Effect of lncRNA THOR on proliferation and migration of colon cancer cells

LncRNA THOR promotes endometrial cancer progression through the AKT and ERK signaling pathways

The long noncoding RNA (lncRNA) THOR is highly conserved and expressed in various human cancer tissues, although its potential role and underlying mechanism in endometrial cancer (EC) remain unknown. This study aims to explore THOR's biological function and molecular mechanism in EC progression. THOR expression in EC tissues and cell lines was detected by quantitative reverse transcription PCR (qRT-PCR) and in situ hybridization (ISH). THOR expression based on The Cancer Genome Atlas (TCGA) and clinical sample analyses was significantly higher in EC tissues than normal tissues, and higher THOR levels were closely associated with poor overall survival in EC. Additionally, a positive correlation between ISH-detected THOR expression and pathological grade was observed. CCK-8, colony formation, and transwell migration and invasion assays revealed that THOR significantly enhances the proliferation, migration, and invasion abilities of EC cells. Moreover, IGF2BP1 protein expression and ERK and AKT protein phosphorylation levels in EC cells increased significantly with THOR overexpression in EC cells. In conclusion, our findings suggest that THOR promotes EC cell growth and invasion, and IGF2BP1-mediated AKT and ERK signaling pathways activation might be involved. Clinically, THOR is significantly expressed in EC, and high THOR expression correlates with poor prognosis, making it a potential prognostic marker for EC.

The Role of Non-Coding RNAs in the Regulation of the Proto-Oncogene MYC in Different Types of Cancer

Alterations in the expression level of the MYC gene are often found in the cells of various malignant tumors. Overexpressed MYC has been shown to stimulate the main processes of oncogenesis: uncontrolled growth, unlimited cell divisions, avoidance of apoptosis and immune response, changes in cellular metabolism, genomic instability, metastasis, and angiogenesis. Thus, controlling the expression of MYC is considered as an approach for targeted cancer treatment. Since c-Myc is also a crucial regulator of many cellular processes in healthy cells, it is necessary to find ways for selective regulation of MYC expression in tumor cells. Many recent studies have demonstrated that non-coding RNAs play an important role in the regulation of the transcription and translation of this gene and some RNAs directly interact with the c-Myc protein, affecting its stability. In this review, we summarize current data on the regulation of MYC by various non-coding RNAs that can potentially be targeted in specific tumor types.

Investigation of the lncRNA THOR in Mice Highlights the Importance of Noncoding RNAs in Mammalian Male Reproduction

THOR is a highly conserved testis-specific long noncoding RNA (lncRNA). The interaction between THOR and the development of the male reproductive system remains unclear. Herein, CRISPR/Cas9 technology was used to establish a stable THOR-deficient mouse model, and the relationship between THOR and the fertility of adult male mice was investigated. The male mice in which THOR was deleted were smaller than the WT male mice. Moreover, their survival rate was reduced by 60%, their fertility was reduced by 50%, their testicular size and sperm motility were reduced by 50%, their testicular cell apoptosis was increased by 7-fold, and their ratio of female-to-male offspring was imbalanced (approximately 1:3). Furthermore, to elucidate the mechanisms of male reproductive system development, the mRNA levels of THOR targets were measured by qRT-PCR. Compared with WT mice, the THOR-deficient mice exhibited significantly decreased mRNA levels of IGF2BP1, c-MYC, IGF1, and IGF2. MEK-ERK signaling pathway expression was downregulated as determined by Western blot. We found that THOR targeted the MER-ERK signaling pathway downstream of IGF2 by binding to IGF2BP1 and affected testicular and sperm development in male mice. These results may also provide perspectives for exploring the roles of lncRNAs in human reproductive development and the pathogenesis and potential therapeutic targets of infertility.

LncRNA LINC00689 Promotes the Tumorigenesis of Glioma via Mediation of miR-526b-3p/IGF2BP1 Axis

Glioma ranks first among the aggressive brain tumors all over the world. LncRNA LINC00689 has been confirmed to play key roles in the progression of cancers, and LINC00689 was upregulated in glioma. However, the biological function of LINC00689 in glioma is unclear. qRT-PCR was applied to detect the expressions of LINC00689 and miR-526b-3p in glioma cells. Dual-luciferase report was performed to examine the relation among LINC00689, miR-526b-3p, and insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1). Then, the growth, migration, and invasion of glioma cells were detected by colony formation, flow cytometry, and transwell assay, respectively. The expressions of p21, cleaved caspase 3, and MAPK signaling-related proteins in glioma cells were tested by western blotting. Finally, xenograft mice model was established to detect the effect of LINC00689 on tumor growth of glioma in vivo. LINC00689 was upregulated in glioma cells, while miR-526b-3p was downregulated. In addition, LINC00689 bound to miR-526b-3p, and IGFBP1 was targeted by miR-526b-3p. Moreover, LINC00689 knockdown or upregulation of miR-526b-3p inhibited the proliferation of glioma cells and induced the apoptosis. Consistently, the migration and invasion of glioma cells were notably reduced by LINC00689 shRNA/miR-526-3p mimics. miR-526b-3p inhibitor or IGF2BP1 upregulation could reverse the effect of LINC00689 knockdown or miR-526b-3p mimics. Finally, knockdown of LINC00689 inhibited the tumor growth of glioma in vivo through regulating miR-526b-3p/IGF2BP1/MAPK axis. In conclusion, silencing of LINC00689 could inhibit the tumorigenesis of glioma via mediation of miR-526b-3p/IGF2BP1 axis. LINC00689 may serve as a new target for the treatment of glioma.

