Clonal Effect Of Lenalidomide On Akt Activation In Low-Risk MDS Patients With Del(5q)

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 5227-5227
Author(s):  
Matilde Y Follo ◽  
Carlo Finelli ◽  
Cristina Clissa ◽  
Sara Mongiorgi ◽  
Carmen Baldazzi ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Cell Lines ◽  
Molecular Mechanisms ◽  
Erythroid Differentiation ◽  
Low Risk ◽  
The Other ◽  
Normal Cells ◽  
Akt Phosphorylation ◽  
Other Hand ◽  
5Q Deletion

Abstract Lenalidomide is an immunomodulating drug currently used in the treatment of del(5q) low-risk MDS patients, where it can suppress the del(5q) clone and restore a normal erythropoiesis. The exact molecular mechanisms underlying the effect of Lenalidomide in del(5q) MDS are not completely clear, although Akt phosphorylation is inhibited in Lenalidomide-sensitive del(5q) cell lines (Gandhi et al, 2006). On the other hand, the activation of the Akt/mTOR pathway has been demonstrated in CD34+ cells from high-risk MDS (Follo et al, 2007), which show alterations on stem cell proliferation, differentiation and apoptosis. These processes are important also in low-risk MDS, that usually show a stable disease but can evolve towards a worse clinical status, characterized by an increased cell proliferation. In this study we firstly investigated the effect of Lenalidomide in 6 patients with del(5q) MDS (IPSS: Low or Int-1). Given the limited number of cells, we analyzed bone marrow total mononuclear cells. As for Akt phosphorylation, we analyzed its localization along with RPS14, in order to specifically detect the del(5q) clone. On the other hand, by Real-Time PCR analyses, we assessed the expression of Globin genes, to evaluate the effect of the drug on erythropoiesis. In addition, we analyzed the effect of Lenalidomide on two cell lines with a different 5q status, one bearing a normal 5q chromosome and one showing the 5q deletion, to further investigate the effect of this drug on cell cycle, erythroid differentiation and inositide signalling pathways. Clinically, 4/6 del(5q) MDS patients showed a favourable response to Lenalidomide. At a molecular level, these cases showed an activation of erythropoiesis, in that Beta-Globin levels increased, as compared with baseline. Moreover, these subjects also displayed a specific phosphorylation of Akt. Interestingly, Akt resulted to be specifically activated in cells not showing the 5q deletion, whereas it was down-regulated in del(5q) cells. The two non responder patients early discontinued Lenalidomide for adverse events, and for these patients neither a clinical assessment of Lenalidomide effect, nor a molecular analysis, were possible. As for cell lines, ongoing analyses are showing that Lenalidomide specifically inhibits the growth of the del(5q) clone, blocking cells in G1 phase. On the other hand, Akt phosphorylation specifically increases in cells with a normal 5q chromosome. Taken together, our data show a specific activation of erythropoiesis in del(5q) low-risk MDS patients responding to Lenalidomide. In addition, our results indicate that Akt is specifically phosphorylated in normal cells without the del(5q), leading to hypothesize that Lenalidomide has a double effect: it can induce apoptosis in clonal del(5q) cells, but it also supports the proliferation and erythroid differentiation of normal cells, as also described in non-del(5q) MDS (Ebert et al, 2008). Therefore, our findings might contribute to elucidate the molecular mechanisms of Lenalidomide and possibly pave the way for the development of innovative therapeutic targeted strategies in MDS. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Combined Application of Pan-AKT Inhibitor MK-2206 and BCL-2 Antagonist Venetoclax in B-Cell Precursor Acute Lymphoblastic Leukemia

2021 ◽  
Vol 22 (5) ◽  
pp. 2771
Author(s):  
Anna Richter ◽  
Elisabeth Fischer ◽  
Clemens Holz ◽  
Julia Schulze ◽  
Sandra Lange ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Tumor Cell ◽  
Cell Lines ◽  
Morphological Changes ◽  
Synergistic Effects ◽  
Lymphoblastic Leukemia ◽  
Tumor Cell Proliferation ◽  
Akt Inhibitor ◽  
Akt Phosphorylation ◽  
Combined Application

