Increased Signaling through p62 in the Marrow Microenvironment Increases Myeloma Cell Growth and Osteoclast Formation

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 642-642 ◽  
Author(s):  
Yuko Hiruma ◽  
Noriyoshi Kurihara ◽  
Diane F. Jelinek ◽  
David Roodman
Keyword(s):  
Cell Growth ◽  
Tumor Growth ◽  
Signaling Pathways ◽  
P38 Mapk ◽  
Stromal Cells ◽  
Therapeutic Target ◽  
Bone Destruction ◽  
Marrow Stromal Cells ◽  
Tnf Α ◽  
Attractive Therapeutic Target

Abstract Marrow stromal cells in the bone microenvironment of multiple myeloma (MM) patients play a critical role in promoting both tumor growth and bone destruction. Binding of MM cells to marrow stromal cells, through VCAM-1 on stromal cells and α4β1 integrin on MM cells, results in increased production of TNF-α, receptor activator of NF-KB ligand (RANKL) and IL-6 by marrow stromal cells. These factors in turn increase osteoclast (OCL) formation and the growth of MM cells. Adhesive interaction between MM cells and marrow stromal cells also decrease the sensitivity of MM cells to chemotherapeutic agents. Many of the downstream effects of these adhesive interactions are mediated through the NF-KB, p38 MAPK and JNK signaling pathways. The adapter protein sequestosome-1 (p62) sits at the crossroads of these signaling pathways and mediates the effects of cytokines and other factors that activate NF-KB, p38 MAPK and JNK. However, the role that increased signaling through p62 plays in MM tumor growth and bone destruction is unknown. It is our hypothesis that increased signaling through p62 in marrow stromal cells is necessary for their capacity to increase the growth of MM cells and OCL formation in MM, and thus p62 may be an attractive therapeutic target for MM. To test these hypotheses, we established long-term Dexter-type marrow cultures to isolate marrow stromal cells from MM patients and normals and measured signaling through p62 and PKCζ activation in MM marrow. We found significantly elevated levels of phosho-PKCζ, total PKCζ and VCAM-1 in MM stromal cells. The enhanced IL-6 production resulted from increased p38 MAPK activity and the increased VCAM-1 expression was NF-KB dependent. We then examined the effects of blocking p62 activity in primary patients and normal stromal cells with p62 siRNA (10μg). We confirmed that p62 expression was decreased by at least 90% in both these stromal cells by Western blot analysis. Stromal cells expressing p62siRNA or control siRNA were cultured with or without MM1.S cells for 3 days in separate experiments. Knocking-down p62 in MM derived marrow stromal cells significantly decreased the levels of PKCζ, VCAM-1 and IL-6 in marrow stromal cells and markedly decreased stromal cell support of MM cell growth and OCL formation. Similarly, marrow stromal cells from p62−/− mice produced much lower levels of IL-6, TNF-α, VCAM-1 and RANKL and minimally supported MM cell growth and OCL formation compared to normal cells. Thus, increased signaling through p62 in marrow stromal cells in patients with MM plays an important role in the increased tumor growth and OCL formation in MM, and support p62 as an attractive therapeutic target for MM.

scholarly journals Increased signaling through p62 in the marrow microenvironment increases myeloma cell growth and osteoclast formation

Blood ◽  
2009 ◽  
Vol 113 (20) ◽  
pp. 4894-4902 ◽  
Author(s):  
Yuko Hiruma ◽  
Tadashi Honjo ◽  
Diane F. Jelinek ◽  
Jolene J. Windle ◽  
Jaekyoon Shin ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Cell Growth ◽  
Signaling Pathways ◽  
P38 Mapk ◽  
Stromal Cells ◽  
Bone Destruction ◽  
Osteoclast Formation ◽  
Marrow Stromal Cells ◽  
Sequestosome 1 ◽  
Multiple Signaling

