CRR was 62% by Cheson criteria. 73% pts underwent HDC-ASCT. Only one patient failed stem cell collection. The median PFS and OS were 45.5 months and 56 months respectively. There were 3 deaths while on therapy- 2 from sepsis and one from acute myeloid leukemia. Grade 3 and 4 adverse events (AEs) were observed in 22% and 68% of the patients, most of them were hematological AEs related to the chemotherapy regimen. Correlation of surface CD20 expression using mean fluorescent intensity (MFI) and response rates is currently under analysis and will be reported at the meeting. Conclusion: The addition of ofatumumab to HyperCVAD/MA led to high rates of MRD negativity by flowcytometry in patients with newly diagnosed MCL. Early MRD negativity (after 2 cycles) was associated with better PFS and OS. Despite higher ORR, CR and MRD negativity rates, survival outcomes were similar to historical cohorts using rituximab-HypeCVAD/MA. This may be in part due to increased number of patients with high-risk disease in our study. Disclosures Reddy: KITE Pharma: Consultancy; Abbvie: Consultancy; Genentech: Research Funding; Celgene: Consultancy; BMS: Consultancy, Research Funding. Sait:Celgene: Consultancy. OffLabel Disclosure: Ofatumumab was investigated in combination with chemotherapy in newly diagnosed mantle cell lymphoma in this clinical trial.

Targeting CD38high Acute Myeloid Leukaemia with “Affinity Optimized” Chimeric Antigen Receptor and Membrane Bound TRAIL Expressing Natural Killer Cells

Targeting CD38high Acute Myeloid Leukaemia with “Affinity Optimized” Chimeric Antigen Receptor and Membrane Bound TRAIL Expressing Natural Killer Cells

Dynamic CD138 surface expression regulates switch between myeloma growth and dissemination in the bone marrow

The canonical plasma cell marker CD138 (syndecan-1) is highly expressed on the myeloma cell surface, but its functional role in vivo is unclear, as well as the ontogeny of CD138-high and CD138-negative (neg) myeloma cells Using the murine Vk*MYC myeloma model we find CD138 expression is heterogeneous and varies with tumor burden. We find CD138-high subset of myeloma cells in the bone marrow is highly proliferative, less apoptotic, and enhanced IL-6R signaling, as compared to CD138-neg subset. Additionally, CD138-high myeloma engrafts better than its CD138-neg counterpart.

Dynamic CD138 surface expression regulates switch between myeloma growth and dissemination

The canonical plasma cell marker CD138 (syndecan-1) is highly expressed on the myeloma cell surface, but its functional role in vivo is unclear, as well as the ontogeny of CD138-high and CD138-negative (neg) myeloma cells. In this study we used an in vivo murine Vk*MYC myeloma model where CD138 is heterogeneously expressed depending on tumor size. We find that in comparison to CD138-neg myeloma cells, the CD138-high subset of myeloma cells is highly proliferative, less apoptotic, and enhanced IL-6R signaling, which is known to promote survival. In addition CD138-high myeloma engrafts better than its CD138-neg counterpart. In contrast, CD138-neg cells are more motile both in vitro and in vivo, and more readily disseminate and spread to other bones in vivo than CD138-high subset. Neutralizing CD138 rapidly triggers migration of myeloma cells in vivo and leads to intravasation, which results in increased dissemination to other bones. Both murine and human myeloma cells can rapidly recycle CD138 surface expression through endocytic trafficking, in response to serum levels. Blocking CD138 enhances myeloma sensitivity to bortezomib chemotherapy and significantly reduces tumor size compared to bortezomib treatment alone. Thus, our data show that CD138 surface expression dynamically regulates a switch between growth vs. dissemination for myeloma, in response to nutrient conditions.

Stromal Support of Metabolic Function through Mitochondrial Transfer in Multiple Myeloma.

Marlein and colleagues demonstrate in multiple myeloma, bone marrow stromal cells transfer mitochondria to myeloma cells to increase cellular respiration, resulting in increased proliferation. The intercellular transfer occurs through the formation of tunneling nanotubes that connect the myeloma cell to the stromal cell and is dependent on surface CD38 expression on myeloma cells. CD38 is an important therapeutic target in myeloma, therefore, regulation of myeloma metabolism may play a role in the activity of this therapeutic approach. The study reinforces the importance of intercellular interactions in the tumor microenvironment and sheds new light on the control of metabolism in myeloma.See related article by Marlein et al., p. 2285.

