ALBERT

Description: [1]  The contemporary coastal ocean, characterized by abundant nutrients and high primary productivity, is generally seen as a significant CO 2 sink at the global scale. However, mechanistic understanding of the coastal ocean carbon cycle remains limited, leading to the unanswered question of why some coastal systems are sources while others are sinks of atmospheric CO 2 . Here we proposed a distinct physical-biogeochemical setting, Ocean-dominated Margin (OceMar), in order for better shaping the concept of the coastal ocean carbon study. OceMars, in contrast to previously recognized River-dominated Ocean Margins (RiOMar), are characterized by dynamic interactions with the open ocean, which may provide non-local CO 2 sources thereby modulating the CO 2 fluxes in OceMars. Using the basin areas of the largest marginal seas of the Pacific and the Atlantic, the South China Sea and the Caribbean Sea as examples of OceMars, we demonstrated that such external CO 2 sources controlled the CO 2 fluxes.

Description: Abstract 566 Bone destruction is a hallmark of multiple myeloma (MM). More than 80% of MM patients have osteolysis, which is characterized by pathological fractures, severe bone pain, spinal cord compression, and hypercalcemia. These symptoms can severely compromise a patient's quality of life and performance status. It has been proposed that MM cells activate osteoclast (OC)-mediated bone resorption and inhibit osteoblast (OB)-mediated bone formation. However, the mechanism underlying the association of MM cells with development of bone lesions remains poorly elucidated. Our previous studies showed that p38 mitogen-activated protein kinase (MAPK), which is constitutively activated in MM cells, is a master regulator of MM-mediated bone destruction. Knocking down or inhibiting p38 MAPK activity in MM cells prevented MM-induced bone destruction in vivo. In the present study, we further investigated the mechanism of MM cell p38 MAPK-induced bone destruction. We hypothesized that p38 MAPK activity in MM cells can regulate OB and OC differentiation and activity by upregulating cytokine production by MM cells. In a cytokine array analysis, we examined the expression and secretion of MM-derived cytokines that regulate OB and OC differentiation. Our results showed for the first time that either knockdown or inhibition of p38 MAPK activity by p38 MAPK short hairpin RNAs or inhibitors significantly downregulated the production of dickkopf-1 (DKK-1) and monocyte chemotactic protein-1 (MCP-1) by MM cells. Real-time PCR and ELISA quantified and confirmed the array analysis results. To determine the role of p38 MAPK-upregulated DKK-1 and MCP-1 production in bone destruction, we administered treatment with neutralizing antibodies to SCID mice injected intravenously with ARP-1 or MM.1S cells. Our results showed that neutralization of DKK-1 and MCP-1 led to fewer bone lesions in these mice. Furthermore, we examined the impact of MM cell p38 MAPK activity on OB and/or OC differentiation. Our results showed that knockdown or inhibition of MM cell p38 MAPK significantly downregulated osteoclastogenesis but upregulated osteoblastogenesis in vitro and in vivo. Although DKK-1 is well known to inhibit OB differentiation, we found that DKK-1, together with MCP-1, promoted OC differentiation and bone resorption. Mechanistic studies further showed that MCP-1 upregulated RANK expression in OC precursors and that DKK-1 increased RANKL secretion from stromal cells and mature OBs, all of which led to activation of the NF-kB and MAPK signaling pathways in OCs. Thus, our study uncovered a novel mechanism by which p38 MAPK signaling in MM cells regulates osteoblastogenesis, osteoclastogenesis, and bone destruction in patients with this disease. These findings strongly suggest that disrupting and targeting MM cell p38 signaling are effective approaches to treating osteolytic bone lesions in MM patients. Disclosures: No relevant conflicts of interest to declare.