Adhesive interactions between multiple myeloma (MM) cells and marrow stromal cells activate multiple signaling pathways including nuclear factor κB (NF-κB), p38 mitogen-activated protein kinase (MAPK), and Jun N-terminal kinase (JNK) in stromal cells, which promote tumor growth and bone destruction. Sequestosome-1 (p62), an adapter protein that has no intrinsic enzymatic activity, serves as a platform to facilitate formation of signaling complexes for these pathways. Therefore, we determined if targeting only p62 would inhibit multiple signaling pathways activated in the MM microenvironment and thereby decrease MM cell growth and osteoclast formation. Signaling through NF-κB and p38 MAPK was increased in primary stromal cells from MM patients. Increased interleukin-6 (IL-6) production by MM stromal cells was p38 MAPK-dependent while increased vascular cell adhesion molecule-1 (VCAM-1) expression was NF-κB–dependent. Knocking-down p62 in patient-derived stromal cells significantly decreased protein kinase Cζ (PKCζ), VCAM-1, and IL-6 levels as well as decreased stromal cell support of MM cell growth. Similarly, marrow stromal cells from p62−/− mice produced much lower levels of IL-6, tumor necrosis factor-α (TNF-α), and receptor activator of NF-κB ligand (RANKL) and supported MM cell growth and osteoclast formation to a much lower extent than normal cells. Thus, p62 is an attractive therapeutic target for MM.

Targeting p62 in Marrow Stromal Cells Is Effective at Inhibiting Myeloma Cell Growth.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 513-513 ◽  
Author(s):  
Noriyoshi Kurihara ◽  
Y. Hiruma ◽  
J. Windle ◽  
C.S. Hong ◽  
J. Shin ◽  
...  
Keyword(s):  
Cell Growth ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Bone Destruction ◽  
Myeloma Cell ◽  
Marrow Stromal Cells ◽  
Bone Microenvironment ◽  
Wild Type ◽  
Myeloma Cells ◽  
Tnf Α

Abstract Release of growth factors from bone by osteoclastic bone destruction and by tumor-stromal cell interactions play critical roles in promoting myeloma cell growth. In particular, expression of the cytokines RANK ligand (RANKL), a potent inducer of osteoclast (OCL) formation, IL-6, tumor necrosis factor-α (TNF-α) and MCP-1 are upregulated in the bone microenvironment in response to myeloma (MM) cells as well as by adhesive interactions between myeloma cells and marrow stromal cells through VCAM-1 on stromal cells. Therefore, agents that can both inhibit OCL formation and block the effects of myeloma stromal cell interactions should have a major impact on both bone destruction and tumor growth. p62 plays a critical role in NF-κB activation induced by TNF-α, RANKL and IL-1 and is involved in multiple signaling pathways that result in enhanced tumor cell survival and bone destruction. It is our hypothesis that inhibiting p62 expression will profoundly diminish osteolytic bone destruction and myeloma growth in patients, by blocking production of RANKL, MCP-1, TNF-α and IL-6 in the tumor-bone microenvironment, and the upregulation of VCAM-1 on stromal cells. Therefore, we used p62 −/− mice to determine the effects of deleting p62 in stromal cells on the growth of myeloma cells. Marrow cells from p62 −/− or wild type mice were used to establish long-term Dexter-type marrow cultures to isolate marrow stromal cells. IL-6 and TNF-α production by p62 −/− stromal cells was decreased compared to WT stromal cells. To determine the effects of the lack of p62 on MM cell growth, GFP-labeled MM.1S cells were co-cultured with p62 −/− stromal cells. Growth of MM.1S cells was decreased by 70% in cocultures of p62 −/− mice, and IL-6 and TNF-α levels were not increased in cocultures of tumor cells with p62 −/− stromal cells. Next, we measured the relative expression levels of VCAM-1 on marrow stromal cells by Western blot in cocultures of human myeloma cells with marrow stromal cells. Stromal cells from the p62 −/− or wild type were cultured with and without MM.1S cells for 3 days in separate experiments. The levels of VCAM-1 in p62 −/− stromal cells were lower than p62 +/− stromal cells. In addition, VCAM-1 levels on p62 −/− bone marrow stromal cells were decreased compared to p62 +/− stromal cells when cocultured with MM cells. The addition of 25 ng/ml mouse TNF-α to p62 −/− stromal cells cocultured with MM.1S cells resulted in enhanced MM.1S growth and VCAM-1 production to similar levels as seen with p62 +/− stromal cells cocultured with MM.1S cells. We then determined the capacity of p62 −/− stromal cells to increase MCP-1 production, a chemoattract for myeloma cells, when they were cocultured with human myeloma cells for 48 hours. The conditioned media were collected after 48 hours of culture. Wild type stromal cells produced increased levels of MCP-1 when cocultured with MM.1S cells. MCP-1 levels in p62 −/− stromal cell conditioned media were decreased compared to wild type stromal cell cultures, regardless of whether MM.1S cells were present in the culture (MCP-1 in p62 +/− stromal cell culture, 980± 70pg/ml vs. p62 −/− 380± 10 pg/ml). These results show that p62 plays an important role in myeloma cell growth through regulation of production of cytokines that are upregulated in the marrow microenvironment in response to myeloma, and suggest that p62 is a novel target for treating myeloma.

