Potentiating the naturally occurring process for repair of damaged heart.

This article reviews the current progresses in application of both exogenous and endogenous progenitor cells/stem cells for cardiac repair, and the current understanding of the naturally-occurring process for physiological myocyte turnover and possibly cardiac repair. In particular the development of methods for potentiating the naturally-occurring mechanism for substantial repair of pathologically damaged cardiac tissues is discussed. In the last decade, tremendous efforts to identify both exogenous and endogenous progenitor cells/stem cells possessing capacities of differentiating into cardiac lineages have been made for potential cardiac repair. Although many impressive progresses have been made in the application of differently sourced progenitor cells/stem cells, such as embryonic stem cells (ESCs), induced pluripotent stem cell (iPS), bone marrow-derived mesenchymal stem cells (MSCs), skeletal myoblasts (SMs), umbilical cord blood cells (UCBs), residential cardiac stem cells (CSCs), cardiac resident fibroblasts (CRFs), or adipose tissue-derived stem cells (ASCs) for repair of damaged heart, however, inevitable controversies exist concerning: (i) the immune compatibility of the exogenous donor progenitors/stem cells, (ii) the tumorigenicity with ESCs and iPS, and (iii) the efficiency of these exogenous or endogenous progenitors/ stem cells to acquire cardiac lineages to reconstitute the lost cardiac tissues. The recent recognition of some active small molecules that can induce myocardial regeneration to repair damaged heart tissues through enhancing the naturally-occurring cardiac-repair mechanism has offered the hope for clinical translation of the technology. Potentiating the naturally-occurring process for cardiac repair by administration of such small molecules has provided a promising strategy for reconstruction of damaged cardiac tissues after heart infarction. Therefore, this article is in favor of the notion that such small molecules with the activity of manipulating gene expressions in such a way of inducing endogenous stem cells to commit cardiac lineage differentiation and consequently myocardial regeneration may fulfill the dream of substantial repair of damaged heart.

Highly sensitive proximity mediated immunoassay reveals HER2 status conversion in the circulating tumor cells of metastatic breast cancer patients.

BACKGROUND: The clinical benefits associated with targeted oncology agents are generally limited to subsets of patients. Even with favorable biomarker profiles, many patients do not respond or acquire resistance. Existing technologies are ineffective for treatment monitoring as they provide only static and limited information and require substantial amounts of tissue. Therefore, there is an urgent need to develop methods that can profile potential therapeutic targets with limited clinical specimens during the course of treatment. METHODS: We have developed a novel proteomics-based assay, Collaborative Enzyme Enhanced Reactive-immunoassay (CEER) that can be used for analyzing clinical samples. CEER utilizes the formation of unique immuno-complex between capture-antibodies and two additional detector-Abs on a microarray surface. One of the detector-Abs is conjugated to glucose oxidase (GO), and the other is conjugated to Horse Radish Peroxidase (HRP). Target detection requires the presence of both detector-Abs because the enzyme channeling event between GO and HRP will not occur unless both Abs are in close proximity. RESULTS: CEER was able to detect single-cell level expression and phosphorylation of human epidermal growth factor receptor 2 (HER2) and human epidermal growth factor receptor 1 (HER1) in breast cancer (BCa) systems. The shift in phosphorylation profiles of receptor tyrosine kinases (RTKs) and other signal transduction proteins upon differential ligand stimulation further demonstrated extreme assay specificity in a multiplexed array format. HER2 analysis by CEER in 227 BCa tissues showed superior accuracy when compared to the outcome from immunohistochemistry (IHC) (83% vs. 96%). A significant incidence of HER2 status alteration with recurrent disease was observed via circulating tumor cell (CTC) analysis, suggesting an evolving and dynamic disease progression. HER2-positive CTCs were found in 41% (7/17) while CTCs with significant HER2-activation without apparent over-expression were found in 18% (3/17) of relapsed BCa patients with HER2-negative primary tumors. The apparent 'HER2 status conversion' observed in recurrent BCa may have significant implications on understanding breast cancer metastasis and associated therapeutic development. CONCLUSION: CEER can be multiplexed to analyze pathway proteins in a comprehensive manner with extreme specificity and sensitivity. This format is ideal for analyzing clinical samples with limited availability.

Identification of polymorphisms associated with hypertriglyceridemia and prolonged survival induced by bexarotene in treating non-small cell lung cancer.