Description: Bone destruction is a hallmark of myeloma, and has a severe impact on patients’ quality of life and survival. Unfortunately, current treatment only offers moderate palliative effects, and this disease remains incurable. The bone changes in myeloma patients results from increased osteoclast-mediated bone resorption and decreased osteoblast-mediated bone formation. In particular, new bone formation that usually occurs at sites of previously resorbed bones is deeply suppressed; as a result, areas of bone destruction rarely heal. Previous studies have shown that myeloma cells inhibit osteoblast differentiation from mesenchymal stem cells (MSCs), and the Wnt/b-catenin signaling pathway is suppressed via myeloma-produced Wnt antagonists such as dickkopf-1. However, the role of dickkopf-1 in myeloma-induced inhibition of bone formation remains controversial since myeloma cells alone do not produce sufficient dickkopf-1 to suppress osteoblast differentiation. In addition, the administration of an antibody against dickkopf-1 in myeloma patients failed to restore new bone formation, indicating there must be an additional mechanism for inhibition of osteoblast differentiation seen in myeloma. While MSCs can differentiate into mature osteoblasts, they are also capable of differentiating into adipocytes, which is a major cell type in marrow stroma. We observed that myeloma cells (cell lines and primary cells isolated from myeloma patients’ bone marrow) injected into human or mouse bone not only reduced osteoblast number, but also increased adipocyte number and activity in bone marrow. Similar observations were seen in the clinical setting where collections of adipocytes were found in the bone marrow of newly diagnosed, untreated myeloma patients. Patients with greater bone destruction had higher adipocyte numbers than those in patients with less bone destruction, indicating a relationship among myeloma cells, adipogenesis, and osteoblastogenesis. We hypothesized that inhibition of osteoblast differentiation is a consequence of myeloma-dependent alterations in the control of the MSCs’ fate into osteoblasts or into adipocytes. In our studies, we co-cultured MSCs with myeloma cells in a mixed medium (that contained both adipocyte and osteoblast media), and we observed co-culture with myeloma cells induced more adipocyte than osteoblast formation. Moreover, co-culture with myeloma cells enhanced adipocyte differentiation in vitro. Interestingly, separation of the cells by transwell inserts significantly reduced such effect. By analysis of the adhesion molecules in myeloma cells, we identified integrin α4β1 as a novel contributor in regulation of adipogenesis and osteoblastogenesis. Thus, our studies indicate that in the presence of myeloma cells, MSCs may be more prone to differentiate into adipocytes than into osteoblasts via α4β1. Our studies also suggest the development of new strategies to improve the care of myeloma patients with bone destruction by targeting α4β1 and its signaling pathways. Disclosures No relevant conflicts of interest to declare.

Description: Abstract 2643 Mantle cell lymphoma (MCL) is a unique subtype of incurable B-cell, non-Hodgkin lymphoma, and its overall survival currently remains only 4–5 years. Management of relapsed or refractory MCL patients is still challenging. Immunotherapy may provide an alternative treatment for patients with MCL. Recent studies demonstrated that PD-1/B7-H1 signaling plays a crucial role in T-cell regulation in various immune responses and is involved in peripheral tolerance, autoimmunity, infection, and antitumor immunity. In the present study, we examined whether B7-H1 plays an important role in immune evasion in MCL. We demonstrated that B7-H1 gene and protein were expressed in most MCL cell lines and primary MCL cells from all patients examined. CD3+ T cells were cultured with irradiated MCL cell lines and primary cells, which were pre-incubated with or without anti-B7-H1 monoclonal antibody or control antibody. The presence of anti-B7-H1 blocking antibody, but not control antibody, increased CD3+ T cell proliferation. We confirmed the effect of B7-H1 in suppression of T cell proliferation by knockdown of B7-H1 gene expression using B7-H1 specific and non-specific control shRNA lentiviral particles. Upon transfection, the B7-H1-specific shRNA reduced both B7-H1 gene and surface protein expression, while the control shRNA did not. The B7-H1 specific shRNA, but not control shRNA, augmented CD3+ T cell proliferation. To address whether B7-H1 contributed to the suppression of host antitumor immunity in MCL, allogeneic CD3+ T cells isolated from normal donors were cocultured with irradiated MCL cell line SP53, control shRNA SP53 (SP53-ctl), or B7-H1 targeted shRNA SP53 (SP53-kd), respectively. After 7 days of coculture, CD3+ T cells were harvested and restimulated with newly irradiated SP53, SP53-ctl or SP53-kd cells. After at least 3 repeated cycles of in vitro restimulation, three cytotoxic T lymphocyte (CTL) lines were generated, and named CTL-SP53, CTL-SP53-ctl and CTL-SP53-kd. CTL-SP53-kd showed increased killing of target cells as compared with CTL-SP53 (P

