Objective Dysfunction of endoplasmic reticulum (ER) proteins is closely related to homeostasis disturbance and malignant transformation of hepatocellular carcinoma (HCC). Reticulons (RTN) are a family of ER-resident proteins critical for maintaining ER function. Nevertheless, the precise roles of RTN in HCC remain largely unclear. The aim of the study is to examine the effect of reticulon family member RTN3 on HCC development and explore the underlying mechanisms.
Design Clinical HCC samples were collected to assess the relationship between RTN3 expression and patients’ outcome. HCC cell lines were employed to examine the effects of RTN3 on cellular proliferation, apoptosis and signal transduction in vitro. Nude mice model was used to detect the role of RTN3 in modulating tumour growth in vivo.
Results We found that RTN3 was highly expressed in normal hepatocytes but frequently downregulated in HCC. Low RTN3 expression predicted poor outcome in patients with HCC in TP53 gene mutation and HBV infection status-dependent manner. RTN3 restrained HCC growth and induced apoptosis by activating p53. Mechanism studies indicated that RTN3 facilitated p53 Ser392 phosphorylation via Chk2 and enhanced subsequent p53 nuclear localisation. RTN3 interacted with Chk2, recruited it to ER and promoted its activation in an ER calcium-dependent manner. Nevertheless, the tumour suppressive effects of RTN3 were abrogated in HBV-positive cells. HBV surface antigen competed with Chk2 for RTN3 binding and blocked RTN3-mediated Chk2/p53 activation.
Conclusion The findings suggest that RTN3 functions as a novel suppressor of HCC by activating Chk2/p53 pathway and provide more clues to better understand the oncogenic effects of HBV.
- cell proliferation
- cell death
- signal transduction
Data availability statement
All data relevant to the study are available upon reasonable request. Please contact YR (email: email@example.com) for any enquiries.
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Contributors SS performed all the experiments. SS and YR designed the experiments. PP and LZ collected clinical data and performed the IHC experiments. YS, HW and LC carried out the statistical analysis. SS and YR cowrote the manuscript. JG, YR, JF and WW conceived the project. All authors have approved the final version of the manuscript.
Funding This work was supported by grants from the National Key R&D Program of China (2018YFC0910303), the National Natural Science Fund (31630088, 31370808, 82073245, 31770855, 81572317, 81972257, 31500645), the Shanghai Rising-Star Program (17QA1400300) and China Postdoctoral Science Foundation (2018M640344).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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