All Publications

  • Current status of targeted microbubbles in diagnostic molecular imaging of pancreatic cancer BIOENGINEERING & TRANSLATIONAL MEDICINE Jugniot, N., Bam, R., Meuillet, E. J., Unger, E. C., Paulmurugan, R. 2020

    View details for DOI 10.1002/btm2.10183

    View details for Web of Science ID 000569340100001

  • Toward the Clinical Development and Validation of a Thy1-Targeted Ultrasound Contrast Agent for the Early Detection of Pancreatic Ductal Adenocarcinoma. Investigative radiology Bam, R. n., Daryaei, I. n., Abou-Elkacem, L. n., Vilches-Moure, J. G., Meuillet, E. J., Lutz, A. n., Marinelli, E. R., Unger, E. C., Gambhir, S. S., Paulmurugan, R. n. 2020


    Early detection of pancreatic ductal adenocarcinoma (PDAC) represents the most significant step toward the treatment of this aggressive lethal disease. Previously, we engineered a preclinical Thy1-targeted microbubble (MBThy1) contrast agent that specifically recognizes Thy1 antigen overexpressed in the vasculature of murine PDAC tissues by ultrasound (US) imaging. In this study, we adopted a single-chain variable fragment (scFv) site-specific bioconjugation approach to construct clinically translatable MBThy1-scFv and test for its efficacy in vivo in murine PDAC imaging, and functionally evaluated the binding specificity of scFv ligand to human Thy1 in patient PDAC tissues ex vivo.We recombinantly expressed the Thy1-scFv with a carboxy-terminus cysteine residue to facilitate its thioether conjugation to the PEGylated MBs presenting with maleimide functional groups. After the scFv-MB conjugations, we tested binding activity of the MBThy1-scFv to MS1 cells overexpressing human Thy1 (MS1Thy1) under liquid shear stress conditions in vitro using a flow chamber setup at 0.6 mL/min flow rate, corresponding to a wall shear stress rate of 100 seconds, similar to that in tumor capillaries. For in vivo Thy1 US molecular imaging, MBThy1-scFv was tested in the transgenic mouse model (C57BL/6J - Pdx1-Cre; KRas; Ink4a/Arf) of PDAC and in control mice (C57BL/6J) with L-arginine-induced pancreatitis or normal pancreas. To facilitate its clinical feasibility, we further produced Thy1-scFv without the bacterial fusion tags and confirmed its recognition of human Thy1 in cell lines by flow cytometry and in patient PDAC frozen tissue sections of different clinical grades by immunofluorescence staining.Under shear stress flow conditions in vitro, MBThy1-scFv bound to MS1Thy1 cells at significantly higher numbers (3.0 ± 0.8 MB/cell; P < 0.01) compared with MBNontargeted (0.5 ± 0.5 MB/cell). In vivo, MBThy1-scFv (5.3 ± 1.9 arbitrary units [a.u.]) but not the MBNontargeted (1.2 ± 1.0 a.u.) produced high US molecular imaging signal (4.4-fold vs MBNontargeted; n = 8; P < 0.01) in the transgenic mice with spontaneous PDAC tumors (2-6 mm). Imaging signal from mice with L-arginine-induced pancreatitis (n = 8) or normal pancreas (n = 3) were not significantly different between the two MB constructs and were significantly lower than PDAC Thy1 molecular signal. Clinical-grade scFv conjugated to Alexa Fluor 647 dye recognized MS1Thy1 cells but not the parental wild-type cells as evaluated by flow cytometry. More importantly, scFv showed highly specific binding to VEGFR2-positive vasculature and fibroblast-like stromal components surrounding the ducts of human PDAC tissues as evaluated by confocal microscopy.Our findings summarize the development and validation of a clinically relevant Thy1-targeted US contrast agent for the early detection of human PDAC by US molecular imaging.

