scholarly journals SUMOylation Inhibition Enhances Dexamethasone Sensitivity in Multiple Myeloma

2021 ◽  
Author(s):  
Li Du ◽  
Wei Liu ◽  
Grace Aldana-Masangkay ◽  
Alex Pozhitkov ◽  
Flavia Pichiorri ◽  
...  
Keyword(s):  
Mouse Models ◽  
Cell Lines ◽  
Chromatin Immunoprecipitation ◽  
Single Agent ◽  
Significant Negative Correlation ◽  
Therapeutic Drug ◽  
Rna Seq ◽  
Key Factors ◽  
Microrna Sequencing

Abstract BackgroundMultiple myeloma (MM) is an incurable plasma cell malignancy. Although Dexamethasone (Dex) is the most widely used therapeutic drug in MM treatment, patients develop Dex resistance leading to progressive disease, demanding an urgent need to investigate the mechanisms driving Dex resistance and develop new reagents to address this problem. We propose SUMOylation as a potential mechanism regulating Dex resistance and SUMOylation inhibition can enhance Dex sensitivity in MM.MethodsUsing MM cell lines and primary MM samples from relapsing MM patients, we evaluated the effects of knockdown of SUMO E1 (SAE2) or using TAK-981, a novel and specific SUMO E1 inhibitor, on Dex sensitivity. Xenograft mouse models were generated to determine the in vivo anti-MM effects of TAK-981 as a single agent and in combination with Dex. miRNA-seq, RNA-seq and GSEA analysis were utilized for evaluating key factors mediating Dex resistance. Chromatin immunoprecipitation (ChIP) assay was performed to determine the binding occupancy of c-Myc on promoter region of miRs. ResultsWe observed a significant negative correlation between SUMO E1 (SAE2) expression and Dex sensitivity in primary MM samples. Knockdown of SAE2 or using TAK-981 significantly enhances myeloma sensitivity to Dex in MM cell lines. Moreover, the enhanced anti-MM activity by TAK-981 and Dex combination has been validated using primary relapsing MM patient samples and xenograft mouse models. SUMOylation inhibition increased glucocorticoid receptor (GR) expression via downregulation miR-130b. Using RNA and microRNA sequencing, we identified miR-551b and miR-25 as important miRs mediating Dex resistance in MM. Overexpression of miR-551b and miR-25 caused resistance to Dex, however, knockdown of miR-551b and miR-25 significantly enhanced Dex sensitivity in MM. SAE2 knockdown or TAK-981 treatment downregulated the expression of miR-551b and miR-25, leading to induction of miR targets ZFP36, ULK1 and p27, resulting in apoptosis and autophagy. We demonstrated c-Myc as a major transcriptional activator of miR-130b, miR-551b and miR-25 and SUMOylation inhibition downregulates these miRs level by decreasing c-Myc level. ConclusionOur study proves SUMOylation plays a crucial role in Dex resistance in MM and SUMOylation inhibition appears to be an attractive strategy to advance to the clinic for MM patients.

scholarly journals SUMOylation inhibition enhances dexamethasone sensitivity in multiple myeloma

2022 ◽  
Vol 41 (1) ◽  
Author(s):  
Li Du ◽  
Wei Liu ◽  
Grace Aldana-Masangkay ◽  
Alex Pozhitkov ◽  
Flavia Pichiorri ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Mouse Models ◽  
Cell Lines ◽  
Single Agent ◽  
Significant Negative Correlation ◽  
Therapeutic Drug ◽  
Rna Seq ◽  
Key Factors ◽  
Microrna Sequencing

