PU.1 Is Downregulated in a Subset of Multiple Myeloma by the Methylation of Its -17 kb Upstream Regulatory Region and the Promoter.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3417-3417
Author(s):  
Yutaka Okuno ◽  
Hiro Tatetsu ◽  
Shikiko Ueno ◽  
Hiroyuki Hata ◽  
Yasuhiro Yamada ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cell Growth ◽  
Cell Lines ◽  
Promoter Region ◽  
Growth Arrest ◽  
Myeloma Cell ◽  
Upstream Region ◽  
Cell Growth Arrest ◽  
Myeloma Cells ◽  
Expression Levels

Abstract It has been reported that disruption of transcription factors critical for hematopoiesis, such as C/EBPa and AML1, is involved in leukemogenesis. PU.1 is a transcription factor important for both myeloid and lymphoid development. We reported that mice in which the levels of PU.1 were 20% of that of wild-type developed acute myeloid leukemia, T cell lymphoma, and a CLL-like disease. These findings strongly suggest that PU.1 has tumor suppressive activity in multiple hematopoietic lineages. Last year, we reported that PU.1 is downregulated in a majority of multiple myeloma cell lines and and freshly isolated CD138 positive myeloma cells from certain number of myeloma patients, and that tet-off inducible exogenous expression of PU.1 in PU.1 negative myeloma cell lines induced cell growth arrest and apoptosis. Based on their PU.1 expression levels, we divided the myeloma patients into two groups, namely PU.1 high and PU.1 low-to-negative, (cutoff index of 25th percentile of the PU.1 expression level distribution among all patients). The PU.1 low-to-negative patients had a significantly poorer prognosis than the PU.1 high patients. To elucidate the mechanisms of downregulation of PU.1, we performed sequence and epigenetic analysis of the promoter region and the -17 kb upstream region that is conserved among mammalians and important for proper expression of PU.1. There are no mutations in these regions of all five myeloma cell lines. In contrast, the -17 kb upstream region was highly methylated in 3 of 4 PU.1 negative myeloma cell lines, while the promoter region was also methylated to various levels in all five myeloma cell lines including one PU.1 positive cell line. These data suggested that the downregulation of PU.1 in myeloma cell lines might be dependent on the methylation of both regulatory regions of PU.1 gene, especially the -17 kb upstream region. We also evaluated the mechanisms of cell growth arrest and apoptosis of myeloma cell lines induced by PU.1. Among apoptosis-related genes, we identified that TRAIL was upregulated after PU.1 induction. To evaluate the effect of upregulation of TRAIL, we stably introduced siRNA for TRAIL into myeloma cell lines expressing PU.1, and we found that apoptosis of these cells was partially suppressed by siRNA for TRAIL, suggesting that apoptosis of myeloma cells induced by PU.1 might be at least partially due to TRAIL upregulation. We are currently performing DNA microarray analysis to compare the expression levels of genes between before and after PU.1 induction, in order to further elucidate the mechanisms of cell growth arrest and apoptosis.

Microarray Analysis of PU.1-Induced Growth Arrest and Apoptosis of Myeloma Cell Lines.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2499-2499
Author(s):  
Shikiko Ueno ◽  
Hiro Tatetsu ◽  
Naoko Harada ◽  
Hiroyuki Hata ◽  
Tadafumi Iino ◽  
...  
Keyword(s):  
T Cells ◽  
B Cells ◽  
Cell Growth ◽  
Cell Lines ◽  
Growth Arrest ◽  
Myeloma Cell ◽  
Down Regulation ◽  
Cell Growth Arrest ◽  
Myeloma Cells ◽  
Enhancer Region

