Image-based high-content reporter assays: limitations and advantages

Two-color fluorescent proteins reporting survivin regulation in breast cancer cells for high throughput drug screening

Reporter gene assay is widely used for high throughput drug screening and drug action mechanism evaluation. In this study, we developed a robust dual-fluorescent reporter assay to detect drugs repressing the transcription of survivin, a cancer biomarker from the inhibitor of apoptosis family, in breast cancer cells cultured in three-dimensional (3D) microbioreactors. Survivin is overexpressed in numerous malignancies but almost silent in normal tissue cells and is considered a lead target for cancer therapy. Breast cancer MCF-7 cells were engineered to express enhanced green fluorescent protein driven by a survivin promoter and red fluorescent protein driven by a cytomegalovirus promoter as internal control to detect changes in survivin expression in cells as affected by drugs. This 3D dual-fluorescent reporter assay was validated with YM155 and doxorubicin, which were known to downregulate survivin in cancer cells, and further evaluated with two widely used anticancer compounds, cisplatin, and epigallocatechin gallate, to evaluate their effects on survivin expression. The results showed that the 3D dual-fluorescent reporter assay was robust for high throughput screening of drugs targeting survivin in breast cancer cells.

A New Method for Screening Natural Products to Stimulate IFN-γ Production in Jurkat Human T Lymphocytes

Interferon-γ (IFN-γ) is a critical cytokine in the defense against viral and bacterial infection. It is mainly produced by natural killer cells and activated T cells. Given its regulatory role in coordinating cellular and humoral immune responses, IFN-γ is considered to be an effective therapeutic agent in the treatment of viral infection. Here we established a fluorescence-based high-content screening model to find small molecules that can stimulate the production of IFN-γ in human Jurkat cells. After a primary screening of 267 natural products, two hits, Astragalus polyphenols and 6-shogaol, were identified to promote the activity of the IFN-γ promoter and subsequently validated by the flow cytometry assay. Obviously, both Astragalus polyphenols and 6-shogaol exhibited potential to induce the transcription and expression of IFN-γ in a dose-dependent manner. These results indicated that our high-content screening model could be a credible and useful platform to contribute to the discovery of novel molecules to promote the expression of IFN-γ and provide leading compounds for the treatment of viral infectious diseases.

Quantification of T-Cell Migratory Phenotypes Using High-Content Analysis

The exploration screening of phenotypic changes in motile T-cells within a signaling environment has always been an arduous task due to the sheer population of these microscopic cells. In recent years, High-Content Analysis (HCA) has gained epochal momentum and has allowed for a wider range of quantitative multiplexed cell-based assays in the field of lymphocyte signaling. In this chapter, we consolidate our understanding and describe the technical approach and methodology to quantify T-cell migratory phenotypes using HCA. Optimizations to be adopted to generate high-quality cytological images of motile T-cells and subsequent analysis using HCA are detailed as well.

High-Content Reporter Assays

While luminescent reporter gene assays allow for a rapid and relatively interference free assessment of the activation state of a luminescent reporter, fluorescent reporters do not. They suffer from artifacts such as compound fluorescence and cellular debris which makes the assessment of whole well fluorescence signals difficult. However, the use of high-content screening allows for the isolation of individual cells, segmentation and thus enables the screener to utilize fluorescent reporters to assess the activation state of such a high-content reporter on a cell by cell level, thus minimizing artifacts. Here we discuss the use of such a high-content reporter that enables screening for compounds useful for HIV reactivation on Jurkat cells with high-content screening.

High content analysis in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating disease characterized by the progressive loss of motor neurons. Neurons, astrocytes, oligodendrocytes and microglial cells all undergo pathological modifications in the onset and progression of ALS. A number of genes involved in the etiopathology of the disease have been identified, but a complete understanding of the molecular mechanisms of ALS has yet to be determined. Currently, people affected by ALS have a life expectancy of only two to five years from diagnosis. The search for a treatment has been slow and mostly unsuccessful, leaving patients in desperate need of better therapies. Until recently, most pre-clinical studies utilized the available ALS animal models. In the past years, the development of new protocols for isolation of patient cells and differentiation into relevant cell types has provided new tools to model ALS, potentially more relevant to the disease itself as they directly come from patients. The use of stem cells is showing promise to facilitate ALS research by expanding our understanding of the disease and help to identify potential new therapeutic targets and therapies to help patients. Advancements in high content analysis (HCA) have the power to contribute to move ALS research forward by combining automated image acquisition along with digital image analysis. With modern HCA machines it is possible, in a period of just a few hours, to observe changes in morphology and survival of cells, under the stimulation of hundreds, if not thousands of drugs and compounds. In this article, we will summarize the major molecular and cellular hallmarks of ALS, describe the advancements provided by the in vitro models developed in the last few years, and review the studies that have applied HCA to the ALS field to date.

Cell-Based Assay Design for High-Content Screening of Drug Candidates

To reduce attrition in drug development, it is crucial to consider the development and implementation of translational phenotypic assays as well as decipher diverse molecular mechanisms of action for new molecular entities. High-throughput fluorescence and confocal microscopes with advanced analysis software have simplified the simultaneous identification and quantification of various cellular processes through what is now referred to as highcontent screening (HCS). HCS permits automated identification of modifiers of accessible and biologically relevant targets and can thus be used to detect gene interactions or identify toxic pathways of drug candidates to improve drug discovery and development processes. In this review, we summarize several HCS-compatible, biochemical, and molecular biology-driven assays, including immunohistochemistry, RNAi, reporter gene assay, CRISPR-Cas9 system, and protein-protein interactions to assess a variety of cellular processes, including proliferation, morphological changes, protein expression, localization, post-translational modifications, and protein-protein interactions. These cell-based assay methods can be applied to not only 2D cell culture but also 3D cell culture systems in a high-throughput manner.

The development of high-content screening (HCS) technology and its importance to drug discovery

INTRODUCTION

High-content screening (HCS) was introduced about twenty years ago as a promising analytical approach to facilitate some critical aspects of drug discovery. Its application has spread progressively within the pharmaceutical industry and academia to the point that it today represents a fundamental tool in supporting drug discovery and development.

AREAS COVERED

Here, the authors review some of significant progress in the HCS field in terms of biological models and assay readouts. They highlight the importance of high-content screening in drug discovery, as testified by its numerous applications in a variety of therapeutic areas: oncology, infective diseases, cardiovascular and neurodegenerative diseases. They also dissect the role of HCS technology in different phases of the drug discovery pipeline: target identification, primary compound screening, secondary assays, mechanism of action studies and in vitro toxicology.

EXPERT OPINION

Recent advances in cellular assay technologies, such as the introduction of three-dimensional (3D) cultures, induced pluripotent stem cells (iPSCs) and genome editing technologies (e.g., CRISPR/Cas9), have tremendously expanded the potential of high-content assays to contribute to the drug discovery process. Increasingly predictive cellular models and readouts, together with the development of more sophisticated and affordable HCS readers, will further consolidate the role of HCS technology in drug discovery.