BACKGROUND: Bexarotene was evaluated in treating advanced non small cell lung cancer (NSCLC) in two phase III trials. Although a significant survival benefit was not observed for the overall bexarotene-treated population (617 patients), a third of bexarotene-treated patients who developed high-grade hypertriglyceridemia exhibited significantly longer survival. PATIENTS AND METHODS: In order to identify genomic polymorphisms that could serve as potential predictive biomarkers for response and improved survival in NSCLC patients, DNA samples extracted from plasma archived from 403 patients were genotyped using Affymetrix 500K whole genome SNP arrays and/or Sequenom iPLEX™ assays. RESULTS: Fourteen SNPs were identified on nine loci that showed significant associations with high-grade hypertriglyceridemia induced by bexarotene. Four such single nucleotide polymorphisms (SNPs) reside on the region upstream of solute carrier family 10, member 2 (SLC10A2), and one SNP is located close to lymphocyte cytosolic protein 1 (LCP1), whose expression correlated with the activity of bexarotene in tumor cells. CONCLUSION: We identified novel polymorphisms exhibiting significant association with bexarotene induced hypertriglyceridemia, implicating their potential in predicting bexarotene-improved survival response.

Development of a high-throughput screening assay for cytoprotective agents in rotenone-induced cell death.

Parkinson's disease (PD) is a neurodegenerative disease featured by selective loss of substantia nigra neurons. Rotenone administration in animals induces neurodegeneration accompanied by α-synuclein-positive Lewy body-like inclusions, recapturing typical histopathological features of PD. In an effort to screen for small-molecule agents to reverse rotenone-induced cytotoxicity, we developed and validated a sensitive and robust assay with neuroblastoma SK-N-SH cells. This assay was amenable to a high-throughput screening format with Z' factor of 0.56. Robotic screening of a bioactive compound library led to the identification of carnosic acid that can effectively protect cells from rotenone treatment. Using a high-content image-based assay and Western blot analysis, we demonstrated that carnosic acid protects cells from rotenone stress by significant induction of HSP70 expression. Therefore, the assay reported here can be used to identify novel cytoprotective agents for clinical therapeutics of PD.

Identification of inhibitors of HSF1 functional activity by high-content target-based screening.

Cancer cells are known to experience a high level of stress and may require constant repair for survival and proliferation. Recent studies showed that inhibition of heat shock factor 1 (HSF1), the key regulator for the stress-activated transcription of heat shock protein (HSP), can reduce the tumorigenic potential of cancer cells. Such a "nononcogene addiction" phenomenon makes HSF1 an attractive cancer drug target. Here, the authors report an image-based high-content screening (HCS) assay for HSF1 functional inhibitors. A heat shock-based methodology was used to stimulate the stress response followed by quantitative measurement of HSF1/HSP70 granules for compound-induced inhibitory effects. The authors discovered a small molecule from a compound library that inhibits HSF1 granule formation substantially in heat-shocked HeLa cells with IC(50) at 80 nM. Electorphoretic mobility shift of HSF1 by this compound suggested significant inhibition of HSF1 phosphorylation, accompanied by reduced expression levels of HSP70 and HSP90 after heat induction. Importantly, HeLa cells stably transfected with HSF1 shRNA were more resistant to the compound treatment under lethal temperature than cells containing HSF1, further validating an HSF1-dependent mechanism of action. The HCS assay the authors developed was robust with a Z' factor of 0.65 in a 384-well plate format, providing a valuable method for identifying small-molecule functional inhibitors of HSF1 for potential cancer treatment.

Identification of small-molecule HSF1 amplifiers by high content screening in protection of cells from stress induced injury.

Small molecule amplifiers of heat shock response have shown promising results in rescuing stress related injury through chaperone amplification. Herein, we report the results of a high content target-based primary screening of several known bioactive libraries. Screening resulted in the identification of three potent gedunin derivatives and a sappanone A derivative. Western blot results confirmed compound-induced activation of HSF1 and increased expression level of HSP70. These compounds rescued cells from cell death caused by proteasome inhibitor MG-132 and RNAi knockdown of HSF1 significantly reversed the cytoprotective effects, confirming an HSF1-dependent mechanism of action. These HSF1 amplifiers were tested in two mammalian cell based models of Huntington's disease (HD) and found to improve survival. Therefore, these screening hits may have therapeutic potential for HD and possibly other protein conformational disorders.

