Abstract 4242: Metformin suppresses GRP78-dependent PI3-Kinase activity in clonogenic side population to enhance the anti-myeloma benefit of bortezomib

Multiple myeloma (MM) patients invariably relapse through mechanisms that remain elusive. Disease recurrence after treatment suggests that rare, tumor-initiating subpopulations with chemoresistant phenotypes persist or emerge to propagate and mediate tumor regrowth. Stem cell-like side population (SP) cells were isolated from myeloma cell lines and patient samples and exhibited resistance to proteasome inhibitors relative to the main population (MP). SP cell-based high-throughput screening detected pharmacologics that enhanced the anti-proliferative effect of bortezomib and revealed the anti-diabetic agent metformin. Bortezomib treatment increased levels of the molecular chaperone glucose-regulated protein GRP78 but metformin co-treatment suppressed bortezomib-induced GRP78 upregulation. Bortezomib treatment also promoted GRP78 co-localization with the signal transducer phosphatidylinositol-3-kinase (PI3K) that activates cell growth and survival pathways. SP cells displayed greater levels of the PI3K product phosphatidylinositol (3,4,5)-trisphosphate (PIP3) and enhanced PI3K-mediated phosphorylation of protein kinase B/AKT compared to MP cells. Metformin treatment or knockdown of GRP78-encoding HSPA5 enhanced sensitivity to bortezomib preferentially in SP cells. Tumor growth was significantly delayed and overall survival prolonged after metformin co-treatment with bortezomib in mice injected with parental or SP cells. Taken together, the results support the pharmacologic repositioning of metformin to inhibit GRP78 induction in therapy-resistant cells and enhance the anti-myeloma benefit of bortezomib.

Note: This abstract was not presented at the meeting.

Citation Format: James J. Driscoll, Sajjeev Jagannathan, Mohamed AY Abdel Malek, Nikhil Vad, Ehsan Malek. Metformin suppresses GRP78-dependent PI3-Kinase activity in clonogenic side population to enhance the anti-myeloma benefit of bortezomib. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4242. doi:10.1158/1538-7445.AM2015-4242

Abstract 1462: Tandem genome-wide and functional screening reveals that MiRNA-29 regulates the proteasome activator PSME4 to promote therapeutic resistance in myeloma

MicroRNAs (miRNAs) are newly recognized, master regulators of the human genome and hence play key roles in cellular pathways that govern proliferation, differentiation and apoptosis during both physiologic and pathologic states. Accordingly, alterations in miRNA levels contribute to myriad diseases including human cancers. MiRNAs have rapidly attracted significant attention as agents with significant potential as diagnostics and therapeutics to improve the outcome of cancer patients. While proteasome inhibitors (PIs) such as bortezomib (Velcade, Millennium-Takeda) have transformed management of the invariably fatal disease multiple myeloma, therapeutic resistance inevitably emerges through mechanisms that remain elusive. A goal of these studies was to investigate the role of individual miRNAs in regulating functional activity of the ubiquitin+proteasome system. Genome-wide expression profiling was performed to identify differentially expressed miRNAs in the PI-resistant cells relative to drug-naive parental cells. A live-cell functional screen that employed a recombinant fluorescent probe comprised of a short-lived reporter bearing a destabilizing modification to promote constitutive proteasomal degradation was used to quantitate the effect of individual miRNAs. MiRNAs-29a/b/c were significantly reduced in the PI-resistant cells and these miRNAs negatively regulated PSME4 which expresses the proteasome activator PA200. Transfection of synthetically-engineered miRNA-29 replacements reduced PSME4 levels, promoted myeloma cell death and overcame drug resistance. Deletion of a nuclear localization signal (NLS) enriched the cytoplasmic distribution and enhanced the functional effect of miRNA-29 replacements. Doxycycline-induced expression of miRNA-29b or miRNA-29 variants that lacked the NLS also dramatically reduced the in vivo growth of subcutaneously injected myeloma tumor cells in NOD/SCID mice. We demonstrate that the loss of a tumor suppressive miRNA activates not only inherently oncogenic pathways to promote the generation of a cancer phenotype but also to promote therapeutic resistance to PIs. We provide a platform to perform a genome-wide interrogation of miRNAs and other non-coding RNAs that regulate the ubiquitin+proteasome system. The significant cytotoxic effect of miRNA-29 replacements observed using MM cell lines and myeloma patient samples as well as ability to reduce tumor growth in vivo validate miRNA-29 replacements as highly effective anti-cancer tools to overcome therapeutic resistance, promote tumor cell death and eventually improve patient outcome.

