Suppressing T cell motility induced by anti–CTLA-4 monotherapy improves antitumor effects

Abstract

A promising strategy for cancer immunotherapy is to disrupt key pathways regulating immune tolerance, such as cytotoxic T lymphocyte-associated protein 4 (CTLA-4). However, the determinants of response to anti-CTLA-4 mAb treatment remain incompletely understood. In murine models, anti-CTLA-4 mAbs alone fail to induce effective immune responses to poorly immunogenic tumors but are successful when combined with additional interventions, including local ionizing radiation (IR) therapy. We employed an established model based on control of a mouse carcinoma cell line to study endogenous tumor-infiltrating CD8 + T lymphocytes (TILs) following treatment with the anti-CTLA-4 mAb 9H10. Alone, 9H10 monotherapy reversed the arrest of TILs with carcinoma cells in vivo. In contrast, the combination of 9H10 and IR restored MHC class I-dependent arrest. After implantation, the carcinoma cells had reduced expression of retinoic acid early inducible-1 (RAE-1), a ligand for natural killer cell group 2D (NKG2D) receptor. We found that RAE-1 expression was induced by IR in vivo and that anti-NKG2D mAb blocked the TIL arrest induced by IR/9H10 combination therapy. These results demonstrate that anti-CTLA-4 mAb therapy induces motility of TIL and that NKG2D ligation offsets this effect to enhance TILs arrest and antitumor activity. IntroductionThe presence of tumor-infiltrating lymphocytes (TILs) is predictive for a positive outcome in human cancer (1), but relatively little is known about how TILs interact with tumor components in vivo (2). Our understanding of this process is based on studies using mouse models and two-photon laser scanning microscopy (TPLSM) (3). Studies using the OT-1 model system with K b -OVA as an antigen in a T lymphoma context and a single study using endogenous TILs in conjunction with vaccination for a viral antigen in a lung carcinoma setting all found that stable TIL-tumor cell interactions are a feature of tumor rejection (2, 4, 5). Recent FDA approval of anti-CTLA-4-based immunotherapies for treatment of melanoma (6) has raised interest in understanding how non-antigen-specific immunotherapies influence the interactions of TILs and tumor cells. However, there are currently no data on such effects in tumors in vivo.The ability of anti-CTLA-4 mAbs to induce immune-mediated tumor regression and specific T cell memory was first demonstrated in mouse tumor models of relatively immunogenic tumors (7). Significant antitumor activity of anti-CTLA-4 mAbs against poorly immunogenic tumors required combination with additional interventions. Increased priming of antitumor T cells by vaccination and/or other "conditioning" effects of chemotherapy and radiotherapy were a prerequisite for effective anti-CTLA-4 mAb-mediated antitumor immunity in the setting of poorly immunogenic tumors (8-10).

Cytotoxic T Lymphocyte Antigen-4 Blockade Enhances Antitumor Immunity by Stimulating Melanoma-Specific T-cell Motility

“…injection of a-CTLA-4 antibodies during the course of imaging). The results from both lines of experiments showed that a-CTLA-4 antibodies seem to increase T-cell motility and are consistent with the results of several published reports (16,17,23).…”

“…2B-E). These results are consistent with published data on the effects of a-CTLA-4 antibodies on T-cell mobility (16,17).…”

“…3E). These data are consistent with published reports (16,17) and suggest that large amounts of a-CTLA-4 antibodies can relatively quickly stimulate tumor-specific Tcell mobility in TDLNs, but not in tumors.…”

“…Despite the general agreement in the field of cancer immunotherapy that a-CTLA-4 antibodies mediate their antitumor effects either via blockade of inhibitory signaling on effector T cells or by depletion of Tregs, several recent reports have suggested that the antibodies actually deliver an inhibitory signal to effector T cells (16,17). The first study to propose this model of CTLA-4-mediated inhibition, known as the reversal of the TCR stop signal by CTLA-4, used microscopy to show that administration of a-CTLA-4 antibodies increases T-cell motility, both in vitro and in vivo (17).…”

“…Most recently, a study investigated the effects of CTLA-4 blockade alone or in combination with radiotherapy on the dynamics of a polyclonal population of CXCR6 þ tumor-infiltrating lymphocytes (TIL; ref. 16). Because checkpoint blockade is known to affect TIL composition and tumors have been shown to contain both tumor-specific and nonspecific T cells (13), the direct effects of a-CTLA-4 antibodies on tumor-specific immune responses have yet to be determined.…”