FLI1 Exonic Circular RNAs as a Novel Oncogenic Driver to Promote Tumor Metastasis in Small Cell Lung Cancer.

Abstract

PURPOSE:

The aberrantly upregulated Friend leukemia virus integration 1 (FLI1) is closely correlated with the malignant phenotype of small cell lung cancer (SCLC). It is interesting to note that the CRISPR gene knockout by Cas9 gRNAs that target the FLI1 coding region and the posttranscriptional knockdown by shRNAs that target the 3' region of FLI1 mRNA yielded distinct antimetastasis effects in SCLC cells. This study attempts to examine if FLI1 exonic circular RNAs (FECR) function as a new malignant driver that determines the metastatic phenotype in SCLC.

EXPERIMENTAL DESIGN:

The clinical relevance of FECRs was examined in 56 primary SCLC tissues and 50 non-small cell lung cancer (NSCLC) tissues. The prognostic value of FECRs was examined by measuring serum exosomal FECRs in a longitudinal cohort of patients with SCLC. The oncogenic activity of FECRs was investigated in both SCLC cell lines and animal xenograft studies. Finally, we explored the molecular mechanisms underlying these noncoding RNAs as a malignant driver.

RESULTS:

Therapeutic comparison of CRISPR Cas9 knockout and shRNA knockdown of FLI1 identified FECRs as a new noncanonical malignant driver in SCLC. Using RNA FISH and quantitative PCR, we found that FECR1 (exons 4-2-3) and FECR2 (exons 5-2-3-4) were aberrantly upregulated in SCLC tissues (P < 0.0001), and was positively associated with lymph node metastasis (P < 0.01). Notably, serum exosomal FECR1 was associated with poor survival (P = 0.038) and clinical response to chemotherapy. Silencing of FECRs significantly inhibited the migration in two highly aggressive SCLC cell lines and reduced tumor metastasis in vivo. Mechanistically, we uncovered that FECRs sequestered and subsequently inactivated tumor suppressor miR584-3p, leading to the activation of the Rho Associated Coiled-Coil Containing Protein Kinase 1 gene (ROCK1).

CONCLUSIONS:

This study identifies FLI1 exonic circular RNAs as a new oncogenic driver that promotes tumor metastasis through the miR584-ROCK1 pathway. Importantly, serum exosomal FECR1 may serve as a promising biomarker to track disease progression of SCLC.

• Authors: Lingyu Li, Wei Li, Naifei Chen, Haixin Zhao, Guang Xu, Yijing Zhao, Xin Pan, Xiaoying Zhang, Lei Zhou, Dehai Yu, Ailing Li, Ji-Fan Hu, Jiuwei Cui
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 25 Issue 4 Pg. 1302-1317 (02 15 2019) ISSN: 1557-3265 [Electronic] United States
• PMID: 30429198 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: ©2018 American Association for Cancer Research.

Chemical References

• FLI1 protein, human
• MIRN584 microRNA, human
• MicroRNAs
• Proto-Oncogene Protein c-fli-1
• RNA, Circular
• RNA, Small Interfering
• ROCK1 protein, human
• rho-Associated Kinases

Topics

• A549 Cells
• Animals
• Apoptosis (genetics)
• CRISPR-Cas Systems (genetics)
• Carcinoma, Non-Small-Cell Lung (blood, genetics, pathology)
• Cell Cycle (genetics)
• Cell Movement (genetics)
• Cell Proliferation (genetics)
• Exons (genetics)
• Exosomes (genetics)
• Heterografts
• Humans
• Mice
• MicroRNAs (genetics)
• Neoplasm Metastasis
• Proto-Oncogene Protein c-fli-1 (antagonists & inhibitors, genetics)
• RNA, Circular (genetics, isolation & purification)
• RNA, Small Interfering (genetics)
• Small Cell Lung Carcinoma (blood, genetics, pathology)
• rho-Associated Kinases (genetics)