Targeting p62ZIP in Marrow Stromal Cells Is Highly Effective at Inhibiting Myeloma Cell Growth and Osteoclast Formation.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 630-630
Author(s):  
Noriyoshi Kurihara ◽  
Tadashi Honjo ◽  
Jolene J. Windle ◽  
J. Shin ◽  
G. D. Roodman
Keyword(s):  
Cell Growth ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Critical Role ◽  
Bone Destruction ◽  
Myeloma Cell ◽  
Marrow Stromal Cells ◽  
Wild Type ◽  
Myeloma Cells ◽  
Tnf Α

Abstract Marrow stromal cells play a critical role in osteolytic bone destruction in multiple myeloma, and promote tumor growth. In particular, adhesive interactions between myeloma cells and marrow stromal cells increase RANK ligand (RANKL), a potent inducer of osteoclast formation, IL-6 and TNF-α production by marrow stromal cells. IL-6 enhances the growth and prevents apoptosis of myeloma cells, and TNF increases production of RANKL and IL-6. Recently, a new member of NF-κB signaling pathway, p62ZIP, has been identified. p62ZIP plays a critical role in NF-κB activation induced by TNF-α and RANKL and is involved in multiple signaling pathways that result in enhanced IL-6 production, tumor cell survival and bone destruction. It is our hypothesis that inhibiting p62ZIP expression will profoundly diminish myeloma growth by blocking the effects of IL-6 produced in the tumor-bone microenvironment in response to TNF-α. Therefore, we used p62ZIP−/− mice to determine the effects of deleting p62ZIP in stromal cells on the growth of myeloma cells. Marrow cells from p62ZIP −/− or wild type mice were used to establish long-term Dexter-type marrow cultures to isolate marrow stromal cells. Marrow stromal cells from p62ZIP −/− or wild type mice were cocultured for 48 h with a GFP-labeled human MM.1S myeloma cell line (MM.1S) and murine and human RANKL, IL-6 and TNF-α levels were determined in conditioned media from these cocultures using commercial ELISA assays. Cocultures of MM.1S with wild type marrow stromal cells resulted in much greater upregulation of murine IL-6 than p62−/− stromal cell coculture (IL-6 in p62−/− stromal cell cultures; 114+70 vs. WT 1900+9 pg/ml). In addition, deleting p62ZIP in stromal cells markedly decreased the growth of tumor cells. Coculture with wild type stromal cells induce 1.4-fold greater increase in MM.1S cell growth at 72 h compared to p62−/− stromal cells. Further, addition of neutralizing antibodies to TNF-α and IL-6 to the cocultures of MM.1S cells with WT stromal cells similarly affected the growth of the MM.1S. Since TNF-alpha can increase the expression of adhesion molecules on stromal cells and tumor cells, we measured expression levels of ICAM-1 and VCAM-1 by Western blot. VCAM-1 and ICAM-1 levels on p62ZIP−/− bone marrow stromal cells were not changed compared to WT stromal cells. We then determined the capacity of p62 −/− cells to support OCL formation by normal spleen CFU-blast. OCL formation was decreased about 50 % in cocultures containing p62−/− stromal cells treated with PTH-rp, IL-6 and TNF-α compare with WT stromal cell culture. These results show that p62 plays an important role in myeloma cell growth and OCL formation induced by cytokines that are upregulated in the marrow microenvironment in patients with myeloma.

p62 Signaling Is Increased in Multiple Myeloma Microenvironment.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 669-669
Author(s):  
Yuko Hiruma ◽  
Noriyoshi Kurihara ◽  
David Roodman
Keyword(s):  
Multiple Myeloma ◽  
Cell Growth ◽  
Western Blot ◽  
Stromal Cells ◽  
Bone Destruction ◽  
Marrow Stromal Cells ◽  
Myeloma Patient ◽  
Bone Microenvironment ◽  
Tnf Α ◽  
Human Stromal Cells

