Scientific Resources

CD38,as a cell surface antigen is highly expressed in several hematologic malignancies including multiple myeloma (MM) and has been proven to be a good target for immunotherapy of the disease. CD38 is also a signaling enzyme responsible for the metabolism of two novel calcium messenger molecules. To be able to target this multifunctional protein,we generated a series of nanobodies against CD38 with high affinities. Crystal structures of the complexes of CD38 with the nanobodies were solved,identifying three separate epitopes on the carboxyl domain. Chromobodies,engineered by tagging the nanobody with fluorescence proteins,provide fast,simple and versatile tools for quantifying CD38 expression. Results confirmed that CD38 was highly expressed in malignant MM cells compared with normal white blood cells. The immunotoxin constructed by splicing the nanobody with a bacterial toxin,PE38 shows highly selective cytotoxicity against patient-derived MM cells as well as the cell lines,with half maximal effective concentration reaching as low as 10(-11) molar. The effectiveness of the immunotoxin can be further increased by stimulating CD38 expression using retinoid acid. These results set the stage for the development of clinical therapeutics as well as diagnostic screening for myeloma. View Publication

We recently reported that chronic lymphocytic leukemia (CLL) subgroups with distinct clonotypic BCRs present discrete patterns of TLR expression,function,and/or tolerance. In this study,to explore whether specific types of BCR/TLR collaboration exist in CLL,we studied the effect of single versus concomitant BCR and/or TLR stimulation on CLL cells from mutated (M-CLL) and unmutated CLL (U-CLL) cases. We stimulated negatively isolated CLL cells by using anti-IgM,imiquimod,and CpG oligodeoxynucleotide for BCR,TLR7,and TLR9,respectively,alone or in combination for different time points. After in vitro culture in the absence of stimulation,differences in p-ERK were identified at any time point,with higher p-ERK levels in U-CLL versus M-CLL. Pronounced p-ERK induction was seen by single stimulation in U-CLL,whereas BCR/TLR synergism was required in View Publication

In human B-acute lymphoblastic leukemia (B-ALL),RAG1-induced genomic alterations are important for disease progression. However,given that biallelic loss of the RAG1 locus is observed in a subset of cases,RAG1's role in the development of B-ALL remains unclear. We chose a p19Arf(-/-)Rag1(-/-) mouse model to confirm the previously published results concerning the contribution of CDKN2A (p19ARF /INK4a) and RAG1 copy number alterations in precursor B cells to the initiation and/or progression to B-acute lymphoblastic leukemia (B-ALL). In this murine model,we identified a new,Rag1-independent leukemia-initiating mechanism originating from a Sca1(+)CD19(+) precursor cell population and showed that Notch1 expression accelerates the cells' self-renewal capacity in vitro. In human RAG1-deficient BM,a similar CD34(+)CD19(+) population expressed p19ARF. These findings suggest that combined loss of p19Arf and Rag1 results in B-cell precursor leukemia in mice and may contribute to the progression of precursor B-ALL in humans. View Publication

Melanoma,a potentially lethal skin cancer,is widely thought to be immunogenic in nature. While there has been much focus on T cell-mediated immune responses,limited knowledge exists on the role of mature B cells. We describe an approach,including a cell-based ELISA,to evaluate mature IgG antibody responses to melanoma from human peripheral blood B cells. We observed a significant increase in antibody responses from melanoma patients (n = 10) to primary and metastatic melanoma cells compared to healthy volunteers (n = 10) (Ptextless0.0001). Interestingly,we detected a significant reduction in antibody responses to melanoma with advancing disease stage in our patient cohort (n = 21) (Ptextless0.0001). Overall,28% of melanoma patient-derived B cell cultures (n = 1,800) compared to 2% of cultures from healthy controls (n = 600) produced antibodies that recognized melanoma cells. Lastly,a patient-derived melanoma-specific monoclonal antibody was selected for further study. This antibody effectively killed melanoma cells in vitro via antibody-mediated cellular cytotoxicity. These data demonstrate the presence of a mature systemic B cell response in melanoma patients,which is reduced with disease progression,adding to previous reports of tumor-reactive antibodies in patient sera,and suggesting the merit of future work to elucidate the clinical relevance of activating humoral immune responses to cancer. View Publication

