Repositioning approved drugs for the treatment of problematic cancers using a screening approach

Advances in treatment strategies together with an earlier diagnosis have considerably increased the average survival of cancer patients over the last four decades. Nevertheless, despite the growing number of new antineoplastic agents introduced each year, there is still no adequate therapy for problematic malignancies such as pancreatic, lung and stomach cancers. Consequently, it is important to ensure that existing drugs used to treat other types of cancers, and potentially other diseases, are not overlooked when searching for new chemotherapy regimens for these problematic cancer types. We describe a screening approach that identifies chemotherapeutics for the treatment of lung and pancreatic cancers, based on drugs already approved for other applications. Initially, the 1280 chemically and pharmacologically diverse compounds from the Prestwick Chemical Library (R) (PCL) were screened against A549 (lung cancer) and PANC-1 (pancreatic carcinoma) cells using the PrestoBlue fluorescent-based cell viability assay. More than 100 compounds from the PCL were identified as hits in one or both cell lines (80 of them, being drugs used to treat diseases other than cancer). Selected PCL hits were further evaluated in a dose-response manner. Promising candidates for repositioning emanating from this study include antiparasitics, cardiac glycosides, as well as the anticancer drugs vorinostat and topotecan

Screening-based approach to discover effective platinum-based chemotherapies for cancers with poor prognosis

Drug combinations are extensively used to treat cancer and are often selected according to complementary mechanisms. Here, we describe a cell-based high-throughput screening assay for identification of synergistic combinations between broadly applied platinum-based chemotherapeutics and drugs from a library composed of 1280 chemically and pharmacologically diverse (mostly FDA approved) compounds. The assay was performed on chemoresistant cell lines derived from lung (A549) and pancreatic (PANC-1) carcinoma, where platinum-based combination regimens are currently applied though with limited success. The synergistic combinations identified during the screening were validated by synergy quantification using the combination index method and via high content fluorescent microscopy analysis. New promising synergistic combinations discovered using this approach include compounds currently not used as anticancer drugs, such as cisplatin or carboplatin with hycanthone and cisplatin with spironolactone in pancreatic carcinoma, and carboplatin and deferoxamine in non-small cell lung cancer. Strong synergy between cisplatin or carboplatin and topotecan in PANC-1 cells, compared to A549 cells, suggests that this combination, currently used in lung cancer treatment regimens, could be applied to pancreatic carcinoma as well. Several drugs used to treat diseases other than cancer, including pyrvinium pamoate, auranofin, terfenadine and haloprogin, showed strong cytotoxicity on their own and synergistic interactions with platinum drugs. This study demonstrates that non-obvious drug combinations that would not be selected based on complementary mechanisms can be identified via high-throughput screening

High-content, arrayed compound screens with rhinovirus, influenza A virus and herpes simplex virus infections

Viruses are genetically and structurally diverse, and outnumber cells by orders of magnitude. They can cause acute and chronic infections, suppress, or exacerbate immunity, or dysregulate survival and growth of cells. To identify chemical agents with pro- or antiviral effects we conducted arrayed high-content image-based multi-cycle infection screens of 1,280 mainly FDA-approved compounds with three human viruses, rhinovirus (RV), influenza A virus (IAV), and herpes simplex virus (HSV) differing in genome organization, composition, presence of an envelope, and tropism. Based on Z’-factors assessing screening quality and Z-scores ranking individual compounds, we identified potent inhibitors and enhancers of infection: the RNA mutagen 5-Azacytidine against RV-A16; the broad-spectrum antimycotic drug Clotrimazole inhibiting IAV-WSN; the chemotherapeutic agent Raltitrexed blocking HSV-1; and Clobetasol enhancing HSV-1. Remarkably, the topical antiseptic compound Aminacrine, which is clinically used against bacterial and fungal agents, inhibited all three viruses. Our data underscore the versatility and potency of image-based, full cycle virus propagation assays in cell-based screenings for antiviral agents

Digital Holographic Imaging for Label-Free Phenotypic Profiling, Cytotoxicity, and Chloride Channels Target Screening

Cellular assays using label-free Digital Holographic Microscopy (DHM) have been previously validated for cell viability assays in a drug screening context. Our automated DHM system allows performing fast and cost-effective screening assays for a wide range of applications for monitoring cell morphological changes and cell movements upon interaction with interfering compounds. In addition to these classic phenotypic assays, it has been demonstrated that target-based cellular assays can also be addressed by DHM for therapeutically relevant chloride channel receptors. Our DH-imaging (DHI) technology, potentially scalable for screening by imaging approaches in a high-throughput manner can also deliver highly informative data through long term experiments. Three examples of phenotypic screens are detailed in the present chapter: a label-free profiling approach, a cell proliferation assay, and methods for monitoring the activity of the GABAA chloride channel receptor

A high-content image-based drug screen of clinical compounds against cell transmission of adenovirus

Human adenoviruses (HAdVs) are fatal to immuno-suppressed individuals, but no effective anti-HAdV therapy is available. Here, we present a novel image-based high-throughput screening (HTS) platform, which scores the full viral replication cycle from virus entry to dissemination of progeny and second-round infections. We analysed 1,280 small molecular weight compounds of the Prestwick Chemical Library (PCL) for interference with HAdV-C2 infection in a quadruplicate, blinded format, and performed robust image analyses and hit filtering. We present the entire set of the screening data including all images, image analyses and data processing pipelines. The data are made available at the Image Data Resource (IDR, idr0081). Our screen identified Nelfinavir mesylate as an inhibitor of HAdV-C2 multi-round plaque formation, but not single round infection. Nelfinavir has been FDA-approved for anti-retroviral therapy in humans. Our results underscore the power of image-based full cycle infection assays in identifying viral inhibitors with clinical potential