Description: Chemotherapy is the most effective treatment for multiple myeloma (MM). Several new drugs have been developed to prolong MM patient survival. However, application of these drugs, such as bortezomib (BTZ), usually induces drug resistance, and patients are prone to quick relapse. It is known that cell death or proliferation is regulated by the crosstalk between apoptosis and autophagy, and autophagy activation inhibits apoptosis by reducing caspase cleavage. Recent studies have shown that autophagy activation plays a role in chemotherapy drug resistance in cancer patients, in particular, BTZ treatment activates autophagy in MM, indicating that inhibition of autophagy could overcome BTZ-induced drug resistance. We have recently reported the generation of monoclonal antibodies (mAbs) against human beta2 microglobuline (b2M), and have found that high dose mAbs have strong apoptotic effects on MM. In this study, using a BTZ treatment-setting, we hypothesized that anti-β2M mAbs could overcome drug resistance and enhance chemotherapy efficacy in MM by inhibiting autophagy. To investigate the combined effects of mAbs and BTZ, MM cells were cultured with addition of BTZ (5 nM) or mAbs (clone D1; 10 mg/ml) or both for 24 hours. Results from Annexin-V binding assay indicated that combined treatment significantly enhanced apoptosis in MM cell lines, such as ARK, ARP-1, MM.1S, and U266, and in primary MM cells as compared with individual treatment, respectively. Next, BTZ-sensitive or -resistant MM cells KAS-6 WT/V10R or OPM-2 WT/V10R were used to determine the importance of BTZ in the synergistic effects, and such synergistic effects was only shown in apoptosis of BTZ-sensitive cells, but not in BTZ-resistant cells. Furthermore, combined treatment significantly increased apoptosis in β2M-overexpressing, but decreased in β2M-knocking down MM cells, which indicated that the synergistic effects is dependent on the surface β2M expression on MM cells. Mechanistic studies further showed that BTZ treatment resulted in an accumulation of cleaved-caspase 9/3 and PARP cleavage, suggesting that combined treatment enhanced caspase activation. In addition, Western blot analysis showed that BTZ treatment upregulated the expression of autophagy proteins, such as LAMP-1, Beclin 1, and LC3B, in a dose dependent manner, whereas combined treatment decreased their expression. Beclin 1, which is a key protein required for autophagy, has been reported to have a potential NF-kB p65 binding site on its promoter. Therefore, we checked if mAbs inhibited BTZ-induced autophagy via NF-kB signaling pathway. Our data showed that BTZ treatment increased p65 nuclear translocation and the levels of phosphorylated p65 in MM cells, while combined treatment significantly reduced both. ChIP assay has further verified that mAb treatment inhibited p65 binding to Beclin 1 promoter. To examine our hypothesis in vivo, MM cells ARP-1 or MM.1S were subcutaneously injected into SCID mice. The mice were then subcutaneously injected with mAbs (0.6 mg/kg) or intraperitoneally injected with BTZ (0.1 mg/kg) individually or in combination. Tumor burdens were assessed by measuring tumor volumes and serum M-protein levels by ELISA. The combination of anti-β2M mAb and BTZ treatment repressed tumor growth and prolonged the survival of tumor-bearing mice as compared with individual treatment. In conclusion, our study for the first time demonstrated that anti-β2M mAbs prevent BTZ resistance and enhance its anti-MM efficacy by reducing the expression of autophagy proteins via NF-kB signaling. Thus, our studies provide a new insight into clinical development of anti-β2M mAbs to overcome chemotherapy drug resistance and improve MM patient survival. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 694 Osteoclasts (OCs), the responsible cells for bone resorption, are derived from monocytic precursor cells, with the stimulation of macrophage colony-stimulating factor (M-CSF) and the receptor activator of nuclear factor κb ligand (RANKL). The formation and activity of OCs can be either promoted by activated T cell derived RANKL, IL-17, or suppressed by T cell derived IFN-γ, IL-10, and IL-4. On the other hand, OCs express MHC, and costimulatory molecules, secrete IL-10, TGF-β, TNF-α and IL-6 and can act as antigen presenting cells to activate T cells, which indicates that OCs can be considered as immune cells. However, the immune function of OCs is largely unknown, and whether activated T cells can regulate the immune function of OCs is also unclear. In this study, we investigated the effect of OCs on T cell responses, and the cross regulation between activated T cells and immune regulatory OCs. Results showed that autologous OCs could inhibit the proliferation of CD4+ T cells activated by allogeneic antigen, tetanus toxin, staphylococcal enterotoxin B, and anti-CD3/CD28 antibodies. The inhibitory rate range varied from 63% to 88%. To identify the mechanism of OC-mediated T cell suppression, we blocked or inhibited TGF-β, IL-10, (prostaglandin E2) PGE-2, and indoleamine 2,3-dioxygenase (IDO) with neutralizing antibodies or specific inhibitors during the coculture. Results showed that only 1-methyl-DL-tryptophan (1-MT, an IDO inhibitor) could rescue the T cell proliferation, which suggested that OCs mediated the T cell suppression through IDO. To confirm this result, we knocked down IDO expression in OCs with siRNA and found that T cell proliferation was restored completely. As normal OCs didn't express IDO, next we investigated which molecules induced IDO expression in OCs, when cocultured with activated T cells. Results showed that blocking IFN-γ and CD40 ligand (CD40L) could inhibit IDO expression in OCs and rescue the T cell proliferation, and recombinant IFN-γ and soluble CD40L could induce IDO expression in OCs, synergistically. In conclusion, our study identified that OCs can function as immune regulatory cells to suppress T cell proliferation through IDO, which is induced by activated T cell derived IFN-γ and CD40L. This study provides new insight into the reciprocal interaction between OCs and T cells and may be helpful to develop novel therapeutic strategies for diseases involved in both bone and immune systems, such as bone-invasive tumors and autoimmune arthritis. Disclosures: No relevant conflicts of interest to declare.