Abstract PU.1 is an Ets family transcription factor, which is important for differentiation of granulocytes, monocytes/macrophages, and B cells. In the Friend leukemia model, it is reported that the failure of PU.1 down-regulation in erythroblasts reportedly results in differentiation arrest that leads to erythroleukemia. In conditional knockout mice of the 3.5 kb length of enhancer region located in14 kb 5′ of the PU.1 gene, PU.1 is down-regulated in myeloid cells and B cells down to 20% of that of wild type, and such mice develop acute myeloid leukemia and CLL-like disease. In addition, a deletion of the 3.5 kb enhancer region, which also contains the suppressor region for PU.1 in T cells, results in ectopic expression of PU.1 in T cells, which leads to T cell lymphoma in those mice. Taken together, the failure of up-regulation or down-regulation of PU.1 in certain differentiation stages for each lineage appears to cause differentiation arrest and hematological malignancies. We recently reported that PU.1 is down-regulated in a majority of myeloma cell lines through the methylation of the promoter and enhancer region located in17 kb 5′ of human PU.1 gene which is homologous to that in14 kb 5′ of murine PU.1 gene. Conditionally expressed PU.1 induced cell growth arrest and apoptosis of those PU.1 low-negative myeloma cell lines, U266 and KMS12PE, suggesting that down-regulation of PU.1 is necessary for myeloma cell growth. In addition, we reported that PU.1 is expressed in normal plasma cells and PU.1 is down-regulated in myeloma cells of some myeloma patients. Myeloma patients with low-to-negative PU.1 expression (lower 25th percentile of PU.1 expression level distribution among 30 patients we examined) may have poor prognosis compared to those with high PU.1 expression, although more patient samples have to be examined to define the significance of the relationship of PU.1 expression levels and prognosis. To elucidate the mechanisms of PU.1 induced cell growth arrest and apoptosis of myeloma cells, we next performed DNA microarray analysis to compare gene expression levels before and after PU.1 induction. We utilized Illumina Sentrix® Human-6 Expression BeadChip. Of 47296 genes, 479 genes were up-regulated (>2fold) and 1697 genes down-regulated (<0.5 fold) either day 1 or 3 after PU.1 induction in U266 cells. Among apoptosis related genes, TRAIL was highly up-regulated in both U266 and KMS12PE cell lines. Stably expressed siRNA for TRAIL partially inhibited apoptosis of U266 cells expressing PU.1, suggesting that TRAIL is related to PU.1 induced cell death of U266 cells. Among cell-cycle related genes, p21WAF1/CIP1 was found up-regulated in U266 cells, which was confirmed with protein levels. We are now examining the roles of the observed up-regulated genes in both U266 and KMS12PE myeloma cell lines.

Conditionally Expressed PU.1 Transactivates TRAIL Gene and Induces Apoptosis in Myeloma Cell Lines.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1676-1676
Author(s):  
Shikiko Ueno ◽  
Hiro Tatetsu ◽  
Hiroyuki Hata ◽  
Tadafumi IIno ◽  
Hiroaki Niiro ◽  
...  
Keyword(s):  
T Cells ◽  
Cell Growth ◽  
Binding Site ◽  
Cell Lines ◽  
Growth Arrest ◽  
Myeloma Cell ◽  
Down Regulation ◽  
Cell Growth Arrest ◽  
Myeloma Cells ◽  
Enhancer Region

