Involvement of Notch-1 signaling in bone marrow stroma-mediated de novo drug resistance of myeloma and other malignant lymphoid cell lines

Blood ◽  
2004 ◽  
Vol 103 (9) ◽  
pp. 3503-3510 ◽  
Author(s):  
Yulia Nefedova ◽  
Pingyan Cheng ◽  
Melissa Alsina ◽  
William S. Dalton ◽  
Dmitry I. Gabrilovich
Keyword(s):  
Bone Marrow ◽  
Cell Growth ◽  
Tumor Cells ◽  
Cell Lines ◽  
Lymphoid Cell ◽  
Malignant Cell ◽  
Notch 1 ◽  
Malignant Lymphoid Cell ◽  
Response To Chemotherapy ◽  
Induced Apoptosis

Abstract The bone marrow (BM) microenvironment plays a critical role in malignant cell growth, patient survival, and response to chemotherapy in hematologic malignancies. However, mechanisms associated with this environmental influence remain unclear. In this study, we investigated the role of Notch family proteins in myeloma and other malignant lymphoid cell line growth and response to chemotherapeutic drugs. All 8 tested cell lines expressed Notch-3 and Notch-4; 7 cell lines expressed Notch-1; and 6 expressed Notch-2 proteins. Interaction with BM stroma (BMS) activated Notch signaling in tumor cells. However, activation of only Notch-1, but not Notch-2, resulted in protection of tumor cells from melphalan- and mitoxantrone-induced apoptosis. This protection was associated with up-regulation of p21WAF/Cip and growth inhibition of cells. Overexpression of Notch-1 in Notch-1- U266 myeloma cells up-regulated p21 and resulted in protection from drug-induced apoptosis. Thus, this is a first report demonstrating that Notch-1 signaling may be a primary mechanism mediating the BMS influence on hematologic malignant cell growth and survival. (Blood. 2004; 103:3503-3510)

Triggering of Toll-Like Receptor-4 In Human Multiple Myeloma Cells Promotes Proliferation and Alters Cell Responses to Immune and Chemotherapy Drug Attack

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1905-1905
Author(s):  
Zhen Cai ◽  
Hanying Bao ◽  
Peilin Lu ◽  
Lijuan Wang ◽  
Donghua He ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cell Proliferation ◽  
T Cell ◽  
Tumor Cells ◽  
Cell Lines ◽  
Myeloma Cell ◽  
Myeloma Cells ◽  
Response To Chemotherapy ◽  
Tlr4 Ligand ◽  
Induced Apoptosis

Abstract Abstract 1905 Multiple myeloma (MM) is a fatal plasma cell malignancy mainly localized in the bone marrow. The clonal expansion of tumor cells is associated with the disappearance of normal plasma cells and with a marked depression in the production of normal immunoglobulin (Ig). This makes MM patients highly vulnerable to bacterial, fungal and viral infections and recurrent infections remain to be a major cause of death in MM patients. It has been shown that most primary myeloma cells and cell lines express multiple Toll-like receptors (TLRs). Among them, TLR4 is most frequently expressed. To investigate TLR-initiated responses in MM cells including proliferation, anti-apoptosis and immune escape, we first screened four commonly used human myeloma cell line (HMCL) for the expression of major TLRs by RT-PCR. Surprisingly, all the HMCL expressed multiple TLRs. We also examined primary myeloma cells from 4 patients with MM and our results showed that TLR4 was expressed by all the tumor cells. We incubated myeloma cells with LPS, the natural ligand for TLR4, and found that cell proliferation increased significantly. Targeting TLRs on malignant B cells can induce resistance to chemotherapeutic agents but can also be exploited for combined therapeutic approaches. As mechanisms involved in the resistance to apoptosis play a major role in MM escape to therapies, we sought to determine the capacity of TLR4 ligand to promote the survival of HMCL cells. Myeloma cells were pretreated for four hours with LPS before being induced apoptosis by adriamycin. Results showed that LPS pretreatment partially protected the cells from adriamycin-induced apoptosis. The TLR signaling pathway activates several signaling elements, including NF-kB and ERK/JNK/p38 MAPKs, which regulate many immunologically relevant proteins. Time-dependent MAPK phosphorylation was measured to assess the activation of these kinases upon treatment with LPS in cell lines. ERK1/2, p38, and JNK phosphorylation and NF-kB were significantly up-regulated following LPS treatment. Moreover, our findings demonstrated that LPS-induced cell proliferation was dependent on JNK, ERK and p38 signaling. IL-18, a recently described member of the IL-1 cytokine superfamily, is now recognized as an important regulator of innate and acquired immune responses. In this study, we found that LPS induced IL-18 secretion and activated MAPK and NF-kB signaling simultaneously. Therefore, our results suggest that activation of the MAPK signaling and secretion of IL-18 are interconnected. Tumors evade immune surveillance by multiple mechanisms, including the production of factors such as TGF-β and VEGF, which inhibit and impair tumor-specific T cell immunity. Our study also showed that T cell proliferation induced by allostimulatory cells decreased when the HMCL were pre-treated with LPS. Moreover, immunoregulatory molecules on HMCL, such as B7-H1, B7-H2 and CD40, were upregulated after treatment with LPS, suggesting that TLR4 ligand LPS facilitates tumor cell evasion of the immune system. Our results show that TLRs are functional on myeloma tumor cells, and the ligands to these TLRs have a functional role in affecting myeloma cell proliferation, survival, and response to chemotherapy and immune attacks. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Overcoming the Supportive Stroma-Induced Proliferation in Waldenstrom's Macroglobulinemia By Selective Inhibition of the FGF/FGF-Receptor Axis