Abstract Background Multiple myeloma (MM) is an incurable plasma cell malignancy. Although Dexamethasone (Dex) is the most widely used therapeutic drug in MM treatment, patients develop Dex resistance leading to progressive disease, demanding an urgent need to investigate the mechanisms driving Dex resistance and develop new reagents to address this problem. We propose SUMOylation as a potential mechanism regulating Dex resistance and SUMOylation inhibition can enhance Dex sensitivity in MM. Methods Using MM cell lines and primary MM samples from relapsing MM patients, we evaluated the effects of knockdown of SUMO E1 (SAE2) or using TAK-981, a novel and specific SUMO E1 inhibitor, on Dex sensitivity. Xenograft mouse models were generated to determine the in vivo anti-MM effects of TAK-981 as a single agent and in combination with Dex. miRNA-seq, RNA-seq and GSEA analysis were utilized for evaluating key factors mediating Dex resistance. Chromatin immunoprecipitation (ChIP) assay was performed to determine the binding occupancy of c-Myc on promoter region of miRs. Results We observed a significant negative correlation between SUMO E1 (SAE2) expression and Dex sensitivity in primary MM samples. Knockdown of SAE2 or using TAK-981 significantly enhances myeloma sensitivity to Dex in MM cell lines. Moreover, the enhanced anti-MM activity by TAK-981 and Dex combination has been validated using primary relapsing MM patient samples and xenograft mouse models. SUMOylation inhibition increased glucocorticoid receptor (GR) expression via downregulation miR-130b. Using RNA and microRNA sequencing, we identified miR-551b and miR-25 as important miRs mediating Dex resistance in MM. Overexpression of miR-551b and miR-25 caused resistance to Dex, however, knockdown of miR-551b and miR-25 significantly enhanced Dex sensitivity in MM. SAE2 knockdown or TAK-981 treatment downregulated the expression of miR-551b and miR-25, leading to induction of miR targets ZFP36, ULK1 and p27, resulting in apoptosis and autophagy. We demonstrated c-Myc as a major transcriptional activator of miR-130b, miR-551b and miR-25 and SUMOylation inhibition downregulates these miRs level by decreasing c-Myc level. Conclusion Our study proves SUMOylation plays a crucial role in Dex resistance in MM and SUMOylation inhibition appears to be an attractive strategy to advance to the clinic for MM patients.

Dual Inhibition of MDM2 and BET Cooperate to Eradicate Acute Myeloid Leukemia

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 674-674 ◽  
Author(s):  
Anne-Louise Latif ◽  
John J Cole ◽  
Joana Monteiro Campos ◽  
William Clark ◽  
Lynn McGarry ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Cell Lines ◽  
Single Agent ◽  
Rna Seq ◽  
Wild Type ◽  
Advisory Committees ◽  
Bet Inhibitor ◽  
Dual Inhibition