Pyrimido[5,4-e][1,2,4]triazine-5,7(1H,6H)-dione derivatives: their cytoprotection effect from rotenone toxicity and preliminary DMPK properties.

Pyrimido[5,4-e][1,2,4]triazine-5,7(1H,6H)-dione derivatives exhibited potent cytoprotective effect from rotenone toxicity. Lead optimization focused on the CC50/EC50 ratio and DMPK properties led to the overall improvement of the compound profile of this series with high CC50/EC50 ratio (92 for 1f), good metabolic stability in rat microsomes and medium to high aqueous solubility.

Pyrimido[5,4-e][1,2,4]triazine-5,7(1H,6H)-dione derivatives as novel small molecule chaperone amplifiers.

Pyrimido[5,4-e][1,2,4]triazine-5,7(1H,6H)-dione derivatives were investigated as novel small molecule amplifiers of heat shock factor 1 transcriptional activity. Lead optimization led to the discovery of compound 4A-13, which displayed potent HSF1 activity under mild heat stress (EC(50)=2.5microM) and significant cytoprotection in both rotenone (EC(50)=0.23microM) and oxygen-glucose deprivation cell toxicity models (80% protection at 2.5microM).

Identification of a small molecule SIRT2 inhibitor with selective tumor cytotoxicity.

As a member of the class III histone deacetylases, Sirtuin-2 (SIRT2) is critical in cell cycle regulation which makes it a potential target for cancer therapeutics. In this study, we identified a novel SIRT2 inhibitor, AC-93253, with IC(50) of 6 microM in vitro. The compound is selective, inhibiting SIRT2 7.5- and 4-fold more potently than the closely related SIRT1 and SIRT3, respectively. AC-93253 significantly enhanced acetylation of tubulin, p53, and histone H4, confirming SIRT2 and SIRT1 as its cellular targets. AC-93253 as a single agent exhibited submicromolar selective cytotoxicity towards all four tumor cell lines tested with a therapeutic window up to 200-fold, comparing to any of the three normal cell types tested. Results from high content analysis suggested that AC-93253 significantly triggered apoptosis. Taken together, SIRT2 selective inhibitor AC-93253 may serve as a novel chemical scaffold for structure-activity relationship study and future lead development.

Chloro-oxime derivatives as novel small molecule chaperone amplifiers.

Chloro-oxime derivatives were investigated as novel small molecule chaperone amplifiers. Lead optimization led to the discovery of compounds that displayed potent HSF1 activation activity, significant cytoprotection in MG-132 stress, ER stress and PolyQ stress cell models (EC(50)<10 microM).

High-content image-based screening for small-molecule chaperone amplifiers in heat shock.

Heat shock proteins represent the major elements of the cellular stress response that protects cells from diseases caused by protein misfolding. Small-molecule amplifiers of heat shock proteins have shown promising results in several animal models, demonstrating the potential importance of such compounds for therapeutics. The expression of many heat shock proteins is controlled by HSF1, which forms stress granules in the nucleus when transcriptionally activated. Activation of the cellular stress also correlates with the translocation of HSP70 into nucleoli. The authors have developed an image-based, multiparametric assay to simultaneously monitor the effects of compounds on HSF1/HSP70 stress granule formation in heat-shocked Hela cells. High-content screening of the compound library was performed with a Z' of 0.62, demonstrating a highly robust assay for large-scale screening. The resulting hits showed prolonged amplification of HSP70 induction in heat-stressed cells but no effects in cells without stress. Treatment of cells with selected hits exhibited significant cytoprotection from both oxygen glucose deprivation and rotenone-induced stresses. Thus, high-content screening of HSF1/HSP70 amplifiers provides a practical opportunity for clinical therapeutics targeting protein misfolding diseases.

Crystal structure of HsEg5 in complex with clinical candidate CK0238273 provides insight into inhibitory mechanism, potency, and specificity.

