| 1. |
- Lemaire, Miguel, et al.
(author)
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The HDAC Inhibitor LBH589 Enhances the Antimyeloma Effects of the IGF-1RTK Inhibitor Picropodophyllin
- 2012
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In: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 18:8, s. 2230-2239
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Journal article (peer-reviewed)abstract
- Purpose: We have previously shown the use of the insulin-like growth factor type 1 receptor tyrosine kinase (IGF-1RTK) inhibitor picropodophyllin (PPP) as an attractive strategy to combat multiple myeloma (MM) in vitro and in vivo. After a combinatorial drug screening, the histone deacetylase inhibitor LBH589 was shown to act in synergy with PPP reducing survival of MM cells. In this study, we tried to elucidate the molecular mechanisms underlying this combinatorial effect. Experimental Design: The in vitro anti-MM effects of PPP and LBH589 alone and in combination were evaluated by studying apoptosis, cell cycle distribution, and downstream transcriptome using both human MM cell lines and cells from the murine 5T3MM model. In vivo the effect on survival of 5T33MM-inoculated mice was evaluated. Results: In the human MM cell line RPMI8226, treatment with PPP and LBH589 in combination resulted in a five-fold increase of apoptosis, and an additive effect on the cleavage of the active forms of caspase-8 was observed as compared with the single drug treatments. Cell cycle analysis revealed an accumulation of cells in the G2-M phase and subsequent downregulation of cell cycle regulating proteins. These data were also confirmed in the 5T33MM cells in vitro. Also, the transcriptome was analyzed by Affymetrix arrays showing gene expression alterations mainly in categories of genes regulating apoptosis and cell adhesion. Combined treatment in vivo resulted in a significantly prolonged survival of 5T33MM-inoculated mice. Conclusions: The results indicate an improved MM treatment opportunity in using a combination of PPP and LBH589.
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| 2. |
- Menu, Eline, et al.
(author)
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Targeting the IGF-1R using picropodophyllin in the therapeutical 5T2MM mouse model of multiple myeloma : beneficial effects on tumor growth, angiogenesis, bone disease and survival
- 2007
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In: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 121:8, s. 1857-1861
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Journal article (peer-reviewed)abstract
- During the last decade, a central role for insulin-like growth factor 1 (IGF-1) in the pathophysiology of multiple myeloma (MM) has been well established. IGF-I provided by the tumor-microenvironment interaction may directly and indirectly facilitate the migration, survival and expansion of the MM cells in the bone marrow (BM). The inhibition of the IGF-1R-mediated signaling pathway has recently been suggested to be a possible new therapeutic principle in MM. Using the mouse 5T2MM model, we now demonstrate that targeting the IGF-1R using picropodophyllin (PPP) in a therapeutical setting not only has strong antitumor activity on the established MM tumor but also influences the BM microenvironment by inhibiting angiogenesis and bone disease, having a profound effect on the survival of the mice. At therapeutically achievable concentrations of PPP, the average survival was 180 days for the PPP-treated mice as compared to 100 days for vehicle-treated mice. PPP used as single drug treatment in the 5T2MM model resulted in a decrease of tumor burden by 65% while the paraprotein concentrations were reduced by 75%. This decrease was associated with a significant inhibition of tumor-associated angiogenesis and osteolysis. The present studies on the biological effects of PPP in the 5T2MM model constitute an important experimental platform for future therapeutic implementation.
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| 3. |
- Bieghs, Liesbeth, et al.