Description: Abstract 2904 The secreted protein sonic hedgehog (SHH) and the hedgehog signaling are of great importance in proliferation and differentiation of cells in the hematopoietic system, and also play a vital role in oncogenesis of B cell malignance. However, the functions and mechanism of SHH signaling in multiple myeloma (MM) is mostly unknown. Thus far, aberrant activation of the hedgehog signaling in tumor growth promoting and/or survival capabilities as well as a paracrine model of SHH secretion have been demonstrated in MM. In the current study, we demonstrated a new autocrine SHH functioning manner in MM cells. The Shh mRNA and the SHH protein were highly expressed both in the MM cell lines and in purified CD138+ MM cells from patients using real-time PCR, Western Blot and immunohistochemistry analyses, respectively; and the SHH protein was also detected in the culture medium. Accordingly, the Hh ligand receptor PTCH1 and PTCH2 as well as the transcriptional factor GLI1 were all overexpressed in MM cells, indicating the activation of Hh signaling pathway. Autocrine SHH played a role in MM cells survival and protected MM cells from apoptosis in vitro, and autocrine SHH accelerated xenograft tumor growth in myeloma-SCID mouse model in vivo. Moreover, autocrine SHH enhanced drug resistance of MM cells, as SHH overexpressed CAG cells (SHH+CAG) had a significantly low apoptosis rate when treated with chemotherapy drugs dexamethasone or bortezomib, as compared with wild type cells (wt-CAG). On the contrary, SHH knockdown cells (SHH-CAG) had a dramatically higher apoptosis rate. Blocking autocrine SHH ligand and treating cells with dexamethasone or bortezomib significantly improved the drug killing effect. Finally, we found that upregulated BLC2 via SHH-Gli1signaling is the signaling pathway by which MM cells enhanced the drug resistance. Our study provides a new insight into the biologic function of the autocrine SHH in proliferation, survival and the drug resistance in the myeloma cells. Disclosures: No relevant conflicts of interest to declare.

Description: Bone destruction is a hallmark of multiple myeloma and severely compromises a patient’s quality of life. Recently, we have demonstrated that p38 mitogen-activated protein kinase (MAPK), which is constitutively activated in myeloma cells, is a master regulator of myeloma-mediated bone destruction. We have observed that myeloma cell p38 MAPK upregulated the production of dickkopf-1 (DKK-1), of which inhibits osteoblast differentiation and bone formation by inhibiting Wnt signaling and enhances osteoclast differentiation and bone resorption by upregulating RANKL production. Our results have shown that treatment of SB203580 (SB20), a p38 MAPK inhibitor, downregulated, while treatment of anisomycin, a p38 MAPK activator, upregulated DKK-1 expression. However, the mechanism underlying the regulation of DKK-1 expression by p38 MAPK in myeloma cells remains poorly elucidated. Previous studies have suggested that CREB is a p38 MAPK-targeted transcriptional factor. We therefore hypothesized that myeloma cell p38 MAPK may upregulate the transcriptional levels of DKK-1 through CREB. To verify whether p38 MAPK regulates CREB phosphorylation in myeloma cells, ARP-1 and U266 cells were treated with SB20 or anisomycin. Western blotting results showed that SB20 treatment significantly reduced, while anisomycin treatment enhanced phosphorylation of CREB in both cell lines. Database analysis of DKK-1 promoter regions predicted a couple of potential CREB-binding sites localized around 1.3 kb upstream from the starting codons. CHIP assay further indicated that CREB specifically bound to the one of the putative binding sites (-1,354 bp). To validate the CHIP assay results, we designed three constructs: construct 1 containing the whole promoter (-2,542 bp to -220 bp), which has previously been shown to have strong transcriptional activity; construct 2, as a truncated portion of the promoter containing the putative CREB-binding sites (-1,392 bp to -220 bp); and construct 3, as a truncated portion of the promoter containing neither CREB-binding sites (-1073 bp to -220 bp). These constructs were amplified by PCR and cloned into a luciferase reporter gene vector (pGL2) respectively. To examine the effect of CREB on the transcription activities of DKK1 in myeloma cells, reporter constructs were transfected into ARP-1 and U266 cells. In line with our findings in CHIP assay, we observed that in both myeloma cells, the construct 2 had similar strong transcriptional activity as the construct 1 did, the construct 3 had little activity. These results demonstrated that there was a CREB-binding site in DKK-1 promoter, and is required for p38 MAPK-upregulated DKK-1 expression in myeloma cells. In conclusion, our results uncover a mechanism of myeloma cell p38 MAPK in osteoblast inhibition and osteoclast activation by which p38 MAPK transcriptionally upregulates DKK-1 expression via CREB. Disclosures: Orlowski: Bristol-Myers Squibb: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Millennium: The Takeda Oncology Company: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Onyx: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Resverlogix: Research Funding; Array Biopharma: Honoraria, Membership on an entity’s Board of Directors or advisory committees; Genentech: Honoraria, Membership on an entity’s Board of Directors or advisory committees; Merck: Membership on an entity’s Board of Directors or advisory committees.

