Endoplasmic reticulum stress‐induced exosomal miR‐27a‐3p promotes immune escape in breast cancer via regulating PD‐L1 expression in macrophages
Authors: Xinghua Zhang
Yulin Xu
Yi Tu
Feng Yao
Xiaoli Yao
Yueyue Guo
Journal: Journal of Cellular and Molecular Medicine (2020)
Discipline: MOLECULAR BIOLOGY & GENETICS
Keywords: MicroRNA-27a-3p; breast cancer; endoplasmic reticulum; exosomes; macrophages
Affiliations: Department of Breast and Thyroid Surgery Renmin Hospital of Wuhan University Wuhan China, Department of Thoracic Surgery Renmin Hospital of Wuhan University Wuhan China

Abstract:  Immune escape of breast cancer cells contributes to breast cancer pathogenesis. Tumour microenvironment stresses that disrupt protein homeostasis can produce endoplasmic reticulum (ER) stress. The miRNA-mediated translational repression of mRNAs has been extensively studied in regulating immune escape and ER stress in human cancers. In this study, we identified a novel microRNA (miR)-27a-3p and investigated its mechanistic role in promoting immune evasion. The binding affinity between miR-27a-3p and MAGI2 was predicted using bioinformatic analysis and verified by dual-luciferase reporter assay. Ectopic expression and inhibition of miR-27a-3p in breast cancer cells were achieved by transduction with mimics and inhibitors. Besides, artificial modulation of MAGI2 and PTEN was done to explore their function in ER stress and immune escape of cancer cells. Of note, exosomes were derived from cancer cells and co-cultured with macrophages for mechanistic studies. The experimental data suggested that ER stress biomarkers including GRP78, PERK, ATF6, IRE1α and PD-L1 were overexpressed in breast cancer tissues relative to paracancerous tissues. Endoplasmic reticulum stress promoted exosome secretion and elevated exosomal miR-27a-3p expression. Elevation of miR-27a-3p and PD-L1 levels in macrophages was observed in response to exosomes-overexpressing miR-27a-3p in vivo and in vitro. miR-27a-3p could target and negatively regulate MAGI2, while MAGI2 down-regulated PD-L1 by up-regulating PTEN to inactivate PI3K/AKT signalling pathway. Less CD4+ , CD8+ T cells and IL-2, and T cells apoptosis were observed in response to co-culture of macrophages and CD3+ T cells. Conjointly, exosomal miR-27a-3p promotes immune evasion by up-regulating PD-L1 via MAGI2/PTEN/PI3K axis in breast cancer. 

Retracted: No

PubPeer comments:
 Pointed out to me by a reader. The Flow Cytometry images in this paper appear to look incorrect. Normally, the colors of the dots indicate the density of the dots, with dark blue dots on the bottom and red dots as the top layer. But in some of the panels, the colors appear in the wrong order, suggesting these might not have been drawn by the software. Here, for example, is Figure 3A. In the left panel, some turquoise dots are floating in the void, while they should always be on top of dark blue dots. Pointed out by me with turquoise arrows. In the right panel, the yellow dots appear to float on top of the red dots, while the red dots should have been on top. ![file] Here are some panels in Figure 4C. More turquoise and green dots hovering over empty spaces: ![file] And in Figure 7A, there are a green and a turquoise dot all by themselves. It is like a mountain top floating in the air without a mountain under it. ![file] Could the authors please clarify how they generated these images? ,