Aberrant PI3K/AKT signaling is a hallmark of acute B-lymphoblastic leukemia (B-ALL) resulting in increased tumor cell proliferation and apoptosis deficiency. While previous AKT inhibitors struggled with selectivity, MK-2206 promises meticulous pan-AKT targeting with proven anti-tumor activity. We herein, characterize the effect of MK-2206 on B-ALL cell lines and primary samples and investigate potential synergistic effects with BCL-2 inhibitor venetoclax to overcome limitations in apoptosis induction. MK-2206 incubation reduced AKT phosphorylation and influenced downstream signaling activity. Interestingly, after MK-2206 mono application tumor cell proliferation and metabolic activity were diminished significantly independently of basal AKT phosphorylation. Morphological changes but no induction of apoptosis was detected in the observed cell lines. In contrast, primary samples cultivated in a protective microenvironment showed a decrease in vital cells. Combined MK-2206 and venetoclax incubation resulted in partially synergistic anti-proliferative effects independently of application sequence in SEM and RS4;11 cell lines. Venetoclax-mediated apoptosis was not intensified by addition of MK-2206. Functional assessment of BCL-2 inhibition via Bax translocation assay revealed slightly increased pro-apoptotic signaling after combined MK-2206 and venetoclax incubation. In summary, we demonstrate that the pan-AKT inhibitor MK-2206 potently blocks B-ALL cell proliferation and for the first time characterize the synergistic effect of combined MK-2206 and venetoclax treatment in B-ALL.

scholarly journals Celsr1 and CAMSAP3 differently regulate intercellular and intracellular cilia orientation in oviduct multiciliated cells

2020 ◽  
Author(s):  
Fumiko Matsukawa Usami ◽  
Masaki Arata ◽  
Dongbo Shi ◽  
Sanae Oka ◽  
Yoko Higuchi ◽  
...  
Keyword(s):  
Cell Polarity ◽  
Planar Cell Polarity ◽  
Molecular Mechanisms ◽  
The Other ◽  
Basal Bodies ◽  
Generating Functional ◽  
Tissue Polarity ◽  
Other Hand ◽  
Multiciliated Cells ◽  
Polarity Regulation

SummaryThe molecular mechanisms by which cilia orientation is coordinated within and between multiciliated cells (MCCs) is not fully understood. By observing the orientation of basal bodies (BB) in MCCs of mouse oviducts, here, we show that Celsr1, a planar cell polarity (PCP) factor involved in tissue polarity regulation, is dispensable for determining BB orientation in individual cells, whereas CAMSAP3, a microtubule minus-end regulator, is critical for this process but not for PCP. MCCs exhibit a characteristic BB orientation and microtubule gradient along the tissue axis, and these intracellular polarities were maintained in the cells lacking Celsr1, although the intercellular coordination of the polarities was partly disrupted. On the other hand, CAMSAP3 regulated the assembly of microtubules interconnecting BBs by localizing at the BBs, and its mutation led to disruption of intracellular coordination of BB orientation, but not affecting PCP factor localization. Thus, both Celsr1 and CAMSAP3 are responsible for BB orientation but in distinct ways; and therefore, their cooperation should be critical for generating functional multiciliated tissues.

Analysis of Investment in Mutual Fund through Systematic Investment Planning - A Smart Investor

2017 ◽  
Vol 5 (6) ◽  
Author(s):  
Mrs J Madhavilatha ◽  
J Bandi
Keyword(s):  
Mutual Fund ◽  
Low Risk ◽  
The Other ◽  
Investment Planning ◽  
Statistical Tools ◽  
Secondary Sources ◽  
Investment Plan ◽  
Other Hand ◽  
Motivating Factor ◽  
Main Barrier

Systematic Investment Plan (SIP) has emerged at alternative investment plan for large number of investors interested in high returns but less risk with investments in installments. The purpose of the study is to find out the motivating factor to invest in systematic investment plan and the problem in this scheme. Data have been collected from Secondary sources. Collected data were analysed using various statistical tools. Results of the study found that for higher return with low risk the investor motivates to invest in systematic investment plan on the other hand knowledge and operational platform is one of the main barrier that investor are facing of scheme.

8-Isocyanoamphilecta-11(20),15-diene, a new antimalarial isonitrile diterpene from the sponge Ciocalapata sp.