Abstract PU.1 is an Ets family transcription factor, which is important for differentiation of both myeloid and lymphoid lineages. In the Friend leukemia model, the failure of PU.1 down-regulation in erythroblasts reportedly results in differentiation arrest, leading to erythroleukemia. In mice conditionally knocked-out of the 3.5 kb length of enhancer region located in14 kb 5′ upstream of the PU.1 gene, PU.1 is down-regulated in myeloid cells and B cells to 20% of that of wild type, and such mice develop acute myeloid leukemia and CLL-like diseases. Since the 3.5 kb enhancer region contains a suppressor region for PU.1 expression in T cells, such mice ectopically express PU.1 in T cells and develop T cell lymphoma. Thus, the failure of proper expression of PU.1 in certain differentiation stages for certain cell lineages appears to result in hematological malignancies. We recently reported that human PU.1 is down-regulated in a majority of myeloma cell lines through the methylation of the promoter and enhancer region located in17 kb 5′ upstream of the PU.1 gene which is homologous to that in14 kb 5′ upstream of murine PU.1 gene. Conditionally expressed PU.1 induced cell growth arrest and apoptosis of two PU.1 low-negative myeloma cell lines, U266 and KMS12PE, suggesting that the down-regulation of PU.1 is essential for myeloma cell growth. We have also reported that PU.1 is expressed in normal plasma cells and PU.1 is down-regulated in myeloma cells of certain myeloma patients, who appear to have poor prognosis. In the present study, to elucidate the mechanisms of the cell growth arrest and apoptosis in PU.1-conditionally expressing myeloma cells, we performed DNA microarray analysis to compare gene expression levels before and after PU.1 expression, utilizing Illumina Sentrix® Human-6 Expression BeadChip. Of 47,296 genes, 479 genes were up-regulated (>2fold) and 1,697 genes down-regulated (<0.5 fold), either 1 or 3 days after PU.1 expression in U266 cells. Among cell-cycle related genes, p21WAF1/CIP1 was found up-regulated in U266 cells, which was confirmed at protein levels. Among apoptosis related genes, TRAIL was highly up-regulated in both U266 and KMS12PE cell lines. Stably expressed siRNA for TRAIL inhibited apoptosis of PU.1-expressing U266 cells, suggesting that TRAIL may have a crucial role in the PU.1- induced apoptosis. We subsequently examined how TRAIL was up-regulated in such PU.1-expressing myeloma cells. We performed chromatin immunoprecipitation assay and found that PU.1 directly binds to the promoter region of the TRAIL gene in U266 cells. We also determined the PU.1 binding site using electrophoretic mobility shift assays. An introduction of mutations in the PU.1 binding site abolished the binding. We also subcloned the TRAIL promoter and exon1 5′ non-coding sequence into pGL4.26 vector and performed reporter assays. Induction of PU.1 by removal of tetracycline in U266 cells induced 4-fold up-regulation of luciferase activity compared to that without PU.1 expression (28.7-fold compared to that with pGL4.26 vector alone) and mutations in the PU.1 binding site completely abolished the up-regulation. Taken together, we hereby conclude that PU.1 can directly transactivate the TRAIL gene in myeloma cells, leading to apoptosis.

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.

scholarly journals Interleukin-6 promotes multiple myeloma cell growth via phosphorylation of retinoblastoma protein

Blood ◽  
1996 ◽  
Vol 88 (6) ◽  
pp. 2219-2227 ◽  
Author(s):  
M Urashima ◽  
A Ogata ◽  
D Chauhan ◽  
MB Vidriales ◽  
G Teoh ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
B Cells ◽  
Cell Growth ◽  
Tumor Cell ◽  
Cell Lines ◽  
Interleukin 6 ◽  
Growth Arrest ◽  
Retinoblastoma Protein ◽  
Myeloma Cell ◽  
Phosphorylated Form

Interleukin-6 (IL-6) mediates autocrine and paracrine growth of multiple myeloma (MM) cells and inhibits tumor cell apoptosis. Abnormalities of retinoblastoma protein (pRB) and mutations of RB gene have been reported in up to 70% of MM patients and 80% of MM-derived cell lines. Because dephosphorylated (activated) pRB blocks transition from G1 to S phase of the cell cycle whereas phosphorylated (inactivated) pRB releases this growth arrest, we characterized the role of pRB in IL-6-mediated MM cell growth. Both phosphorylated and dephosphorylated pRB were expressed in all serum-starved MM patient cells and MM-derived cell lines, but pRB was predominantly in its phosphorylated form. In MM cells that proliferated in response to IL-6, exogenous IL-6 downregulated dephosphorylated pRB and decreased dephosphorylated pRB-E2F complexes. Importantly, culture of MM cells with RB antisense, but not RB sense, oligonucleotide (ODN) triggered IL- 6 secretion and proliferation in MM cells; however, proliferation was only partially inhibited by neutralizing anti-IL-6 monoclonal antibody (MoAb). In contrast to MM cells, normal splenic B cells express dephosphorylated pRB. Although CD40 ligand (CD40L) triggers a shift from dephosphorylated to phosphorylated pRB and proliferation of B cells, the addition of exogenous IL-6 to CD40L-treated B cells does not alter either pRB or proliferation, as observed in MM cells. These results suggest that phosphorylated pRB is constitutively expressed in MM cells and that IL-6 further shifts pRB from its dephosphorylated to its phosphorylated form, thereby promoting MM cell growth via two mechanisms; by decreasing the amount of E2F bound by dephosphorylated pRB due to reduced dephosphorylated pRB, thereby releasing growth arrest; and by upregulating IL-6 secretion by MM cells and related IL-6- mediated autocrine tumor cell growth.

