Bachelor of Science, Southern Arkansas University (2008)
Doctor of Philosophy, University of Arkansas for Medical Sciences, Interdisciplinary Biomedical Sciences: Cancer Biology (2014)
Sanjiv Gambhir, Postdoctoral Faculty Sponsor
Current Research and Scholarly Interests
Using yeast surface display system and directed evolution approach, the goal of my project is to design a peptide ligand specific to B7-H3/CD276 or Thy-1, a tumor-specific blood vessel receptor. This ligand will be conjugated to contrast agents such as microbubbles and dyes for molecular ultrasound and photoacoustic imaging for early cancer detection. Ultimately, ultrasound-aided tumor characterization and detection is desired in clinic for breast cancer patients.
Juergen Willmann, Willmann lab (9/11/2017)
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
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 DOI 10.1111/wrr.12603
View details for PubMedID 29316036
- Hypoxia-Induced Endoplasmic Reticulum Stress Tumor Hypoxia World Scientific. 2017
Identification of Doxorubicin as an Inhibitor of the IRE1a-XBP1 Axis of the Unfolded Protein Response.
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
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
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
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
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
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