shRNA‑mediated silencing of TARBP2 inhibits NCI‑H1299 non‑small cell lung cancer cell invasion and migration via the JNK/STAT3/AKT pathway

New insights into the function and therapeutic potential of RNA-binding protein TRBP in viral infection, chronic metabolic diseases, brain disorders and cancer

RNA-binding proteins (RBPs) and non-coding RNAs are crucial trans-acting factors that bind to specific cis-acting elements in mRNAs, thereby regulating their stability and translation. The trans-activation response (TAR) RNA-binding protein (TRBP) recognizes precursor microRNAs (pre-miRNAs), modulates miRNA maturation, and influences miRNA interference (mi-RNAi) mediated by the RNA-induced silencing complex (RISC). TRBP also directly binds and mediates the degradation of certain mRNAs. Thus, TRBP acts as a hub for regulating gene expression and influences a variety of biological processes, including immune evasion, metabolic abnormalities, stress response, angiogenesis, hypoxia, and metastasis. Aberrant TRBP expression has been proven to be closely related to the initiation and progression of diseases, such as viral infection, chronic metabolic diseases, brain disorders, and cancer. This review summarizes the roles of TRBP in cancer and other diseases, the therapeutic potential of TRBP inhibition, and the current status of drug discovery on TRBP.

Pre-Administration of Berberine Exerts Chemopreventive Effects in AOM/DSS-Induced Colitis-Associated Carcinogenesis Mice via Modulating Inflammation and Intestinal Microbiota

Inflammatory activation and intestinal flora imbalance play an essential role in the development and progression of colorectal cancer (CRC). Berberine (BBR) has attracted great attention in recent years due to its heath-related benefits in inflammatory disorders and tumors, but the intricate mechanisms have not been fully elucidated. In this study, the effects and the mechanism of BBR on colon cancer were investigated in an azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colitis-associated carcinogenesis mice model. Our results showed that pre-administration of BBR showed a decrease in weight loss, disease activity index (DAI) score, and the number of colon tumors in mice, compared with the model group. The evidence from pathological examination indicated that the malignancy of intestinal tumors was ameliorated after pre-administration of BBR. Additionally, pre-administration with BBR suppressed the expression of pro-inflammatory factors (interleukin (IL)-6, IL-1β, cyclooxygenase (COX)-2 and tumor necrosis factor (TNF)-α) and the cell-proliferation marker Ki67, while expression of the tight junction proteins (ZO-1 and occludin) were increased in colon tissue. Moreover, the levels of critical pathway proteins involved in the inflammatory process (p-STAT3 and p-JNK) and cell cycle regulation molecules (β-catenin, c-Myc and CylinD1) exhibited lower expression levels. Besides, 16S rRNA sequence analysis indicated that pre-administration of BBR increased the ratio of Firmicutes/Bacteroidetes (F:M) and the relative abundance of potentially beneficial bacteria, while the abundance of cancer-related bacteria was decreased. Gavage with Lactobacillus rhamnosus can improve the anti-tumor effect of BBR. Overall, pre-administration of BBR exerts preventive effects in colon carcinogenesis, and the mechanisms underlying these effects are correlated with the inhibition of inflammation and tumor proliferation and the maintenance of intestinal homeostasis.

Downregulation of ZNF395 Drives Progression of Pancreatic Ductal Adenocarcinoma through Enhancement of Growth Potential

BACKGROUND

Progression of pancreatic intraepithelial neoplasia (PanIN) to invasive carcinoma is a critical factor impacting the prognosis of patients with pancreatic tumors. However, the molecular mechanisms involved are not fully understood. We have reported that the process frequently involves loss of chromosome 8p, causing downregulation of DUSP4, thus conferring invasive ability on cancer cells. Here, we focus on ZNF395, whose expression was also found to be decreased by 8p loss and was predicted to be a growth suppressor gene.

METHODS

Pancreatic cancer cell lines inducibly expressing ZNF395 were established to assess the functional significance of ZNF395 in pancreatic carcinogenesis. Immunohistochemistry was also performed to analyze the expression levels of ZNF395 in pancreatic cancer tissues.