2009 ◽  
Vol 87 (5) ◽  
pp. 612-618 ◽  
Author(s):  
Chatchai Wattanapiromsakul ◽  
Naphatson Chanthathamrongsiri ◽  
Somchai Bussarawit ◽  
Supreeya Yuenyongsawad ◽  
Anuchit Plubrukarn ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Cell Lines ◽  
Nmr Spectra ◽  
Human Fibroblasts ◽  
Fibroblast Cell ◽  
The Other ◽  
Ergosterol Peroxide ◽  
Other Hand ◽  
Mcf 7 ◽  
Fibroblast Cell Lines

A new isonitrile diterpene of the amphilectane family, 8-isocyanoamphilecta-11(20),15-diene (4), was isolated from the sponge Ciocalapata sp., along with three known isonitriles, 8,15-diisocyano-11(20)-amphilectene (1), 7-isocyanoamphilecta-11(20),15-diene (2), and 8-isocyanoamphilecta-11(20),14-diene (3), and two steroidal peroxides, ergosterol peroxide (5) and 5α,9α-epidioxy-8α,14α-epoxy-(22E)-ergosta-6,22-dien-3β-ol (6). The structure of the new isonitrile was elucidated spectroscopically. In addition, anomalous multiplicities in the NMR spectra of some isolated isonitriles were observed and are reported here. The four isonitriles were strongly active against Plasmodium falciparum K1 with IC50 in a range of 0.09–1.07 μmol/L. Except for 1, which was cytotoxic against both MCF-7 and fibroblast cell lines, the other three diterpenes showed no significant cytotoxicity against either targeted cell lines. On the other hand, the steroidal peroxides 5 and 6, which were less active in the antimalarial bioassay (IC50 values of 6.28 and 7.13 µmol/L, respectively), were strongly cytotoxic against MCF-7 (IC50 values of 0.025 and 0.003 µmol/L, respectively), with very little toxicity against human fibroblasts.

The Oral PKC-β Inhibitor Enzastaurin (LY317615) Suppress Phosphorylation and Induces Apoptosis in Multiple Myeloma Cell Lines by Inhibition of AKT Pathway.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1371-1371
Author(s):  
Antonino Neri ◽  
Sandra Marmiroli ◽  
Pierfrancesco Tassone ◽  
Luigia Lombardi ◽  
Lucia Nobili ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Western Blot ◽  
Cell Lines ◽  
Molecular Mechanisms ◽  
Caspase 3 ◽  
Time Dependent ◽  
Parp Cleavage ◽  
Akt Phosphorylation ◽  
Downstream Target ◽  
Pkc Β

Abstract The PKC pathway has been shown to play a role in the regulation of cell proliferation in several hematologic malignancies. In this study we tested the oral PKC-β inhibitor, Enzastaurin (LY317615 - Eli Lilly) for its therapeutic efficacy in Multiple Myeloma (MM). We first analyzed PKC-β I and II expression by Western blot in a panel of 19 human MM cell lines, showing that 9 cell lines express either 1 or both isoforms. We next examined the growth inhibition effect of Enzastaurin in the same panel of MM cell lines using either WST-1 or MTT assay and cell viability assessment by Tripan Blue exclusion. Eighteen cell lines have IC50 value ranging from 1,2 μM to 12,5 μM. To examine molecular mechanisms whereby Enzastaurin induces cytotoxicity, we performed cell cycle profiling using PI and observed a significant increase of the percentage of cells in the sub G0–G1 fraction. To determine whether Enzastaurin-induced cell death is mediated by apoptosis, we studied by ELISA and Western blot caspase 3 and PARP cleavage. We observed induction of caspase 3 and PARP cleavage in a dose and time dependent fashion. Notably, the broad caspase (Z-VAD-FMK) inhibitor reduced Enzastaurin-induced cytotoxicity. We next determined whether Enzastaurin could inhibit AKT phosphorylation in MM cell lines with constitutive phosphorylation of AKT. Enzastaurin decreased AKT phosphorylation in a dose and time dependent fashion. Phosphorylation of GSK3β, a downstream target protein of AKT, was also markedly inhibited. Phosphorylation of PDK-1, a known upstream activator of AKT, was not affected by Enzastaurin. In conclusion, our results indicate that Enzastaurin-induced cytotoxicity is mediated via activation of caspase. This effect is associated with significant inhibition of AKT activity and its downstream target GSK3 β. Enzastaurin does not alter the phosphorylation of the upstream AKT activator PDK-1. These data suggest that Enzastaurin inhibit AKT signalling pathway and support its evaluation in a murine model of human MM.

scholarly journals Plasmin Promotes Keratinocyte Migration and Phagocytic-killing Accompanied by Suppression of Cell Proliferation which may Facilitate Re-epithelialization of Wound Beds