A Critical Role for PIM2 Kinase in Multiple Myeloma Through NF-κB Activation

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1839-1839
Author(s):  
Veerendra Munugalavadla ◽  
Leanne Berry ◽  
Jae Chang ◽  
Geoffrey Del Rosario ◽  
Jake Drummond ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cell Growth ◽  
Cyclin D1 ◽  
Cell Lines ◽  
Combination Treatment ◽  
Single Agent ◽  
Myeloma Cell ◽  
Myeloma Cells ◽  
Pim Kinases ◽  
Pi3k Inhibition

Abstract Abstract 1839 The PIM kinases are a family of 3 growth factor- & cytokine-induced proteins hypothesized to have redundant survival and growth functions. Although PIM-1, -2 have been noted as highly expressed in multiple myeloma (MM) (Claudio JO et al., 2002), there are few data to support potential therapeutic utility of PIM inhibition in this indication. Here we show that the myeloma cell lines express all PIM protein isoforms to varying extents, and we describe the properties of a novel pan-PIM inhibitor GNE-652 with picomolar biochemical potency, an excellent selectivity profile, and favorable ADME properties. Myeloma cell lines and patient samples exhibit a striking prevalence of response to GNE-652 (23 of 25 lines with IC50 < 1 micromolar, median < 0.1 micromolar) and synergy in combination with the PI3K inhibitor GDC-0941 (mean combination index values ∼0.2 (n=25)). MM cells respond to this combination with cell cycle arrest and marked apoptosis in vitro. Conversely, a PIM-1, -3 selective inhibitor, GNE-568, failed to suppress MM cell growth and also failed to provide synergy in combination with PI3K inhibition, suggesting PIM-2 is a critical driver of MM cell growth & survival. Additional results suggest that PIM signaling converges on both TORC1 and AKT to generate differential synergies with PI3K/AKT/mTOR pathway inhibitors. PIM has been shown to potentially inactivate PRAS40, a negative regulator of TORC1 (Zhang et al., 2009). We demonstrate that PIM or PI3K inhibition caused a loss of phosphorylation on PRAS40 and resulted in a physical association of PRAS40 and TORC1 and a decrease in phosphorylated p70S6K and S6RP. These reductions were apparent in 7 of 7 cell lines assayed and enhanced by the combination of PI3K and PIM inhibition. Consistent with prior reports (Hammerman et al., 2005), we show that a second node of convergence between PIM and TORC1 is 4E-BP1. Both GDC-0941 and GNE-652 treatments reduced phosphorylation of 4E-BP1 in all the myeloma cell lines tested. Since dephosphorylated 4E-BP1 competes with eIF4G for the mRNA cap binding factor eIF4E, we assayed immunoprecipitates of eIF4E for the presence of eIF4G and 4E-BP1 and observed increased BP1 and decreased 4G. The combination treatment significantly enhanced the loss of 4G relative to either single agent, and importantly, even at 5 × IC50 concentrations for single agents, combination drug treatment achieved greater extent of effect than single agent treatment. It has been hypothesized that a subset of mRNAs are particularly sensitive to inhibition of cap-dependent translation, including a number of oncogenes such as cyclin D1. We noted across 7 different myeloma cell lines, strong decreases in levels of cyclin D1, and D3 that were further decreased by combination treatment of PIM and PI3K inhibition. In summary, we have identified several points at which PIM and PI3K/AKT/mTOR converge to provide synergy in multiple myeloma cell lines. As PIM isoforms are highly expressed in MM cells, we hypothesized that this could be due to proteosomal-mediated stability, and interestingly, MG132 and velcade each stabilized all PIM isoforms. It is commonly known that the JAK/STAT pathway regulates PIM transcription, but we show JAK inhibitors failed to abolish the expression of PIM in myeloma cells, suggesting a role for additional regulators. Recent genome sequencing studies from human myeloma samples (Chapman MA et al., 2011) confirmed the prevalence of NF-kB pathway activation, consistent with prior observations made in MM cell lines (Demchenko YN et al., 2010). The relationship of PIM and NF-kB is controversial in the literature (Hammerman PS et al., 2004 & Zhu N et al., 2002), with some groups placing PIM upstream of NF-kB and others the converse. Using an IκBα inhibitor, BMS-345541, we have examined the role for NF-kB in the regulation of PIM kinases. Here, we show that the BMS-345541 could preferentially suppress PIM2 expression in a dose dependent manner while PIM 1, 3 levels are modestly affected, suggesting that the high levels of PIM2 expression observed are partly driven by deregulation of the NF-kB pathway in MM. In conclusion, we provide pharmacological and biochemical evidence to suggest that PIM2 differentially regulate growth and survival of myeloma cells. Our results provide the rationale for further preclinical development of PIM inhibitors and the basis for a possible clinical development plan in multiple myeloma. Disclosures: Munugalavadla: Genentech: Employment. Berry:Genentech: Employment. Chang:Genentech: Employment. Rosario:Genentech: Employment. Drummond:Genentech: Employment. Du:Genentech: Employment. Fitzgerald:Genentech: Employment. Friedman:Genentech: Employment. Gould:Genentech: Employment. Maecker:Genentech: Employment. Moffat:Genentech: Employment. Slaga:Genentech: Employment. Xiaojing:Genentech: Employment. West:Genentech: Employment. Yu:Genentech: Employment. Ebens:Genentech: Employment.