RESULTS

Induction of ZNF395 in pancreatic cancer cells resulted in marked activation of JNK and suppression of their proliferation through a delay in cell cycle progression. Immunohistochemistry revealed that ZNF395 was expressed ubiquitously in both normal pancreatic ducts and PanINs but was significantly reduced in invasive cancers, especially those showing poor differentiation.

CONCLUSION

ZNF395 acts as a novel tumor suppressor gene. Its downregulation caused by 8p loss in intraepithelial cells accelerates their proliferation through dysregulation of the cell cycle, leading to progression to invasive cancer.

TARBP2 promotes tumor angiogenesis and metastasis by destabilizing antiangiogenic factor mRNAs

Tumor angiogenesis is a crucial step in the further growth and metastasis of solid tumors. However, its regulatory mechanism remains unclear. Here, we showed that TARBP2, an RNA‐binding protein, played a role in promoting tumor‐induced angiogenesis both in vitro and in vivo through degrading the mRNAs of antiangiogenic factors, including thrombospondin1/2 (THBS1/2), tissue inhibitor of metalloproteinases 1 (TIMP1), and serpin family F member 1 (SERPINF1), by targeting their 3′untranslated regions (3′UTRs). Overexpression of TARBP2 promotes tumor cell–induced angiogenesis, while its knockdown inhibits tumor angiogenesis. Clinical cohort analysis revealed that high expression level of TARBP2 was associated with poor survival of lung cancer and breast cancer patients. Mechanistically, TARBP2 physically interacts with the stem‐loop structure located in the 3′UTR of antiangiogenic transcripts, leading to mRNA destabilization by the dsRNA‐binding domains 1/2 (dsRBDs1/2). Notably, the expression level of TARBP2 in human tumor tissue is negatively correlated with the expression of antiangiogenic factors, including THBS1/2, and brain‐specific angiogenesis inhibitor 1 (BAI1). Moreover, TARBP2 expression is strongly associated with tumor angiogenesis in a group of human lung cancer samples. Collectively, our results highlight that TARBP2 is a novel tumor angiogenesis regulator that could promote tumor angiogenesis by selectively downregulating antiangiogenic gene expression.

Hypoxia-induced let-7f-5p/TARBP2 feedback loop regulates osteosarcoma cell proliferation and invasion by inhibiting the Wnt signaling pathway

Osteosarcoma (OS) is the most common bone tumor in children and adolescents and is characterized by high metastatic and recurrence rates. In the past, it has been shown that microRNAs may play critical roles in hypoxia-related OS proliferation and invasion. However, the mechanisms by which OS cells acquire this malignant phenotype have remained largely unknown. In the present study, we report that let-7f-5p and TARBP2 were expressed in lower amounts in human OS cell lines when compared with the hFOB normal human osteoblastic cell line; however, both types of cells were repressed by hypoxia. let-7f-5p and TARBP2 significantly inhibited the proliferation and invasion of OS cells. Furthermore, TARBP2 as a downstream and functional target of let-7f-5p regulated the expression of let-7f-5p, and there was a regulatory feedback loop between let-7f-5p and TARBP2. This loop reduced the expression of let-7f-5p and TARBP2 in OS cells to a very low level, which was induced by hypoxia. Furthermore, the hypoxia-induced let-7f-5p/TARBP2 feedback loop contributed to activation of the Wnt signaling pathway. Taken together, our data clearly showed that the feedback loop between let-7f-5p and TARBP2 induced by the hypoxia-promoted OS cell malignant phenotype increased with activation of the Wnt signaling pathway.

Actinidia Chinensis Planch Root extract attenuates proliferation and metastasis of hepatocellular carcinoma by inhibiting the DLX2/TARBP2/JNK/AKT pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Many studies have confirmed that traditional Chinese herbs exert potential anti-tumor effects. Actinidia Chinensis Planch root has been used as a traditional Chinese medicine (TCM) for thousands of years. However, the mechanism of anti-tumor effects of Actinidia Chinensis Planch root has not been clearly clarified.