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1822-1822
Author(s):  
Cinzia Federico ◽  
Antonio Sacco ◽  
Katia Todoerti ◽  
Arianna Giacomini ◽  
Gaia C Ghedini ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Bone Marrow ◽  
Cell Growth ◽  
Board Of Directors ◽  
Tumor Cells ◽  
Cell Lines ◽  
Research Funding ◽  
Significant Inhibition ◽  
Advisory Committees ◽  
Dose Dependent

The human fibroblast growth factor receptor (FGF-R) family plays an essential role in a wide range of cellular processes, such as cell growth, proliferation, differentiation, migration and survival. It has been reported that FGF-Rs are expressed in hematopoietic cells; and FGF/FGFR signaling deregulation is largely involved in hematologic malignancies, including Waldenström macroglobulinemia (WM). WM is still an incurable disease, and patients succumb due to disease progression. Therefore, novel therapeutics designed to specifically target deregulated signaling pathways in WM are required. We aimed to investigate the role of FGF/FGF-R system in FGF-dependent WM cell lines by using an anti-pan FGF trap molecule (NSC12), responsible for FGF/FGF-R blocking. We first interrogated the GSE9656 dataset in order to confirm the expression of FGFs and FGF-Rs in WM cells, demonstrating an enrichment of several FGF- and FGF-R-isoforms in primary WM patients' derived tumor cells compared to the normal cellular counterpart (P<0.05); and demonstrated the ability of NSC12 to inhibit FGF-secretion within the conditioned media of NCS12-treated WM cells, as shown by ELISA. Wide-transcriptome profiling of NSC12-treated WM cells (BCWM.1; MWCL1) revealed a significant inhibition of Myc-target related genes, coupled with silencing of genes involved in cell cycle progression, cell proliferation, PI3K-AKT-mTOR signaling, oxidative phosphorylation (Hallmark; FDR<0.25; P<0.05). This prompted us to evaluate the anti-tumor functional sequelae exerted by NSC12 in WM cells: NSC12 induced significant inhibition of WM cell growth (BCWM1 and WMCL1) in a dose-dependent fashion (0.1-10μM; IC50 ~3μM), even in the presence of bone marrow microenvironment. In addition, a significant effect was also observed in primary tumor cells from WM patients; while no effect was observed on healthy donor-derived peripheral blood mononuclear cells. The growth inhibitory effect was associated with induction of apoptotic cell death, caspase activation and PARP cleavage, as demonstrated by flow cytometry and western blot, respectively. Moreover, we also observed a NSC12 dose-dependent increase of mitochondrial reactive oxigen species (ROS), at protein level. Cell cycle analysis revealed a reduction of the S-phase and increase of G0/G1 phase. Mechanistically, NSC12 targeted WM cells by inhibiting MAPK, JAK/STAT3 and PI3K-Akt pathways known to be FGFRs-activated signaling cascades. Importantly, the same effect was maintained in WM cells even in the presence of the supporting BM microenvironment. Functional studies demonstrated the ability of NSC12 to impair the adhesion of both cell lines to the supportive primary bone marrow stromal cells, in vitro. NCS12-dependnet anti-WM activity was also tested in combination with bortezomib, carfilzomib, everolimus and ibrutinib: the combinatory treatment (48h) resulted in a more significant dose-dependent inhibition of WM cell survival and proliferation (P<0.05), thus suggesting the rational for combining FGF-blockade with proteasome-, mTOR-, or BTK-inhibitors. In vivo studies are being performed, in order to further corroborate the anti-WM activity of NSC12 using WM animal models. Disclosures Ronca: Associazione Italiana per la Ricerca sul Canctro (AIRC): Research Funding. Rossi:Astellas: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria; Mundipharma: Honoraria; BMS: Honoraria; Sandoz: Honoraria; Amgen: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Jazz: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Consultancy; Roche: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Roccaro:AstraZeneca: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Associazione Italiana per al Ricerca sul Cancro (AIRC): Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; European Hematology Association: Research Funding; Associazione Italiana per al Ricerca sul Cancro (AIRC): Research Funding; Transcan2-ERANET: Research Funding; AstraZeneca: Research Funding; European Hematology Association: Research Funding; Transcan2-ERANET: Research Funding.