Sphingolipids As a Novel Target For The Treatment Of Multiple Myeloma

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3163-3163 ◽  
Author(s):  
Jagadish Kummetha Venkata ◽  
Robert K Stuart ◽  
Luciano J Costa ◽  
Ningfei An ◽  
Houjian Cai ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cell Death ◽  
Cell Growth ◽  
Cell Lines ◽  
Stromal Cells ◽  
Myeloma Cell ◽  
Sphingolipid Metabolism ◽  
Myeloma Cells ◽  
S1p Receptors

Abstract Introduction Multiple Myeloma (MM) is the second most common hematological malignancy in the United States and accounts for ∼10,600 deaths annually. MM remains an incurable disease and almost all patients will eventually relapse and become refractory to currently available therapeutic agents. There is an unmet need for better understanding of the disease’s molecular pathways and identifying novel therapeutic targets. Sphingolipid metabolism is being increasingly recognized as a key pathway in cancer biology. In particular, sphingosine kinases (SK1 and SK2) provide a potential site for manipulation of the ceramide / sphingosine 1-phosphate (S1P) rheostat that regulates the balance between tumor cell proliferation and apoptosis, as well as tumor sensitivity to drugs. Currently, very little is known about sphingolipid metabolism in MM. We herein for the first time provide a detailed analysis of sphingolipid metabolism in MM and demonstrate the potential of targeting SK2 for the treatment of MM. Methods We first quantified sphingolipid metabolites and sphingolipid metabolizing genes in myeloma cell lines, in freshly isolated human primary CD138+ myeloma cells, and in a publically available gene expression dataset from MM patients. We then tested the anti-myeloma activity of SK2-specific shRNA and determined the efficacy of a selective SK2 inhibitor (ABC294640) in killing myeloma cell lines and primary human myeloma cells in vitro. The mechanistic pathway of apoptosis was analyzed by immunoblotting and flowcytometry. MM cell lines stably expressing luciferase and eGFP were generated for xenograft experiments and for in vitro co-cultures with stromal cells. Results From the publically available GSE6477 microarray data set, we found that one third of the genes involved in sphingolipid metabolism were significantly different in CD138+ MM cells from newly diagnosed MM patients compared to normal individuals, including SK2 and S1P receptors. In 5 MM cell lines compared to immortalized B cells (IBC), 19 key sphingolipid metabolites were measured, and we found that ceramides were significantly reduced whereas S1P was significantly increased. mRNA analyses of 11 sphingolipid metabolizing genes including S1P receptors in 7 MMs showed that SK1, SK2, and alkaline ceramidases were significantly increased compared to IBC. Furthermore, we isolated CD138+ myeloma cells from 21 MM patients and found that 13 of the patients had higher SK2 expression in CD138+ MM cells compared to CD138-cells. These data demonstrated abnormal sphingolipid metabolism and dys-regulated SK2 in myeloma cells. We generated SK2-specific shRNA and found that SK2 shRNA down-regulated SK2 mRNA, inhibited proliferation, and induced death in myeloma cells, suggesting that SK2 is important in myeloma cell survival. We then tested the efficacy of ABC294640 (the most-advanced, non-lipid SK2 inhibitor) in 6 MM cell lines. ABC294640 inhibited myeloma cell growth with an IC50s of ∼30 μM, including steroid-resistant and doxorubicin-resistant myeloma cells. ABC294640 inhibited MM cell growth as early as 6 hours after exposure and induced apoptotic cell death as demonstrated by Annexin V staining, PARP cleavage and caspase 9 activation. ABC294640 inhibited primary human CD138+MM cells with the same efficacy as with MM cell lines, demonstrating the potential of ABC294640 for the treatment of MM. Additionally, we found that blocking S1P receptors with FTY720 (a S1PR agonist with receptor degradation) induced apoptosis in MM cells. We performed extensive mechanistic and signaling pathway analyses and found that ABC294640 inhibited Mcl-1 and C-Myc expression, but had no effects on Bcl2. Furthermore, ABC294640 induced cell death by directing Mcl-1 to proteosomal degradation. MM is dependent on the bone marrow niche microenvironment for survival and progression. We found that ABC294640 was effective in inducing apoptosis in MM cells even in the presence of stromal cells. Finally, we are currently testing the in vivo effect of ABC294640 alone and in combination with bortezomib, thalidomide and dexamethasone in MM xenograft model transplanted with MM cells stably expressing luciferase. Our early preliminary results were encouraging. Conclusion Our data demonstrate that sphingolipid metabolism is abnormal and provides an attractive target in the treatment of refractory/relapsed MM. Disclosures: Costa: Otsuka: Research Funding.

Analysis of Intratumor Heterogeneity in Multiple Myeloma Using Methylcellulose Clonogenic Assays.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2346-2346
Author(s):  
Bonnie K. Arendt ◽  
Raphael Fonseca ◽  
Gregory Ahmann ◽  
Diane F. Jelinek
Keyword(s):  
Multiple Myeloma ◽  
Cell Growth ◽  
Cell Line ◽  
Cell Lines ◽  
Growth Regulation ◽  
Myeloma Cell ◽  
Intratumor Heterogeneity ◽  
Parental Cell Line ◽  
Myeloma Cells ◽  
Igf I