Abstract Background: There remains a critical requirement for novel therapies for Acute Myeloid Leukemia (AML). Bromodomain and extra-terminal domain (BET) inhibitors are emerging as exciting therapeutic agents for hematopoietic malignancies. Pharmacological inhibition of BET bromodomains targets malignant cells by preventing reading of acetylated lysine residues, thus disrupting chromatin-mediated signal transduction, which reduces transcription at oncogenic loci. Although a heterogeneous disease, most AML retains wild type p53. However, p53 is often rendered functionally deficient by over-expression of MDM2. Potentiating the p53 response though MDM2 antagonism is therefore potentially beneficial to most AML subtypes. We hypothesized that dual inhibition of MDM2 and BET would be synthetic lethal to p53 wild type AML. Methods: For in vitro experiments CPI203 (BET inhibitor, Constellation Pharmaceuticals) and nutlin-3 (MDM2 antagonist, Sigma) were assessed on p53 wild type cell lines (OCI-AML3, MOLM-13 and MV411) and p53 wild type primary murine AML. To assess the combination's dependency on wild type p53; p53 mutated cell lines (KG1a, KASUMI-1 and THP1) were tested. Cell viability was assessed using resazurin (Alamar blue dye) across numerous dose ratios on the OCI-AML3 cell line and analysed using the Envision Fluorescent Reader. Drug combination indices (CI) were evaluated using Calcusyn (version 2.0). Apoptosis was assessed using flow cytometry staining for Annexin V and propidium iodide (PI) on all p53 wild type and mutated cell lines. For in vivo experiments CPI0610 (clinical grade BET inhibitor, Constellation Pharmaceuticals) and RG7112 (MDM2 inhibitor, Roche) were tested as single agents, in combination and with relevant vehicle controls. RNA seq was performed on the GAIIX sequencer and gene ontology analysis was performed using DAVID/INGENUITY pathway analysis (IPA). Results: In the OCI-AML3 cell line, resazurin analysis demonstrated that combining CPI203 with nutlin-3 was potently synergistic in decreasing viable cells for a 1:12.5 (mean CI=0.07) and 1:25 ratio (mean CI=0.299), and synergistic for a 1:50(mean CI=0.44) and 1:100(mean CI= 0.66) ratios. There was no benefit in using the combination treatment on the p53 mutated cell lines. Apoptosis was enhanced at least 1.5 fold (median 1.7, range 1.5-2.65) by the drug combination versus the single agents, in the panel of p53 wild type cell lines tested. Analysis of whole genome RNA seq on OCI-AML3 treated cells, showed that genes up-regulated by the combination of CPI203 and nutlin-3, had a thirty-fold enrichment for p53 signalling (FDR (<0.05). Down-regulated genes were enriched for FOXM1-dependent cell cycle progression genes. To evaluate the combination in vivo, we used a Trib-2 driven primary AML where leukemogenesis is induced through inhibition of C/EBPα. Myeloblasts were transduced with GFP on the same retroviral construct asTrib-2 for disease tracking. Treatment was commenced in all mice (n=40), post confirmation of disease engraftment. Three mice from each treatment group were sacrificed after 48hrs and cells sorted for GFP to perform RNA seq in this in vivo setting. After 21 days of treatment all mice were sacrificed (n=27, one vehicle control succumbed to disease 15 days post engraftment). End of treatment results (primary read out was the GFP% which equates to the blast%) demonstrated superior in vivo efficacy of dual inhibition of MDM2 and BET in comparison with controls in eradicating AML, p<0.0001, (see figure). Importantly, normal haematopoiesis was spared - as evidenced by normal full blood counts and comparable myeloid, B-cell and T-cell populations with our C57bl6 wild type controls. RNA seq of the murine blasts revealed that many more genes significantly (FDR<0.05) changed expression in the combination treated mice than single agent treated mice. The p53 pathway was the most common up-stream regulator of genes changing expression post combination treatment, p<0.0001. The combination affected many more genes in the p53 pathway than RG7112 alone (120 genes versus 20 genes respectively), in line with our in vitro results. Conclusion: This combination of BET and MDM2 inhibition is effective and superior to single agent therapy on all p53 wild type AMLs tested, in vitro and in vivo. In both contexts this is associated with potentiating the p53 response and could be relevant to many patients with p53 wild type AML. Figure 1. Figure 1. Disclosures Latif: Novartis: Honoraria. Copland:Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees.

scholarly journals Experimental Models for Studying HPV-Positive and HPV-Negative Penile Cancer: New Tools for An Old Disease

Cancers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 460
Author(s):  
Beatriz Medeiros-Fonseca ◽  
Antonio Cubilla ◽  
Haissa Brito ◽  
Tânia Martins ◽  
Rui Medeiros ◽  
...  
Keyword(s):  
Mouse Models ◽  
Cell Lines ◽  
Penile Cancer ◽  
Hpv Infection ◽  
Experimental Models ◽  
In Vivo Models ◽  
Recent Developments ◽  
Key Aspects

Penile cancer is an uncommon malignancy that occurs most frequently in developing countries. Two pathways for penile carcinogenesis are currently recognized: one driven by human papillomavirus (HPV) infection and another HPV-independent route, associated with chronic inflammation. Progress on the clinical management of this disease has been slow, partly due to the lack of preclinical models for translational research. However, exciting recent developments are changing this landscape, with new in vitro and in vivo models becoming available. These include mouse models for HPV+ and HPV− penile cancer and multiple cell lines representing HPV− lesions. The present review addresses these new advances, summarizing available models, comparing their characteristics and potential uses and discussing areas that require further improvement. Recent breakthroughs achieved using these models are also discussed, particularly those developments pertaining to HPV-driven cancer. Two key aspects that still require improvement are the establishment of cell lines that can represent HPV+ penile carcinomas and the development of mouse models to study metastatic disease. Overall, the growing array of in vitro and in vivo models for penile cancer provides new and useful tools for researchers in the field and is expected to accelerate pre-clinical research on this disease.