Abstract The bone microenvironment plays a critical role in promoting both tumor growth and bone destruction in myeloma (MM). Marrow stromal cells produce factors, which stimulate both the growth of MM cells and osteoclastic bone destruction and are key regulators of these processes. Marrow stromal cells produce these factors in increased amounts when they bind MM cells through adhesive interactions mediated via VCAM-1 on stromal cells and β1 integrins on the surface of MM cells. We have examined the role of sequestosome-1 (p62), a recently described member of the NF-κB signaling pathway, in this process, since it sits at the crossroads of multiple signaling pathways potentially involved in both osteoclastogenesis and MM cell growth. In previous studies, we found that stromal cells lacking p62 minimally supported the growth of MM cells or osteoclast (OCL) formation compared to wild-type p62 containing stromal cells. We have further shown that stromal cells lacking p62 produce much lower levels of TNF-α, interleukin (IL)-6, MCP-1 and RANK ligand (RANKL), factors which increase OCL formation, and express lower levels of VCAM-1. However, the mechanisms responsible for this decreased cytokine production and VCAM-1 expression in multiple myeloma patient stromal cells lacking p62 are unknown. Further, it is unknown that targeting PKCζ, a downstream enzyme activity activated by p62, will have similar effects on myeloma patient stromal cells. Our hypotheses are that inhibiting PKCζ expression will block the effects of cytokines produced in the MM-bone microenvironment in response to TNF-α, decrease VCAM-1 expression in stromal cells, and markedly diminish osteolytic bone destruction and MM growth in MM patients. To test these hypotheses, we established long-term Dexter-type marrow cultures to isolate marrow stromal cells from MM patient and normals and screened for p62 and PKCζ/λ activation in MM marrow. We measured levels of PKCζ and p62 by Western blot analysis in marrow stromal cells from 13 patients and 11 healthy controls. We found significantly elevated levels of phosho-PKCζ/λ and total PKCζ in MM patients although the levels varied greatly among the patients. We next measured the relative expression levels of VCAM-1 on marrow stromal cells by Western blot in these marrow stromal cells. Since inhibiting p62 expression should profoundly diminish osteolytic bone destruction and myeloma growth in patients, by blocking production of RANKL, MCP-1, TNF-α and IL-6 in the tumor-bone microenvironment, and the upregulation of VCAM-1 on stromal cells, we assessed the effects of blocking p62 activity in human stromal cells. p62 siRNA (40 nM) was transduced into human stromal cells using a commercial transfection substrate. We confirmed that p62 expression was decreased by at least 50% in these stromal cells by Western blot analysis using an anti-p62 antibody. Stromal cells from the p62siRNA and control siRNA treatment and non-treatment stromal cells were cultured with or without MM1s cells for 3 days in separate experiments. The levels of VCAM-1 in p62siRNA transducer stromal cells were lower than control siRNA and untreated stromal cells. In addition, IL-6 production by MM1.s was increased when cocultured with control stromal cells but not with p62siRNA treated bone marrow stromal cells. These results show that p62 plays an important role in myeloma cell growth induced by cytokines that are upregulated in the marrow microenvironment and myeloma cells in patients with myeloma. Therefore, p62 is an attractive therapeutic target for MM growth and bone destruction.

p62 as a Therapeutic Target for Myeloma Cell Growth and Osteoclast Formation.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2857-2857
Author(s):  
Fumito Ishizuka ◽  
Jolene Windle ◽  
David Roodman ◽  
Noriyoshi Kurihara
Keyword(s):  
Cell Growth ◽  
P38 Mapk ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Critical Role ◽  
Mapk Signaling ◽  
Marrow Stromal Cells ◽  
Fusion Peptides ◽  
Binding Domains ◽  
Cell Support