Abstract Multiple myeloma (MM) is a fatal disease characterized by the accumulation of malignant plasma cells in the bone marrow. Although progress has been made in better understanding growth control of this disease, effective treatment of MM patients with this disease is likely complicated by the extensive patient to patient variability that exists, as well variability within the tumor population itself. Thus, there is abundant evidence that intraclonal or intratumor heterogeneity exists in myeloma as revealed by morphologic and phenotypic heterogeneity in primary myeloma cells isolated from a single patient. We have had a long-standing interest in the growth regulation of myeloma cells and have hypothesized, along with other investigators, that there may only be a subset of myeloma cells that exhibits extensive proliferative potential. Understanding how cellular compartments within the malignant clone, as defined by identical immunoglobulin variable region sequence, may vary in growth regulation properties in isolation or in the company of less proliferative tumor cell subsets is key to understanding disease progression and how to better target the putative proliferative subset in myeloma. In this study, we have used a methylcellulose clonogenic assay to study intraclonal heterogeneity in a panel of human MM cell lines. Each of these cell lines, DP-6, KAS-6/1, KP-6, and, exhibit a variable response to IL-6 and IGF-I, and our goal was to evaluate growth responsiveness of individual subclones from each of these cell lines. Myeloma cell lines were plated at a concentration of 200-1000 cells in 1 ml Methocult H4533 in 35 mm gridded dishes with or without various cytokines. Following 3 weeks of culture, colonies were scored and those consisting of >40 cells were isolated, expanded, and studied further. Of interest, subclones isolated from each of the cell lines displayed significant differences in growth response to various cytokines in addition to specific morphologic and phenotypic differences. In this regard, results emerging from the DP-6 cell line were particularly intriguing. We have previously shown that the DP-6 cell line displays a proliferative response to both IL-6 and IGF-I and expresses autocrine IL-6 at a low level. Analysis of the growth properties of individual DP-6 clones revealed the existence of DP-6 cells (clone 1-15) that proliferate at a rapid rate in the apparent absence of exogenous growth factors. Whereas a neutralizing antibody to IL-6 did not inhibit cell growth, addition of a blocking antibody to the IGF-IR, (αIR3), completely blocked growth factor independent proliferation. Phenotypic analysis also displayed variation between the parental cell line and its subclone. For instance, the parental DP-6 cells largely expressed CD45 at a high level, whereas the clone 1-15 did not. Finally, we have also further characterized MM cell line subclones by gene profiling and FISH (fluorescence in situ hybridization) analysis to link specific phenotype and genotypes with patterns of cell growth. These results provide additional evidence that intratumor heterogeneity exists in myeloma. These studies further demonstrate how growth regulation may vary considerably among cellular subsets of the malignant population. Understanding what factors regulate the balance of specific myeloma cell subpopulations is key to an understanding of tumor progression. In summary, these studies provide a necessary foundation for future studies of the growth potential of subsets found in primary MGUS, SMM and MM patient samples.

PU.1-Induced IRF4 Down-Regulation and Subsequent IRF7 up-Regulation in Myeloma Cells

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2957-2957 ◽  
Author(s):  
Niina Ueno ◽  
Shikiko Ueno ◽  
Shinya Endo ◽  
Nao Nishimura ◽  
Hiro Tatetsu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
T Cells ◽  