scholarly journals BET bromodomain inhibitor birabresib in mantle cell lymphoma: in vivo activity and identification of novel combinations to overcome adaptive resistance

ESMO Open ◽  
2018 ◽  
Vol 3 (6) ◽  
pp. e000387 ◽  
Author(s):  
Chiara Tarantelli ◽  
Elena Bernasconi ◽  
Eugenio Gaudio ◽  
Luciano Cascione ◽  
Valentina Restelli ◽  
...  
Keyword(s):  
Mantle Cell Lymphoma ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
Antitumour Activity ◽  
Single Agent ◽  
Treatment Strategies ◽  
Bet Inhibitor ◽  
Mantle Cell

BackgroundThe outcome of patients affected by mantle cell lymphoma (MCL) has improved in recent years, but there is still a need for novel treatment strategies for these patients. Human cancers, including MCL, present recurrent alterations in genes that encode transcription machinery proteins and of proteins involved in regulating chromatin structure, providing the rationale to pharmacologically target epigenetic proteins. The Bromodomain and Extra Terminal domain (BET) family proteins act as transcriptional regulators of key signalling pathways including those sustaining cell viability. Birabresib (MK-8628/OTX015) has shown antitumour activity in different preclinical models and has been the first BET inhibitor to successfully undergo early clinical trials.Materials and methodsThe activity of birabresib as a single agent and in combination, as well as its mechanism of action was studied in MCL cell lines.ResultsBirabresib showed in vitro and in vivo activities, which appeared mediated via downregulation of MYC targets, cell cycle and NFKB pathway genes and were independent of direct downregulation of CCND1. Additionally, the combination of birabresib with other targeted agents (especially pomalidomide, or inhibitors of BTK, mTOR and ATR) was beneficial in MCL cell lines.ConclusionOur data provide the rationale to evaluate birabresib in patients affected by MCL.

scholarly journals Targeted Brain Tumor Therapy by Inhibiting the MDM2 Oncogene: In Vitro and In Vivo Antitumor Activity and Mechanism of Action

Cells ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1592
Author(s):  
Surendra R. Punganuru ◽  
Viswanath Arutla ◽  
Wei Zhao ◽  
Mehrdad Rajaei ◽  
Hemantkumar Deokar ◽  
...  
Keyword(s):  
Brain Tumor ◽  
Antitumor Activity ◽  
Cell Lines ◽  
Tumor Therapy ◽  
Single Agent ◽  
M Cell ◽  
In Vivo Antitumor Activity ◽  
The Brain

There is a desperate need for novel and efficacious chemotherapeutic strategies for human brain cancers. There are abundant molecular alterations along the p53 and MDM2 pathways in human glioma, which play critical roles in drug resistance. The present study was designed to evaluate the in vitro and in vivo antitumor activity of a novel brain-penetrating small molecule MDM2 degrader, termed SP-141. In a panel of nine human glioblastoma and medulloblastoma cell lines, SP-141, as a single agent, potently killed the brain tumor-derived cell lines with IC50 values ranging from 35.8 to 688.8 nM. Treatment with SP-141 resulted in diminished MDM2 and increased p53 and p21cip1 levels, G2/M cell cycle arrest, and marked apoptosis. In intracranial xenograft models of U87MG glioblastoma (wt p53) and DAOY medulloblastoma (mutant p53) expressing luciferase, treatment with SP-141 caused a significant 4- to 9-fold decrease in tumor growth in the absence of discernible toxicity. Further, combination treatment with a low dose of SP-141 (IC20) and temozolomide, a standard anti-glioma drug, led to synergistic cell killing (1.3- to 31-fold) in glioma cell lines, suggesting a novel means for overcoming temozolomide resistance. Considering that SP-141 can be taken up by the brain without the need for any special delivery, our results suggest that SP-141 should be further explored for the treatment of tumors of the central nervous system, regardless of the p53 status of the tumor.