2004 ◽  
Vol 11 (3-4) ◽  
pp. 233-240 ◽  
Author(s):  
Imre Szabo ◽  
Miklos Simon ◽  
Janos Hunyadi
Keyword(s):  
Cell Proliferation ◽  
The Other ◽  
Epidermal Keratinocytes ◽  
Thymidine Uptake ◽  
Hacat Keratinocytes ◽  
Chemotactic Migration ◽  
Cell Functions ◽  
Other Hand ◽  
Phagocytic Killing

Abstract Keratinocytes were shown to induce the activation of plasminogen activator resulting in the formation of plasmin and the initiation of proteolysisin vitro. Activation of surface bound plasminogen may localize protease activity in the pericellular microenvironment and play a role in inducing both a conformational change and cell locomotion. Plasmin, however, can induce non-proteolytic effects on certain cell functions in a variety of cell lineages. In the present study we examined the effects of plasmin on keratinocytes with a focus on its role in the process of re-epithelialization, which included studies of cell migration, phagocytic-killing and cell proliferation. Migration of freshly isolated human epidermal keratinocytes was analyzed utilizing the agarose gel assay in the presence of 10% human serum. Plasmin at the concentration of 25 U/l induced a 160% increase in the chemotactic migration of keratinocytes that was completely blocked by the plasmin inhibitor α2-antiplasmin (Serpin). In the absence of serum, plasmin also induced a reversible chemotactic migration of HaCaT keratinocytes as determined utilizing the microchemotaxis assay. Dose-response analysis showed a bi-phasic effect of plasmin with a maximum increase of 52% in keratinocyte chemotaxis at a concentration of 25 U/l. HaCaT cells on the other hand, showed no detectablein vitrochemokinesis by plasmin. Phagocytic-killing of Candida albicans by freshly isolated epidermal keratinocytes was enhanced in the presence of 25 U/l plasmin which was also reversible by the addition of Serpin. Spontaneous proliferation of HaCaT keratinocytes as determined by3H-Thymidine uptake on the other hand, was reduced by 47 and 13% in cultures with 25 U/l plasmin for 24 and 48 h respectively, in a Serpin reversible manner. These data suggest that plasmin-induced chemotactic migration of epidermal keratinocytes is accompanied by enhanced phagocytic-killing coupled with suppression of proliferation of these cells which may facilitate re-epithelialization following skin injury.

scholarly journals Total Thyroidectomy Versus Lobectomy for Thyroid Cancer: Single-Center Data and Literature Review

2021 ◽  
Author(s):  
Carla Colombo ◽  
Simone De Leo ◽  
Marta Di Stefano ◽  
Matteo Trevisan ◽  
Claudia Moneta ◽  
...  
Keyword(s):  
Thyroid Cancer ◽  
Total Thyroidectomy ◽  
Risk Group ◽  
Tertiary Care ◽  
Thyroid Stimulating Hormone ◽  
Low Risk ◽  
The Other ◽  
Intermediate Risk ◽  
Other Hand

Abstract Background Controversies remain about the ideal risk-based surgical approach for differentiated thyroid cancer (DTC). Methods At a single tertiary care institution, 370 consecutive patients with low- or intermediate-risk DTC were submitted to either lobectomy (LT) or total thyroidectomy (TT) and were followed up. Results Event-free survival by Kaplan–Meier curves was significantly higher after TT than after LT for the patients with either low-risk (P = 0.004) or intermediate-risk (P = 0.032) tumors. At the last follow-up visit, the prevalence of event-free patients was higher in the TT group than in the LT low-risk group (95% and 87.5%, respectively; P = 0.067) or intermediate-risk group (89% and 50%; P = 0.008). No differences in persistence prevalence were found among microcarcinomas treated by LT or TT (low risk, P = 0.938 vs. intermediate-risk, P = 0.553). Nevertheless, 15% of the low-risk and 50% of the intermediate-risk microcarcinomas treated by LT were submitted to additional treatments. On the other hand, macrocarcinomas were significantly more persistent if treated with LT than with TT (low-risk, P = 0.036 vs. intermediate-risk, P = 0.004). Permanent hypoparathyroidism was more frequent after TT (P = 0.01). After LT, thyroglobulin (Tg)/thyroid-stimulating hormone (TSH) had shown decreasing trend in 68% of the event-free patients and an increasing trend in the persistent cases. Conclusions Lobectomy can be proposed for low-risk microcarcinomas, although in a minority of cases, additional treatments are needed, and a longer follow-up period usually is required to confirm an event-free outcome compared with that for patients treated with TT. On the other hand, to achieve an excellent response, TT should be favored for intermediate-risk micro- and macro-DTCs despite the higher frequency of postsurgical complications.