Transcription Factor ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
Growth Arrest ◽  
Myeloma Cell ◽  
Down Regulation ◽  
Cell Growth Arrest ◽  
Myeloma Cells

Abstract PU.1 is an Ets family transcription factor, which is necessary for differentiation of both myeloid and lymphoid lineages. It was previously reported that conditional knockout of the upstream regulatory element (URE) located in 14 kb 5' of the PU.1 gene resulted in down-regulation of PU.1 expression in granulocytes and B lymphocytes by 80% compared to that of wild type and induced acute myeloid leukemia and CLL-like diseases in mice. Since the URE contains a suppressor region for PU.1 expression in T cells, such mice express PU.1 in T cells and develop T cell lymphoma. Thus, the failure of proper expression of PU.1 in certain differentiation stages in certain cell lineages appears to result in hematological malignancies. We previously reported that PU.1 is down-regulated in various myeloma cell lines. In addition, PU.1 is expressed in normal plasma cells and PU.1 is down-regulated in myeloma cells of certain myeloma patients, who appear to have poor prognosis. In those myeloma cell lines, the promoter and URE of the PU.1 gene are highly methylated. A demethylation agent, 5-aza-2'-deoxycytidine, induced PU.1 up-regulation, growth arrest, and apoptosis in myeloma cell lines, KMS12PE and KHM11. In addition, conditionally expressed PU.1 induced cell growth arrest and apoptosis in PU.1-low-negative myeloma cell lines, U266 and KMS12PE, suggesting that PU.1 is a tumor suppressor for myeloma cells. To elucidate the mechanisms of the cell growth arrest and apoptosis in myeloma cells induced by PU.1, we performed DNA microarray analysis to compare gene expression levels before and after PU.1 expression. Among cell-cycle related genes, p21WAF1/CIP1 was found up-regulated in U266 cells, while among apoptosis related genes, TRAIL was highly up-regulated in both U266 and KMS12PE cell lines. With further investigation, we concluded that PU.1 directly transactivated the TRAIL gene in myeloma cells, leading to apoptosis. Based on the DNA microarray data generated, we found that IRF4 is downregulated in U266 myeloma cells after PU.1 induction. It has been reported that knockdown of IRF4 induces apoptosis in myeloma cell lines. Therefore, we examined whether IRF4 was down-regulated in three myeloma cell lines, U266, KMS12PE, and KHM11 following PU.1 induction. Conditional expression of PU.1 by tet-off system induced IRF4 down-regulation in U266and KMS12PE cells. With lentiviral transduction method, ectopic expression of PU.1 also induced IRF4 down-regulation, cell-cycle arrest, and apoptosis in KHM11 cells. To investigate the role of IRF4 in PU.1-expressing U266 cells, we stably expressed IRF4, partially rescuing U266 cells from apoptosis. IRF4 is known to directly bind to the IRF7 promoter and down-regulate IRF7 expression in activated B cell-like (ABC) subtype of diffuse large B-cell lymphoma cells. Therefore, we examined whether IRF4 bound to the IRF7 promoter in KMS12PEand U266cells using chromatin immunoprecipitation assays. We found that IRF4 directly bound to the IRF7 promoter in both myeloma cell lines. When we overexpressed PU.1, IRF4 levels were decreased and the IRF4 binding to the IRF7 promoter was significantly reduced in those cell lines. Moreover, knockdown of IRF7 significantly rescued PU.1-expressing U266cells from apoptosis. These data strongly suggest that PU.1-induced apoptosis is associated with IRF4 down-regulation and subsequent IRF7 up-regulation in myeloma cells. Since IRF4 is essential transcription factor for myeloma cell survival, up-regulation of PU.1 by demethylation agents, including 5-aza-2'-deoxycytidine may serve as a promising therapeutic modality of multiple myeloma by inducing down-regulation of IRF4. Disclosures No relevant conflicts of interest to declare.