Citation Format: James J. Driscoll, Sajjeev Jagannathan. Tandem genome-wide and functional screening reveals that MiRNA-29 regulates the proteasome activator PSME4 to promote therapeutic resistance in myeloma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1462. doi:10.1158/1538-7445.AM2014-1462

Abstract LB-140: The Hsp90 inhibitor ganetespib overcomes EGFR-based intratumoral heterogeneity to block glioma proliferation

Intratumoral heterogeneity is evident as distinct subpopulations of cancer cells within and between tumor lesions that profoundly impact therapeutic response and patient outcome. While the advent of targeted therapies to exploit a tumor's dependence on critical proliferative or survival pathways has significantly improved patient outcomes in a range of solid tumor types, it is also apparent that targeted therapeutics do not help all molecularly selected patients and even when clinical benefit is observed, it is often of limited duration. To address this question, we have explored the invariably fatal adult brain tumor glioblastoma multiforme (GBM). Heterogeneous forms of the epidermal growth factor receptor (EGFR) arise through amplification or mutation as signature pathogenetic events in this highly aggressive disease. While EGFR deregulation promotes tumor cell proliferation, drug resistance and tumor survival, functional blockade of the EGFR kinase activity alone does not achieve maximal therapeutic benefit. Since intratumoral heterogeneity represents a major impediment to the development of effective therapeutics in GBM, we sought to identify small molecules cytotoxic to glioma cells engineered to overexpress either wildtype (WT), constitutively active mutant EGFR-vIII, kinase-dead (KD) form or a basal level of EGFR-WT using a live cell-based, high-throughput screen (HTS) of ∼2,000 FDA-approved or bioactive compounds. Our screen revealed that the Hsp90 inhibitor ganetespib (STA-9090, Synta Pharmaceuticals, Lexington, MA) was highly cytotoxic (IC50 ∼20nM) to glioma cells that overexpressed each of the EGFR forms. Real-time measurements were then performed to demonstrate that ganetespib at nM concentrations reduced the proliferation of brain tumor cells expressing EGFR-WT, -vIII or KD forms, induced apoptosis and inhibited glioma migration. Ganetespib also potently reduced the proliferation of human GBM patient-derived tumor-initiating stem cells but not that of untransformed glial cells. Ganetespib effectively impaired the growth of subcutaneously implanted human brain tumor xenotransplants that expressed either EGFR-WT, -vIII or both EGFR forms placed in immunocompromised mice. In addition, ganetespib provided a survival benefit compared to untreated mice. The Hsp90 inhibitor ganetespib is a highly potent agent that impairs the growth-promoting functional kinase-dependent and independent activities of EGFR to overcome context-dependent intratumoral heterogeneity with potential benefits for GBM patients.

Citation Format: James J. Driscoll, Nitin S. Narayanan, Sajjeev Jagannathan. The Hsp90 inhibitor ganetespib overcomes EGFR-based intratumoral heterogeneity to block glioma proliferation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-140. doi:10.1158/1538-7445.AM2014-LB-140

Correlation of long non-coding RNA expression with metastasis, drug resistance and clinical outcome in cancer

The therapeutic response and clinical outcome of patients diagnosed with the same cancer type and that receive identical treatment is highly variable to reflect the genetic heterogeneity within tumor cells. Non-coding RNAs (ncRNAs) are recently discovered molecules that regulate eukaryotic gene expression and represent a significant advance towards a better understanding of the mechanisms that govern cellular growth. NcRNAs are essential for the proper regulation of cell proliferation and survival under physiologic conditions and are deregulated in many pathologies, e.g., human cancers. NcRNAs have been associated with cancer diagnosis, staging, treatment response, metastasis and survival and include distinct subtypes, e.g., long ncRNAs (lncRNAs) and microRNAs (miRNAs). LncRNAs have been linked to essential growth-promoting activities and their deregulation contributes to tumor cell survival. A prominent example is the Hox transcript antisense intergenic lncRNA, HOTAIR, that cooperates with the polycomb repressive complex to reprogram chromatin organization. HOTAIR expression is deregulated in a spectrum of cancers and HOTAIR expression correlates with patient survival. Here, we highlight emerging evidence that supports a role for lncRNAs in cancer with implications for the development of novel diagnostics and therapeutics.