HsEg5 is an important mitotic kinesin responsible for bipolar spindle formation at early mitosis. A rich body of evidence shows that inhibition of HsEg5 can result in mitotic arrest followed by cellular apoptosis. Recently identified HsEg5 inhibitor, CK0238273, exhibits potent antitumor activity and is currently in clinical trial. Here we report the cocrystal structure of the motor domain of HsEg5 in complex with CK0238273 at a 2.15 A resolution. Compared to the previously published HsEg5-Monastrol complex structure, CK0238273 shares the same induced-fit pocket with similar allosteric inhibitory mechanism. However, CK0238273 shows better fitting to the binding pocket with 65% increase of hydrophobic interaction area than that of Monastrol. Some unique hydrophilic interactions were also observed mostly between the phenyl ring and 8-chloro on quinazolinone of CK0238273 with ARG221 and GLY217. We believe that the combination of these interactions defines the superior potency and specificity of CK0238273.

Bexarotene (LGD1069, Targretin), a selective retinoid X receptor agonist, prevents and reverses gemcitabine resistance in NSCLC cells by modulating gene amplification.

Acquired drug resistance is a major obstacle in cancer therapy. As for many other drugs, this is also the case for gemcitabine, a nucleoside analogue with activity against non-small cell lung cancer (NSCLC). Here, we evaluate the ability of bexarotene to modulate the acquisition and maintenance of gemcitabine resistance in Calu3 NSCLC models. In the prevention model, Calu3 cells treated repeatedly with gemcitabine alone gradually developed resistance. However, with inclusion of bexarotene, the cells remained chemosensitive. RNA analysis showed a strong increase of rrm1 (ribonucleotide reductase M1) expression in the resistant cells (Calu3-GemR), a gene known to be involved in gemcitabine resistance. In addition, the expression of genes surrounding the chromosomal location of rrm1 was increased, suggesting that resistance was due to gene amplification at the chr11 p15.5 locus. Analysis of genomic DNA confirmed that the rrm1 gene copy number was increased over 10-fold. Correspondingly, fluorescence in situ hybridization analysis of metaphase chromosomes showed an intrachromosomal amplification of the rrm1 locus. In the therapeutic model, bexarotene gradually resensitized Calu3-GemR cells to gemcitabine, reaching parental drug sensitivity after 10 treatment cycles. This was associated with a loss in rrm1 amplification. Corresponding with the in vitro data, xenograft tumors generated from the resistant cells did not respond to gemcitabine but were growth inhibited when bexarotene was added to the cytotoxic agent. The data indicate that bexarotene can resensitize gemcitabine-resistant tumor cells by reversing gene amplification. This suggests that bexarotene may have clinical utility in cancers where drug resistance by gene amplification is a major obstacle to successful therapy.

Influence of Bcl-2 family members on the cellular response of small-cell lung cancer cell lines to ABT-737.

ABT-737 is a novel and potent Bcl-2 antagonist with single-agent activity against small-cell lung cancer (SCLC) cell lines. Here, we evaluated the contribution of Bcl-2 family members to the in vitro cellular response of several SCLC cell lines to ABT-737. Relatively higher levels of Bcl-2, Bcl-X(L), Bim and Noxa, and lower levels of Mcl-1 characterized naïve SCLC cell lines that were sensitive to ABT-737. Conversely, a progressive decrease in the relative levels of Bcl-2 and Noxa and a progressive increase in Mcl-1 levels characterized the increased resistance of H146 cells following chronic exposure to ABT-737. Knockdown of Mcl-1 with small interfering RNA sensitized two resistant SCLC cell lines H196 and DMS114 to ABT-737 by enhancing the induction of apoptosis. Likewise, up-regulation of Noxa sensitized H196 cells to ABT-737. Combination treatment with DNA-damaging agents was extremely synergistic with ABT-737 and was associated with the down-regulation of Mcl-1 and the up-regulation of Noxa, Puma, and Bim in H196 cells. Thus, SCLC cells sensitive to ABT-737 expressed the target proteins Bcl-2 and Bcl-X(L), whereas Mcl-1 and factors regulating Mcl-1 function seem to contribute to the overall resistance of SCLC cells to ABT-737. Overall, these observations provide further insight as to the mechanistic bases for ABT-737 efficacy in SCLC and will be helpful for profiling patients and aiding in the rational design of combination therapies.

Studies leading to potent, dual inhibitors of Bcl-2 and Bcl-xL.

