Endoplasmic reticulum stress-induced exosomal miR-27a-3p promotes immune escape in breast cancer via regulating PD-L1 expression in macrophages.

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.

Yao X ，Tu Y ，Xu Y ，Guo Y ，Yao F ，Zhang X ... -  《-》

Endoplasmic Reticulum Stress Causes Liver Cancer Cells to Release Exosomal miR-23a-3p and Up-regulate Programmed Death Ligand 1 Expression in Macrophages.

Endoplasmic reticulum (ER) stress promotes tumor cell escape from immunosurveillance. However, the underlying mechanisms remain unknown. We hypothesized that ER stress induces hepatocellular carcinoma (HCC) cells to release exosomes, which attenuate antitumor immunity by modulating the expression of programmed death ligand 1 (PD-L1) in macrophages. In this study, we demonstrated that expression of several ER stress markers (glucose-regulated protein 78, activating transcription factor 6, protein kinase R-like ER kinase, and inositol-requiring enzyme 1α) was up-regulated in HCC tissues and negatively correlated with the overall survival and clinicopathological scores in patients with HCC. Expression of ER stress-related proteins positively correlated with CD68+ macrophage recruitment and PD-L1 expression in HCC tissues. High-throughput sequencing analysis identified miR-23a-3p as one of the most abundant microRNAs in exosomes derived from tunicamycin (TM)-treated HCC cells (Exo-TMs). miR-23a-3p levels in HCC tissues negatively correlated with overall survival. Treatment with Exo-TMs up-regulated the expression of PD-L1 in macrophages in vitro and in vivo. Bioinformatics analysis suggests that miR-23a-3p regulates PD-L1 expression through the phosphatase and tensin homolog (PTEN)-phosphatidylinositol 3-kinase-protein kinase B (AKT) pathway. This notion was confirmed by in vitro transfection and coculture experiments, which revealed that miR-23a-3p inhibited PTEN expression and subsequently elevated phosphorylated AKT and PD-L1 expression in macrophages. Finally, coculture of T cells with Exo-TM-stimulated macrophages decreased CD8+ T-cell ratio and interleukin-2 production but increased T-cell apoptosis in vitro. Conclusion: ER-stressed HCC cells release exosomes to up-regulate PD-L1 expression in macrophages, which subsequently inhibits T-cell function through an exosome miR-23a-PTEN-AKT pathway. Our findings provide insight into the mechanism how tumor cells escape from antitumor immunity.

Liu J ，Fan L ，Yu H ，Zhang J ，He Y ，Feng D ，Wang F ，Li X ，Liu Q ，Li Y ，Guo Z ，Gao B ，Wei W ，Wang H ，Sun G ... -  《-》

LncRNA MALAT1 promotes tumorigenesis and immune escape of diffuse large B cell lymphoma by sponging miR-195.

PD-L1 enhanced the tumorigenesis and immune escape abilities of cancers. The upstream mechanisms of PD-L1 in regulating tumorigenesis and immune escape of diffuse large B cell lymphoma (DLBCL) remained unclear. Human DLBCL cell line OCI-Ly10 and DLBCL patient samples were used in this study. MALAT1 was knocked down by shRNA. MiR-195 was inhibited by miR-195 inhibitor. Levels of MALAT1, PD-L1, miR-195 and CD8 were detected by RT-qPCR. Protein levels of PD-L1, Ras, p-ERK1/2, ERK1/2, Slug, E-cadherin, N-cadherin, Vimentin were detected by western blotting. The interaction between MALAT1 and miR-195, miR-195 and PD-L1 were detected by luciferase assay. OCI-Ly10 cell proliferation and apoptosis were detected by MTT and Annexin V/PI assays, respectively. Migration was detected by transwell assay. Cytotoxicity of CD8+ T cells was detected by LDH cytotoxicity kit. Proliferation and apoptosis of CD8+ T cell co-cultured with OCI-Ly10 cells were analyzed by CFSE and Annexin V/PI staining. MALAT1, PD-L1 and CD8 were up-regulated in DLBCL tissues while miR-195 was down-regulated. MiR-195 was negatively correlated with MALAT1 and PD-L1. MALAT1 could sponge miR-195 to regulate the expression of PD-L1. shMALAT1 treatment increased miR-195 level and decreased PD-L1 level. It also inhibited cell proliferation, migration and immune escape ability while increased apoptosis ratio of OCI-Ly10 cells. shMALAT1 treatment in OCI-Ly10 cells also promoted proliferation and inhibited apoptosis of CD8+ T cells. Knocking down of MALAT1 also suppressed EMT-like process via Ras/ERK signaling pathway. These effects were all rescued by miR-195 inhibitor. Long non-coding RNA MALAT1 sponged miR-195 to regulate proliferation, apoptosis and migration and immune escape abilities of DLBCL by regulation of PD-L1.

Wang QM ，Lian GY ，Song Y ，Huang YF ，Gong Y ... -  《-》

[Plasma exosomal miR-335-5p serves as a diagnostic indicator and inhibits immune escape in triple-negative breast cancer].

Chen T ，Dong Y ，Wu X 《-》

Transforming growth factor beta orchestrates PD-L1 enrichment in tumor-derived exosomes and mediates CD8 T-cell dysfunction regulating early phosphorylation of TCR signalome in breast cancer.

Tumor cells promote immune evasion through upregulation of programmed death-ligand 1 (PD-L1) that binds with programmed cell death protein 1 (PD1) on cytotoxic T cells and promote dysfunction. Though therapeutic efficacy of anti-PD1 antibody has remarkable effects on different type of cancers it is less effective in breast cancer (BC). Hence, more details understanding of PD-L1-mediated immune evasion is necessary. Here, we report BC cells secrete extracellular vesicles in form of exosomes carry PD-L1 and are highly immunosuppressive. Transforming growth factor beta (TGF-β) present in tumor microenvironment orchestrates BC cell secreted exosomal PD-L1 load. Circulating exosomal PD-L1 content is highly correlated with tumor TGF-β level. The later also found to be significantly associated with CD8+CD39+, CD8+PD1+ T-cell phenotype. Recombinant TGF-β1 dose dependently induces PD-L1 expression in Texos in vitro and blocking of TGF-β dimmed exosomal PD-L1 level. PD-L1 knocked down exosomes failed to suppress effector activity of activated CD8 T cells like tumor exosomes. While understanding its effect on T-cell receptor signaling, we found siPD-L1 exosomes failed to block phosphorylation of src family proteins, linker for activation of T cells and phosphoinositide phospholipase Cγ of CD8 T cells more than PD-L1 exosomes. In vivo inhibition of exosome release and TGF-β synergistically attenuates tumor burden by promoting Granzyme and interferon gamma release in tumor tissue depicting rejuvenation of exhausted T cells. Thus, we establish TGF-β as a promoter of exosomal PD-L1 and unveil a mechanism that tumor cells follow to promote CD8 T-cell dysfunction.

Chatterjee S ，Chatterjee A ，Jana S ，Dey S ，Roy H ，Das MK ，Alam J ，Adhikary A ，Chowdhury A ，Biswas A ，Manna D ，Bhattacharyya A ... -  《-》