MiR-29b replacement inhibits proteasomes and disrupts aggresome+autophagosome formation to enhance the antimyeloma benefit of bortezomib

Evading apoptosis is a cancer hallmark that remains a serious obstacle in current treatment approaches. Although proteasome inhibitors (PIs) have transformed management of multiple myeloma (MM), drug resistance emerges through induction of the aggresome+autophagy pathway as a compensatory protein clearance mechanism. Genome-wide profiling identified microRNAs (miRs) differentially expressed in bortezomib-resistant myeloma cells compared with drug-naive cells. The effect of individual miRs on proteasomal degradation of short-lived fluorescent reporter proteins was then determined in live cells. MiR-29b was significantly reduced in bortezomib-resistant cells as well as in cells resistant to second-generation PIs carfilzomib and ixazomib. Luciferase reporter assays demonstrated that miR-29b targeted PSME4 that encodes the proteasome activator PA200. Synthetically engineered miR-29b replacements impaired the growth of myeloma cells, patient tumor cells and xenotransplants. MiR-29b replacements also decreased PA200 association with proteasomes, reduced the proteasome's peptidase activity and inhibited ornithine decarboxylase turnover, a proteasome substrate degraded through ubiquitin-independent mechanisms. Immunofluorescence studies revealed that miR-29b replacements enhanced the bortezomib-induced accumulation of ubiquitinated proteins but did not reveal aggresome or autophagosome formation. Taken together, our study identifies miR-29b replacements as the first-in-class miR-based PIs that also disrupt the autophagy pathway and highlight their potential to synergistically enhance the antimyeloma effect of bortezomib.

Zero-sum two-player game theoretic formulation of affine nonlinear discrete-time systems using neural networks

In this paper, the nearly optimal solution for discrete-time (DT) affine nonlinear control systems in the presence of partially unknown internal system dynamics and disturbances is considered. The approach is based on successive approximate solution of the Hamilton-Jacobi-Isaacs (HJI) equation, which appears in optimal control. Successive approximation approach for updating control and disturbance inputs for DT nonlinear affine systems are proposed. Moreover, sufficient conditions for the convergence of the approximate HJI solution to the saddle point are derived, and an iterative approach to approximate the HJI equation using a neural network (NN) is presented. Then, the requirement of full knowledge of the internal dynamics of the nonlinear DT system is relaxed by using a second NN online approximator. The result is a closed-loop optimal NN controller via offline learning. A numerical example is provided illustrating the effectiveness of the approach.

MicroRNA theragnostics for the clinical management of multiple myeloma

Theragnostics represent cutting-edge, multi-disciplinary strategies that combine diagnostics with therapeutics in order to generate personalized therapies that improve patient outcome. In oncology, the approach is aimed at more accurate diagnosis of cancer, optimization of patient selection to identify those most likely to benefit from a specific therapy and to generate effective therapeutics that enhance patient survival. MicroRNAs (miRNAs) are master regulators of the human genome that orchestrate myriad cellular pathways to control growth during physiologic and pathologic conditions. Compelling evidence shows that miRNA deregulation promotes events linked to tumor initiation, metastasis and drug resistance as seen in multiple myeloma (MM), an invariably fatal hematologic malignancy. miRNAs are readily detected in body fluids, for example, serum, plasma, urine, as well as circulating tumor cells to demonstrate their potential as readily accessible, non-invasive diagnostic and prognostic biomarkers and potential therapeutics. Specific miRNAs are aberrantly expressed early in myelomagenesis and may more readily detect high-risk disease than current methods. Although only recently discovered miRNAs have rapidly advanced from preclinical studies to evaluation in human clinical trials. The development of miRNA theragnostics should provide widely applicable tools for the targeted delivery of personalized medicines to improve the outcome of patients with MM.