A novel N6-methyladenosine (m6A)-dependent fate decision for the lncRNA THOR

Previous studies have revealed the critical roles of the N6-methyladenosine (m6A) modification of long non-coding RNAs (lncRNAs) in cancers, but the relationship between the oncogenic role of the lncRNA THOR (a representative of cancer/testis lncRNAs) and m6A modification remains unclear. Here, we show that the internal m6A modification of the lncRNA THOR via an m6A-reader-dependent modality regulates the proliferation of cancer cells. Our findings demonstrated that the loss of the lncRNA THOR inhibits the proliferation, migration, and invasion of cancer cells in vitro and in vivo. In addition, m6A is highly enriched on lncRNA THOR transcripts, which contain GA (m6A) CA, GG (m6A) CU, and UG (m6A) CU sequence motifs. RIP-qRT-PCR and RNA pull-down assay results revealed that the specific m6A readers YTHDF1 and YTHDF2 can read the m6A motifs and regulate the stability of the lncRNA THOR (stabilization and decay). These m6A-dependent RNA-protein interactions can maintain the oncogenic role of the lncRNA THOR. Collectively, these findings highlight the critical role of the m6A modification in oncogenic lncRNA THOR and reveal a novel long non-coding RNA regulatory mechanism, providing a new way to explore RNA epigenetic regulatory patterns in the future.

LncRNA LINC00662 promotes colon cancer tumor growth and metastasis by competitively binding with miR-340-5p to regulate CLDN8/IL22 co-expression and activating ERK signaling pathway

BACKGROUND

LncRNA LINC00662 is closely related to the occurrence and development of cancer. This study aims to explore the effect of LINC00662 on colon cancer tumor growth and metastasis and its molecular mechanism.

METHODS

CCK8, colony formation, transwell, scratch wound, TUNEL, flow cytometry, RT-PCR, western blotting and immunohistochemistry assays were used to detect the proliferation, apoptosis, invasion and migration of colon cancer cell and mRNA and protein expressions. Luciferase reporter and RNA pull down assays were used to detect the combination of LINC00662 and miR-340-5p or IL22 and the combination of miR-340-5p and CLDN8/IL22. Co-immunoprecipitation were used to detect the co-expression of CLDN8 and IL22 in colon cell lines. The targets of LINC00662 were predicated by Starbase v2.0. The target genes of miR-340-5p were predicated by miRDB and TargetScan. GO and KEGG enrichment analysis were performed by DAVID website.

RESULTS

LINC00662 was up-regulation in colon cancer tissues and cell lines. Univariate Cox regression analysis showed that the LINC00662 expression level was related to the poor prognosis. LINC00662-WT and miR-340-5p mimics co-transfection depressed luciferase activity and IL22/CLDN8-WT and miR-340-5p inhibitors co-transfection memorably motivated luciferase activity. LINC00662 overexpression promoted cell proliferation, invasion and migration, and inhibited cell apoptosis in colon cancer. In vivo xenograft studies in nude mice manifested that LINC00662 overexpression prominently accelerate tumor growth. There was an opposite reaction in the biological functions of colon cells and tumor growth between LINC00662 overexpression and LINC00662 inhibition in vitro and in vivo. The functions of miR-340-5p mimics regulating the biological functions of colon cells and tumor growth were consistent with those of LINC00662 inhibition. CLDN8 and IL22, as target genes of miR-340-5p, reversed the functions of LINC00662 affecting the biological functions of colon cells and the protein levels of Bax, Bcl-2, XIAP, VEGF, MMP-2, E-cadherin and N-cadherin. Co-immunoprecipitation experiments indicated that CLDN8 directly interact with IL22 in colon cell lines. LINC00662 regulated CLDN8 and IL22 expressions and the activation of ERK signaling pathway via targeting miR-340-5p.

CONCLUSION

LINC00662 overexpression promoted the occurrence and development of colon cancer by competitively binding with miR-340-5p to regulate CLDN8/IL22 co-expression and activating ERK signaling pathway.