(author)
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The IGF-1 receptor inhibitor picropodophyllin potentiates the anti-myeloma activity of a BH3-mimetic
- 2014
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In: Oncotarget. - : Impact Journals, LLC. - 1949-2553. ; 5:22, s. 11193-11208
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Journal article (peer-reviewed)abstract
- The ABT-analogous 737, 263 and 199 are BH3 mimetics showing potent anti-myeloma (MM) activity, but only on defined molecular subgroups of MM patients presenting a Bcl-2high/Mcl-1low profile. IGF-1 is a major survival factor in MM regulating the expression of Bcl-2 proteins and might therefore be a resistance factor to these ABT-analogous. We first show that IGF-1 protected human MM cell lines (HMCLs) against ABT-737. Concurrently, the IGF-1 receptor inhibitor picropodophyllin (PPP) synergistically sensitized HMCL, primary human MM and murine 5T33MM cells to ABT-737 and ABT-199 by further decreasing cell viability and enhancing apoptosis. Knockdown of Bcl-2 by shRNA protected MM cells to ABT-737, while Mcl-1 shRNA sensitized the cells. PPP overcame the Bcl-2 dependency of ABT-737, but failed to completely overcome the protective effect of Mcl-1. In vivo, co-treatment of 5T33MM bearing mice significantly decreased tumor burden and prolonged overall survival both in a prophylactic and therapeutic setting. Interestingly, proteasome inhibitor resistant CD138- 5T33MM cells were more sensitive to ABT-737, whereas PPP alone targeted the CD138+ cells more effectively. After co-treatment, both subpopulations were targeted equally. Together, the combination of an IGF-1R inhibitor and an ABT-analogue displays synergistic anti-myeloma activity providing the rational for further (pre)clinical testing.
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| 4. |
- De Bruyne, Elke, et al.
(author)
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IGF-1 suppresses Bim expression in multiple myeloma via epigenetic and posttranslational mechanisms
- 2010
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In: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 115:12, s. 2430-2440
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Journal article (peer-reviewed)abstract
- Insulin-like growth factor-1 (IGF-1) is an important growth and survival factor in multiple myeloma (MM). Here, we demonstrate that IGF-1 induces significant down-regulation of the proapoptotic BH3-only protein Bim in MM cells. Reduced Bim levels by RNA interference (RNAi) protected cells from drug-induced cell death. The IGF-1-mediated down-regulation of Bim was the result of (1) reduced transcription by activation of the Akt pathway and inactivation of the transcription factor FoxO3a, (2) increased proteasome-mediated degradation of the Bim extra-long protein by activation of the mitogen-activated protein kinase pathway, and (3) epigenetic regulation of both the Bim and the FoxO3a promoter. Treatment of cells with the histone deacetylase inhibitor LBH589 resulted in a clear up-regulation in the expression of Bim. Furthermore, the methylation inhibitor 5-aza-2'deoxycytidine (decitabine) significantly increased the effects of LBH589. On IGF-1 treatment, the Bim promoter region was found to be unmethylated, whereas chromatin immunoprecipitation analysis of the IGF-1-treated cells showed both a reduced histone H3 tail Lys9 (H3K9) acetylation and an increased H3K9 dimethylation, which contributed actively to its silencing. These data identify a new mechanism in the IGF-1-dependent survival of MM cells and emphasize the need for IGF-1-targeted drug therapy.
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| 5. |
- Fristedt Duvefelt, Charlotte, et al.
(author)
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Increased resistance to proteaome inhibitors in multiple myeloma mediated by cIAP2 : implications for a combinatorial treatment
- 2015
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In: Oncotarget. - 1949-2553. ; 6:24, s. 20621-20635
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Journal article (peer-reviewed)abstract
- Despite the introduction of new treatment options for multiple myeloma (MM), a majority of patients relapse due to the development of resistance. Unraveling new mechanisms underlying resistance could lead to identification of possible targets for combinatorial treatment. Using TRAF3 deleted/mutated MM cell lines, we evaluated the role of the cellular inhibitor of apoptosis 2 (cIAP2) in drug resistance and uncovered the plausible mechanisms underlying this resistance and possible strategies to overcome this by combinatorial treatment. In MM, cIAP2 is part of the gene signature of aberrant NF-kappa B signaling and is heterogeneously expressed amongst MM patients. In cIAP2 overexpressing cells a decreased sensitivity to the proteasome inhibitors bortezomib, MG132 and carfilzomib was observed. Gene expression analysis revealed that 440 genes were differentially expressed due to cIAP2 overexpression. Importantly, the data imply that cIAPs are rational targets for combinatorial treatment in the population of MM with deleted/mutated TRAF3. Indeed, we found that treatment with the IAP inhibitor AT-406 enhanced the anti-MM effect of bortezomib in the investigated cell lines. Taken together, our results show that cIAP2 is an important factor mediating bortezomib resistance in MM cells harboring TRAF3 deletion/mutation and therefore should be considered as a target for combinatorial treatment.
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