ZFX-mediated upregulation of CEBPA-AS1 contributes to acute myeloid leukemia progression through miR-24-3p/CTBP2 axis

Emerging reports demonstrated that long non-coding RNAs (lncRNAs) play a role in the pathogenesis and metastasis of cancers. However, the biological functions and underlying mechanisms of LncRNA CEBPA-AS1 in acute myeloid leukemia (AML) remain largely elusive. The level of CEBPA-AS1 was examined in AML clinical tissues and cell lines via fluorescence in situ hybridization (FISH) and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). In vivo and in vitro functional tests were applied to identify the pro-oncogenic role of CEBPA-AS1 in AML development. The overexpressed CEBPA-AS1 was linked to poor survival in AML patients. Moreover, the relationships among CEBPA-AS1, Zinc Finger Protein X-Linked (ZFX), and miR-24-3p were predicted by bioinformatics and validated by RNA immunoprecipitation (RIP) and luciferase reporter assays. Our findings unveiled that transcription factor ZFX particularly interacted with the promoter of CEBPA-AS1 and activated CEBPA-AS1 transcription. Downregulation of CEBPA-AS1 inhibited the proliferation and invasion while promoted apoptosis of AML cells in in vitro, as well as in vivo, xenograft tumor growth was modified. However, overexpression of CEBPA-AS1 observed the opposite effects. Furthermore, CEBPA-AS1 acted as a competitive endogenous RNA (ceRNA) of miR-24-3p to attenuate the repressive effects of miR-24-3p on its downstream target CTBP2. Taken together, this study emphasized the pro-oncogenic role of CEBPA-AS1 in AML and illustrated its connections with the upstream transcription factor ZFX and the downstream regulative axis miR-24-3p/CTBP2, providing important insights to the cancerogenic process in AML.

Circular RNA circHERC4 as a novel oncogenic driver to promote tumor metastasis via the miR-556-5p/CTBP2/E-cadherin axis in colorectal cancer

BACKGROUND

The main cause of death in colorectal cancer patients is metastasis. Accumulating evidences suggest that circRNA plays pivotal roles in cancer initiation and development. However, the underlying molecular mechanisms of circRNAs that orchestrate cancer metastasis remain vague and need further clarification.

METHODS

Two paired CRC and adjacent normal tissues were used to screen the upregulated circRNAs by circRNA-seq; then, cell invasion assay was applied to confirm the functional invasion-related circRNAs. According to the above methods, circHERC4 (hsa_circ_0007113) was selected for further research. Next, we investigated the clinical significance of circHERC4 in a large cohort of patients with CRC. The oncogenic activity of circHERC4 was investigated in both CRC cell lines and animal xenograft studies. Finally, we explored the molecular mechanisms underlying circHERC4 as a malignant driver.

RESULTS

We demonstrated that circHERC4 was aberrantly elevated in CRC tissues (P < 0.001), and was positively associated with lymph node metastasis and advanced tumor grade (P < 0.01). Notably, the expression of circHERC4 was associated with worse survival in patients with CRC. Silencing of circHERC4 significantly inhibited the proliferation and migration of two highly aggressive CRC cell lines and reduced liver and lung metastasis in vivo. Mechanistically, we revealed that circHERC4 inactivated the tumor suppressor, miR-556-5p, leading to the activation of CTBP2/E-cadherin pathway which promotes tumor metastasis in CRC.

CONCLUSIONS

CircHERC4 exerts critical roles in promoting tumor aggressiveness through miR-556-5p/CTBP2/E-cadherin pathway and is a prognostic biomarker of the disease, suggesting that circHERC4 may serve as an exploitable therapeutic target for patients with CRC.

Low expression of CTBP2 and CASP8AP2 predicts risk of relapse in childhood B-cell precursor acute lymphoblastic leukemia: a retrospective cohort study

CtBP is a known corepressor abundantly expressed in cancer and regulates genes involved in cancer initiation, progression, and metastasis. This study aimed to investigate the prognostic significance of CTBP2 expression in a cohort of pediatric patients with B cell precursor acute lymphoblastic leukemia (BCP-ALL). It further evaluated the role of combined CTBP2 and CASP8AP2 expression in risk of relapse of BCP-ALL. The expression of CTBP2 mRNA was retrospectively detected by a qRT-PCR approach in bone marrow samples from 104 children with newly diagnosed BCP-ALL. CASP8AP2 was assessed simultaneously in the 100 patients included in this study. The receiver operating characteristic (ROC) curve analysis determined the cut off levels for CTBP2 and CASP8AP2 expression with good predictive significance for relapse of BCP-ALL. Patients with low CTBP2 expression had inferior relapse-free survival (RFS) and event-free survival (EFS) when compared to patients with high-CTBP2 expression. The expression level of CTBP2 was significantly associated with CASP8AP2 expression (r = 0.449, P < 0.001). Patients were stratified into three groups according to the combined evaluation of the two gene expression, and patients with simultaneous low-expression had the worst outcome (6-year RFS: 64.6%±12.8%, P < 0.001). Multivariate analysis demonstrated the expression of CTBP2 and CASP8AP2, minimal residual disease (MRD) at day 33 remained as independent prognostic factors for RFS. Based on the final Cox hazards model, we proposed an algorithm to calculate the risk index, which was more precise for predicting relapse. In conclusion, low expression of CTBP2 and CASP8AP2 correlated with poor outcome and predicted risk of relapse in pediatric BCP-ALL.

Expression and prognostic significance of CTBP2 in human gliomas

Deregulated expression of C-terminal-binding protein 2 (CTBP2) has been observed previously in a number of tumors, such as hepatocellular carcinoma and prostatic cancer, in the colorectal cancer SW480 cell line and in the human embryonic kidney 293 cell line. In the present study, western blot analysis and immunohistochemistry were performed to investigate whether gliomas exhibit deregulated CTBP2 expression. Kaplan-Meier survival analyses were performed to evaluate the associations between CTBP2 expression, clinicopathological data and patient survival in glioma patients. The results revealed that CTBP2 expression was significantly upregulated in high grade glioma tissues compared with that in low grade glioma and normal brain tissues. Furthermore, increased CTBP2 expression in gliomas was significantly associated with a higher World Health Organization (WHO) tumor grade (P<0.005) and poorer disease-specific survival (P<0.005). In conclusion, these results suggest that CTBP2 may act as an intrinsic regulator of progression in glioma cells and thus may serve as an important prognostic factor for the disease.