We analyzed in B-chronic lymphocytic leukemia (B-CLL) whole blood assays the activity of therapeutic mAbs alemtuzumab,rituximab,and type II glycoengineered anti-CD20 mAb GA101. Whole blood samples were treated with Abs,and death of CD19(+) B-CLL was measured by flow cytometry. Alemtuzumab efficiently lysed B-CLL targets with maximal lysis at 1-4 h (62%). In contrast,rituximab induced a more limited cell death (21%) that was maximal only at 24 h. GA101 killed B-CLL targets to a similar extent but more rapidly than rituximab,with 19.2 and 23.5% cell death at 4 and 24 h,respectively,compared with 7.9 and 21.4% for rituximab. Lysis by both rituximab and GA101 correlated directly with CD20 expression levels (r(2) = 0.88 and 0.85,respectively). Interestingly,lysis by all three Abs at high concentrations was mostly complement dependent,because it was blocked by the anti-C5 Ab eculizumab by 90% in the case of alemtuzumab and rituximab and by 64% in the case of GA101. Although GA101 caused homotypic adhesion,it induced only limited (3%) direct cell death of purified B-CLL cells. Both rituximab and GA101 showed the same efficiency in phagocytosis assays,but phagocytosis was not significant in whole blood due to excess Igs. Finally,GA101 at 1-100 μg/ml induced 2- to 3-fold more efficient NK cell degranulation than rituximab in isolated B-CLL or normal PBMCs. GA101,but not rituximab,also mediated significant NK cell degranulation in whole blood samples. Thus,complement and Ab-dependent cellular cytotoxicity are believed to be the major effector mechanisms of GA101 in whole blood assays. View Publication

Patients with mantle cell lymphoma (MCL) typically respond to initial treatment but subsequently relapse. This pattern suggests that a population of MCL cells is both drug resistant and capable of clonogenic growth. The intracellular enzyme retinaldehyde dehydrogenase (ALDH) provides resistance to several toxic agents. ALDH can also identify stem cells in normal adult tissues and tumorigenic cancer stem cells in several human malignancies. We studied ALDH expression in MCL and found small populations of ALDH(+) cells that were highly clonogenic. Moreover,ALDH(+) MCL cells were relatively quiescent and resistant to a wide range of agents. Normal B cells can be activated by specific unmethylated cytosine-phosphate-guanosine (CpG) DNA motifs through toll-like receptor 9,and we found that the synthetic CpG oligonucleotide 2006 (CpG) reduced the frequency of quiescent ALDH(+) MCL cells,induced terminal plasma cell differentiation,and limited tumor formation in vitro and in vivo. Treatment with CpG also significantly enhanced the activity of the proteasome inhibitor bortezomib that was associated with induction of the unfolded protein response. Our data suggest that CpG may target clonogenic and resistant ALDH(+) cells as well as improve the activity of proteasome inhibitors in MCL. View Publication

T-cell expression of programmed death receptor-1 (PD-1) down-regulates the immune response against malignancy by interacting with cognate ligands (eg,PD-L1) on tumor cells; however,little is known regarding PD-1 and natural killer (NK) cells. NK cells exert cytotoxicity against multiple myeloma (MM),an effect enhanced through novel therapies. We show that NK cells from MM patients express PD-1 whereas normal NK cells do not and confirm PD-L1 on primary MM cells. Engagement of PD-1 with PD-L1 should down-modulate the NK-cell versus MM effect. We demonstrate that CT-011,a novel anti-PD-1 antibody,enhances human NK-cell function against autologous,primary MM cells,seemingly through effects on NK-cell trafficking,immune complex formation with MM cells,and cytotoxicity specifically toward PD-L1(+) MM tumor cells but not normal cells. We show that lenalidomide down-regulates PD-L1 on primary MM cells and may augment CT-011's enhancement of NK-cell function against MM. We demonstrate a role for the PD-1/PD-L1 signaling axis in the NK-cell immune response against MM and a role for CT-011 in enhancing the NK-cell versus MM effect. A phase 2 clinical trial of CT-011 in combination with lenalidomide for patients with MM should be considered. View Publication