scholarly journals The peptide-semicarbazone S-2209, a representative of a new class of proteasome inhibitors, induces apoptosis and cell growth arrest in multiple myeloma cells

2009 ◽  
Vol 144 (6) ◽  
pp. 875-886 ◽  
Author(s):  
Philipp Baumann ◽  
Karin Müller ◽  
Sonja Mandl-Weber ◽  
Johann Leban ◽  
Robert Doblhofer ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cell Growth ◽  
Proteasome Inhibitors ◽  
Growth Arrest ◽  
Cell Growth Arrest ◽  
Myeloma Cells ◽  
New Class

CD40 activation mediates p53-dependent cell cycle regulation in human multiple myeloma cell lines

Blood ◽  
2000 ◽  
Vol 95 (3) ◽  
pp. 1039-1046 ◽  
Author(s):  
G. Teoh ◽  
Y.-T. Tai ◽  
M. Urashima ◽  
S. Shirahama ◽  
M. Matsuzaki ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cell Lines ◽  
Growth Arrest ◽  
Myeloma Cell ◽  
Luciferase Reporter ◽  
Temperature Sensitive ◽  
Multiple Myeloma Cell ◽  
Cd40 Activation ◽  
Human Multiple Myeloma ◽  
Rpmi 8226

It has been reported that the activation of multiple myeloma (MM) cells by CD40 induces proliferation, growth arrest, and apoptosis. To determine whether the biologic sequelae of CD40 activation in MM cells depends on p53 function, we identified temperature-sensitive p53 mutations in the RPMI 8226 (tsp53E285K) and the HS Sultan (tsp53Y163H) MM cell lines. These cells were then used as a model system of inducible wtp53-like function because wild-type-like p53 is induced at permissive (30°C) but not at restrictive (37°C) temperatures. Using p21-luciferase reporter assays, we confirmed that CD40 induces p53 transactivation in RPMI 8226 and HS Sultan cells cultured under permissive, but not restrictive, conditions. Furthermore, CD40 activation of these MM cells under permissive, but not restrictive, temperatures increased the expression of p53 and p21 mRNA and protein. Importantly, CD40 activation induced the proliferation of RPMI 8226 and HS Sultan cells at restrictive temperatures and growth arrest and increased subG1 phase cells at permissive temperatures. These data confirmed that CD40 activation might have distinct biologic sequelae in MM cells, depending on their p53 status.

Sign in / Sign up

Export Citation Format

Share Document