Immune Modulatory Effects of Hypercholesterolemia: Can Atorvastatin Convert the Detrimental Effect of Hypercholesterolemia on the Immune System?

Background and purpose: Many observations showed that hypercholesterolemia can disrupts immune response. Statin drugs that were used for the treatment of hypercholesterolemia patients can interfere in regulation of the immune response and cytokine secretion. The primary aim of the current study was to investigate the immune response among hypercholesterolemia patients, who were treatment-naive and healthy subjects. The secondary goal of the study was to determine whether atorvastatin can reverse the detrimental effect of hypercholesterolemia on the immune system. Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from 50 patients afflicted with hypercholesterolemia who were treatment-naive along with 50 sex- and age-matched hypercholesterolemia patients receiving atorvastatin and 50 sex- and age-matched healthy subjects. Quantitative PCR and ELISA methods were used for gene and protein expression analysis of T helper 1 (Th1) and Th2 related cytokines. Additionally, the expression of the cluster of differentiation (CD) markers on T, B, and NK cells were measured by flow cytometry method. Results: The results showed that hypercholesterolemia and atorvastatin downregulated the expression of Th1- related cytokines and elevated the levels of Th2-related cytokines. The expression of cell surface markers, CD25 and CD69, was significantly decreased in the treatment-naive, and atorvastatin groups. Conclusion: It seems that atorvastatin is not able to repair the deleterious effects of hypercholesterolemia on the immune system, and elevated levels of cholesterol along with the administration of atorvastatin tilt the Th1/Th2 balance in favor of Th2 and reduce T cell activation.

Central Function for JAM-a in Multiple Myeloma Patients with Extramedullary Disease

During the last years, multiple myeloma (MM) has been recognized to present in some patients with extra-medullary disease (EMD) manifestation with different pathophysiological and clinical characteristics. Recently, we reported junctional adhesion molecule-A (JAM-A) as a novel target and a clinical biomarker in MM [Solimando et al. Leukemia 32(3):736-743, 2018]. Here, we hypothesized that alterations in the adhesion molecules, particularly JAM-A expression, on MM plasma cells (MM-PCs) may play a pivotal role in high-risk EMD patients.Therefore, we evaluated JAM-A expression in 60 MM patient bone marrow (BM) aspirates and biopsies at different disease stages with flow cytometry and immunohistochemistry. We compared these results with RNA-Seq data from 647 newly diagnosed MM (NDMM) patients collected in the MMRF (MM Research Foundation) CoMMpass study. Using bioinformatics, we investigated JAM-A related pathways with hierarchical cluster analysis. Subsequently, we functionally tested these JAM-A related pathways regarding epithelial mesenchymal transition, invasion and MM dissemination in vitro.The median OS differed significantly in subjects with elevated membrane JAM-A expression levels, dividing the patients in EMD JAM-Ahighgroup with a median OS of 84.1 months, whereas median OS in JAM-Alowpatients was not reached, irrespective from the EMD status (log-rank=4.19, P=0.04). Immunohistochemistry analysis of BM biopsies confirmed these findings. RNA-Seq analysis corroborated the prognostic impact of JAM-A (log-rank= 3.8, P= 0.051).High-risk myeloma patients with EMD and JAM-A expression displayed a unique gene-expression signature. Additionally, we constructed a novel expression cluster subgroup MM model, revealing complex molecular disease patterns and associations between clinical traits and expression markers. MM patients clustering according to JAM-A expression levels and EMD manifestation revealed a clear link to the epithelial-mesenchymal-transition and focal adhesion pathways. Notably, functional knockdown of JAM-A in vitro not only reduced cell viability, but also diminished MM adhesion molecules and CD138 surface expression. Furthermore, mTOR/PI3K in vitro inhibition with BEZ235 significantly down regulated surface expression in JAM-Ahigh MM cell lines. Interestingly, when we inhibited mTOR/PI3K in JAM-AlowMM cells, we observed JAM-A induction.In the present study we shed more light on the EMD pathophysiology. Conclusively, our results support that JAM-A can serve as promising prognostic marker for high risk EMD MM patients. Our data provide a biological rationale for a JAM-A guided decision-making process to better combine molecular and immunochemo-therapy modalities in the EMD MM patient subset. DisclosuresNo relevant conflicts of interest to declare.