    View details for DOI 10.1097/RLI.0000000000000697

    View details for PubMedID 32569010

  • Efficacy of affibody-based ultrasound molecular imaging of vascular B7-H3 for breast cancer detection. Clinical cancer research : an official journal of the American Association for Cancer Research Bam, R. n., Lown, P. S., Stern, L. A., Sharma, K. n., Wilson, K. E., Bean, G. R., Lutz, A. M., Paulmurugan, R. n., Hackel, B. J., Dahl, J. n., Abou-Elkacem, L. n. 2020


    Human B7-H3 (hB7-H3) is a promising molecular imaging target differentially expressed on the neovasculature of breast cancer and has been validated for pre-clinical ultrasound (US) imaging with anti-B7-H3-antibody functionalized microbubbles (MB). However, smaller ligands such as affibodies (ABY) are more suitable for the design of clinical-grade targeted-MB.Binding of ABYB7-H3 was confirmed with soluble and cell-surface B7-H3 by flow-cytometry. MB were functionalized with ABYB7-H3 or anti-B7-H3-antibody (AbB7-H3). Control and targeted-MB were tested for binding to hB7-H3-expressing cells (MS1hB7-H3) under shear stress conditions. US imaging was performed with MBABY-B7-H3 in an orthotopic mouse model of human MDA-MB-231 co-implanted with MS1hB7-H3 or control MS1WT cells and a transgenic mouse model of breast cancer development.ABYB7-H3 specifically binds to MS1hB7-H3 and murine-B7-H3-expressing monocytes. MBABY-B7-H3 (8.5 ± 1.4 MB/cell) and MBAb-B7-H3 (9.8 ± 1.3 MB/cell) showed significantly higher (p<0.0001) binding to the MS1hB7-H3 cells compared to control MBNon-targeted (0.5 ± 0.1 MB/cell) under shear stress conditions. In vivo, MBABY-B7-H3 produced significantly higher (p<0.04) imaging signal in orthotopic tumors co-engrafted with MS1hB7-H3 (8.4 ± 3.3 a.u.) compared to tumors with MS1WT cells (1.4 ± 1.0 a.u.). In the transgenic mouse tumors, MBABY-B7-H3 (9.6 ± 2.0 a.u.) produced higher (p<0.0002) imaging signal compared to MBNon-targeted (1.3 ± 0.3 a.u.), while MBABY-B7-H3 signal in normal mammary glands and tumors with B7-H3-blocking significantly reduced (p<0.02) imaging signal.MBABY-B7-H3 enhances B7-H3 molecular signal in breast tumors, improving cancer detection, while offering the advantages of a small size ligand and easier production for clinical imaging.

    View details for DOI 10.1158/1078-0432.CCR-19-1655

    View details for PubMedID 31924738

  • Nondestructive Detection of Targeted Microbubbles Using Dual-Mode Data and Deep Learning for Real-Time Ultrasound Molecular Imaging. IEEE transactions on medical imaging Hyun, D. n., Abou-Elkacem, L. n., Bam, R. n., Brickson, L. L., Herickhoff, C. D., Dahl, J. J. 2020


    Ultrasound molecular imaging (UMI) is enabled by targeted microbubbles (MBs), which are highly reflective ultrasound contrast agents that bind to specific biomarkers. Distinguishing between adherent MBs and background signals can be challenging in vivo. The preferred preclinical technique is differential targeted enhancement (DTE), wherein a strong acoustic pulse is used to destroy MBs to verify their locations. However, DTE intrinsically cannot be used for real-time imaging and may cause undesirable bioeffects. In this work, we propose a simple 4-layer convolutional neural network to nondestructively detect adherent MB signatures. We investigated several types of input data to the network: "anatomy-mode" (fundamental frequency)", contrast-mode" (pulse-inversion harmonic frequency), or both, i.e.", dual-mode", using IQ channel signals, the channel sum, or the channel sum magnitude. Training and evaluation were performed on in vivo mouse tumor data and microvessel phantoms. The dual-mode channel signals yielded optimal performance, achieving a soft Dice coefficient of 0.45 and AUC of 0.91 in two test images. In a volumetric acquisition, the network best detected a breast cancer tumor, resulting in a generalized contrast-to-noise ratio (GCNR) of 0.93 and Kolmogorov-Smirnov statistic (KSS) of 0.86, outperforming both regular contrast mode imaging (GCNR=0.76, KSS=0.53) and DTE imaging (GCNR=0.81, KSS=0.62). Further development of the methodology is necessary to distinguish free from adherent MBs. These results demonstrate that neural networks can be trained to detect targeted MBs with DTE-like quality using nondestructive dual-mode data, and can be used to facilitate the safe and real-time translation of UMI to clinical applications.