Brain microenvironment-induced reduction in microRNAs to promote metastatic tumor growth, drug resistance, and survival

e22030

Background: Brain metastases remain a serious obstacle that negatively impacts cancer patient survival. Most deaths due to cancer result from the progressive growth of metastatic, drug-resistant lesions. Moreover, the incidence of brain metastases is rising as a result of an aging population, superior imaging modalities, earlier cancer detection and more effective treatment of systemic disease. Methods: To investigate the role of the brain microenvironment in metastasis, tumor cells were co-cultured with astrocytes - the most abundant normal cell type in the metastatic brain tumor niche. This led to increased tumor cell viability, proliferation and chemoresistance. Microarray-based profiling was then performed to address the effect of the brain microenvironment on miRNA expression levels in tumor cells. Results: Profiling revealed that astrocyte co-culture reduced miRNAs-768-3p, 886-5p and 200c in tumor cells. Inhibition of miRNA-768-3p increased KRas expression, and a specific binding site was identified in the KRas 3’UTR and validated using a luciferase construct. miRNA-768-3p levels were reduced in patient-derived brain metastases relative to normal adult brain. Additionally, miRNA-768-3p was also lower in brain metastases compared to the primary tumors in matched paired samples. Our data demonstrates that the brain microenvironment modulates miRNA-768-3p in metastatic lesions to enhance KRas-mediated tumor survival and promote metastasis. Conclusions: The brain microenvironment regulates the expression of individual miRNAs in tumor cells to promote growth, survival and drug resistance. The brain microenvironment down-regulates the level of certain miRNAs to promote oncogenic signaling and tumor growth while our studies indicate that chemically-engineered miRNA mimics can restore the loss-of-function to reduce the viability of cancer cells. miRNA replacement therapy is a promising and novel therapeutic concept that could save thousands of patients from ineffective treatment, improve patient quality-of-life, overall survival and reduce the devastating impact of brain metastases on the healthcare system.

Abstract LB-277: Microenvironment-induced changes in miRNA levels promote brain metastasis, drug resistance and KRA expression

Brain metastases remain a serious obstacle that negatively impacts cancer patient survival. Nearly 180,000 patients in the U.S. are diagnosed annually with metastatic brain lesions, more than ten times the incidence of primary brain tumors such as glioblastoma. Brain metastases remain a challenging complication despite advances in surgical, chemo-radiation and targeted therapies. Most deaths due to cancer result from the progressive growth of metastatic, drug-resistant lesions. Moreover, the incidence of brain metastases is rising as a result of superior imaging modalities, earlier cancer detection and more effective treatment of systemic disease. To investigate the role of the brain microenvironment in metastasis, lung and breast tumor cells were co-cultured with astrocytes, the most abundant normal cell type in the metastatic brain tumor niche. Astrocyte co-culture led to increased tumor cell viability, proliferation and chemoresistance. After co-culture with astreocytes, tumor cells were then removed and total RNA was isolated. A panel of individual microRNAs (miRNAs) were identified that were reduced in tumor cells after co-culture. The rationale for developing miRNA therapeutic replacements is based upon the premise that aberrantly expressed miRNAs play a key role in controlling tumorigenesis, drug resistance and metastasis. Correcting these miRNA deficiencies through antagonisitc or replacement of miRNA function may provide a therapeutic benefit. Microarray-based profiling revealed that astrocyte co-culture reduced miRNAs-768-3p, 886-5p and 200c in the lung tumor cells. Vector-based forced expression of sequence complementary to miRNA768-3p or transfection of inhibitory miRNA-768-3p oligonucleotide inhibitors into tumor cells led to increased cell growth. Also, inhibition of miRNA-768-3p increased KRas expression, and a specific binding site was identified in the KRas 3′UTR was validated using a luciferase construct. Moreover, shRNA-mediated KRas knockdown reduced growth-promotion by the miRNA-768-3p inhibitor. MiRNA-768-3p levels were lower in tissue samples obtained from patients diagnosed with brain metastases relative to normal human adult brain tissue. In addition, the level of miRNA-768-3p was lower in tissue from patients diagnosed with brain metastases compared to the primary tumors in matched paired samples obtained from the same patient. The results demonstrate that the brain microenvironment modulates numerous miRNA, sush as miRNA-768-3p, in metastatic lesions to enhance KRas-mediated tumor growth and drug resistance and ultimately to promote brain metastasis. The therapeutic application of miRNA may allow for the rapid and coordinated manipulation of proteins that regualte multiple key intracellular pathways that promote tumorigenesis and metastasis.