CAL-101, a Specific Inhibitor of the p110δ Isoform of Phosphatidylinositide 3-Kinase Induces Cytotoxicity in Multiple Myeloma (MM)

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2753-2753 ◽  
Author(s):  
Hiroshi Ikeda ◽  
Teru Hideshima ◽  
Yutaka Okawa ◽  
Sonia Vallet ◽  
Samantha Pozzi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Growth ◽  
Tumor Cells ◽  
Cell Lines ◽  
Stromal Cells ◽  
Bone Marrow Stromal Cells ◽  
Specific Inhibitor ◽  
Marrow Stromal Cells ◽  
Akt Pathway ◽  
Synergistic Cytotoxicity

Abstract The phosphatidylinositide 3-kinase (PI3K)/Akt pathway mediates cell proliferation, cell cycle regulation, apoptosis, and autophagy. Of the 8 distinct mammalian isoforms of PI3K, it is the class I PI3Ks (p110α, p110β, p110δ, and p110γ) that are responsible for Akt activation. Recently, p110δ expression has been shown in colon and bladder carcinoma, glioblastoma, and acute myeloid leukemia cells. In this study, we demonstrate expression and examined biologic sequelae of p110δ signaling in MM using a novel specific inhibitor CAL-101. Overexpression of p110δ protein was observed in 24/24 primary tumor cells from MM patients. High level of p110δ expression was detected in two (INA-6 and LB) of the 11 MM cell lines examined. Treatment of INA-6 and LB cells with CAL-101 (1.0 μM for 1.5, 3, 6 hr) significantly inhibited phosphorylation of Akt at serine 473 and threonine 308, suggesting that p110δ is the isoform responsible for PI3K signaling in these cells. Furthermore, CAL-101 induced cytotoxicity in INA-6 cells in a dose-dependent fashion, with an IC50 of 0.625 μM-1.25 μM at 48 h. In contrast, minimal cytotoxicity was observed in p110δ-negative cell lines. Importantly, CAL-101 (0.625 μM) triggered cytotoxicity against tumor cells from MM patients without affecting the survival of normal peripheral blood mononuclear cells at concentrations as high as 20 μM. The specificity of CAL-101 towards p110δ was confirmed by the observation that p110δ small interfering RNA knock-down, but not control, caused inhibition of cell growth and cytotoxicity that was consistent with CAL-101 treatment, further confirming the key role of p110δ in MM cells. Interleukin 6 (IL-6) and insulin-like growth factor I (IGF-I) and cell-cell contact with stromal cells have been shown to induce proliferative and anti-apoptotic responses in MM cells that abrogate cytotoxic effects of conventional therapies. Importantly, neither either IL-6 and IGF-1 treatment nor co-culture of MM cells with bone marrow stromal cells abrogated CAL-101-induced MM cell growth inhibition. Moreover, CAL-101 inhibited adherence of MM cells to bone marrow stromal cells. Since the PI3K/Akt pathway is involved in autophagy, we also examined whether CAL-101 induced autophagic cell death in MM cells. CAL-101 (6 hr treatment) significantly increased LC3-II expression, assessed by western blot and immunofluorescent analyses; conversely, autophagy inhibitor 3-MA (100 μM) blocked LC3-II expression induced by CAL-101. Acridine orange staining and electron microscopic analysis to assess the relative number of autolysosomes further confirmed induction of autophagy by CAL-101. Finally, combined CAL-101 with bortezomib showed synergistic cytotoxicity against MM cells (combination index = 0.64). In conclusion, our studies showed that p110δ is a novel therapeutic target in MM and provide the basis for clinical evaluation of CAL-101 in ongoing Phase 1/2 trial in hematologic malignancies including MM.

