Theranostics 2019; 9(12):3526-3540. doi:10.7150/thno.32796

Research Paper

Circular RNAs negatively regulate cancer stem cells by physically binding FMRP against CCAR1 complex in hepatocellular carcinoma

Yan-Jing Zhu1*, Bo Zheng1*, Gui-Juan Luo1*, Xu-Kai Ma2*, Xin-Yuan Lu1, Xi-Meng Lin1, Shuai Yang4, Qing Zhao5, Tong Wu1, Zhi-Xuan Li1, Xiao-Long Liu7, Rui Wu8, Jing-Feng Liu7, Yang Ge9, Li Yang2, Hong-Yang Wang1✉, Lei Chen1,4✉

1. The International Cooperation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai 200438, China.
2. Key Laboratory of Computational Biology, CAS-MPG Partner Institute for Computational Biology, Shanghai Institutes for Biological Sciences, University of Chinese Academy of Science, Chinese Academy of Sciences, Shanghai 200031, China
3. Department of Pathology, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Changhai Road 225, Shanghai 200438, China
4. Fudan University Shanghai Cancer Center; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
5. Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha, Hunan, China.
6. Department of Oncology, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, North Moyu Road 700, Shanghai, China
7. The United Innovation of Mengchao Hepatobiliary Technology Key Laboratory of Fujian Province, Mengchao Hepatobiliary Hospital of Fujian Medical University, Fuzhou 350025, China
8. Department of Biliary Surgery I, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Changhai Road 225, Shanghai 200438, China
9. School of Public Health, Shanghai JiaoTong University, 200240, China
*These authors contributed equally to this work.

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Citation:
Zhu YJ, Zheng B, Luo GJ, Ma XK, Lu XY, Lin XM, Yang S, Zhao Q, Wu T, Li ZX, Liu XL, Wu R, Liu JF, Ge Y, Yang L, Wang HY, Chen L. Circular RNAs negatively regulate cancer stem cells by physically binding FMRP against CCAR1 complex in hepatocellular carcinoma. Theranostics 2019; 9(12):3526-3540. doi:10.7150/thno.32796. Available from http://www.thno.org/v09p3526.htm

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Abstract

Circular RNA (circRNA) possesses great pre-clinical diagnostic and therapeutic potentials in multiple cancers. It has been reported playing roles in multiple malignant behaviors including proliferation, migration, metastasis and chemoresistance. However, the underlying correlation between circRNAs and cancer stem cells (CSCs) has not been reported yet.

Methods: circZKSCAN1 level was detected in HCC tissue microarrays to clarify its prognostic values. Gain and loss function experiments were applied to investigate the role of circZKSCAN1 in HCC stemness. Bioinformatic analysis was used to predict the possible downstream RNA binding protein and further RNA immunoprecipitation sequencing was carried out to identify the RBP-regulated genes.

Results: The absence of circZKSCAN1 endowed several malignant properties including cancer stemness and tightly correlated with worse overall and recurrence-free survival rate in HCC. Bioinformatics analysis and RNA immunoprecipitation-sequencing (RIP-seq) results revealed that circZKSCAN1 exerted its inhibitive role by competitively binding FMRP, therefore, block the binding between FMRP and β-catenin-binding protein-cell cycle and apoptosis regulator 1 (CCAR1) mRNA, and subsequently restrain the transcriptional activity of Wnt signaling. In addition, RNA-splicing protein Quaking 5 was found downregulated in HCC tissues and responsible for the reduction of circZKSCAN1.

Conclusion: Collectively, this study revealed the mechanisms underlying the regulatory role of circZKSCAN1 in HCC CSCs and identified the newly discovered Qki5-circZKSCAN1-FMRP-CCAR1-Wnt signaling axis as a potentially important therapeutic target for HCC treatment.

Keywords: circular RNA, hepatocellular carcinoma, cancer stem cell, RNA-binding protein