The Fusion Circular RNA F-circEA1 Promotes Non-small Cell Lung Carcinoma Progression through ALK Downstream Signaling

Abstract Background Circular RNA has a stable closed structure, which plays an important role in the occurrence and development of tumors. However, there are no reports on the relationship between fusion circular RNA and EML4-ALK variant 1, or their underlying molecular mechanisms in non-small cell lung carcinoma (NSCLC). Methods To test F-circEA1 in NCI-H3122 cells (carrying the EML4-ALK variant 1 gene) by RT-PCR, FISH and Sanger sequencing; To determine cell proliferation with a CCK-8 assay. Transwell experiments were used to detect cell migration and invasion. Cell cycle stage and apoptosis were detected by flow cytometry. The sensitivity of cells to crizotinib was tested using a CCK-8 assay. RT-PCR and western blots were used to measure the expression of EML4-ALK1 and downstream signaling factors associated with ALK. Subcutaneously transplanted tumors were used in nude mice to determine the effect of F-circEA1 on tumor formation and the expression of EML4-ALK1 by immunohistochemistry. Statistical analyses were carried by GraphPad Prism 8.0 and differences between groups were compared using Student's t test. Difference with p value <0.05 is statistically significant.Results F-circEA1 was present both in the cytoplasm and nucleus of NCI-H3122 cells. F-circEA1 was contributed to cell proliferation, metastasis, invasion. F-circEA1 induced cell arrest, promoted cell apoptosis and improved drug sensitivity to crizotinib. After knockdown with F-circEA1, subcutaneously transplanted tumors in nude mice grew slowly, the expression of EML4-ALK1 in tumor tissues decreased significantly. The mRNA and protein levels of EML4-ALK1 decreased after knockdown of F-circEA1 but increased after its overexpression. The protein expression of downstream ALK signaling factors increased after overexpression of F-circEA1, but not at the mRNA level.Conclusions We have confirmed a potential carcinogenenic and therapeutic role for F-circEA1 in NSCLC. Our experimental results may provide a new biomarker, treatment method, and prognostic monitoring index for use in the clinic.

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CELF2 suppresses non-small cell lung carcinoma growth by inhibiting the PREX2-PTEN interaction

Carcinogenesis ◽

10.1093/carcin/bgz113 ◽

2019 ◽

Vol 41 (3) ◽

pp. 377-389 ◽

Cited By ~ 3

Author(s):

Yiu To Yeung ◽

Suyu Fan ◽

Bingbing Lu ◽

Shuying Yin ◽

Sen Yang ◽

...

Keyword(s):

Cell Proliferation ◽

Phosphatase Activity ◽

Lung Carcinoma ◽

Rna Binding ◽

Small Cell Lung Carcinoma ◽

Small Cell ◽

Low Grade ◽

Small Cell Lung ◽

Cell Lung Carcinoma ◽

Human Cancers

Abstract The phosphoinositide 3-kinase (PI3-K)/Akt signaling pathway is important in the regulation of cell proliferation through its production of phosphatidylinositol 3,4,5-triphosphate (PIP3). Activation of this pathway is frequently observed in human cancers, including non-small cell lung carcinoma. The PI3-K/Akt pathway is negatively regulated by the dual-specificity phosphatase and tensin homolog (PTEN) protein. PTEN acts as a direct antagonist of PI3-K by dephosphorylating PIP3. Studies have shown that PTEN phosphatase activity is inhibited by PREX2, a guanine nucleotide exchanger factor (GEF). Multiple studies revealed that CELF2, an RNA binding protein, cooperates synergistically with PTEN as a tumor suppressor in multiple cancers. However, the underlying mechanism as to how CELF2 enhances PTEN activity remains unclear. Here, we report that CELF2 interacts with PREX2 and reduces the association of PREX2 with PTEN. Consistent with this observation, PTEN phosphatase activity is upregulated with CELF2 overexpression. In addition, overexpression of CELF2 represses both Akt phosphorylation and cell proliferation only in the presence of PTEN. In an ex vivo study, CELF2 gene delivery could significantly inhibit patient-derived xenografts (PDX) tumor growth. To further investigate the clinical relevance of this finding, we analyzed 87 paired clinical lung adenocarcinoma samples and the results showed that CELF2 protein expression is downregulated in tumor tissues and associated with poor prognosis. The CELF2 gene is located on the chromosome 10p arm, a region frequently lost in human cancers, including breast invasive carcinoma, low-grade glioma and glioblastoma. Analysis of TCGA datasets showed that CELF2 expression is also associated with shorter patient survival time in all these cancers. Overall, our work suggests that CELF2 plays a novel role in PI3-K signaling by antagonizing the oncogenic effect of PREX2.

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