Tumor-Derived Extracellular Vesicles Inhibit Natural Killer Cell Function in Pancreatic Cancer

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies. Tumor-derived extracellular vesicles (EVs) induce pre-metastatic niche formation to promote metastasis. We isolated EVs from a highly-metastatic pancreatic cancer cell line and patient-derived primary cancer cells by ultracentrifugation. The protein content of EVs was analyzed by mass spectrometry. The effects of PDAC-derived EVs on natural kill (NK) cells were investigated by flow cytometry. The serum EVs’ TGF-β1 levels were quantified by ELISA. We found that integrins were enriched in PDAC-derived EVs. The expression of NKG2D, CD107a, TNF-α, and INF-γ in NK cells was significantly downregulated after co-culture with EVs. NK cells also exhibited decreased levels of CD71 and CD98, as well as impaired glucose uptake ability. In addition, NK cell cytotoxicity against pancreatic cancer stem cells was attenuated. Moreover, PDAC-derived EVs induced the phosphorylation of Smad2/3 in NK cells. Serum EVs’ TGF-β1 was significantly increased in PDAC patients. Our findings emphasize the immunosuppressive role of PDAC-derived EVs and provide new insights into our understanding of NK cell dysfunction regarding pre-metastatic niche formation in PDAC.

An Immunological Glance on Pancreatic Ductal Adenocarcinoma

“…For example, one common in vitro setting is the retrieval of cell culture supernatants (also called conditioned medium), rich in various factors from the "donor" population, to overlay onto and stimulate a "receiver/target" cell population. Herein, it was demonstrated that exosomes secreted by cancer cells induce expansion of immature myeloid cells [18], M1 and M2 macrophages [19], while inhibiting the function of NK cells [69,70]. These results might explain how the cancer cells contribute to the immune environment that is observed in patients.…”

“…NK cells and their role in preventing relapse after pancreatectomy [67] and metastasis [68] can be mimicked in mouse models, thus offering clues about potential post-pancreatectomy premisses. However, their killing capacity may be hindered by a plethora of signalling molecules (such as TGF-β 1 derived from exosomes, or soluble UL16 binding protein) that promote the escape of cancer cells from the recognition by NK cells [57,[68][69][70]. Intriguingly, PDAC patients harbor a high number of circulating NK cells (CD56 + CD3 − ) in the peripheral blood [57].…”

Extracellular Vesicles and Tumor-Immune Escape: Biological Functions and Clinical Perspectives

“…The presence of TGF-β was also recently observed in EVs from highly metastatic pancreatic cancer cell lines and patient-derived primary cancer cells [52]. Authors show that pancreatic TEVs were able to downregulate the expression of NKG2D, CD107a, TNF-α, and INF-γ in NK cells leading to the impairment of NK cell functions.…”

Pancreatic Adenocarcinoma Invasiveness and the Tumor Microenvironment: From Biology to Clinical Trials

“…Another cell that is able to exert an anti-tumor response is the natural killer (NK) cell. These cells are equipped to recognize and kill cells that are either malignant or infected with virus [ 97 ]. However, PDAC is able “educate” NK cells to prevent them from exerting their cytotoxic function [ 98 , 99 ].…”

“…However, PDAC is able “educate” NK cells to prevent them from exerting their cytotoxic function [ 98 , 99 ]. PDAC cells may impair NK cell function through the secretion of extracellular vesicles containing integrins and immune regulatory factors which may promote the anergy in NK cells to prevent cytotoxic function [ 97 , 99 ].…”