Physiologic Patient Derived 3D Spheroids for Anti-neoplastic Drug Screening to Target Cancer Stem Cells

Summary

This protocol describes generation of patient-derived spheroids, and downstream analysis including quantification of proliferation, cytotoxicity testing, flow cytometry, immunofluorescence staining and confocal imaging, in order to assess drug candidates’ potential as anti-neoplastic therapeutics. This protocol supports precision medicine with identification of specific drugs for each patient and stage of disease.

Abstract

In this protocol, we outline the procedure for generation of tumor spheroids within 384-well hanging droplets to allow for high-throughput screening of anti-cancer therapeutics in a physiologically representative microenvironment. We outline the formation of patient derived cancer stem cell spheroids, as well as, the manipulation of these spheroids for thorough analysis following drug treatment. Specifically, we describe collection of spheroid morphology, proliferation, viability, drug toxicity, cell phenotype and cell localization data. This protocol focuses heavily on analysis techniques that are easily implemented using the 384-well hanging drop platform, making it ideal for high throughput drug screening. While we emphasize the importance of this model in ovarian cancer studies and cancer stem cell research, the 384-well platform is amenable to research of other cancer types and disease models, extending the utility of the platform to many fields. By improving the speed of personalized drug screening and the quality of screening results through easily implemented physiologically representative 3D cultures, this platform is predicted to aid in the development of new therapeutics and patient-specific treatment strategies, and thus have wide-reaching clinical impact.

Introduction

Worldwide cancer-related mortality reached a toll of 9.8 million deaths in 2018¹, highlighting the need for the development of improved therapeutics. Unfortunately, the cost of developing cancer drugs is increasing, with the development of a single drug costing approximately 650 million USD² indicating the need for improved strategies to develop new anti-cancer drugs. Cancer stem cells (CSCs), which are characterized by increased chemoresistance³, the capacity to self-renew, and the ability to seed new tumors⁴ are thought to be responsible for tumor recurrence

Protocol

All patient samples are collected under an approved IRB protocol from consenting patients, whose samples are de-identified after tumor debulking and ascites collection.

1. Generation of Spheroids from Small Cell Numbers in 384-well Hanging Drop Plates

1. Place the hanging drop plate in a sonicator filled with sterile deionized (DI) water and sonicate for 20 min.
2. With a gloved hand, remove the plate from the sonicator and wash it with running DI water.
3. Allow the plate to sit in a bath of 0.1% Pluronic acid for 24 h to prevent protein adsorption and spheroid adherence to the wells.
4. Remove plates with a g....

Results

Spheroids formed with cell lines or patient-derived CSCs can be formed with a range of small cell numbers within hanging droplets (Figure 2A). Spheroids form reliably with as few as 10 cells per well, which allows for conservation of rare patient samples. Cells within these spheroids are surrounded by other cells in 3 dimensions as they would be in vivo, allowing for physiologic cell-cell contacts and diffusion rates. Tumor cells within the spheroids proliferate causing the spheroids to expa.......