scholarly journals PL3.6 Targeting GSK-3 activity promotes mitotic catastrophe via centrosome destabilisation and enhances the effect of radiotherapy in glioma models

2019 ◽  
Vol 21 (Supplement_3) ◽  
pp. iii4-iii4
Author(s):  
A Bruning-Richardson ◽  
H Sanganee ◽  
S Barry ◽  
D Tams ◽  
T Brend ◽  
...  
Keyword(s):  
Cell Lines ◽  
Cancer Progression ◽  
Combination Treatment ◽  
Single Agent ◽  
Drug Penetration ◽  
In Vivo Models ◽  
Human Astrocytes ◽  
Normal Human

Abstract BACKGROUND Targeting kinases as regulators of cellular processes that drive cancer progression is a promising approach to improve patient outcome in GBM management. The glycogen synthase kinase 3 (GSK-3) plays a role in cancer progression and is known for its pro-proliferative activity in gliomas. The anti-proliferative and cytotoxic effects of the GSK-3 inhibitor AZD2858 were assessed in relevant in vitro and in vivo glioma models to confirm GSK-3 as a suitable target for improved single agent or combination treatments. MATERIAL AND METHODS The immortalised cell line U251 and the patient derived cell lines GBM1 and GBM4 were used in in vitro studies including MTT, clonogenic survival, live cell imaging, immunofluorescence microscopy and flow cytometry to assess the cytotoxic and anti-proliferative effects of AZD2858. Observed anti-proliferative effects were investigated by microarray technology for the identification of target genes with known roles in cell proliferation. Clinical relevance of targeting GSK-3 with the inhibitor either for single agent or combination treatment strategies was determined by subcutaneous and orthotopic in vivo modelling. Whole mount mass spectroscopy was used to confirm drug penetration in orthotopic tumour models. RESULTS AZD2858 was cytotoxic at low micromolar concentrations and at sub-micromolar concentrations (0.01 - 1.0 μM) induced mitotic defects in all cell lines examined. Prolonged mitosis, centrosome disruption/duplication and cytokinetic failure leading to cell death featured prominently among the cell lines concomitant with an observed S-phase arrest. No cytotoxic or anti-proliferative effect was observed in normal human astrocytes. Analysis of the RNA microarray screen of AZD2858 treated glioma cells revealed the dysregulation of mitosis-associated genes including ASPM and PRC1, encoding proteins with known roles in cytokinesis. The anti-proliferative and cytotoxic effect of AZD2858 was also confirmed in both subcutaneous and orthotopic in vivo models. In addition, combination treatment with AZD2858 enhanced clinically relevant radiation doses leading to reduced tumour volume and improved survival in orthotopic in vivo models. CONCLUSION GSK-3 inhibition with the small molecule inhibitor AZD2858 led to cell death in glioma stem cells preventing normal centrosome function and promoting mitotic failure. Normal human astrocytes were not affected by treatment with the inhibitor at submicromolar concentrations. Drug penetration was observed alongside an enhanced effect of clinical radiotherapy doses in vivo. The reported aberrant centrosomal duplication may be a direct consequence of failed cytokinesis suggesting a role of GSK-3 in regulation of mitosis in glioma. GSK-3 is a promising target for combination treatment with radiation in GBM management and plays a role in mitosis-associated events in glioma biology.

scholarly journals Targeting CD205 with the antibody drug conjugate MEN1309/OBT076 is an active new therapeutic strategy in lymphoma models

Haematologica ◽  
2020 ◽  
Vol 105 (11) ◽  
pp. 2584-2591 ◽  
Author(s):  
Eugenio Gaudio ◽  
Chiara Tarantelli ◽  
Filippo Spriano ◽  
Francesca Guidetti ◽  
Giulio Sartori ◽  
...  
Keyword(s):  
Cell Lines ◽  
Single Agent ◽  
B Cell Lymphoma ◽  
Antibody Drug Conjugate ◽  
In Vivo Models ◽  
Drug Conjugate ◽  
Anti Tumor Activity ◽  
Class Antibody ◽  
Antibody Drug

