1 / 2

Inhibition of The Secretion of Tumor Exosomes PD-L1 May Become An Important Anti-cancer Target – MD Anderson Report

https://www.creative-biogene.com/blog/index.php/2018/07/29/inhibition-of-the-secretion-of-tumor-exosomes-pd-l1-may-become-an-important-anti-cancer-target-md-anderson-report/

Download Presentation

Inhibition of The Secretion of Tumor Exosomes PD-L1 May Become An Important Anti-cancer Target – MD Anderson Report

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Inhibition of The Secretion of Tumor Exosomes PD- L1 May Become An Important Anti-cancer Target – MD Anderson Report biog No reactions Tumor-microenvironment interactions play an important role in tumor progression, metastasis, and therapeutic resistance, and there is increasing evidence that tumor cell-derived exosomes can systematically regulate or reprogram tumor microenvironments through transferring molecules such as microRNAs, mRNAs, and proteins. PD-L1 is a classical immunological surface protein that inhibits the anti-tumor function of T cells by binding to receptor programmed cell death- 1 (PD-1) and effectively protects tumors from immune surveillance. Exosomes are reported to contain certain types of proteins, including membrane proteins that promote cancer metastasis, such as EGFR and MET. As a membrane-bound protein, whether PD-L1 is present in cancer-derived exosomes, or playing a role in tumor progression remains unknown. The researchers applied continuous centrifugation from cell culture supernatants of MDA-MB-231 (231) human breast cancer cells and 4T1 mouse breast tumor cells with PD-L1 expression or PD-L1 knockout (PD-L1 KO) to separate exosomes. Transmission electron microscopy showed that these exosomes were generally spherical and membrane-encapsulated, measuring 30-100 nm. PD-L1 was detected in exosomes isolated from culture supernatants of PD-L1-expressing human breast cancer cells (231-PD-L1) and mouse breast cancer cells (4T1-PD-L1), however, exosomes extracted in 231-PD-L1 KO or 4T1- PD-L1KO cell culture supernatants showed similar levels of exosomal marker proteins CD63 and CD81, but no PD-L1 expression was detected. It is worth noting that treatment of the exosomal secretion inhibitor GW4869 reduced exosome production in 231 cells and levels of PD-L1 in exosomes (eg. reduction of exogenous marker proteins CD63 and CD81 or reduction in total exosome protein), however, there was no effect on PD-L1 expression in cell lysates. In addition, in vitro binding assays revealed that PD-1-Fc protein simultaneously pulled down PD-L1 (exo-PD-L1) and CD81 in 231-PD-L1- derived exosomes. Immunofluorescence (IF) staining of 231 cells and immunohistochemistry (IHC) double staining of human breast cancer tissue demonstrated colocalization of PD-L1 and CD63 in multivesicular (MVB), which is the release of pre- and extracellular exosomes. Precursor form, which further support the presence of PD-L1 in exosomes in vitro and in vivo. In order to assess the biological function of exo-PD-L1, the prime thing researchers want to figure out is whether it can transfer PD-L1 to other cells with low (MCF-7) or no PD-L1 expression (BT549-PD-L1 KO). They detected the transfer of PD-L1 from exo-PD-L1 to MCF7 or BT549-PD-L1 KO cells. The acquisition of PD-L1 protein is not a result of PD-L1 gene expression because of the lack of PD-L1 mRNA in these cells. They also established 231-PD-L1 EGFP cells and visually demonstrated that 231-PD-L1 EGFP-derived exosomes transfer PD-L1 EGFP to BT549 cells. To verify whether this condition also occurred in vivo, they co-injected mouse 4T1-PD-L1 KO cells with exosomes or PBS from 4T1-PD-L1 Flag (EX-PD-L1

  2. Flag), 4T1-PD-L1KO (EX-PD-L1 KO) into the mammary fat pad of BALB/c mice, then tumors were harvested after 5 days. IF staining of tumor tissue sections showed that EX-PD-L1 Flag instead of EX-PD-L1 KO made 4T1-PD-L1 KO cells positive for PD-L1 Flag. Importantly, the results of flow cytometry analysis further revealed that PD-L1 transported by exosomes is located on the surface of target cells and is capable of binding PD-1. The results indicate that exosomes are capable of transferring functional PD-L1 to other cells. The researchers further examined whether exosomal PD-L1 affects T cell function as exosome PD-L1 binds directly to PD-1. The results showed that exo-PD-L1 significantly inhibited the killing effect of T cells on BT549-PD-L1 KO cells. Furthermore, in order to explore whether exo-PD-L1 inhibits CD3/CD28-triggered T cell activation signaling pathway, they induce PD-1 expression to produce T cell blasts by treating peripheral blood mononuclear cells (PBMC) with phytohemagglutinin (PHA). The results indicate that exo-PD-L1 significantly inhibits ERK phosphorylation and NF-κB activation in CD3/CD28-induced T cells, as well as PHA-induced interleukin-2 (IL-2) secretion, in a dose-dependent manner, all of which are indicators of T cell activation. In addition, exo-PD-L1 from other cancer cell lines, such as colon (RKO) and lung (HCC827) cancer cells, involve similar functions in blocking T cell activation. Collectively, these data support exosomal PD-L1 inhibition of T cell activation. https://www.creative-biogene.com/blog/index.php/2018/07/29/inhibition-of-the-secretion-of-tumor-exosomes-pd-l1-may- become-an-important-anti-cancer-target-md-anderson-report/

More Related