Ingenium 2020
Tumor derived exosomes regulate dendritic cell maturation and activation Rosh Bharthia, Carolina M. Gorgulhoa, Nils Ludwigb,c, Theresa L. Whitesidee, Michael T. Lotzea, c-f DAMP Laboratory, UPMC Hillman Cancer Center, Pittsburgh, PA, bDepartment of Pathology, cUPMC Hillman Cancer Center, Pittsburgh, PA, dDepartment of Immunology, e Department of Pathology, fDepartment of Bioengineering, University of Pittsburgh, Pittsburgh, PA a
Rosh Bharthi
Rosh Bharthi is a bioengineering undergraduate at the Swanson School of Engineering. His current research interests include exosomes and how they play a role in tumor immunology. After graduating, he plans on attending medical school while still continuing his experience in bioengineering and research.
Michael T. Lotze, MD, is Professor of Surgery, Immunology, and Bioengineering; Vice Chair of Research within the Department of Surgery; Director of the DAMP Laboratories at the UPMC Hillman Cancer Center. His research work includes modern immunotherapy and gene therapy, Michael T. Lotze dendritic cell and cytokine therapies, and investigation of the role of mitochondria, metabolism, and unscheduled cell death in cancer. Dr. Lotze is the co-inventor of 10 patents in dendritic cell vaccines and antigen discovery and serves as associate editor of the Journal of Immunotherapy; he is also an award-winning NCI-trained scientist (1978-1990), the inaugural Director of Surgical Oncology at Pitt (1990-2000), former Vice President of Research at GlaxoSmithKline (2001), founding director of the UPCI Academy, former Chief Scientific Officer at Lion/Iovance Biotherapeutics and innovative educator as a prolific scientist/ tumor immunologist with over 500 publications and several books.
Significance Statement
It was initially unknown whether HMGB1-containing exosomes could trigger a dendritic cell response, potentially causing chronic inflammation. Understanding this would explain another mechanism for how cancer and chronic inflammation are related. From this study, exosomes do not contain HMGB1 nor do they stimulate dendritic cells. While this disproves the idea of tumor-derived exosomes causing chronic inflammation, the fact that tumor-derived exosomes did not activate dendritic cells could imply that exosomes are a potential vehicle for delivering antigens without stressing the immune system.
Category: Experimental research
Keywords: Tumor-derived exosomes, HMGB1, dendritic cells
Abstract
Exosomes are nanovesicles ranging from around 50nm150nm that can carry various types of molecules, such as signaling molecules, lipids, and nucleic acids. In the context of cancer, exosomes are responsible for modulating the tumor microenvironment and signaling nearby cells to allow tumor development. HMGB1 is a damage-associated molecular pattern (DAMP) molecule known to be secreted by tumor cells and promote chronic inflammation when continually present in the body; some studies have also shown that HMGB1 is contained in exosomes. It has not been shown whether HMGB1 contained in exosomes can be responsible for causing dendritic cells to become activated, and thus starting the inflammation pathway. Exosomes were isolated from cell culture supernatants and characterized. Afterwards, Western blots were run to examine protein cargo, including but not limited to HMGB1, and flow analysis was used to determine whether exosomes from tumors might activate or suppress dendritic cells. HMGB1 was not present in exosomes, but RAGE and SQSTM-1/p62 was found to be present. Furthermore, exosomes inhibit dendritic cells, but not to the same magnitude that their corresponding tumor cells do.
1. Introduction
Exosomes are nanovesicles secreted by cells. They are formed by the cell membrane involuting and forming a vesicle inside the cytoplasm. This vesicle is then involuted once more, forming a multivesicular body (MVB), which contains many vesicles within it [1]. The MVB then fuses with the cell membrane, releasing the numerous exosome vesicles within. This pathway is mainly to package ubiquitinated proteins in exosomes and release them from the cell [2]. While exosomes were initially considered as a waste secretion system, research has shown that exosomes can carry a wide variety of cargo, such as lipids, proteins, mRNA, and miRNA which can then be taken up by nearby cells, thus acting as a signaling system [2]. The implications of this signaling system could be generalized to various physiological phenomena, such as angiogenesis. Exosomes play an important role in the context of the immune system and tumor immunology. Research has shown that exosomes secreted by antigen-presenting cells (APCs) are able to activate immune responses based on MHC-peptide complexes found on the surface of exosomes [3]. Additionally, Regulatory T cells (Tregs) release exosomes that suppress production of T cells [4]. Tumor-derived exosomes (TEX) can both stimulate and inhibit an immune response. These exosomes carry inhibitory proteins typically released by the tumor cells which can prevent activation of T cells [5]. On the other hand, TEX contain factors capable of stimulating APCs [5]. From these examples, it is clear that exosomal cargo plays a role in modulating the immune response, and understanding how this signaling works or could be utilized is crucial. It is known that HMGB1, a notable example of a damageassociated molecular patterns or DAMP, released from tumor cells can lead to chronic inflammation and that chronic inflammation 7