Overexpression of the antiapototic proteins Bcl-2 and Bcl-xL provides a common mechanism through which cancer cells gain a survival advantage and become resistant to conventional chemotherapy. Inhibition of these prosurvival proteins is an attractive strategy for cancer therapy. We recently described the discovery of a selective Bcl-xL antagonist that potentiates the antitumor activity of chemotherapy and radiation. Here we describe the use of structure-guided design to exploit a deep hydrophobic binding pocket on the surface of these proteins to develop the first dual, subnanomolar inhibitors of Bcl-xL and Bcl-2. This study culminated in the identification of 2, which exhibited EC50 values of 8 nM and 30 nM in Bcl-2 and Bcl-xL dependent cells, respectively. Compound 2 demonstrated single agent efficacy against human follicular lymphoma cell lines that overexpress Bcl-2, and efficacy in a murine xenograft model of lymphoma when given both as a single agent and in combination with etoposide.

Discovery and structure-activity relationship of antagonists of B-cell lymphoma 2 family proteins with chemopotentiation activity in vitro and in vivo.

Development of a rationally designed potentiator of cancer chemotherapy, via inhibition of Bcl-X(L) function, is described. Lead compounds generated by NMR screening and directed parallel synthesis displayed sub-microM binding but were strongly deactivated in the presence of serum. The dominant component of serum deactivation was identified as domain III of human serum albumin (HSA); NMR solution structures of inhibitors bound to both Bcl-X(L) and HSA domain III indicated two potential optimization sites for separation of affinities. Modifications at both sites resulted in compounds with improved Bcl-X(L) binding and greatly increased activity in the presence of human serum, culminating in 73R, which bound to Bcl-X(L) with a K(i) of 0.8 nM. In a cellular assay 73R reversed the protection afforded by Bcl-X(L) overexpression against cytokine deprivation in FL5.12 cells with an EC(50) of 0.47 microM. 73R showed little effect on the viability of the human non small cell lung cancer cell line A549. However, consistent with the proposed mechanism, 73R potentiated the activity of paclitaxel and UV irradiation in vitro and potentiated the antitumor efficacy of paclitaxel in a mouse xenograft model.

Visualization and interpretation of high content screening data.

High content screening is a method for identifying small molecule modulators of mammalian cell biology. The nature of the experiment generates an enormous amount of data in the form of photographic images of cells after treatment with compounds of interest. The interpretation of data from these experiments is challenging both in terms of automatically perceiving the images, extracting, and understanding differences between screened compounds and visualizing the results. This paper discusses the application of statistical and visual methods that have been used to interpret data from a simplified DNA stain (DAPI) screen to quickly identify compounds of interest. An understanding of the mechanism of action of the screened compounds can be obtained by comparing them to control compounds of known mechanism of action. Statistical and visual methods will be shown that facilitate easy comparison of screened compounds against these control compounds. As an example, a subset of the internal repository at ArQule was screened, together with control compounds that were known to induce characteristic mitotic arrest. Subsequent data processing described in this paper permitted the easy identification of compounds that were similar to (and very different from) the control compounds.

Indoloprodigiosins from the C-10 bipyrrolic precursor: new antiproliferative prodigiosin analogs.

The condensation of the C-10 methoxybipyrrole precursor (3) of prodigiosin with indoles and a related pyrrole derivative yields novel analogs of prodigiosin. Biological evaluation of these products revealed compounds that inhibit cancer cell proliferation from 50 nM to 50 microM.

Identification of a small molecule that induces mitotic arrest using a simplified high-content screening assay and data analysis method.

High-content screening has emerged as a new and powerful technique for identifying small-molecule modulators of mammalian cell biology. The authors describe the development and execution of a high-content screen to identify small molecules that induce mitotic arrest in mammalian cancer cells. Many widely used chemotherapeutics, such as Taxol and vinblastine, induce mitotic arrest, and the creation of new drugs that also induce mitotic arrest may have tremendous therapeutic value. In their screen, the authors employed a simple DNA stain (DAPI) and a sensitive nonparametric statistical test to identify compounds from an internal collection of approximately 13,000 high-quality lead-like small molecules. Subsequent analysis of 1 active compound indicated that it induces mitotic arrest, assessed using a high-content phosphohistone H3 detection assay, and caused cell proliferation defects in multiple cancer cell lines. The active compound, a quinazolinone originating from a natural product-like subset of the screened compounds, is active in cells at approximately 500 nM and appears to act by inhibiting the polymerization of tubulin.