Discussion

The 384-well hanging drop plate platform for 3D spheroid formation is an easily implemented tool for any cell biology or cancer biology labs. This physiologic platform enables the study of cell lines, as well as, primary patient samples within physiologically relevant 3D cultures while allowing for high throughput drug screening. The platform also ensures that the culture conditions are highly tunable, enabling tight control over plating densities, cell co-culture ratios, extracellular components, and medium composi.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
0.25% trypsin-EDTA	Gibco	ILT25200056
10 mL serological pipet	Fisher Scientific	13-678-11E
10,000 cSt Si oil	Millipore Sigma	63148-62-9	Used to coat spheroid array mold to facilitate removal of tissue processing gels, like Histogel, from the mold.
100 mm tissue culture dish	Thermo Scientific	130182
15 mL conical tube	Celltreat	FL4021
1x DMEM for Serum Free Medium	Gibco	11965-092
1x F12 for Serum Free Medium	Gibco	11765-054
1x phosphate buffered saline (PBS)	Gibco	ILT10010023
4’,6-diamidino-2-phenylindole (DAPI)	Thermo Fisher	D1306
40 µm filter	Fisher Scientific	22363547
6-well plate	Fisher Scientific	353046
Accutase	Innovative Cell Technologies Inc.	1449	A gentle cell detachment enzyme composed of proteolytic and collagenolytic enzymes.
ACK Lysing Buffer	Thermo Scientific	A1049201
alamarBlue	Invitrogen	DAL1025	Resazurin dye used to measure viability and proliferation of cells based on their ability to reduce resazurin to resorufin, which is highly fluorescent.
ALDEFLUOR assay kit	Stem Cell Tech	1700	Kit to identify stem and progenitor cells that express high levels of aldehyde dehydrogenase , an indicator of cancer stem cells. The kit is composed of ALDEFLUOR Reagent, DEAB, Hydrochloric Acid, Dimethylsulphoxide, and ALDEFLUOR Assay Buffer.
ALDEFLUOR Diethylaminobenzaldehyde (DEAB)	Stem Cell Tech	1705	Diethylaminobenzaldehyde (DEAB) is an inhibitor of ALDH isozymes, used to determine non-specific ALDH staining.
Andor iXon x3 CCD Camera	Oxford Instruments	-
Antibiotics and Antimycotics	Gibco	15240-062
APC-isotype IgG2b	Miltenyi biotec	130-092-217	Isotype control to quantify non-specific staining of IgG2b antibodies.
B27 Supplement	Gibco	17504044
basic Fibroblast Growth Factor	Stem Cell Technologies	78003.1
BD Lo-Dose U-100 Insulin Syringes	Fisher Scientific	14-826-79
BioTek Synergy HT Microplate Reader	BioTek	7091000
CD133-APC	Miltenyi biotec	130-113-184	Fluorescent antibody targeting CD133, a cancer stem cell marker.
cellSens Dimension Software	Olympus
Cisplatin	Sigma-Aldrich	P4394	Platinum based chemotherapy agent that functions as an alkylating agent that disrupts DNA.
DAPI (4',6-Diamidino-2-Phenylindole, Dihydrochloride)	Invitrogen	D1306
Epidermal Growth Factor	Gibco	PHG0311
EVOS XL Core Cell Imaging System	Life Technologies	AME3300
Fetal Bovine Serum - premium (FBS)	Atlanta Biologicals	S11150
Ficoll 400	Sigma-Aldrich	F4375
Hemacytometer	Hausser Scientific	1490
Histogel	Thermo Scientific	HG-4000-012	Tissue processing gel that can penetrate and hold the specimen within the gel while preventing discoloration around the specimen upon staining.
Human Adipose-Derived Mesenchymal Stem Cells	Lonza	PT-5006
Human Microvascular Endothelial Cells	Lonza	CC2543
Insulin-Transferrin-Selenium Supplement	Gibco	51500-056
Live/Dead viability kit	Invitrogen	L3224	Kit for the fluorescence based detection of live (calcein-AM) and dead cells (Ethidium Homodimer-1).
MEM Non-essential Amino Acids	Gibco	11140-050
MetaMorph 7.8 Software	Molecular Devices	-
Olympus IX81 Inverted Confocal Microscope	Olympus	-
Olympus IX83 Research Inverted Microscope	Olympus
Parafilm M	Thomas Scientific	7315D35	Thermoplastic polymer strips that serve to limit droplet evaporation in hanging drop plates while still allowing for gas exchange.
Perfecta 3D 384 Well Hanging Drop Plates	3D Biomatrix	HDP1384-8	Available through Sigma-Aldrich
phalloidin AlexaFluor488	Invitrogen	A12379	Phalloidin is a peptide to fluorescently label F-actin in fixed cells.
ProJet 3500 HD Max	3D Systems	-	3D printer
Sterile DI water	Fisher Scientific	353046
Trypan Blue	Gibco	15250061	Azo dye used to differentiate between live and dead cells based on its ability to pass through the damaged membrane of dead cells, but not the intact membrane of live cells.
VisiJet M3 Crystal	3D Systems	-	A biocompatible polymer material for 3D printing.
Yokogawa CSU-X1 Confocal Scanner Unit	Yokogawa	-