Abstract 2314: Pharmacology studies of chimeric antigen receptor (CAR) T cells in luminescent xenograft and 3D in vitro tumor models
Authors: Li Ruyi , Gan Shanshan , Zhang Leixin , Broudy Thomas , Hu Yong 
Published: August 2019

Chimeric antigen receptor (CAR) T cell therapy is a type of immunotherapy that uses a patient’s T cells, engineered with chimeric antigen receptors, to attack the patient’s cancer cells. The U.S. Food and Drug Administration (FDA) has recently approved two CAR T therapies: Yescarta® to treat adults with lymphoma and Kymriah® to treat pediatric and young adult patients with acute lymphoblastic leukemia. With significant efficacy shown in patients, more CAR T cells are being developed at pre-clinical phases with new targets or chimeric antigen designs. This work shows that the efficacy of CAR T cells could be evaluated using xenograft mouse models.

Two investigative studies on CAR T cells were performed, in a lymphoma orthotopic model and an ovarian cancer subcutaneous model. Luciferase-labeled Raji (Raji-luc) cells were injected into immuno-deficient B-NDG mice (Biocytogen), and 9 days after tumor inoculation, CAR T-1 and CAR T-2 were given through single IV injections. About one week later, significant tumor growth inhibition was observed in both CAR T cell treated groups. At Day 37 of post-tumor inoculation, all animals in the control group died, while the CAR T treated group had a 75% survival rate.

The same batch of CAR T cells were tested using BioDuro’s proprietary 3D culture method which is aligned to human tumor microenvironmental conditions (3D-hTME). Raji-luc cells were mixed with CAR T cells at Effector: Target (E: T) ratios of 1:0.5, 1:2 and 1:8, then seeded in semi-gel form 3D culture in 96-well plates. The luminescent signals were read by imager after 4- or 24-hours of incubation at 37oC. Consistent with our in vivo results, the CAR T cells had an increased killing effect on Raji-luc cells, with higher E:T ratio and increased incubation time.

To test CAR T cells in solid tumors, a similar study was done in luciferase-labeled SK-OV-3 (SK-OV-3-luc) subcutaneous xenografts. SK-OV-3-luc cells were inoculated subcutaneously into B-NDG mice and the CAR T treatment was given 9 days later by single IV injection. Tumor volumes were measured with calipers or by luminescent signal using an in vivo imager. The results showed that starting from Day 20, the animals treated with CAR T cells had significantly smaller tumors in comparison to the control animals.

In summary, xenograft models with luciferase-labeled cancer cell lines can be used to investigate the efficacy of experimental CAR T therapies to treat liquid or solid tumors. Additionally, the use of in vitro 3D-hTME culture shows promising results as a potential earlier-stage screen for preclinical assessment of CAR T activity.

Citation Format: Ruyi Li, Shanshan Gan, Leixin Zhang, Thomas Broudy, Yong Hu. Pharmacology studies of chimeric antigen receptor (CAR) T cells in luminescent xenograft and 3D in vitro tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2314.