Antibody drug conjugates represent an important class of anti-cancer drugs in both solid tumors and hematological cancers. Here, we report preclinical data on the anti-tumor activity of the first-in-class antibody drug conjugate MEN1309/OBT076 targeting CD205. The study included preclinical in vitro activity screening on a large panel of cell lines, both as single agent and in combination and validation experiments on in vivo models. CD205 was first shown frequently expressed in lymphomas, leukemias and multiple myeloma by immunohistochemistry on tissue microarrays. Anti-tumor activity of MEN1309/OBT076 as single agent was then shown across 42 B-cell lymphoma cell lines with a median IC50 of 200 pM and induction of apoptosis in 25/42 (59.5%) of the cases. The activity appeared highly correlated with its target expression. After in vivo validation as the single agent, the antibody drug conjugate synergized with the BCL2 inhibitor venetoclax, and the anti-CD20 monoclonal antibody rituximab. The first-in-class antibody drug targeting CD205, MEN1309/OBT076, demonstrated strong pre-clinical anti-tumor activity in lymphoma, warranting further investigations as a single agent and in combination.

Defibrotide (DF) Targets Tumor-Microenvironmental Interactions and Sensitizes Multiple Myeloma and Solid Tumor Cells to Cytotoxic Chemotherapeutics.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 286-286 ◽  
Author(s):  
Constantine S. Mitsiades ◽  
Cecile Rouleau ◽  
Krishna Menon ◽  
Beverly Teicher ◽  
Massimo Iacobelli ◽  
...  
Keyword(s):  
Stem Cell ◽  
Tumor Cell ◽  
Tumor Cells ◽  
Cell Lines ◽  
Solid Tumor ◽  
Single Agent ◽  
Conventional Chemotherapy ◽  
Adhesive Properties

Abstract Introduction: Defibrotide (DF) is a polydisperse oligonucleotide with anti-thrombotic, thrombolytic, anti-ischemic, and anti-adhesive properties, which selectively targets the microvasculature and has minimal hemorrhagic risk. DF is an effective treatment for veno-occlusive disease (VOD), an important regimen-related toxicity in stem cell transplantation characterized by endothelial cell injury. DF also augments stem cell mobilization by modulating adhesion in vivo. Because of its cytoprotective effect on the endothelium, we specifically investigated whether DF protects tumor cells from cytotoxic anti-tumor agents. Further, because of its broad anti-adhesive properties, we evaluated whether DF modulates the interaction of MM cells with bone marrow stromal cells (BMSCs), which confers growth, survival and drug resistance in the BM milieu. Methods: In vitro studies in isogenic dexamethasone (Dex)-sensitive and resistant MM cell lines (MM-1S and MM1R, respectively) showed that DF does not attenuate the sensitivity of MM cells to Dex, the proteasome inhibitor bortezomib (PS-341), melphalan (MEL), vinca alkaloids (vincristine, vinblastine), taxanes (paclitaxel) or platinum (cisplatin), but does decrease their sensitivity to doxorubicin. These selective effects in vitro of DF in protecting tumor cells against doxorubicin and modestly sensitizing MM cells to platinum was also confirmed in solid tumor breast (MCF-7) and colon (HT-29) carcinoma cell lines. Although DF had minimal in vitro inhibitory effect on MM or solid tumor cell growth in vitro, it showed in vivo activity as a single agent and enhanced the responsiveness of MM tumors to cytotoxic chemotherapeutics, such as MEL or cyclophosphamide, in human MM xenografts in SCID/NOD mice. The in vivo single-agent activity and chemosensitizing properties of DF, coupled with its lack of major in vitro activity, suggested that DF may not directly target tumor cells, but rather modulate tumor cell interaction with BMSCs. In an ex vivo model of co-culture of primary MM tumor cells with BMSCs (which protects MM cells against conventional chemotherapy), DF alone had a only modest effect on tumor cell viability, but it significantly enhanced MM cell sensitivity to cytotoxic chemotherapy (e.g. MEL), suggesting that a major component of the biological effects of DF may be attributable not to direct targeting of tumor cells, but to modulation of the interactions that tumor cells develop with the local stromal milieu. Conclusion: Our studies show that DF mediates in vivo anti-MM activity by abrogating interactions of MM cells with their BM milieu, thereby enhancing sensitivity and overcoming resistance to conventional chemotherapy. These data support future clinical trials of DF, in combination with both conventional and novel therapies, to improve patient outcome in MM.