    View details for DOI 10.1109/TMI.2020.2986762

    View details for PubMedID 32286963

  • Reciprocal Crosstalk Between YAP1/Hippo Pathway and the p53 Family Proteins: Mechanisms and Outcomes in Cancer. Frontiers in cell and developmental biology Raj, N., Bam, R. 2019; 7: 159


    The YAP1/Hippo and p53 pathways are critical protectors of genome integrity in response to DNA damage. Together, these pathways secure cellular adaptation and maintain overall tissue integrity through transcriptional re-programing downstream of various environmental and biological cues generated during normal tissue growth, cell proliferation, and apoptosis. Genetic perturbations in YAP1/Hippo and p53 pathways are known to contribute to the cells' ability to turn rogue and initiate tumorigenesis. The Hippo and p53 pathways cooperate on many levels and are closely coordinated through multiple molecular components of their signaling pathways. Several functional and physical interactions have been reported to occur between YAP1/Hippo pathway components and the three p53 family members, p53, p63, and p73. Primarily, functional status of p53 family proteins dictates the subcellular localization, protein stability and transcriptional activity of the core component of the Hippo pathway, Yes-associated protein 1 (YAP1). In this review, we dissect the critical points of crosstalk between the YAP1/Hippo pathway components, with a focus on YAP1, and the p53 tumor suppressor protein family. For each p53 family member, we discuss the biological implications of their interaction with Hippo pathway components in determining cell fate under the conditions of tissue homeostasis and cancer pathogenesis.

    View details for DOI 10.3389/fcell.2019.00159

    View details for PubMedID 31448276

    View details for PubMedCentralID PMC6695833

  • Affibody-Indocyanine Green Based Contrast Agent for Photoacoustic and Fluorescence Molecular Imaging of B7-H3 Expression in Breast Cancer. Bioconjugate chemistry Bam, R., Laffey, M., Nottberg, K., Lown, P. S., Hackel, B. J., Wilson, K. E. 2019


    Spectroscopic photoacoustic (sPA) molecular imaging has high potential for identification of exogenous contrast agents targeted to specific markers. Antibody-dye conjugates have recently been used extensively for preclinical sPA and other optical imaging modalities for highly specific molecular imaging of breast cancer. However, antibody-based agents suffer from long circulation times that limit image specificity. Here, the efficacy of a small protein scaffold, the affibody (ABY), conjugated to indocyanine green (ICG), a near-infrared fluorescence dye, as a targeted molecular imaging probe is demonstrated. In particular, B7-H3 (CD276), a cellular receptor expressed in breast cancer, was imaged via sPA and fluorescence molecular imaging to differentiate invasive tumors from normal glands in mice. Administration of ICG conjugated to an ABY specific to B7-H3 (ABYB7-H3-ICG) showed significantly higher signal in mammary tumors compared to normal glands of mice. ABYB7-H3-ICG is a compelling scaffold for molecular sPA imaging for breast cancer detection.

    View details for DOI 10.1021/acs.bioconjchem.9b00239

    View details for PubMedID 31082216

  • Cell-based selections aid yeast-display discovery of genuine cell-binding ligands: Targeting oncology vascular biomarker CD276 Stern, L., Lown, P., Kobe, A., Abou-Elkacem, L., Bam, R., Willmann, J., Hackel, B. AMER CHEMICAL SOC. 2019
  • Inhibition of IRE1 results in decreased scar formation. Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society Boyko, T. V., Bam, R. n., Jiang, D. n., Wang, Z. n., Bhatia, N. n., Tran, M. C., Longaker, M. T., Koong, A. C., Yang, G. P. 2018


    Wound healing is characterized by the production of large amounts of protein necessary to replace lost cellular mass and extracellular matrix. The unfolded protein response (UPR) is an important adaptive cellular response to increased protein synthesis. One of the main components of the UPR is IRE1, an endoplasmic reticulum transmembrane protein with endonuclease activity that produces the activated form of the transcription factor XBP1. Using luciferase reporter mice for Xbp1 splicing, we showed that IRE1 was up-regulated during excisional wound healing at the time in wound healing consistent with that of the proliferative phase, when the majority of protein synthesis for cellular proliferation and matrix deposition occurs. Furthermore, using a small molecule inhibitor of IRE1 we demonstrated that inhibition of IRE1 led to decreased scar formation in treated mice. Results were recapitulated in a hypertrophic scar mouse model. These data help provide a cellular pathway to target in the treatment of hypertrophic scarring and keloid disorders.

