A Spheroid Killing Assay by CAR T Cells

Summary

This protocol is designed to assess immunotherapeutic redirected T-cell (CAR T-cell) cytotoxicity against 3D structured cancerous cells (spheroids) in real time.

Abstract

Immunotherapy has become a field of growing interest in the fight against cancer otherwise untreatable. Among all immunotherapeutic methods, chimeric antigen receptor (CAR) redirected T cells obtained the most spectacular results, in particular with pediatric B-acute lymphoblastic leukemia (B-ALL). Classical validation methods of CAR T cells rely on the use of specificity and functionality assays of the CAR T cells against target cells in suspension and in xenograft models. Unfortunately, observations made in vitro are often decoupled from results obtained in vivo and a lot of effort and animals could be spared by adding another step: the use of 3D culture. The production of spheroids out of potential target cells that mimic the 3D structure of the tumor cells when they are engrafted into the animal model represents an ideal alternative. Here, we report an affordable, reliable and easy method to produce spheroids from a transduced colorectal cell line as a validation tool for adoptive cell therapy (exemplified here by CD19 CAR T cells). This method is coupled with an advanced live imaging system that can follow spheroid growth, effector cells cytotoxicity and tumor cell apoptosis.

Introduction

Adoptive cell transfer (ACT) represents the next generation cancer treatment. It relies on the injection of effector cells (T- or NK-cells) into a patient. These cells can be genetically modified with a receptor that will guide them to their target, the tumor, and destroy it. Recently this approach was shown to be feasible when a Chimeric Antigen Receptor (CAR) directed against the B-cell marker CD19 was introduced into the patient T cells to kill his/her cancer¹. In the case of CAR, which is an artificial receptor, the design consists of specific antibody fragments, the antigen binding domain reduced to an entity designated single chain variab....

Protocol

1. Generation of Spheroids from Colorectal Cancer Cell Line

1. Wash HCT 116 (stably transduced to express Cluster of Differentiation 19 (CD19) and Green Fluorescence Protein (GFP)) cell monolayers with phosphate buffered saline (PBS; 5 mL for a 25 cm² or 10 mL for a 75 cm² flask). Add trypsin (0.5 mL for a 25 cm² or 1 mL for a 75 cm² flask) and incubate cells at 37 °C for 5 min.
2. Check cell detachment under a microscope and neutralize cell dissociation enzyme with complete Roswell Park Memorial Institute 160 medium (RPMI 1640) (RPMI 1640 + 10% FCS + Gentamycin; 10 mL for a 25 cm² or 20 mL fo....

Results

As can be seen in Figure 1, it is crucial to check by flow cytometry the level of expression of CD19 CAR on T cells (Figure 1A) and the level of CD19 on HCT116 tumor cell lines (Figure 1B). Figure 2 exemplifies the outcome of a typical spheroid experiment. The automated imaging apparatus takes pictures in four different channels: bright field, phase, green and red fluore.......

Discussion

The use of spheroids as an innovative tool to validate future cancer treatment has become a field of growing interest in the past years. Spheroids represent an intermediate step between classical 2D in vitro analysis and in vivo assessment. The method further holds a lot of promise regarding their potency in terms of tumor micro-environment mimicking as well as gene profiling⁷. The protocol presented in this publication was adapted from Saheen et al.¹¹ to the Incuc.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Dulbecco’s Phosphate Buffered Saline	SIGMA-ALDRICH	D8537-500ML	Lot Number: RNBG7037
75 cm² growth area flasks	VWR	430639	Lot Number: 2218002
75 cm² growth area flasks	VWR	734-2705	Lot Number: 3718006
Trypsin-EDTA	SIGM-ALDRICH	T3924-100ml	Lot Number: SLBTO777
RPMI 1640 med L-glutamin, 10 x 500 mL	Life Technology (Gibco)	21875-091	Lot Number: 1926384
Fetal Bovine Serum	Gibco	10500064	Lot Number: 08Q3066K
Gentamicin	Thermo Fischer	15750060	Lot Number: 1904924A
Trypan Blue Solution, 0.4%	Thermo Fischer	15250061	Lot Number: 1886513
96 well plate, round bottom	VWR	734-1797	Lot Number: 33117036
Dynabeads Human T-Activator CD3/CD28	Thermo Fischer	11132D	-
X-VIVO 15 with Gentamicin L-Gln, Phenol Red, 1 L	BioNordika	BE02-060Q	Lot Number: 8MB036
CTS Immune Cell Serum Replacement	Thermo Fischer	A2596102	Lot Number: 1939319
IL-2 Proleukin	Novartis		Lot Number: 505938M
IncuCyte Annexin V Red Reagent	Essen Bioscience	4641	Lot Number: 17A1025-122117
Reagent Reservoir	VWR	89094-672	Lot Number: 89094-672
15 mL tubes	VWR	734-1867	Lot Number: 19317044
anti-human CD19-PE	BD Biosciences	555413	Lot Number: 4016990 RRID: AB_395813
Biotin-SP (long spacer) AffiniPure F(ab')2 Fragment Goat Anti-Mouse IgG	Jackson ImmunoResearch	115-066-072	Lot Number: 129474: RRID: AB_2338583
Streptavidin-PE	BD Biosciences	554061	Lot Number: 5191579: RRID: AB_10053328
HCT 116 Colorectal Carcinoma Line	ATCC	CCL-247	-
Incucyte S3	Essen Bioscience