scholarly journals Evolution of Cyanobacteria by Exchange of Genetic Material among Phyletically Related Strains

1998 ◽  
Vol 180 (13) ◽  
pp. 3453-3461 ◽  
Author(s):  
Knut Rudi ◽  
Olav M. Skulberg ◽  
Kjetill S. Jakobsen
Keyword(s):  
16S Rdna ◽  
Molecular Mechanisms ◽  
Large Subunit ◽  
Genetic Material ◽  
The Other ◽  
Small Subunit Rrna ◽  
Nucleotide Substitutions ◽  
Bisphosphate Carboxylase ◽  
Other Hand ◽  
Conserved Gene

ABSTRACT The cyanobacterial radiation consists of several lineages of phyletically (morphologically and genetically) related organisms. Several of these organisms show a striking resemblance to fossil counterparts. To investigate the molecular mechanisms responsible for stabilizing or homogenizing cyanobacterial characters, we compared the evolutionary rates and phylogenetic origins of the small-subunit rRNA-encoding DNA (16S rDNA), the conserved gene rbcL(encoding d-ribulose 1,5-bisphosphate carboxylase-oxygenase large subunit), and the less conserved gene rbcX. This survey includes four categories of phyletically related organisms: 16 strains of Microcystis, 6 strains of Tychonema, 10 strains of Planktothrix, and 12 strains ofNostoc. Both rbcL and rbcX can be regarded as neutrally evolving genes, with 95 to 100% and 50 to 80% synonymous nucleotide substitutions, respectively. There is generally low sequence divergence within the Microcystis,Tychonema, and Planktothrix categories both forrbcLX and 16S rDNA. The Nostoc category, on the other hand, consists of three genetically clustered lineages for these loci. The 16S rDNA and rbcLX phylogenies are not congruent for strains within the clustered groups. Furthermore, analysis of the phyletic structure for rbcLX indicates recombinational events between the informative sites within this locus. Thus, our results are best explained by a model involving both intergenic and intragenic recombinations. This evolutionary model explains the DNA sequence clustering for the modern species as a result of sequence homogenization (concerted evolution) caused by exchange of genetic material for neutrally evolving genes. The morphological clustering, on the other hand, is explained by structural and functional stability of these characters. We also suggest that exchange of genetic material for neutrally evolving genes may explain the apparent stability of cyanobacterial morphological characters, perhaps over billions of years.

Anti-cancer activity of NVP-TAE226, a potent dual FAK/IGF-IR kinase inhibitor, against pancreatic carcinoma

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 13162-13162 ◽  
Author(s):  
S. Hatakeyama ◽  
D. Tomioka ◽  
E. Kawahara ◽  
N. Matsuura ◽  
K. Masuya ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Pancreatic Carcinoma ◽  
Cell Lines ◽  
Cancer Cell ◽  
Cancer Cell Proliferation ◽  
Normal Cells ◽  
P Glycoprotein ◽  
Anti Cancer ◽  
Cancer Activity

13162 Background: Focal adhesion kinase (FAK) is a non-receptor cytoplasmic tyrosine kinase that regulates multiple cell functions. Elevated expression levels of FAK have been detected in various tumor samples and are closely correlated with invasive potential. Activation of integrins and the growth factor receptors result in FAK autophosphorylation at Y397 and the presentation of suitable binding sites for proteins containing either SH2 or phosphotyrosine binding domains. Recent evidences suggest that FAK plays important roles in cancer cell proliferation and survival. IGF-IR function is required for tumor cell survival, but dispensable for survival of normal cells. Therefore, a dual inhibitor of both kinases may selectively block the growth, migration, and survival of FAK- and IGF-IR- expressing tumor cells compared to proliferating and migrating normal cells. Methods: In this study, anti-cancer activity of NVP-TAE226 that is identified as a potent and selective FAK inhibitor was evaluated in cancer cell lines panel and MIA PaCa-2 pancreatic carcinoma in vivo model. Results: Mean GI50 value of NVP-TAE226 against 37 cancer cell lines was 0.76 μmole/L. Inhibition of cancer cell proliferation was not affected by expression of P-glycoprotein, suggesting that NVP-TAE226 is not served as a substrate of P-glycoprotein. Oral administration of NVP-TAE226 efficiently inhibited MIA PaCa-2 human pancreatic tumor growth at all doses tested. Tumor stasis was observed at a dose of 30 mg/kg, qd for 7×/week and tumor regression was observed at a dose of 100 mg/kg, qd for 5×/week. All animals tolerated NVP-TAE226 treatment up to 100 mg/kg, 5×/wk, qd, po for 2 weeks with no body weight loss. Inhibition of downstream signaling such as phosphorylation of Akt at Serine473 was accompanied by inhibition of FAK phosphorylation in human pancreatic carcinoma cell lines. Conclusions: NVP-TAE226 is a novel class of selective and small molecule kinase inhibitors with a potent in vivo activity and potential therapeutic application. No significant financial relationships to disclose.