Cooperative Repression of IRF4 and Induction of IRF7 By CDK4/6 Inhibition Sensitizes Mantle Cell Lymphoma Cells to IMiD-Mediated Apoptosis Independent of p16 Deletion or c-Myc Overexpression

Lenalidomide (Len) and pomalidomide (Pom) are standard of care therapies for multiple myeloma (MM) and also exhibit clinical efficacy in some lymphomas such as diffuse large B cell lymphoma (DLBCL) and mantle cell lymphoma (MCL). As single agents, each rarely achieves complete remission despite a high overall response rate and durability; however, they potentiate the clinical response to diverse partners including Rituximab in MCL. As immunomodulatory drugs (IMiDs), Len and Pom target multiple cell types in vivo and have been shown to promote the expansion of NK cells in MCL. Len in combination with BTK inhibitors apparently leads to synthetic lethality in the activated B cell-like DLBCL cell lines, but the mechanism that mediates IMiD sensitivity in MCL cells remains largely unknown.We found that Len markedly enhanced ACP196 (second generation BTK inhibitor) killing of the CCMCL1 MCL cell line, despite c-Myc overexpression and deletion of p16INK4a, but not the JEKO-1 cells, which harbor TP53 deletion. Therefore Len appears to enhance killing by BTK inhibition but does not confer sensitivity to resistant MCL cells. Next, we investigated how inhibition of CDK4 might sensitize MCL cells to Len or Pom killing, given that dysregulation of cyclin D1 and CDK4 (CDK6 is silenced in MCL) underlies uncontrolled proliferation and disease progression, and inhibition of CDK4 is clinically efficacious in MCL. Indeed, priming of CCMCL1 cells by prior induction of G1 arrest with the selective CDK4/6 inhibitor palbociclib markedly sensitized them to Len-induced apoptosis, but only marginally so in JEKO-1 cells. Kinetic studies revealed that Len reduced the IRF4 protein markedly in CCMCL1 cells arrested in G1 by CDK4 inhibition, but marginally so in cycling CCMCL1 cells and not at all in Len-resistant JEKO-1 or Maver-1 cells. Reduction of IRF4 protein by Len in prolonged G1 arrest was concomitant with induction of IRF7 protein and tightly associated with apoptosis, as evidenced by PARP and caspase-3 cleavage. Moreover, inhibition of CDK4 conferred sensitivity to Pom in the Len-resistant JEKO-1 cells, and it was concurrent with reduction of IRF4 and induction of IRF7.The triple combination of Len, Ibrutinib, and Rituximab in MCL has been shown to be clinically active in relapsed MCL. To explore the underpinning, we found by RNA-seq that CD20 mRNA expression was downregulated in normal primary human peripheral B cells when they were activated into the cell cycle and in primary MCL cells, suggesting an inverse correlation between cell cycling and CD20 mRNA expression. However, surface CD20 expression was not collinear with CD20 mRNA expression and there was no evidence for upregulation of CD20 by BTK inhibition. On this basis, upregulation of the rituximab target CD20 is unlikely to be the primary mechanism for improved clinical response to this triple combination in MCL.In summary, our data suggest cooperative repression of IRF4 and induction of IRF7 as a central mechanism that underlies enhancement of Len and Pom killing by inhibition of BTK or CDK4, independent of deletion of the physiologic CDK4/6 inhibitor p16INK4a or overexpression of c-Myc. Furthermore, it appears that induction of prolonged early G1 arrest by Palbociclib confers Pom sensitivity independent of p53, implicating a potential to combine Palbociclilb with Pom for treatment of MCL with p53 loss or mutation. DisclosuresNo relevant conflicts of interest to declare.

IFITM3-Mediated Regulation of Cell Membrane Dynamics Is Essential for Malignant B-Cell Transformation