Abstract Abstract 2857 Poster Board II-833 We reported that sequestosome 1 (p62) plays a critical role in the formation of signaling complexes that result in NF-kB, p38 MAPK, and PI3K activation in the marrow microenvironment of patients with multiple myeloma (MM), and that p62 is a potential therapeutic target for MM. In contrast to treating patients with inhibitors of each of the multiple signaling pathways activated in marrow stromal cells by MM cells (e.g. NF-kB or p38 MAPK), blocking the function of p62 should inhibit the activation of the multiple pathways mediated by p62 and have a broader effect on the bone marrow microenvironment. The goal of this study was to identify the domains of p62 responsible for increased MM cell growth and osteoclast (OCL) formation mediated by NF-kB and p38 MAPK signaling in marrow stromal cells when they interact with myeloma cells, and develop inhibitory peptides as potential therapeutic agents that interfere with p62's role in these signaling complexes. To pursue this objective, we transfected p62−/− stromal cells with p62 deletion constructs and assessed their effects on NF-kB and p38 MAPK signaling induced by MM cells or TNF-a. p62−/− stromal cells support of MM growth or OCL formation was significantly decreased compared to WT stromal cells. We made a series of 5' deletion constructs of p62 that lacked specific p62 domains: ΔPB1 (Δ1) lacks homodimerization domain and binding to PKCz, ΔPB1, ZZ (Δ2) lacks PB1 and RIP1 binding domains, and ΔPB1, ZZ, TBS, (Δ3) the PB1, RIP1, p38 and TRAF6 binding domains have been deleted. These constructs were tested for their capacity to restore p62 function in p62−/−stromal cells and support MM cell growth and OCL formation. GFP-labeled MM1.S myeloma cells were cocultured with p62−/− and WT marrow stromal cells transduced with the different p62 deletion constructs. Transduction of p62−/− stromal cells with the full-length p62 construct restored the capacity of p62−/− stromal cells to enhance the growth of MM cells to levels induced by WT stromal cells. Transduction of p62−/− stromal cells with the Δ1 construct also restored stromal cell support of MM growth. Therefore, the PB1 domain is not important for this function. Transduction of p62−/− stromal cells with the Δ2 construct, resulted in an inability of the stromal cells to support MM cell growth. Additional loss of the p38 and TRAF6 binding domains did not further impair p62−/− stromal cells support of MM cell growth. These results suggest that the RIP1 binding domain plays a critical role in supporting the growth of MM cells by marrow stromal cells. We then examined the capacity of p62−/− stromal cells transduced with various p62 deletion constructs to support OCL formation. Normal CFU-GM, a source of OCL precursors, were cocultured with p62−/− stromal cells transfected with the different p62 cDNA deletion constructs. The Δ1 construct completely rescued p62−/− support of OCL formation. However, Δ2 construct transduced p62−/− stromal cells only partly restored stromal cell support of OCL formation. Transduction of the Δ3 construct did not restore the capacity of the p62−/− stromal cells to support OCL formation. Similarly, transduction of the Δ2 and Δ3 construction decreased WT stromal cell support of MM cell growth. We then tested the feasibility of using transduction domain (PTD) fusion peptides as a potential means of delivering dominant negative p62 constructs into stromal cells in vitro and in vivo to block MM cell growth and VCAM-1 expression induced by marrow stromal cells. PTD binding domain fusion peptides containing NEMO binding protein that blocks NF-kB activity was used as a model system to determine the feasibility of transducing marrow stromal cells with p62 constructs. Addition of PTD-NEMO fusion peptides to stromal cells significantly inhibited WT stromal cell to enhance MM cell growth and VCAM-1 expression on stromal cells, which is the capacity of dependent, in part, on NF-kB signaling. These results demonstrate that the ZZ, p38 MAPK and TRAF-6 domains of p62 together are required for stromal cell support of MM cell growth and OCL formation and suggest that PTD constructs containing dominant negatives for p62 may be a feasible method for blocking p62 function in the MM marrow microenvironment. Disclosures: Roodman: Novartis: Consultancy, Research Funding, Speakers Bureau; Amgen: Consultancy; Celgene: Consultancy; Acceleron: Consultancy.

The ZZ Domain of Sequestosome-1/p62 Plays An Important Role In Stromal Cell Support of Myeloma Cell Growth and Osteoclast Formation

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 128-128
Author(s):  
Jumpei Teramachi ◽  
Jolene J. Windle ◽  
David Roodman ◽  
Noriyoshi Kurihara
Keyword(s):  
Cell Growth ◽  
Cell Line ◽  
P38 Mapk ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Bone Destruction ◽  
Mapk Signaling ◽  
Sequestosome 1 ◽  
Stromal Cell Line ◽  
Cell Support