AIM OF THE STUDY

To explore the molecular biological mechanisms underlying the inhibitory effect of Actinidia Chinensis Planch root extract (acRoots) on hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

In our previous study, we used mRNA chip analyses to identify genes regulated by acRoots. Further analyses of altered genes led to the identification of a key regulator of genes that responds to acRoots. We explored the effects of acRoots on the proliferation and invasion of HCC cells via cell counting as well as transwell assays, and further explored the molecular mechanisms underlying the effects of acRoots on HCC cells using qRT-PCR, western blot, and Chip-PCR.

RESULTS

Increasing the concentration of acRoots as well as prolonging its action time enhanced the inhibitory activity of acRoots as well as its cytotoxicity against HCC cells. High TARBP2 expression in HCC cells, which is associated with advanced-stage HCC and poor prognoses in HCC patients, was downregulated by treatment with acRoots. Furthermore, acRoots inhibited proliferation, invasion, and epithelial-to-mesenchymal transition by downregulating TARBP2 expression. HCC cells with higher TARBP2 expression were more sensitive to acRoots. The expression of TARBP2 and DLX2 in HCC patients and HCC cell lines was significantly positively correlated, and DLX2 as a transcription factor may promote TARBP2 expression, thereby further activating the JNK/AKT signaling pathway leading to the inhibition of HCC.

CONCLUSIONS

acRoots inhibited the malignant behavior of HCC cells by inhibiting TARBP2 expression, which is affected by the transcription factor DLX2, leading to a reduction in JNK/AKT signaling pathway activation.

Nuclear TARBP2 Drives Oncogenic Dysregulation of RNA Splicing and Decay

Post-transcriptional regulation of RNA stability is a key step in gene expression control. We describe a regulatory program, mediated by the RNA binding protein TARBP2, that controls RNA stability in the nucleus. TARBP2 binding to pre-mRNAs results in increased intron retention, subsequently leading to targeted degradation of TARBP2-bound transcripts. This is mediated by TARBP2 recruitment of the m⁶A RNA methylation machinery to its target transcripts, where deposition of m⁶A marks influences the recruitment of splicing regulators, inhibiting efficient splicing. Interactions between TARBP2 and the nucleoprotein TPR then promote degradation of these TARBP2-bound transcripts by the nuclear exosome. Additionally, analysis of clinical gene expression datasets revealed a functional role for TARBP2 in lung cancer. Using xenograft mouse models, we find that TARBP2 affects tumor growth in the lung and that this is dependent on TARBP2-mediated destabilization of ABCA3 and FOXN3. Finally, we establish ZNF143 as an upstream regulator of TARBP2 expression.

Ethyl acetate extract from Inula helenium L. inhibits the proliferation of pancreatic cancer cells by regulating the STAT3/AKT pathway

Sesquiterpene lactones are bioactive compounds that have been identified as responsible for the anticancer activity of the medicinal herb, Inula helenium L. (IHL). However, the mechanisms of action involved in the anti‑pancreatic cancer activity of IHL have yet to be elucidated. The present study used an optimized extraction strategy to obtain sesquiterpene lactones from IHL (the resulting product termed ethyl acetate extract of IHL; EEIHL), and examined the potential mechanisms involved in the anti‑pancreatic cancer activity of EEIHL. Ethanol and ethyl acetate were used to extract sesquiterpene lactones from IHL to give the final product EEIHL. Cell Counting Kit‑8, colony formation and Annexin V/propidium iodide assays were used to detect the anti‑proliferative activity of EEIHL. Cell migration was determined with a wound healing assay. mRNA and protein expression levels were analyzed by reverse transcription‑quantitative polymerase chain reaction and western blot analyses, respectively. It was identified that low concentrations of EEIHL caused CFPAC‑1 cell cycle arrest in the G0/G1 phase, whereas high concentrations of EEIHL induced mitochondria‑dependent apoptosis. In addition, EEIHL could inhibit the phosphorylation of the signal transducer and activator of transcription (STAT)3/AKT pathway, potentially resulting in impeded cell mobility. In conclusion, EEIHL could activate mitochondrial‑dependent apoptosis and inhibit cell migration through the STAT3/AKT pathway in CFPAC-1 cells.