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PD-1 blockade restores impaired function of ex vivo expanded CD8+ T cells and enhances apoptosis in mismatch repair deficient EpCAM+PD-L1+ cancer cells

Authors Kumar R, Yu F, Zhen YH, Li B, Wang J, Yang Y, Ge HX, Hu P, Xiu J

Received 13 December 2016

Accepted for publication 27 May 2017

Published 13 July 2017 Volume 2017:10 Pages 3453—3465


Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Ashok Kumar Pandurangan

Peer reviewer comments 3

Editor who approved publication: Dr Faris Farassati

Rajeev Kumar,1,2 Fang Yu,1 Yuan-Huan Zhen,3 Bo Li,2 Jun Wang,1 Yuan Yang,1,2 Hui-Xin Ge,4 Ping-Sheng Hu,1,2 Jin Xiu1,2

1Clinical Research Centre, The Affiliated Hospital of Guizhou Medical University, Guiyang, People’s Republic of China; 2Cancer Immunology and Immunotherapy Centre, The Affiliated Hospital of Guizhou Medical University, Guiyang, People’s Republic of China; 3Department of Colorectal Surgery, The Affiliated Hospital of Guizhou Medical University, Guiyang, People’s Republic of China; 4Department of Surgery, The Affiliated Cancer Hospital of Guizhou Medical University, Guiyang, People’s Republic of China

Background: Adoptive T cell therapy has been proven to be a promising modality for the treatment of cancer patients in recent years. However, the increased expression of inhibitory receptors could negatively regulate the function and persistence of transferred T cells which mediates T cell anergy, exhaustion, and tumor regression. In this study, we investigated increased cytotoxic activity after the blockade of PD-1 for effective immunotherapy.
Methods: The cytotoxic function of expanded CD8+ CTLs and interactions with tumor cells investigated after blocking of PD-1. Ex vivo expanded CD8+ CTLs were co-cultured with mismatch repair (MMR) stable or deficient (high microsatellite instability [MSI-H]) EpCAM+ tumor cells. The levels of IFN-γ and GrB were detected by enzyme-linked immunosorbent spot assay. Flow cytometry and confocal microscopy were used to assess CD107a mobilization, cytosolic uptake, and cell migration.
Results: A dramatic increase in PD-1 expression on the surface of CD8+ CTLs during ex vivo expansion was observed. PD-1 level was downregulated by approximately 40% after incubation of the CD8+ CTLs with monoclonal antibody which enhanced the secretion of IFN-γ, GrB, and CD107a. Additionally, PD-1 blockade enhanced cell migration and cytosolic exchange between CD8+ CTLs and MMR deficient (MSI-H) EpCAM+PD-L1+ tumor cells.
Conclusion: The blockade of PD-1 enhanced the cytotoxic efficacy of CD8+ CTLs toward MMR deficient tumor cells. In conclusion, we propose that blocking of PD-1 during the expansion of CD8+ CTLs may improve the clinical efficacy of cell-based adoptive immunotherapy.

Keywords: PD-1, CTLs, MSI-H, EpCAM+PD-L1+, cancer immunotherapy

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