PD-1 Is Expressed on B-Cells in Waldenstrom Macroglobulinemia and Promotes Malignant Cell Viability and Proliferation

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3015-3015
Author(s):  
Stephen M. Ansell
Keyword(s):  
Bone Marrow ◽  
Flow Cytometry ◽  
B Cells ◽  
Cell Growth ◽  
Cell Lines ◽  
Stromal Cells ◽  
Malignant Cell ◽  
Growth And Survival ◽  
Waldenström Macroglobulinemia ◽  
Waldenstrom Macroglobulinemia

The tumor microenvironment plays an important role in regulating malignant cell growth and mechanisms to enhance anti-tumor immune function have been shown to improve patient outcome. Interactions between programmed death 1 (PD-1) and its ligands (PD-L1 and PD-L2) have been shown to be an important checkpoint in immune regulation. While it is well known that PD-1 is expressed on normal T cells and signaling through PD-1 inhibits T cell function, PD-1 is also expressed on a subset of B-cells but little is known about PD-1 signaling in B-cells. The goal of this study was to determine if the PD-1 is expressed on malignant B cells in Waldenstrom macroglobulinemia (WM) and whether this pathway plays a role in the survival and growth of malignant B cells in this B cell lymphoma. Using flow cytometry, we found that the cell lines MWCL-1, BCWM.1 and RPCI, all derived from patients with Waldenstrom macroglobulinemia, expressed PD-1 to varying degrees on their cell surface. PD-1 expression in the cell lines was further confirmed by RT PCR analysis. Using flow cytometry and immunohistochemistry to examine bone marrow specimens from WM patients, we further confirmed PD-1 expression on CD19+ CD138+ malignant B-cells. Furthermore, intense staining for the ligands PD-L1 and PD-L2 was found by in bone marrows of WM patients when compared to normal bone marrow specimens. When WM cell lines are co-cultured with stromal cells engineered to express PD-L1 or PD-L2, there was a consistent increase in cell viability compared to controls. When malignant B cells from WM patients were co-cultured with stromal cells expressing the ligands, viability was unchanged but there was an increase in cell proliferation, most noticeably when cocultured with cells expressing PD-L2. To determine potential mechanisms that account for upregulation of PD-1 on malignant B-cells, we tested whether cytokines that promote WM cell growth and survival, including IL-6, IL-21 and BAFF, increased PD-1 expression. We found that WM cell lines and patient derived CD19+CD138+WM B-cells (n=4) treated with IL-21 demonstrated an increase in PD-1 expression compared to untreated controls. We conclude that PD-1 is expressed on malignant B-cells in WM and that signaling through PD-1 may promote WM cell growth and survival. Blocking PD-1/PD ligand interactions may therefore be a potential therapeutic strategy in patients with Waldenstrom macroglobulinemia. Disclosures No relevant conflicts of interest to declare.

scholarly journals Differential effects of flaxseed oil (Linum usitatissimum) on cell growth between malignant and non‐malignant cell lines