Abstract Abstract 128 The marrow microenvironment provides a critical supportive role in myeloma (MM) and enhances both tumor growth and bone destruction through activation of multiple signaling pathways in stromal cells. We reported that sequestosome 1 (p62) plays a key role in the formation of signaling complexes that result in NF-kB, p38 MAPK, and PI3K activation in the marrow microenvironment of patients with MM. These results suggest that p62 is a potential therapeutic target for blocking the supportive effects of the marrow microenvironment in MM. The goal of this study was to identify the domains of p62 responsible for increased MM cell growth and osteoclast (OCL) formation mediated by NF-kB and p38 MAPK signaling, as a means to develop inhibitory peptides/molecules as potential therapeutic agents for MM. To pursue this objective, we generated deletion constructs of p62 that lacked specific p62 domains: ΔSH2, ΔPB1, ΔZZ, Δp38, ΔTBS and ΔUBA domains. We then transfected these constructs into a p62-knockout (KO) stromal cell-line we established from p62-KO mice and examined their RANKL, IL-6, and VCAM-1 expression induced by TNF-a. GFP-labeled MM1.S myeloma cells or normal CFU-GM, a source of OCL precursors, were then co-cultured with the p62-KO cells transduced with the different p62 deletion constructs and compared to wild type (WT) stromal cells. IL-6 production and VCAM-1 expression induced by TNF-a was 50% lower in non-transduced p62-KO stromal cells compared to WT stromal cells. Further, in contrast to WT cells, RANKL was not induced by TNF-a in the p62-KO stromal cell-line, and OCL formation in co-cultures of p62-KO stromal cells with CFU-GM was very low. Transduction of p62-KO stromal cells with the ΔSH2, ΔPB1, Δp38 and ΔUBA constructs restored stromal cell support of MM growth, VCAM-1 and IL-6 production. However, p62-KO stromal cells transduced with the ΔZZ construct did not increase MM cell growth, or increase IL-6 and VCAM-1 expression, or fully restore the capacity of the p62-KO stromal cells to support OCL formation. These results demonstrate that the ZZ domain of p62 is required for stromal cell support of MM cell growth, increased IL-6 and VCAM-1 expression, and OCL formation. These results suggest that dominant negative constructs or small molecules that target the ZZ domain of p62 should block p62 function and inhibit support of MM cells and OCL formation by the marrow microenvironment. Disclosures: Roodman: Amgen, Celgene, Acceleron & Millennium: Consultancy.

Targeting MEK1/2 Signaling Cascade by AS703026, a Novel Selective MEK1/2 Inhibitor, Induces Pleiotropic Anti-Myeloma Activity in Vitro and In Vivo.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3848-3848 ◽  
Author(s):  
Yu-Tzu Tai ◽  
Kihyun Kim ◽  
Xian-Feng Li ◽  
Mariateresa Fulciniti ◽  
Weihua Song ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Growth ◽  
Tumor Growth ◽  
Stromal Cells ◽  
Bone Marrow Stromal Cells ◽  
Marrow Stromal Cells ◽  
Time Dependent ◽  
Dependent Manner

Abstract Abstract 3848 Poster Board III-784 The mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway plays a crucial role in the pathogenesis of human multiple myeloma (MM) by promoting interactions of MM cells with bone marrow stromal cells (BMSCs) that secrete cytokines and growth factors for MM cell growth, survival, and resistance to chemotherapeutic drugs. Accumulating studies have supported targeting this signaling pathway in MM. Here we investigate cytotoxicity of AS703026, a novel selective MEK1/2 inhibitor with highly oral bioavailability, in MM cell lines and patient MM cells and define its mechanisms of action. AS703026, more potently (∼9-10 fold) than AZD6244, inhibits growth and survival of MM cells and cytokine-induced osteoclast differentiation. It specifically blocks baseline and adhesion-induced pERK1/2, but not pSTAT3. Selective MEK1/2 inhibition by AS703026 led to a cessation of cell proliferation accompanied by G0-G1 cell cycle arrest, as shown by increased subG0 cells, and concurrently abolished S phase cells. AS703026 also reduced expression of c-maf oncogene in a time-dependent manner, suggesting a MEK1/2-dependent regulation of c-maf that may contribute MM cell growth inhibition. AS703026 further induced apoptosis in MM cells, as manifested by caspase 3 and PARP cleavages in a time-dependent manner. It blocked osteoclastogenesis in vitro, as measured by number of TRAP-positive multinuclear cells following culturing PBMCs with RANKL and M-CSF. Importantly, AS703026 sensitized drug-resistant MM cells to a broad spectrum of conventional (dexamethasone, melphalan), as well as novel or emerging (lenalidomide, perifosine, bortezomib, rapamycin) anti-MM therapies. Synergistic or additive cytotoxicity (combination index < 1) induced by these combinations was further validated by annexin-V/PI staining and flow cytometric analysis. Combining these agents led to a significantly increased apoptosis and cell death than AS703026 alone, confirming enhanced cytotoxicity against MM cells. In vivo studies demonstrate that treatment of MM cell line H929-bearing mice with AS703026 (n=4 at 30 mg/kg; n=6 at 15 mg/kg), but not vehicle alone (n=6), blocked MM tumor growth in a dose-dependent manner (p<0.008 at 30 mg/kg; p<0.02 at 15 mg/kg). Immunoblotting and immunohistochemistrical staining showed that AS703026-reduced tumor growth was associated with downregulated pERK1/2, induced PARP cleavage, and decreased microvessels in vivo. Moreover, AS703026 (<200 nM) triggered significant cytotoxicity against the majority of patients with relapsed and refractory MM (>84%, n=18), regardless mutation status of 3 RAS and BRAF genes. Bone marrow stromal cells-induced viability of MM patient cells is similarly blocked within the same dose range. Our results therefore strongly support clinical protocols evaluating AS703026, alone or with other anti-MM agents, to improve patient outcome in MM. Disclosures: Chauhan: Progenra, Inc: Consultancy. Richardson:Keryx Biopharmaceuticals: Honoraria. Clark:EMD Serono: Employment. Ogden:EMD Serono: Employment. Andreas:EMD Serono: Employment. Rastelli:EMD Serono: Employment. Anderson:Millennium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

