Multifactorial T-cell Hypofunction That Is Reversible Can Limit the Efficacy of Chimeric Antigen Receptor–Transduced Human T cells in Solid Tumors

Abstract

Purpose Immunotherapy using vaccines or adoptively transferred tumor infiltrating lymphocytes (TILs) is limited by T cell functional inactivation within the solid tumor microenvironment. The purpose of this study was to determine if a similar tumor-induced inhibition occurred with genetically-modified cytotoxic T cells expressing chimeric antibody receptors (CARs) targeting tumor-associated-antigens. Methods Human T cells expressing CAR targeting mesothelin or fibroblast activation protein and containing CD3ζ and 4-1BB cytoplasmic domains were intravenously injected into immunodeficient mice bearing large, established human mesothelin- expressing flank tumors. CAR TILs were isolated from tumors at various time points and evaluated for effector functions and status of inhibitory pathways. Results CAR T cells were able to traffic into tumors with varying efficiency and proliferate. They were able to slow tumor growth, but did not cause regressions or cures. The CAR TILs underwent rapid loss of functional activity that limited their therapeutic efficacy. This hypofunction was reversible when the T cells were isolated away from the tumor. The cause of the hypofunction appeared to be multifactorial and was associated with upregulation of intrinsic T cell inhibitory enzymes (diacylglycerol kinase and SHP-1) and the expression of surface inhibitory receptors (PD-1, LAG3, TIM3, 2B4). Conclusions Advanced generation human CAR T cells are reversibly inactivated within the solid tumor microenvironment of some tumors by multiple mechanisms. The model described here will be an important tool for testing T cell-based strategies or systemic approaches to overcome this tumor-induced inhibition. Our results suggest that PD-1 pathway antagonism may augment human CAR T cell function.

Adenovirus Improves the Efficacy of Adoptive T-cell Therapy by Recruiting Immune Cells to and Promoting Their Activity at the Tumor

“…Although CD19-expressing hematologic malignancies in particular seem amenable to adoptive chimeric antigen receptor (CAR) T-cell therapy (2), efficacy in solid tumors is lacking possibly due to T-cell hypofunction (3)(4)(5). Recently, several approaches have been developed to improve the activity of genetically redirected antitumor T cells in solid tumors, with the main focus being on modification of T-cell costimulatory genes, receptor affinities, and optimal target molecules (3,4).…”

Chimeric antigen receptor T cells are vulnerable to immunosuppressive mechanisms present within the tumor microenvironment

“…4 In contrast to prior studies with a different 5,6 tumor outgrowth was delayed but no regressions were seen. One explanation for this finding could be that the tumors underwent a process of "immunoediting" in which they downregulated or lost mesothelin expression allowing for the outgrowth of antigennegative tumor variants.…”

Targeting the PD-1/PD-L1 axis in multiple myeloma: a dream or a reality?

“…A potential concern is that ligation of PD-1 on the CAR T cell will induce anergy. 68 Preclinical models have demonstrated enhanced efficacy of a CAR T cell administered in conjunction with PD-1 antibody. 69 Concerns remain regarding potential toxicity as a result of overexcitation of immune effectors.…”