2010 ◽  
Vol 24 (S1) ◽  
Author(s):  
Alison Linda Buckner ◽  
Carly Buckner ◽  
Domenic Lombardo ◽  
Mamdouh Abou‐Zaid ◽  
Robert Lafrenie
Keyword(s):  
Cell Growth ◽  
Cell Lines ◽  
Linum Usitatissimum ◽  
Malignant Cell ◽  
Flaxseed Oil ◽  
Differential Effects

scholarly journals An inhibitor of the EGF receptor family blocks myeloma cell growth factor activity of HB-EGF and potentiates dexamethasone or anti–IL-6 antibody-induced apoptosis

Blood ◽  
2004 ◽  
Vol 103 (5) ◽  
pp. 1829-1837 ◽  
Author(s):  
Karène Mahtouk ◽  
Michel Jourdan ◽  
John De Vos ◽  
Catherine Hertogh ◽  
Geneviève Fiol ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Growth Factor ◽  
Cell Growth ◽  
Cell Lines ◽  
Stromal Cells ◽  
Egf Receptor ◽  
Myeloma Cell ◽  
Factor Activity ◽  
Myeloma Cells ◽  
Induced Apoptosis

Abstract We previously found that some myeloma cell lines express the heparin-binding epidermal growth factor–like growth factor (HB-EGF) gene. As the proteoglycan syndecan-1 is an HB-EGF coreceptor as well as a hallmark of plasma cell differentiation and a marker of myeloma cells, we studied the role of HB-EGF on myeloma cell growth. The HB-EGF gene was expressed by bone marrow mononuclear cells in 8 of 8 patients with myeloma, particularly by monocytes and stromal cells, but not by purified primary myeloma cells. Six of 9 myeloma cell lines and 9 of 9 purified primary myeloma cells expressed ErbB1 or ErbB4 genes coding for HB-EGF receptor. In the presence of a low interleukin-6 (IL-6) concentration, HB-EGF stimulated the proliferation of the 6 ErbB1+ or ErbB4+ cell lines, through the phosphatidylinositol 3-kinase/AKT (PI-3K/AKT) pathway. A pan-ErbB inhibitor blocked the myeloma cell growth factor activity and the signaling induced by HB-EGF. This inhibitor induced apoptosis of patients'myeloma cells cultured with their tumor environment. It also increased patients' myeloma cell apoptosis induced by an anti–IL-6 antibody or dexamethasone. The ErbB inhibitor had no effect on the interaction between multiple myeloma cells and stromal cells. It was not toxic for nonmyeloma cells present in patients' bone marrow cultures or for the growth of hematopoietic progenitors. Altogether, these data identify ErbB receptors as putative therapeutic targets in multiple myeloma.

Adhesion of human lymphoid cell lines to immobilized carbohydrates and to bone-marrow stromal cell layers by surface sugar receptors

1993 ◽  
Vol 54 (6) ◽  
pp. 1017-1021 ◽  
Author(s):  
Sigrun Gabius ◽  
Ralf Wawotzny ◽  
Sabine Wilholm ◽  
Ulrikc Martin ◽  
Bernhard Wörmann ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Lines ◽  
Lymphoid Cell ◽  
Stromal Cell ◽  
Bone Marrow Stromal Cell ◽  
Marrow Stromal Cell ◽  
Human Lymphoid Cell ◽  
Cell Layers ◽  
Sugar Receptors ◽  
Lymphoid Cell Lines

scholarly journals Primary tumor cells of myeloma patients induce interleukin-6 secretion in long-term bone marrow cultures

Blood ◽  
1994 ◽  
Vol 84 (7) ◽  
pp. 2269-2277 ◽  
Author(s):  
HM Lokhorst ◽  
T Lamme ◽  
M de Smet ◽  
S Klein ◽  
RA de Weger ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Tumor Cells ◽  
Cell Lines ◽  
Plasma Cell ◽  
Plasma Cells ◽  
Adherent Cells ◽  
Myeloma Cells ◽  
Bone Marrow Cultures ◽  
Marrow Cultures