Pim Inhibition Suppresses Osteoclastogenesis and Tumor Growth in Myeloma

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 4203-4203 ◽  
Author(s):  
Jumpei Teramachi ◽  
Masahiro Hiasa ◽  
Asuka Oda ◽  
Hirofumi Tenshin ◽  
Ryota Amachi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Tumor Growth ◽  
Stromal Cells ◽  
Bone Marrow Stromal Cells ◽  
Research Funding ◽  
Bone Destruction ◽  
Cathepsin K ◽  
Marrow Stromal Cells ◽  
Bone Lesions ◽  
Rank Ligand

Abstract Devastating bone destruction in multiple myeloma (MM) still remains a significant clinical problem. In pursuing factors responsible for MM tumor expansion and bone destruction, we found that the serine/threonine kinase Pim-2 is constitutively over-expressed as an anti-apoptotic mediator, and further up-regulated in MM cells when cocultured with bone marrow stromal cells or osteoclasts (OCs) (Leukemia, 2011). We also demonstrated that Pim inhibition is able to induce bone formation while suppressing MM tumor growth (Leukemia, 2015). However, the impact of Pim inhibition on MM-induced bone resorption remains unknown. Therefore, the present study was undertaken to clarify the role of Pim-2 in osteoclastogenesis enhanced in MM and the therapeutic effects of Pim inhibition on mutual interaction between MM cells and OCs. Pim-2 was highly expressed almost exclusively in cathepsin K-positive mature OCs on the surface of bone but not in other bone marrow cells in normal mouse bone tissues. RANK ligand and TNF-α induced the expression of Pim-2 in monocytes and RAW264.7 preosteoclastic cells at mRNA and protein levels. Inhibitors of the classical NF-κB pathway, SN50 or IMG2001, abolished Pim-2 up-regulation in RAW264.7 cells by RANK ligand or TNF-α, while Pim inhibition marginally affected the nuclear translocation of NF-κB subunits, p50 and p65, as well as the promoter activity of NF-κB, suggesting Pim-2 up-regulation downstream of the NF-κB pathway. Pim-2 appeared to be up-regulated along with c-fos, NFATc1 and cathepsin K during osteoclastogenesis. The Pim inhibitor SMI-16a potently suppressed the RANK ligand-induced expression of c-fos, NFATc1 and cathepsin K in RAW264.7 cells, and abolished osteoclastogenesis and bone resorption enhanced by MM cell conditioned media on hydroxyapatite-coated dishes. Furthermore, the Pim inhibition was found to suppress [Ca2+ ]i oscillation and thereby nuclear translocation of NFATc1, a critical transcription factor for osteoclastogenesis. MM cells and acid-producing OCs are mutually interacted in bone lesions to enhance MM tumor growth and bone destruction while creating an acidic milieu, thereby forming a progressive vicious cycle. Pim-2 was also up-regulated in MM cells when cocultured with OCs as well as bone marrow stromal cells, and to lesser extent merely by acidic conditions. Interestingly, acidic conditions rather preferentially enhanced the cytotoxic effects of the Pim inhibitor SMI-16a on MM cells even in cocultures with OCs or bone marrow stromal cells. Finally, treatment with SMI-16a reduced OC numbers in bone lesions together with tumor reduction and the restoration of bone formation in mouse MM models with intra-tibial injection of murine 5TGM1 MM cells. These results collectively demonstrated that Pim-2 play a critical role in osteoclastogenesis and tumor growth in acidic bone lesions in MM, and further corroborated that Pim-2 is a pivotal therapeutic target for MM bone disease and tumor progression. Disclosures Abe: Novartis Pharma K.K.: Speakers Bureau; Takeda Pharmaceutical Company Limited: Research Funding; Kyowa Hakko Kirin Company, Limited: Research Funding; Astellas Pharma Inc.: Research Funding; Ono Pharmaceutical Co.,Ltd.: Research Funding; GlaxoSmithKline plc: Research Funding.