The BH3 Mimetic, ABT-737, Is Effective Against Bcl-2 Overexpressing Lymphoid Tumors.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 826-826 ◽  
Author(s):  
Kylie D. Mason ◽  
Cassandra J. Vandenberg ◽  
Mark F. van Delft ◽  
Andrew H. Wei ◽  
Suzanne Cory ◽  
...  
Keyword(s):  
Cell Lines ◽  
Genetic Manipulation ◽  
Single Agent ◽  
B Cell Lymphoma ◽  
Cell Types ◽  
Clinical Samples ◽  
Bh3 Mimetic ◽  
Mouse Lymphoma

Abstract Lymphoid tumors often respond poorly to conventional cytotoxics, a common cause being their impaired sensitivity to apoptosis, such as that caused by Bcl-2 overexpression. A strategy to overcoming this is to use mimics of the natural antagonists of pro-survival Bcl-2, the BH3 only proteins. A promising BH3 mimetic is ABT-737, which targets Bcl-2 and closely related pro-survival proteins. We evaluated its potential utility by testing it on cell lines, clinical samples and on a relevant mouse lymphoma model. We assessed the sensitivity of B cell lymphoma cell lines and primary CLL samples to ABT-737, either alone or in combination. To ascertain its efficacy in vivo, we utilized a mouse model based on the Eμ-myc tumor that is readily transplantable and amenable to genetic manipulation. When syngeneic recipient mice were inoculated with tumors, they develop widespread lymphoma, fatal unless treated by agents such as cyclophosphamide. We found that ABT-737, on its own, was cytotoxic only to a subset of cell lines and primary CLL samples. However, it can synergize potently with agents such as dexamethasone, suggesting that this agent might be useful in combination with currently used chemotherapeutics. In the Eμ myc mouse lymphoma model, treatment with ABT-737 alone did not control the disease as multiple independently derived tumors proved refractory to treatment with this agent. However, ABT-737 was partially effective as a single agent for treating bitransgenic tumors derived from crosses of the Eμmyc and Eμ-bcl-2 transgenic mice. ABT-737 therapy prolonged the survival of recipient mice transplanted with tumors from 30 to 60 days. When combined with a low dose of cyclophosphamide (50mg/kg), long term stable remissions were achieved, which were sustained even longer than control mice treated with much higher doses of cyclophosphamide (300mg/kg). We found that ABT-737 was well tolerated as a single agent and when combined with low doses of cytotoxics such as cyclophosphamide. Thus, ABT-737 may prove to be efficacious for those tumors highly dependent on Bcl-2 for their survival. We found that despite its high affinity for Bcl-2, Bcl-xL and Bcl-w, many cell types proved refractory to ABT-737 as a single agent. We show that this resistance reflects its inability to target another pro-survival relative Mcl-1. Down-regulation of Mcl-1 by several strategies conferred sensitivity to ABT-737. Furthermore, enforced Mcl-1 expression in the Eμmyc/bcl-2 bitransgenic mouse lymphoma model conferred marked resistance as mice transplanted with such tumors died as rapidly as the untreated counterparts. However, enhanced Bcl-2 overexpression on these tumors had little impact on the in vivo response, suggesting that ABT-737 can be utilized even when Bcl-2 is markedly overexpressed. ABT-737 appears to be a promising agent for the clinic. It potently sensitizes certain lymphoid tumors to conventional cytotxics in vitro. The synergy observed between dexamethasone and ABT-737 on some lymphoid lines in culture suggests that it is attractive for clinical testing. Encouragingly, ABT-737 appeared efficacious in vivo against Bcl-2 overexpressing tumors when combined with a reduced dose of cyclophosphamide, suggesting that it will be useful for treating even those Bcl-2-overexpressing tumors that are normally highly chemoresistant.

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