Background & Hypothesis: B cell receptor (BCR) signaling and oncogenic tyrosine kinases that mimic BCR-signaling in B-lineage leukemia and lymphoma depend on assembly of membrane proximal signaling complexes. Signalosomes in normal BCR- and oncogene (e.g. BCR-ABL1, RAS-pathway lesions) signal transduction are recruited to phospholipid anchors in lipid rafts. The robustness of these complexes depends on cholesterol accumulation in lipid rafts. Here we identified the interferon-induced transmembrane protein IFITM3 as a central regulator of cholesterol in lipid rafts.Results: IFITM3 is mostly localized to endosomal compartments. By antagonizing VAP-A and oxysterol-binding protein 1 (OSBP1), IFITM3 promotes cholesterol accumulation and solidifies the endosomal membrane. This mechanism is particular important in anti-viral immunity, to “trap”intraluminal viral particles for lysosomal degradation. In B-cells, IFITM3 can translocate to the cell membrane and form a complex with the BCR and its co-receptors CD19, CD81 and CD21. While the functional significance of membrane expression of IFITM3 on B-cells was not known, we found that higher IFITM3 mRNA levels at the time of diagnosis represents a strong predictor of poor clinical outcome for children (COG P9906; P=0.006; n=207) and adults (ECOG E2993; P=0.014; n=215) with B-ALL. In addition, higher than median IFITM3 mRNA levels at the time of diagnosis were associated with a higher risk of relapse and positive MRD status at the end of induction chemotherapy in B-ALL and other B-cell malignancies. Interestingly, IFITM3 is a transcriptional target and strongly repressed by IKZF1 (Ikaros) a potent tumor suppressor in B- ALL and high IFITM3 mRNA levels represents a biomarker for patients with IKZF1-deletion.While its membrane-topology can vary in different cell types, we found that IFITM3 functions as a dual-pass transmembrane protein in tight association with CD19 and the Iga and Igb signaling chains of the BCR in B-ALL and B-cell lymphoma cells. To study the function of Ifitm3 in a model for human pre-B ALL, pre-B cells from Ifitm3-/- mice were transformed with BCR-ABL1 or oncogenic NRASG12D. Strikingly, deletion of IFITM3 resulted in destabilization of lipid rafts, loss of CD19 surface expression and loss of PI3K signaling. Ifitm3-/- leukemia cells could not sustain oncogenic signaling from BCR-ABL1 or oncogenic NRASG12D and failed to initiate fatal leukemia in transplant recipient mice. These changes were paralleled by G0/1 cell cycle arrest (P<0.001), loss of colony formation capacity (P=0.0004) and increased propensity to apoptosis.In mechanistic studies, we identified type II transmembrane topology for IFITM3 at plasma membrane with extracellular C and intracellular N terminus which interacted with CD19, LYN, SYK, PI3K and AKT (see schematic, left). Disruption of endocytic motif (20YEML23) by substitution of Tyr20 to Phe induced IFITM3 gain of function and forced accumulation of IFITM3 on the cell membrane, constitutive CD19-PI3K signaling, intracellular calcium mobilization, homotypic cellular aggregation and massively increased proliferation of pre-B ALL cells (see schematic, right). Conversely, inducible overexpression of IKZF1 transcriptionally silenced IFITM3, resulting in loss of IFITM3 expression, reduction of lipid rafts and impairment of membrane-associated oncogenic signaling. Through Filipin-based cholesterol staining, we found Ifitm3-/- pre-B cells have reduced levels of cholesterol in lipid rafts, which causes disruption of lipid rafts formation, as reflected by decreased levels of ganglioside GM1. Notably, the homeostatic cholesterol fluidity by presence of IFITM3 on plasma membrane was also required for initiation of B- and T cell receptor signaling in mature B- and T cell lymphoma to induce Ca2+ mobilization.Conclusions: These findings identify novel role of the viral immunity IFITM3 surface receptor as a central regulator of cell membrane cholesterol fluidity and critical mediator of sustained oncogenic tyrosine kinase (BCR-ABL1) and RAS (NRASG12D) signaling in B cell malignancies. In promoting cholesterol aggregates in lipid rafts, IFITM3 protects healthy individuals from potentially lethal viral infections, but also enables oncogenic signaling by providing a robust membrane scaffold for tyrosine kinase and RAS-pathway oncogenes. DisclosuresWiita:Sutro Biopharma: Research Funding; TeneoBio: Research Funding.

Drug-Free Macromolecular Therapeutics Induce Apoptosis in Cells Isolated from Patients with B Cell Malignancies with Enhanced Apoptosis Induction By Pretreatment with Gemcitabine

