Abstract 4101: Control of orthotopic melanoma and breast tumor growth and metastases is achieved by alphav beta3 CAR T cells and is augmented via PD-1 blockade
Authors: Cobb Dustin A. , Mollica Philip , Liu Lixia , Dziegielewska Barbara , Lee Daniel W. 
Published: April 2023

Abstract
Purpose: The purpose of this study was to determine the efficacy of αvβ3 CAR T cells deployed against melanoma and triple-negative breast cancer tumors, two malignancies recognized for harnessing the αvβ3 pathway for angiogenic and invasion purposes.
Procedures: CAR T cells expressing an anti-αvβ3 scFv containing either a CD28 or 4-1BB co-stimulatory domain and CD3zeta were generated by retroviral transduction. In vitro cytotoxicity of αvβ3 CAR T cells was assessed by co-culture with melanoma or breast tumor cells and evaluated by impedance-based real-time cell analysis and effector cytokine production by ELISA. Xenograft studies, including melanoma and orthotopic breast tumors, were carried out in NSG mice to evaluate in vivo efficacy of systemically administered αvβ3 CAR T cells. Immunohistochemistry was performed to evaluate T cell infiltration of tumors and changes in the microenvironment. NSG mice implanted with orthotopic tumors were monitored for disease progression and development of metastases using bioluminescent imaging.
Results: αvβ3 CAR T cells exert rapid cytotoxicity and prominent cytokine production against all melanoma and triple-negative breast tumor lines tested. Systemic administration of αvβ3 CAR T cells potently inhibited growth of SK-MEL-28 melanoma xenografts as demonstrated by significant differences in tumor volume relative to control CARs. In orthotopic MD-AMB-231 breast tumors, αvβ3 CAR T cells were able to control tumor growth, prevent the formation of spontaneous lung metastases from the primary tumor, and resulted in improved survival. αvβ3 CAR T cells also mediated control and clearance of established lung metastases established via intravenous injection of breast tumor cells. Histological analysis of tumors at endpoint revealed striking infiltration of residual tumors by T cells in mice administered αvβ3.28z CARs, but to a lesser extent in αvβ3.BBz CAR-treated xenografts. Infiltration was accompanied by tumors up-regulating PD-L1 expression in response to treatment. Coadministration of αvβ3 CAR T cells with anti-PD-1 treatment led to augmentation of the therapeutic response against melanoma tumors.
Conclusions: These studies highlight a renewed potential for targeting integrins, specifically αvβ3, for the treatment of solid tumors. These data suggest that αvβ3 CAR T cell therapy for melanoma can be further improved by combination therapy with checkpoint inhibition. Together with our prior work demonstrating robust efficacy of αvβ3 CAR T cells to treat orthotopic glioblastoma and DIPG, these results highlight the broad applicability of utilizing CAR T cells targeting αvβ3 for treatment of multiple cancer types with reduced risk of on-target, off-tumor toxicity due to the restricted expression of αvβ3 in normal tissues. Results of these studies warrant further development of αvβ3 CAR T cells for clinical use.
Citation Format: Dustin A. Cobb, Philip Mollica, Lixia Liu, Barbara Dziegielewska, Daniel W. Lee. Control of orthotopic melanoma and breast tumor growth and metastases is achieved by alphav beta3 CAR T cells and is augmented via PD-1 blockade. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4101.