    View details for PubMedID 29316036

  • Hypoxia-Induced Endoplasmic Reticulum Stress Tumor Hypoxia Chou, C., Bam, R., Yang, Z., Bui, J., Jiang, D., Koong, A. World Scientific. 2017
  • Identification of Doxorubicin as an Inhibitor of the IRE1a-XBP1 Axis of the Unfolded Protein Response. Scientific reports Jiang, D., Lynch, C., Medeiros, B. C., Liedtke, M., Bam, R., Tam, A. B., Yang, Z., Alagappan, M., Abidi, P., Le, Q., Giaccia, A. J., Denko, N. C., Niwa, M., Koong, A. C. 2016; 6: 33353-?


    Activation of the IRE1α-XBP1 branch of the unfolded protein response (UPR) has been implicated in multiple types of human cancers, including multiple myeloma (MM). Through an in silico drug discovery approach based on protein-compound virtual docking, we identified the anthracycline antibiotic doxorubicin as an in vitro and in vivo inhibitor of XBP1 activation, a previously unknown activity for this widely utilized cancer chemotherapeutic drug. Through a series of mechanistic and phenotypic studies, we showed that this novel activity of doxorubicin was not due to inhibition of topoisomerase II (Topo II). Consistent with its inhibitory activity on the IRE1α-XBP1 branch of the UPR, doxorubicin displayed more potent cytotoxicity against MM cell lines than other cancer cell lines that have lower basal IRE1α-XBP1 activity. In addition, doxorubicin significantly inhibited XBP1 activation in CD138(+) tumor cells isolated from MM patients. Our findings suggest that the UPR-modulating activity of doxorubicin may be utilized clinically to target IRE1α-XBP1-dependent tumors such as MM.

    View details for DOI 10.1038/srep33353

    View details for PubMedID 27634301

    View details for PubMedCentralID PMC5025885

  • Primary myeloma interaction and growth in coculture with healthy donor hematopoietic bone marrow BMC CANCER Bam, R., Khan, S., Ling, W., Randal, S. S., Li, X., Barlogie, B., Edmondson, R., Yaccoby, S. 2015; 15


    Human primary myeloma (MM) cells do not survive in culture; current in vitro and in vivo systems for growing these cells are limited to coculture with a specific bone marrow (BM) cell type or growth in an immunodeficient animal model. The purpose of the study is to establish an interactive healthy donor whole BM based culture system capable of maintaining prolonged survival of primary MM cells. This normal BM (NBM) coculture system is different from using autologous BM that is already affected by the disease.Whole BM from healthy donors was cultured in medium supplemented with BM serum from MM patients for 7 days, followed by 7 days of coculture with CD138-selected primary MM cells or MM cell lines. MM cells in the coculture were quantified using flow cytometry or bioluminescence of luciferase-expressing MM cells. T-cell cytokine array and proteomics were performed to identify secreted factors.NBM is composed of adherent and nonadherent compartments containing typical hematopoietic and mesenchymal cells. MM cells, or a subset of MM cells, from all examined cases survived and grew in this system, regardless of the MM cells' molecular risk or subtype, and growth was comparable to coculture with individual stromal cell types. Adherent and nonadherent compartments supported MM growth, and this support required patient serum for optimal growth. Increased levels of MM growth factors IL-6 and IL-10 along with MM clinical markers B2M and LDHA were detected in supernatants from the NBM coculture than from the BM cultured alone. Levels of extracellular matrix factors (e.g., MMP1, HMCN1, COL3A1, ACAN) and immunomodulatory factors (e.g., IFI16, LILRB4, PTPN6, AZGP1) were changed in the coculture system. The NBM system protected MM cells from dexamethasone but not bortezomib, and effects of lenalidomide varied.The NBM system demonstrates the ability of primary MM plasma cells to interact with and to survive in coculture with healthy adult BM. This model is suitable for studying MM-microenvironment interactions, particularly at the early stage of engagement in new BM niches, and for characterizing MM cell subpopulations capable of long-term survival through secretion of extracellular matrix and immune-related factors.