Abstract Long-term bone marrow cultures (LTBMC) from patients with multiple myeloma (MM) and normal donors were analyzed for immunophenotype and cytokine production. Both LTBMC adherent cells from myeloma and normal donor origin expressed CD10, CD13, the adhesion molecules CD44, CD54, vascular cell adhesion molecule 1, very late antigen 2 (VLA-2), and VLA- 5, and were positive for extracellular matrix components fibronectin, laminin, and collagen types 3 and 4. LTBMC from myeloma patients and normal donors spontaneously secreted interleukin-6 (IL-6). However, levels of IL-6 correlated with the stage of disease; highest levels of IL-6 were found in LTBMC from patients with active myeloma. To identify the origin of IL-6 production, LTBMC from MM patients and normal donors were cocultured with BM-derived myeloma cells and cells from myeloma cell lines. IL-6 was induced by plasma cell lines that adhered to LTBMC such as ARH-77 and RPMI-8226, but not by nonadhering cell lines U266 and FRAVEL. Myeloma cells strongly stimulated IL-6 secretion in cocultures with LTBMC adherent cells from normal donors and myeloma patients. When direct cellular contact between LTBMC and plasma cells was prevented by tissue-culture inserts, no IL-6 production was induced. This implies that intimate cell-cell contact is a prerequisite for IL-6 induction. Binding of purified myeloma cells to LTBMC adherent cells was partly inhibited by monoclonal antibodies against adhesion molecules VLA-4, CD44, and lymphocyte function-associated antigen 1 (LFA-1) present on the plasma cell. Antibodies against VLA-4, CD29, and LFA-1 also inhibited the induced IL-6 secretion in plasma cell-LTBMC cocultures. In situ hybridization studies performed before and after coculture with plasma cells indicated that LTBMC adherent cells produce the IL-6. These results suggest that the high levels of IL-6 found in LTBMC of MM patients with active disease are a reflection of their previous contact with tumor cells in vivo. These results provide a new perspective on tumor growth in MM and emphasize the importance of plasma cell-LTBMC interaction in the pathophysiology of MM.

Hypoxia-activated ligand HAL-1/13 is lupus autoantigen Ku80 and mediates lymphoid cell adhesion in vitro

2001 ◽  
Vol 280 (4) ◽  
pp. C897-C911 ◽  
Author(s):  
Eileen M. Lynch ◽  
Robert B. Moreland ◽  
Irene Ginis ◽  
Susan P. Perrine ◽  
Douglas V. Faller
Keyword(s):  
Tumor Cell ◽  
Tumor Cells ◽  
Cell Lines ◽  
Lymphoid Cell ◽  
Ectopic Expression ◽  
Lymphoid Cells ◽  
Expression Cloning ◽  
Hypoxic Exposure ◽  
Tumor Cell Lines ◽  
Human Lymphoid Cell

Hypoxia is known to induce extravasation of lymphocytes and leukocytes during ischemic injury and increase the metastatic potential of malignant lymphoid cells. We have recently identified a new adhesion molecule, hypoxia-activated ligand-1/13 (HAL-1/13), that mediates the hypoxia-induced increases in lymphocyte and neutrophil adhesion to endothelium and hypoxia-mediated invasion of endothelial cell monolayers by tumor cells. In this report, we used expression cloning to identify this molecule as the lupus antigen and DNA-dependent protein kinase-associated nuclear protein, Ku80. The HAL-1/13-Ku80 antigen is present on the surface of leukemic and solid tumor cell lines, including T and B lymphomas, myeloid leukemias, neuroblastoma, rhabdomyosarcoma, and breast carcinoma cells. Transfection and ectopic expression of HAL-1/13-Ku80 on (murine) NIH/3T3 fibroblasts confers the ability of these normally nonadhesive cells to bind to a variety of human lymphoid cell lines. This adhesion can be specifically blocked by HAL-1/13 or Ku80-neutralizing antibodies. Loss of expression variants of these transfectants simultaneously lost their adhesive properties toward human lymphoid cells. Hypoxic exposure of tumor cell lines resulted in upregulation of HAL-1/13-Ku80 expression at the cell surface, mediated by redistribution of the antigen from the nucleus. These studies indicate that the HAL-1/13-Ku80 molecule may mediate, in part, the hypoxia-induced adhesion of lymphocytes, leukocytes, and tumor cells.

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