Cancer cell-derived exosomal circUHRF1 induces natural killer cell exhaustion and may cause resistance to anti-PD1 therapy in hepatocellular carcinoma
Authors: Jia-Cheng Lu
Xiao-Jun Guo
Jia-Bin Cai
Chao Gao
Ai-Wu Ke
Xiao-Yong Huang
Guo-Ming Shi
Peng-Fei Zhang
Journal: Molecular Cancer (2020)
Discipline: MOLECULAR BIOLOGY & GENETICS
Keywords: NK cells; circUHRF1; hepatocellular carcinoma; exosomes; immunosuppression
Affiliations: Liver Cancer Institute, Zhongshan Hospital of Fudan University, 180 Fenglin Road, Shanghai, People's Republic of China, 200032., Key Laboratory of Carcinogenesis and Cancer Invasion, Ministry of Education, Shanghai, 200032, People's Republic of China., Department of Medical Oncology, Zhongshan Hospital, Fudan University, Shanghai, 200032, P.R. China., Liver Cancer Institute, Zhongshan Hospital of Fudan University, 180 Fenglin Road, Shanghai, People's Republic of China, 200032. ., Key Laboratory of Carcinogenesis and Cancer Invasion, Ministry of Education, Shanghai, 200032, People's Republic of China. .

Abstract:  Objective: Natural killer (NK) cells play a critical role in the innate antitumor immune response. Recently, NK cell dysfunction has been verified in various malignant tumors, including hepatocellular carcinoma (HCC). However, the molecular biological mechanisms of NK cell dysfunction in human HCC are still obscure. Methods: The expression of circular ubiquitin-like with PHD and ring finger domain 1 RNA (circUHRF1) in HCC tissues, exosomes, and cell lines was detected by qRT-PCR. Exosomes were isolated from the culture medium of HCC cells and plasma of HCC patients using an ultracentrifugation method and the ExoQuick Exosome Precipitation Solution kit and then characterized by transmission electronic microscopy, NanoSight and western blotting. The role of circUHRF1 in NK cell dysfunction was assessed by ELISA. In vivo circRNA precipitation, RNA immunoprecipitation, and luciferase reporter assays were performed to explore the molecular mechanisms of circUHRF1 in NK cells. In a retrospective study, the clinical characteristics and prognostic significance of circUHRF1 were determined in HCC tissues. Results: Here, we report that the expression of circUHRF1 is higher in human HCC tissues than in matched adjacent nontumor tissues. Increased levels of circUHRF1 indicate poor clinical prognosis and NK cell dysfunction in patients with HCC. In HCC patient plasma, circUHRF1 is predominantly secreted by HCC cells in an exosomal manner, and circUHRF1 inhibits NK cell-derived IFN-γ and TNF-α secretion. A high level of plasma exosomal circUHRF1 is associated with a decreased NK cell proportion and decreased NK cell tumor infiltration. Moreover, circUHRF1 inhibits NK cell function by upregulating the expression of TIM-3 via degradation of miR-449c-5p. Finally, we show that circUHRF1 may drive resistance to anti-PD1 immunotherapy in HCC patients. Conclusions: Exosomal circUHRF1 is predominantly secreted by HCC cells and contributes to immunosuppression by inducing NK cell dysfunction in HCC. CircUHRF1 may drive resistance to anti-PD1 immunotherapy, providing a potential therapeutic strategy for patients with HCC. 

Retracted: No

PubPeer comments:
 These authors found that circUHRF1 could be released in the form of exosomes seems not right. However, the method for purifying exosomes is only by using the ExoQuick Exosome Precipitation Solution, which produced many non-membranes contaminants in the exosomes samples (please see the ISEV standard for extracellular vesicles). For example, as the TME image shown in fig2A, non-membranes particles could be observed clearly. Their data just indicated that circUHRF1 could be present in culture, while whether in exosomes particles or other non-membranous RNA-protein complexes remained missing. Therefore, the author should correct the demonstration. ,