Cell-based high-content screening with label-free Digital Holographic Imaging

We automated a system for performing quantitative cellular assays using label-free Digital Holographic Microscopy (DHM) and validated its applicability for cell viability assays in a drug screening context 1-2. Our system allows performing fast and cost-effective screening assays for a wide range of chemical biology and drug discovery applications. In addition to classic phenotypes recordings related to morphological changes and cell movements, we have demonstrated that target-based cellular assays can also be addressed by DHM for therapeutically relevant chloride channel receptors 3. DH-imaging (DHI) technology, scalable for screening by imaging approaches in a high-throughput manner can also deliver highly informative data through long term experiments (time lapse). Examples of label free imaging screens we validated or currently under development will be described:<br><ul><li>Profiling cancer cell-line sensitivities with small molecules</li><li>Monitoring the activity of the GABA A chloride channel receptor ('an optical electrode')</li><li>Assessing cardiotoxycity of compounds using human cardiomyocytes derived from induced pluripotent stem cells (iPSCs) 4.</li></ul

Image-Based Marker-Free Screening of GABA(A) Agonists, Antagonists, and Modulators

The ionotropic GABA(A) receptors represent the main target for different groups of widely used drugs having hypnotic and anxiolytic effects. So far, most approaches used to assess GABA activity involve invasive low -throughput electrophysiological techniques or rely on fluorescent dyes, preventing the ability to conduct noninvasive and thus nonperturbing screens. To address this limitation, we have developed an automated marker-free cell imaging method, based on digital holographic microscopy (DHM). This technology allows the automatically screening of compounds in multiple plates without having to label the cells or use special plates. This methodological approach was first validated by screening the GABA(A) receptor expressed in HEK cells using a selection of active compounds in agonist, antagonist, and modulator modes. Then, in a second blind screen of a library of 3041 compounds (mostly composed of natural products), 5 compounds having a specific agonist action on the GABA(A) receptor were identified. The hits validated from this unbiased screen were the natural products muscimol, neurosteroid alphaxalone, and three compounds belonging to the avermectin family, all known for having an agonistic effect on the GABA(A) receptor. The results obtained were exempt from false negatives (structurally similar unassigned hits), and false-positive hits were detected and discarded without the need for performing electrophysiological measurements. The outcome of the screen demonstrates the applicability of our screening by imaging method for the discovery of new chemical structures, particularly regarding chemicals interacting with the ionotropic GABA(A) receptor and more generally with any ligand-gated ion channels and transporters

Marker-Free Automatic Quantification of Drug-Treated Cardiomyocytes with Digital Holographic Imaging

We use quantitative phase digital holographic microscopy (QP-DHM) to image and quantify the beating movement of cardiomyocytes, derived from induced pluripotent stem cells (iPSCs), in control and drug-treated conditions. The development of an analysis algorithm has allowed extracting from the recorded quantitative phase signal (QPS) a set of several parameters that can efficiently characterize the cardiomyocytes beating patterns. Based on this approach, we monitored the effects of E-4031 (a class III antiarrhythmic drug) and isoprenaline (a common medication for bradycardia and heart block problems) on the cardiomyocyte beating patterns. Our results show that some effects specific to the mode of action of the drugs used can be identified. This stresses that QP-DHM can represent a promising label-free approach to identify new drug candidates by measuring their effects on iPSC-derived cardiomyocytes

The FDA-approved drug Nelfinavir inhibits lytic cell-free, but not cell-associated non-lytic transmission of human adenovirus

Adenoviruses (AdVs) are prevalent and give rise to chronic and recurrent disease. The human AdV (HAdV) species B and C, such as HAdV-C2, C5 and B14, cause respiratory disease, and constitute a health threat for immuno-compromised individuals. HAdV-Cs are well known for lysing cells, owing to the E3 CR1-β-encoded adenovirus death protein (ADP). We previously reported a high-throughput image-based screening frame-work and identified an inhibitor of HAdV-C2 multi-round infection, Nelfinavir mesylate. Nelfinavir is the active ingredient of Viracept, an FDA-approved inhibitor of the human immuno-deficiency virus (HIV) aspartyl protease, and used to treat acquired immuno-deficiency syndrome (AIDS). It is not effective against single round HAdV infections. Here, we show that Nelfinavir inhibits the lytic cell-free transmission of HAdV, indicated by the suppression of comet-shaped infection foci in cell culture. Comet-shaped foci occur upon convection-based trans-mission of cell-free viral particles from an infected cell to neighbouring uninfected cells. HAdV lacking ADP was insensitive to Nelfinavir, but gave rise to comet-shaped foci indicating that ADP enhances but is not required for cell lysis. This was supported by the notion that HAdV-B14 and B14p1 lacking ADP were highly sensitive to Nelfinavir, although HAdV-A31, B3, B7, B11, B16, B21, D8, D30 or D37 were less sensitive. Conspicuously, Nelfinavir unco-vered slow-growing round-shaped HAdV-C2 foci, independent of neutralizing antibodies in the medium, indicative of non-lytic cell-to-cell transmission. Our study demonstrates the repurposing potential of Nelfinavir with post-exposure efficacy against different HAdVs, and describes an alternative non-lytic cell-to-cell transmission mode of HAdV