Background Anti-CD20 mAbs are an important element in the therapeutic armamentarium for B-cell malignancies such as chronic lymphocytic leukemia (CLL). Although new targeted drugs (Ibrutinib & Idelalisib) and recently developed anti-CD20 mAbs (obinutuzumab & ofatumumab) have significant activity, the clinical management is limited by toxicity or low sensitivity to anti-CD20 mAbs. Herein we propose Drug-Free Macromolecular Therapeutics (DFMT) as a novel class of therapeutics that amplifies CD20 crosslinking and triggers apoptosis. The unique features of DFMT include augmentation of multivalent CD20 crosslinking, immune effector independence and no cytotoxic agents. Its effectiveness has been demonstrated in vitro and in preclinical Non-Hodgkin Lymphoma (NHL) models including a CD20-deficient rituximab (RTX)-resistant model, in which DFMT combined with a long-circulating polymer-gemcitabine conjugate (2P-GEM), induced prolonged survival and tumor clearance from bone marrows.[Zhang R, et al. PNAS 2014; Li L, et al. ACS Nano 2018] Therefore, we conducted assessment of DFMT on patient samples.Methods Malignant B cells were isolated from patients diagnosed by the hematologic malignancies service at the Huntsman Cancer Institute. The majority of isolates were from CLL patients. CD20 expression of each sample was evaluated by flow cytometry. DFMT consisting of two nanoconjugates was used to treat the cells in consecutive administration: first, cells were incubated with Fab‘-MORF1 (bispecific engager, Fab’ fragment of RTX conjugated with a morpholino oligonucleotide); after 1 h, a crosslinking effector (CLE) containing multiple copies of complementary morpholino oligonucleotide (MORF2) was added and the cells were continually incubated for another 6-20 h (depending on assays). The CLE can be prepared by conjugation of MORF2 to either N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer precursor or human serum albumin. Crosslinking of CD20 receptors is initiated by the multiple hybridization of MORF1/MORF2 at the cell surface, and results in apoptosis (Fig. 1A). Annexin V and caspase 3 assays were used to quantify B-cell apoptosis. RTX followed by goat-anti-human (GAH) secondary antibody was used for comparison. GAH was added to imitate the function of Fcγ+ immune effector cells for crosslinking of RTX. When enough cells were available, a detailed evaluation of apoptosis induction was performed, i.e. plasma membrane rupture, genomic DNA fragmentation, mitochondrial membrane permeabilization, Bcl-2 inhibition and confocal imaging to document specific biorecognition at the cell surface. In some samples, pretreatment with GEM or 2P-GEM for 48 hours followed by DFMT or RTX/GAH was conducted, and the effect of GEM in enhancing apoptosis induction was evaluated.Results The efficacy of DFMT was assessed in 44 samples including 35 CLL along with a few other B cell lymphomas such as diffuse large B cell lymphoma (DLBCL), marginal zone lymphoma (MZL), follicular lymphoma (FL), etc. DFMT induced apoptosis in 65.9% of patient samples.High-risk mutations such as 17p13 and 11q22 deletions, usually considered as poor prognostic factors in CLL, did not hamper the therapeutic efficacy of DFMT treatment. In cases with poor responses, we noted low CD20 expression levels (Fig 1B). We previously showed that pre-treatment with GEM can enhance surface CD20 expression and restore responsiveness to anti-CD20 mAb. Therefore, we pre-treated the low CD20 patient samples with GEM followed by treatment of DFMT, which induced significantly more apoptosis than RTX/GAH control (Fig 1C). In addition to increased target expression (CD20), this superior activity is likely due to synergy between GEM and DFMT, as we have shown that CD20 crosslinking triggered by DFMT stimulates a cascade of apoptotic events that eventually lead to up-regulation of the pro-apoptotic proteins Bax and inhibition of NF-ĸB, which in turn sensitizes cells to GEM.[Li L, et al. ACS Nano 2018]Conclusion DFMT effectively increased apoptosis of tumor cells from patients with a variety of B-cell malignancies, irrespective of genomic aberrations. The apoptotic response to DFMT was significantly correlated with CD20 expression, and could be enhanced by GEM-induced upregulation of CD20. DFMT alone or in combination with 2P-GEM warrants further evaluation as a therapeutic for refractory B cell malignancies. [Display omitted] DisclosuresYang:Baston Biologics Company: Membership on an entity's Board of Directors or advisory committees; University of Utah: Patents & Royalties: PCT/US2014/023784 and PCT/US2017/37736. Deininger:Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Blueprint: Consultancy. Shami:Lone Star Biotherapies: Equity Ownership; Pfizer: Consultancy; JSK Therapeutics: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Baston Biologics Company: Membership on an entity's Board of Directors or advisory committees. Kopeček:University of Utah: Patents & Royalties: PCT/US2014/023784 and PCT/US2017/37736; Baston Biologics Company: Membership on an entity's Board of Directors or advisory committees.