Description: Currently, chemotherapy is the most effective treatment for multiple myeloma (MM). Although some new drugs have been shown to prolong survival in MM patients, these patients are prone to rapid relapse after high-dose treatment. Recent studies show that several bone marrow (BM) stromal cells are potentially involved in drug resistance. However, the role of other stromal cells is unclear. Adipocytes (ADs) are a major component of BM stromal cells. ADs have been shown to be involved in tumor rapid growth, metastasis, and apoptosis. Clinical studies suggest that BM ADs are associated with an increased risk of MM. Moreover, ADs isolated from patient BM biopsies were shown to support MM proliferation and migration. However, no published study has examined the importance of ADs in MM drug resistance. In addition, autophagy activation has been shown to induce drug resistance in cancer patients. We hypothesized that BM ADs protect MM cells from chemotherapy drug-induced apoptosis by autophagy activation. To examine the role of ADs in MM drug resistance, MM cells were cocultured with ADs at a ratio of 1:5 for 24 hours in medium with melphalan, dexamethasone, or bortezomib, the commonly used drugs for the treatment of MM. MM cells included primary MM cells isolated from BM aspirates of 5 MM patients and 6 MM cell lines. Human ADs were generated from mesenchymal stem cells derived from the BM mononuclear cells of healthy human fetal bones or BM aspirates of MM patients or healthy adult donors, cultured in AD medium for 2 weeks. ADs generated in vitro contained cytoplasmic Oil red O+ lipid droplets and produced triglycerol. Our results showed less drug-induced MM apoptosis in cocultures of MM cells and ADs compared with cultures of MM cells alone. Western blot analysis showed that treatment with melphalan upregulated the levels of cleaved caspase-9 and -3, but not -8, and PARP in MM cells. Compared with cultures alone, cocultures with ADs showed significantly lower levels of cleaved caspase-9, -3, and PARP in melphalan-treated MM cells. Mechanistic studies further showed that cocultures of ADs, compared with cultures alone, significantly upregulated the expression of autophagy proteins LC3B, Atg3, Atg5, and LAMP-1, but not Beclin-1. The addition of autophagy inhibitors 3-methyl adenine and chloroquine diphosphate to the cocultures remarkably enhanced apoptosis and caspase activation. Furthermore, we observed that cocultures of MM cells and ADs with either cell-cell contact or those separated by transwell inserts conferred similar protection from drug-induced apoptosis. We identified that AD-produced adipokines such as adiponection, leptin, adipsin, IL-6, MCP-1, TNF-a, and IGF-1, but not VEGF and CRP, were abundant in all examined ADs. Among these adipokines, adiponection, leptin, and adipsin were mainly produced from ADs and not from BM stromal cells, whereas other adipokines were produced from both cells. The addition of antibodies against these adipokines to the cocultures enhanced apoptosis and reduced autophagy, whereas addition of these adipokines to the cultures alone inhibited apoptosis and enhanced autophagy. In vivo studies validated these findings that injection of BM-derived ADs into the implanted human bones of SCID-hu mice bearing primary MM cells reduced response to treatment with melphalan and induced autophagy activation. Taken together, our findings elucidate a novel mechanism of MM drug resistance, through BM ADs. Our studies also provide evidence that targeting BM ADs may be a new approach to improve the efficacy of chemotherapy for the treatment of MM. Disclosures: No relevant conflicts of interest to declare.

Description: Key Points CD138+ MM cells are a major source of SHH. Autocrine SHH enhances MM drug resistance.