Exogenous signaling repairs defective T cell signaling inside the tumor microenvironment for better immunity
Casey Moore, Joonbeom Bae, Longchao Liu, Huiyu Li, Yang-Xin Fu, Jian Qiao
Casey Moore, Joonbeom Bae, Longchao Liu, Huiyu Li, Yang-Xin Fu, Jian Qiao
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Research Article Immunology Oncology

Exogenous signaling repairs defective T cell signaling inside the tumor microenvironment for better immunity

Abstract

It is known that tumor-reactive T cells are initially activated in the draining lymph node, but it is not well known whether and how tumor-infiltrating lymphocytes (TILs) are reactivated in the tumor microenvironment (TME). We hypothesize that defective T cell receptor (TCR) signaling and cosignals in the TME limit T cell reactivation. To address this, we designed a mesenchymal stromal cell–based delivery of local membrane-bound anti-CD3 and/or cosignals to explore their contribution to reactivate T cells inside the TME. Combined anti-CD3 and CD40L rather than CD80 led to superior antitumor efficacy compared with either alone. Mechanistically, TCR activation of preexisting CD8+ T cells synergized with CD40L activation of DCs inside the TME for optimum tumor control. Exogenous TCR signals could better reactivate TILs that then exited to attack distal tumors. This study supplies further evidence that TCR signaling for T cell reactivation in the TME is defective but can be rescued by proper exogenous signals.

Authors

Casey Moore, Joonbeom Bae, Longchao Liu, Huiyu Li, Yang-Xin Fu, Jian Qiao

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Figure 3

Exogenous TCR engager compliments endogenous antigen presentation for optimal T cell activation.

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Exogenous TCR engager compliments endogenous antigen presentation for op...
(A) C57BL/6J mice were inoculated with 1 × 106 MC38 tumor cells and treated peritumorally (p.t.) on the left (L) or right (R) side with 1 × 106 MSC, MSC-CD3-CD40L (both L) or MSC-CD3 (R), and MSC-CD40L (L) on days 11, 14, and 17. (B) MSC, BMDC, and OT-I T cells were cocultured at a 1:1:10 ratio with or without OVA protein or α-CD40L blocking antibody for 48 hours, and IFN-γ in the supernatant was measured by cytometric bead array (CBA). (C) Schematic of experimental design for results from D and Supplemental Figure 4B. BMDC (10,000) were cocultured with OT-I CD8+ T cells purified from mouse spleen (100,000) with increasing concentrations of OVA peptide (0, 4, 20, 100 μg/mL) for 48 hours. Supernatant from coculture wells was collected for Supplemental Figure 4B, and OT-I CD8+ T cells were pooled from triplicate wells, washed, and reseeded onto MSC or MSC-CD3 for 48 hours. (D) IFN-γ production after additional 48 hours of coculture. Data are presented as mean ± SEM from a representative experiment (n = 5 [A] and n = 3 [B and D]) of 2 independent experiments. Statistical analysis was performed using 2-way ANOVA (A, B, and D) with Holm-Šidák multiple-comparison test (B and D). ****P ≤ 0.0001, ***P ≤ 0.001, *P ≤ 0.05.