Targeting miR-23a in CD8+ cytotoxic T lymphocytes prevents tumor-dependent immunosuppression
Regina Lin, … , Bo Zhu, Qi-Jing Li
Regina Lin, … , Bo Zhu, Qi-Jing Li
Published October 27, 2014
Citation Information: J Clin Invest. 2014;124(12):5352-5367. https://doi.org/10.1172/JCI76561.
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Research Article Oncology

Targeting miR-23a in CD8+ cytotoxic T lymphocytes prevents tumor-dependent immunosuppression

Abstract

CD8+ cytotoxic T lymphocytes (CTLs) have potent antitumor activity and therefore are leading candidates for use in tumor immunotherapy. The application of CTLs for clinical use has been limited by the susceptibility of ex vivo–expanded CTLs to become dysfunctional in response to immunosuppressive microenvironments. Here, we developed a microRNA-targeting (miRNA-targeting) approach that augments CTL cytotoxicity and preserves immunocompetence. Specifically, we screened for miRNAs that modulate cytotoxicity and identified miR-23a as a strong functional repressor of the transcription factor BLIMP-1, which promotes CTL cytotoxicity and effector cell differentiation. In a cohort of advanced lung cancer patients, miR-23a was upregulated in tumor-infiltrating CTLs, and expression correlated with impaired antitumor potential of patient CTLs. We determined that tumor-derived TGF-β directly suppresses CTL immune function by elevating miR-23a and downregulating BLIMP-1. Functional blocking of miR-23a in human CTLs enhanced granzyme B expression, and in mice with established tumors, immunotherapy with just a small number of tumor-specific CTLs in which miR-23a was inhibited robustly hindered tumor progression. Together, our findings provide a miRNA-based strategy that subverts the immunosuppression of CTLs that is often observed during adoptive cell transfer tumor immunotherapy and identify a TGF-β–mediated tumor immune-evasion pathway.

Authors

Regina Lin, Ling Chen, Gang Chen, Chunyan Hu, Shan Jiang, Jose Sevilla, Ying Wan, John H. Sampson, Bo Zhu, Qi-Jing Li

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Figure 1

Identification of miR-23a as a negative correlate of CTL effector function.

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Identification of miR-23a as a negative correlate of CTL effector functi...
(A and B) pMel-1 CTLs primed with splenic B cells or LPS-matured bone marrow–derived DCs for 4–6 days were assessed for (A) in vitro cytotoxicity at an E/T ratio of 5:1 and (B) expression of CTL effector molecules. Histograms are representative of n = 3 independent experiments, and the bar graph represents the mean ± SEM of n = 3 independent experiments. (C) After 3 days of in vitro priming by DCs or B cells, pMel-1 CTLs were isolated for miRNA expression profiling. Heat map of miRNAs differentially expressed by DC- and B cell–primed CTLs from n = 3 independent miRNA profiling experiments. Asterisks with miRNAs refer to the passenger strands of the respective miRNA species. (D) Validation of differential miR-23a expression in CTLs under the respective priming conditions with 3 additional batches of samples. Numbers and bar graph represent the mean ± SEM miR-23a expression relative to that of naive CD8+ T cells. (E) DC-primed pMel-1 CTLs were retrovirally transduced with either an empty mock vector or a miR-23a overexpression vector. Three days after transduction, CD8+GFP+ CTL effector molecule expression was assessed by flow cytometry.