Assay and Drug Development Technologies - 27

PERSPECTIVE
Drug Discovery Goes Three-Dimensional:
Goodbye to Flat High-Throughput Screening?
Richard M. Eglen and David H. Randle
Corning Life Sciences, Tewksbury, Massachusetts.
ABSTRACT
Immortalized cells, generated from two-dimensional cell culture
techniques, are widely used in compound screening, lead
optimization, and drug candidate selection. However, such cells
lack many characteristics ofcells in vivo. This could account for
the high failure rates of lead candidates in clinical evaluation.
New approaches from cell biology, materials science, and bioengineering
are increasing the utility ofthree-dimensional (3D)
culture. These approaches have become more compatible with
automation and, thus, provide more physiologically relevant
cells for high-throughput/high-content screening, notably in
oncology drug discovery. Techniques range from simple 3D
spheroids, comprising one or more cell types, to complex
multitissue organoids cultured in extracellular matrix gels or
microfabricated chips. Furthermore, each approach can be
applied to stem cells, such as induced pluripotent stem cells,
thereby providing additional phenotypic relevance and the
exciting potential to enable screening in disease-specific cell
types.
INTRODUCTION
I
n drug discovery, the use of cellular assays is routine,
with strong evidence showing that compound hits and
leads identified from such assays translate into better
candidates for clinical evaluation. Over the past decade,
cell-based screening technology in this area has rapidly
developed in three major directions: (1) novel analytical
technologies used to analyze cell responsiveness in highthroughput
screening (HTS) or high-content screening (HCS)
formats, (2) new approaches to generate and genetically
manipulate the assay cells using, for example, CRISPR-Cas-9
(clustered, regularly interspaced, short palindromic repeats-
CRISPR-associated protein) genome engineering,1 and (3)
increasing the relevance of the cell phenotype used in the
assay to the in vivo situation.2 Indeed, the use of tumorReprinted
with permission from Assay Drug Dev Technol 2015;13(5):262-265.
derived cells has evolved to include broader use of human
primary cells-particularly those derived from stem cell
progenitors.2
Much of cell culture is undertaken in two dimensions (2D).
Has the importance ofthree-dimensional (3D) cell culture now
been recognized in drug discovery?3 The answer is certainly
'yes', given that the limitations of 2D cell culture may contribute
to poor translation of preclinical assays to the clinic.4
The field of3D culture has been the subject ofseveral excellent
reviews.3-10 In this study, we briefly discuss approaches to
culturing cells in 3D for use in HTS/HCS, lead optimization,
and candidate selection.
3D CULTURE
Cells adopt 2D or 3D conformations based on the orientation
of integrin-mediated adhesions to the extracellular matrix
(ECM). Most cell culture, whether in medical research or
drug discovery, is conducted using 2D systems.5 These consist
of cells grown in a monolayer that proliferate on flat polystyrene
or glass surfaces. However, early work with cultured
cells was undertaken with 3D tissue explants, where it was
recognized that the cultures retained many oftheir in vivo-like
phenotypes.8,9 3D cell models have a minimum depth of
50 mm and possess both stroma and structure; two features
absent in 2D cell culture. This preservation of tissue or organoid
structures (notably in tumors) and consequently their
optimal physiological function (such as cell proliferation
rates, interaction with stromal elements, tissue organization,
and drug sensitivity) are important in providing scientists
with better models for conducting drug discovery.8-10
Cell tumor models are based on multicellular layer models
(cell layers grown on porous membranes), matrix-embedded
culture (cells embedded into 3D scaffolds), or multicellular
spheroids.5,11 While there are several 3D cell culture formats,
the use of natural-based ECMs and cell aggregates, such as
spheroids, predominates. Many cells, however, spontaneously
aggregate in spheroids ex vivo, establishing specific
microenvironments and displaying apical and basolateral
polarities similar to those found in vivo. Cellular spheroids
can be generated from many cells, including embryoid
bodies, mammospheres, tumor spheroids, hepatospheres,
and neurospheres.
DOI: 10.1089/adt.2015.647
ª 2022 MARY ANN LIEBERT, INC. ASSAY and Drug Development Technologies 27
Assay and Drug Development Technologies

Table of Contents for the Digital Edition of Assay and Drug Development Technologies