    View details for DOI 10.1186/s12885-015-1892-7

    View details for Web of Science ID 000365267500009

    View details for PubMedID 26545722

  • CYR61/CCN1 overexpression in the myeloma microenvironment is associated with superior survival and reduced bone disease BLOOD Johnson, S. K., Stewart, J. P., Bam, R., Qu, P., Barlogie, B., van Rhee, F., Shaughnessy, J. D., Epstein, J., Yaccoby, S. 2014; 124 (13): 2051-2060


    Secreted protein CCN1, encoded by CYR61, is involved in wound healing, angiogenesis, and osteoblast differentiation. We identified CCN1 as a microenvironmental factor produced by mesenchymal cells and overexpressed in bones of a subset of patients with monoclonal gammopathy of undetermined significance (MGUS), asymptomatic myeloma (AMM), and multiple myeloma (MM). Our analysis showed that overexpression of CYR61 was independently associated with superior overall survival of MM patients enrolled in our Total Therapy 3 protocol. Moreover, elevated CCN1 was associated with a longer time for MGUS/AMM to progress to overt MM. During remission from MM, high levels of CCN1 were associated with superior progression-free and overall survival and stratified patients with molecularly defined high-risk MM. Recombinant CCN1 directly inhibited in vitro growth of MM cells, and overexpression of CYR61 in MM cells reduced tumor growth and prevented bone destruction in vivo in severe combined immunodeficiency-hu mice. Signaling through αvβ3 was required for CCN1 prevention of bone disease. CYR61 expression may signify early perturbation of the microenvironment before conversion to overt MM and may be a compensatory mechanism to control MM progression. Therapeutics that upregulate CYR61 should be investigated for treating MM bone disease.

    View details for DOI 10.1182/blood-2014-02-555813

    View details for Web of Science ID 000350397200001

    View details for PubMedID 25061178

  • Role of Bruton's tyrosine kinase (BTK) in growth and metastasis of INA6 myeloma cells BLOOD CANCER JOURNAL Bam, R., Venkateshaiah, S. U., Khan, S., Ling, W., Randal, S. S., Li, X., Zhang, Q., van Rhee, F., Barlogie, B., Epstein, J., Yaccoby, S. 2014; 4


    Bruton's tyrosine kinase (BTK) and the chemokine receptor CXCR4 are linked in various hematologic malignancies. The aim of the study was to understand the role of BTK in myeloma cell growth and metastasis using the stably BTK knockdown luciferase-expressing INA6 myeloma line. BTK knockdown had reduced adhesion to stroma and migration of myeloma cells toward stromal cell-derived factor-1. BTK knockdown had no effect on short-term in vitro growth of myeloma cells, although clonogenicity was inhibited and myeloma cell growth was promoted in coculture with osteoclasts. In severe combined immunodeficient-rab mice with contralaterally implanted pieces of bones, BTK knockdown in myeloma cells promoted their proliferation and growth in the primary bone but suppressed metastasis to the contralateral bone. BTK knockdown myeloma cells had altered the expression of genes associated with adhesion and proliferation and increased mammalian target of rapamycin signaling. In 176 paired clinical samples, BTK and CXCR4 expression was lower in myeloma cells purified from a focal lesion than from a random site. BTK expression in random-site samples was correlated with proportions of myeloma cells expressing cell surface CXCR4. Our findings highlight intratumoral heterogeneity of myeloma cells in the bone marrow microenvironment and suggest that BTK is involved in determining proliferative, quiescent or metastatic phenotypes of myeloma cells.

    View details for DOI 10.1038/bcj.2014.54

    View details for Web of Science ID 000341925600004

    View details for PubMedID 25083818

  • Role of Bruton's tyrosine kinase in myeloma cell migration and induction of bone disease AMERICAN JOURNAL OF HEMATOLOGY Bam, R., Ling, W., Khan, S., Pennisi, A., Venkateshaiah, S. U., Li, X., van Rhee, F., Usmani, S., Barlogie, B., Shaughnessy, J., Epstein, J., Yaccoby, S. 2013; 88 (6): 463-471