Displacement of Bim From Anti-Apoptotic Proteins Is the Primary Factor for Determining ABT-737 Activity in Multiple Myeloma Cell Lines.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2851-2851
Author(s):  
Alejo A Morales ◽  
Metin Kurtoglu ◽  
David Siefker ◽  
Shannon M Matulis ◽  
Delia M Gutman ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Cell Death ◽  
Cell Lines ◽  
Cell Types ◽  
Myeloma Cell ◽  
Resistant Cell ◽  
The Other ◽  
Multiple Myeloma Cell ◽  
Other Hand

Abstract Abstract 2851 Poster Board II-827 ABT-737 and its orally active analog ABT-263 are Bcl-2-family inhibitors that are currently in clinical trials for a variety of cancers including hematological malignancies such as multiple myeloma. Previously, we reported that the sensitivity of multiple myeloma cell lines to ABT-737 correlates with the interactions, but not the expression, of Bcl-2 proteins. Analysis of 6 multiple myeloma cell lines revealed that expression of Bcl-2 proteins did not correlate with sensitivity, however the sensitive cells (8226/S, MM.1S and KMS-11) have a substantial amount of their pro-apoptotic Bcl-2 protein, Bak, bound to Bcl-xL. On the other hand, in the insensitive cell lines (U266, KMS-11 and OPM2), Bak was found to be associated with Mcl-1, a family member that does not bind ABT-737 and thereby confers resistance to this drug. Furthermore, we also showed that release of the BH3-only protein Bim by ABT-737 from Bcl-xL and Bcl-2 also contributes to cell death in 8226/S and MM.1S. The purpose of the current study is to further investigate the role of Bim in ABT-737-induced cell death in the multiple myeloma lines. Similar to Bak, a substantial amount of Bim is bound to Bcl-xL and Bcl-2 in the ABT-737-sensitive cell lines, MM.1S and KMS-18, while in the insensitive cell lines, it is highly bound to Mcl-1. Surprisingly, in the ABT-737-sensitive 8226/S cells, Bim appears to bind to Mcl-1. However in these cells, ABT-737 treatment resulted in upregulation of Noxa, which is a BH3-only protein that binds Mcl-1 and can release Bim. Taken together these data suggest that although binding of Bim to Mcl-1 may confer resistance to ABT-737, in certain cell types this treatment could also induce Noxa expression that antagonizes Mcl-1-mediated resistance. Consistent with this hypothesis, Mcl-1 overexpression as well as knockdown of Noxa expression significantly protected 8226/S cells from ABT-737-induced cell death while they had no effect in MM.1S cells. To further demonstrate the role of Bim in ABT-737-induced cell death, ABT-resistant 8226/S, KMS-11, KMS-18 and U266 cell lines were generated. In the resistant cell lines of 8226/S and KMS-18, Bim is exclusively bound to Mcl-1, which was overexpressed as compared to the parental cells. Bak binding was not affected by acquisition of ABT-737 resistance. This result is in agreement with the findings that interaction of Bim and Mcl-1 confers resistance to ABT-737. On the other hand, in ABT-resistant U266 and KMS-11 cell lines, Bim expression was down-regulated while Mcl-1 levels were not changed. Thus, it appears that in cells where Bim is already bound to Mcl-1, further resistance is achieved by down-regulating the expression of this BH3-only protein. Overall, these results suggest that the complex interactions between Bcl-2 proteins need to be investigated in order to understand how multiple myeloma cells may respond to ABT-737 treatment. Disclosures: Boise: University of Chicago: Patents & Royalties.

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