Citation Format: James J. Driscoll, Arasakumar Subramani, Samer Alsidawi, Sajjeev Jagannathan, Kazutaka Sumita, Atsuo Sasaki, Ronald E. Warnick, Sean Lawler. Microenvironment-induced changes in miRNA levels promote brain metastasis, drug resistance and KRA expression. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-277. doi:10.1158/1538-7445.AM2013-LB-277

Abstract 1708: Metabolic regulation of the ubiquitin+proteasome system

The ubiquitin+proteasome system (UPS) is a highly complex network that maintains protein homeostasis and cell viability through the highly regulated and selective turnover of targeted proteins. The proteasome is the major intracellular protease in eukaryotes and serves as the catalytic core of the UPS. The cytotoxic effect of proteasome inhibition has been translated therapeutically to dramatically improve the overall survival of patients diagnosed with the plasma cell malignancy multiple myeloma (MM). Bortezomib has emerged as the standard-of-care therapy for MM to catapult the UPS into a position of prominence in cancer biology and drug development but significant obstacles remain since many patients do not respond to bortezomib, clinical responses are not sustained and drug resistance inevitably emerges through unknown mechanisms. Gene profiling was performed as an unbiased approach to address the precise molecular events that promote bortezomib-resistance. Results indicated that effectors of energy metabolism were differentially expressed in cells resistant to bortezomib. Subunits of the cellular energy sensor AMP-activated protein kinase (AMPK) were expressed at lower levels in resistant cells relative to the parental cells. Real-time, cell-based metabolic measurements demonstrated that bortezomib rapidly and dramatically reduced tumor cell oxygen-consumption while bortezomib-resistant cells were less sensitive to metabolic deregulation. Genetic ablation of the AMPKα1/α2 encoding-genes also reduced the effect of bortezomib to promote autophagosome formation as well as bortezomib-induced cytotoxicity. Similarly, knockout of the AMPK-substrate and autophagy-initiating kinase ULK1 also reduced bortezomib-induced autophagosome formation and cell death. Proteasome inhibition promoted ULK-1 association with the autophagosome initiators ATG13, FIP200 and beclin-1. The AMPK activator AICAR further enhanced bortezomib-induced cytotoxicity in myeloma, lymphoma, leukemic and solid tumor cells. Proteasome inhibitors induce AMPK+ULK-mediated autophagosome formation that is coupled to apoptosis and can be exploited as a novel anti-cancer therapeutic strategy.

Citation Format: James J. Driscoll, Sajjeev Jagannathan. Metabolic regulation of the ubiquitin+proteasome system. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1708. doi:10.1158/1538-7445.AM2013-1708

Standardization and assessment of cell culture media quantities in roller poly ethylene terephthalate bottles employed in the industrial rabies viral vaccine production

Vero cells are utilized for production of rabies vaccine. This study deals with the optimize quantity media require for the rabies vaccine production in the smooth roller surface. The rabies virus (Pasteur vaccine strain) is infected to monolayer of the various experimented bottles. To analyze the optimal quantity of media for the production of rabies viral harvest during the process of Vero cell derived rabies vaccine. The trials are started from 200 to 400 mL (PTARV-1, PTARV-2, PTARV-3, PTARV-4 and PTARV-5). The samples are taken in an appropriate time intervals for analysis of In Process Quality Control (IPQC) tests. The collected viral harvests are further processed to rabies vaccine in a pilot level and in addition to scale up an industrial level. Based on the evaluation the PTARV-2 (250 mL) show highly encouraging results for the Vero cell derived rabies vaccine production.

Predictive models of hepatotoxicity using gene expression data from primary rat hepatocytes

With the aim of evaluating the usefulness of an in vitro system for assessing the potential hepatotoxicity of compounds, the paper describes several methods of obtaining mathematical models for the prediction of compound-induced toxicity in vivo. These models are based on data derived from treating rat primary hepatocytes with various compounds, and thereafter using microarrays to obtain gene expression 'profiles' for each compound. Predictive models were constructed so as to reduce the number of 'probesets' (genes) required, and subjected to rigorous cross-validation. Since there are a number of possible approaches to derive predictive models, several distinct modelling strategies were applied to the same data set, and the outcomes were compared and contrasted. While all the strategies tested showed significant predictive capability, it was interesting to note that the different approaches generated models based on widely disparate probesets. This implies that while these models may be useful in ascribing relative potential toxicity to compounds, they are unlikely to provide significant information on underlying toxicity mechanisms. Improved predictivity will be obtained through the generation of more comprehensive gene expression databases, covering more 'toxicity space', and by the development of models that maximize the observation, and combination, of individual differences between compounds.