Blocking the ZZ Domain of Sequestosome 1/p62 Suppress the Enhancement of Myeloma Cell Growth and Osteoclast Formation by Marrow Stromal Cells

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 888-888 ◽  
Author(s):  
Jumpei Teramachi ◽  
Kyaw Ze Yar Myint ◽  
Rentian Feng ◽  
Xiangqun Xie ◽  
Jolene J. Windle ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Growth ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Mononuclear Cells ◽  
Apoptotic Cell ◽  
Bone Destruction ◽  
Osteoclast Formation ◽  
Marrow Stromal Cells ◽  
Sequestosome 1

Abstract Abstract 888 The marrow microenvironment enhances both tumor growth and bone destruction in multiple myeloma (MM) through MM cell-induced activation of multiple signaling pathways in bone marrow stromal cells (BMSC) by TNFα. We reported that sequestosome-1 (p62) acts as a signaling hub for NF-kB, MAPK and PI3K activation in BMSC of MM patients and enhances MM growth and osteoclast (OCL) formation. p62 is composed of 5 domains that are involved in protein–protein interactions required for formation of these signaling complexes, but which domain of p62 mediates increase MM growth and OCL formation is unclear. Therefore, deletion constructs of p62 that lacked each of the 5 domains (PB1, ZZ, p38, TBS or UBA) were transfected into a p62−/− stromal cell line. We found that the ZZ domains mediated BMSC enhancement of MM cell growth, IL-6 production, VCAM-1 expression and OCL formation. Using virtual modeling of the ZZ domain, we identified 6 candidate p62-ZZ inhibitory molecules and tested them for their capacity to block enhanced MM cell growth, OCL formation, IL-6 production, and VCAM-1 expression on BMSC induced by TNFα. When MM1.S, RPMI8266, ANBL6 MM cell-lines or CD138+ primary MM cells were cultured in the absence of BMSC with p62-ZZ inhibitor #3 (10mM), this inhibitor directly induced cell death. The p62-ZZ inhibitor-induced cell death was characterized by an increase in reactive oxygen species (ROS) production by inhibiting NF-kB activation, and apoptotic cell death by triggering the activation of caspases 3, 7, and 9. This inhibitor had an IC50 of 4.6mM for MM1.S survival. In contrast, CFU-Blast formation by human CD34+ cells was not inhibited by p62-ZZ inhibitor #3 (10mM). p62-ZZ inhibitor #3 (10mM) treatment of human OCL precursors derived from CFU-GM, inhibited OCL formation by blocking precursor proliferation. To examine the specificity of the p62-ZZ inhibitor #3, we tested its effects on OCL formation by CD11b+ mononuclear cells from wild type (WT) and p62−/− mice cultured with TNFα for 7 days. p62-ZZ inhibitor #3 blocked WT OCL formation but did not block p62−/− OCL formation. The p62-ZZ inhibitor also blocked VCAM-1 expression and IL-6 production by normal and MM patient stromal cells induced by TNFα compared to vehicle. Importantly, the inhibitor (10mM) did not block stromal cell proliferation. Further, the inhibitor blocked TNFα induced PKCζ phosphorylation in stromal cells and MM1.S when the cells were pretreated with the p62-ZZ inhibitor for 3 hours. These results demonstrate that p62-ZZ inhibitor #3 specifically blocks both stromal cells independent and dependent MM cell growth and OCL formation but does not affect hematopoietic or stromal cell growth. These results support p62 as a potential novel therapeutic target for MM. Disclosures: Roodman: Amgen: Consultancy; Millennium: Consultancy.

Sign in / Sign up

Export Citation Format

Share Document