    Myeloma cells typically grow in bone, recruit osteoclast precursors and induce their differentiation and activity in areas adjacent to tumor foci. Bruton's tyrosine kinase (BTK), of the TEC family, is expressed in hematopoietic cells and is particularly involved in B-lymphocyte function and osteoclastogenesis. We demonstrated BTK expression in clinical myeloma plasma cells, interleukin (IL)-6- or stroma-dependent cell lines and osteoclasts. SDF-1 induced BTK activation in myeloma cells and BTK inhibition by small hairpin RNA or the small molecule inhibitor, LFM-A13, reduced their migration toward stromal cell-derived factor-1 (SDF-1). Pretreatment with LFM-A13 also reduced in vivo homing of myeloma cells to bone using bioluminescence imaging in the SCID-rab model. Enforced expression of BTK in myeloma cell line enhanced cell migration toward SDF-1 but had no effect on short-term growth. BTK expression was correlated with cell-surface CXCR4 expression in myeloma cells (n = 33, r = 0.81, P < 0.0001), and BTK gene and protein expression was more profound in cell-surface CXCR4-expressing myeloma cells. BTK was not upregulated by IL-6 while its inhibition had no effect on IL-6 signaling in myeloma cells. Human osteoclast precursors also expressed BTK and cell-surface CXCR4 and migrated toward SDF-1. LFM-A13 suppressed migration and differentiation of osteoclast precursors as well as bone-resorbing activity of mature osteoclasts. In primary myeloma-bearing SCID-rab mice, LFM-A13 inhibited osteoclast activity, prevented myeloma-induced bone resorption and moderately suppressed myeloma growth. These data demonstrate BTK and cell-surface CXCR4 association in myeloma cells and that BTK plays a role in myeloma cell homing to bone and myeloma-induced bone disease. Am. J. Hematol. 88:463-471, 2013. © 2013 Wiley Periodicals, Inc.

    View details for DOI 10.1002/ajh.23433

    View details for Web of Science ID 000319293000004

    View details for PubMedID 23456977

  • NAMPT/PBEF1 enzymatic activity is indispensable for myeloma cell growth and osteoclast activity EXPERIMENTAL HEMATOLOGY Venkateshaiah, S. U., Khan, S., Ling, W., Bam, R., Li, X., van Rhee, F., Usmani, S., Barlogie, B., Epstein, J., Yaccoby, S. 2013; 41 (6): 547-557


    Multiple myeloma (MM) cells typically grow in focal lesions, stimulating osteoclasts that destroy bone and support MM. Osteoclasts and MM cells are hypermetabolic. The coenzyme nicotinamide adenine dinucleotide (NAD(+)) is not only essential for cellular metabolism; it also affects activity of NAD-dependent enzymes, such as PARP-1 and SIRT-1. Nicotinamide phosphoribosyltransferase (NAMPT/PBEF/visfatin, encoded by PBEF1) is a rate-limiting enzyme in NAD(+) biosynthesis from nicotinamide. Coculture of primary MM cells with osteoclasts induced PBEF1 upregulation in both cell types. PBEF1 expression was higher in experimental myelomatous bones than in nonmyelomatous bone and higher in MM patients' plasma cells than in healthy donors' counterparts. APO866 is a specific PBEF1 inhibitor known to deplete cellular NAD(+). APO866 at low nanomolar concentrations inhibited growth of primary MM cells or MM cell lines cultured alone or cocultured with osteoclasts and induced apoptosis in these cells. PBEF1 activity and NAD(+) content were reduced in MM cells by APO866, resulting in lower activity of PARP-1 and SIRT-1. The inhibitory effect of APO866 on MM cell growth was abrogated by supplementation of extracellular NAD(+) or NAM. APO866 inhibited NF-κB activity in osteoclast precursors and suppressed osteoclast formation and activity. PBEF1 knockdown similarly inhibited MM cell growth and osteoclast formation. In the SCID-rab model, APO866 inhibited growth of primary MM and H929 cells and prevented bone disease. These findings indicate that MM cells and osteoclasts are highly sensitive to NAD(+) depletion and that PBEF1 inhibition represents a novel approach to target cellular metabolism and inhibit PARP-1 and bone disease in MM.

    View details for DOI 10.1016/j.exphem.2013.02.008

    View details for Web of Science ID 000320013800007

    View details for PubMedID 23435312