Knockdown of CUG-binding protein 1 induces apoptosis of human laryngeal cancer cells

The natural compound neobractatin inhibits cell proliferation mainly by regulating the RNA binding protein CELF6

The fruits of Garcinia bracteata can be eaten raw or processed into spices, which are considered to possess nutritional and medicinal value. Neobractatin (NBT) is a natural compound isolated from Garcinia bracteate. This study showed that NBT showed antitumor effect by upregulation of CELF6. CELF6, an RNA-binding protein of the CELF family, is involved in cancer cell proliferation. However, the role of CELF6 in human cervical cancer remains unknown. Here, we showed that CELF6 overexpression significantly suppressed HeLa cell proliferation. Mechanistically, the RNA immunoprecipitation sequencing (RIP-seq) results suggested that CELF6 physically targeted the cyclin D1 transcript, affecting protein stability. Overexpression of CELF6 increased the degradation of cyclin D1. Consistent results were obtained for the effect of NBT, which increased the expression of CELF6 at both the mRNA and protein levels. An in vivo study further confirmed the regulatory effect of NBT on CELF6 and cyclin D1 levels in a HeLa xenograft model. Similar effects of NBT on CELF6 were also shown in K562 cells in vitro and in vivo. In conclusion, our findings identified CELF6 as a tumor suppressor and a novel therapeutic target in cervical cancer. The upregulation of CELF6 expression by NBT and its antiproliferative effect on HeLa cells indicated that NBT from G. bracteata might be a small-molecule compound targeting CELF6.

MiR-330-3p functions as a tumor suppressor that regulates glioma cell proliferation and migration by targeting CELF1

INTRODUCTION

Glioma is a common type of neoplasm that occurs in the central nervous system. miRNAs have been demonstrated to act as critical regulators of carcinogenesis and tumor progression in multiple cancers, but the molecular mechanism of miR-330-3p in glioma remained unclear. The purpose of the study was to explore the role of miR-330-3p in glioma cell reproduction and migration.

MATERIAL AND METHODS

The expression levels of miR-330-3p and CELF1 in 27 glioma tissue specimens and human glioma cell lines were examined by qRT-PCR and western blot. The TargetScan database was used to predict the relationship between miR-330-3p and CELF1. Then the target relationship was verified using dual-luciferase reporter assay. The effects of miR-330-3p/CELF1 on glioma cell proliferation were evaluated by MTT and colony formation assay. Wound healing assay was employed to measure the migration ability of glioma cells.

RESULTS

MiR-330-3p was found lowly expressed in glioma tissues and cells compared with adjacent tissues and normal astrocytes, while CELF1 expression was relatively high in the glioma tissues and cells. Dual-luciferase reporter assay confirmed that miR-330-3p could directly target CELF1. Furthermore, miR-330-3p could down-regulate the expression of CELF1, therefore suppressing glioma cell reproduction and migration.

CONCLUSIONS

MiR-330-3p inhibited the propagation and migration of glioma cells by repressing CELF1 expression.

RNA-binding protein CELF6 is cell cycle regulated and controls cancer cell proliferation by stabilizing p21

CELF6, a member of the CELF family of RNA-binding proteins, regulates muscle-specific alternative splicing and contributes to the pathogenesis of myotonic dystrophy (DM), however the role of CELF6 in cancer cell proliferation is less appreciated. Here, we show that the expression of CELF6 is cell cycle regulated. The cell cycle-dependent expression of CELF6 is mediated through the ubiquitin-proteasome pathway, SCF-β-TrCP recognizes a nonphospho motif in CELF6 and regulates its proteasomal degradation. Overexpression or depletion of CELF6 modulates p21 gene expression. CELF6 binds to the 3'UTR of p21 transcript and increases its mRNA stability. Depletion of CELF6 promotes cell cycle progression, cell proliferation and colony formation whereas overexpression of CELF6 induces G1 phase arrest. The effect of CELF6 on cell proliferation is p53 and/or p21 dependent. Collectively, these data demonstrate that CELF6 might be a potential tumor suppressor, CELF6 regulates cell proliferation and cell cycle progression via modulating p21 stability.

CELF1/p53 axis: a sustained antiproliferative signal leading to villus atrophy under total parenteral nutrition

Intestinal villus atrophy is a major complication of total parenteral nutrition (TPN). Our previous study revealed that TPN-induced villus atrophy is accompanied by elevated expression of CUGBP, Elav-like family member 1 (CELF1); however, its mechanism of action has not been fully understood. Herein, we report a pivotal role of CELF1/p53 axis, which induces a sustained antiproliferative signal, leading to suppressed proliferation of intestinal epithelial cells (IECs). By using a rat model of TPN, we found synchronous upregulation of CELF1 and p53 in jejunum mucosa, accompanied by a 51% decrease in crypt cell proliferation rate. By using HCT-116 cells as an IEC model in vitro, we found that the expression of CELF1 altered dynamically in parallel to proliferation rate, suggesting a self-adaptive expression pattern in IECs in vitro. Furthermore, ectopic overexpression of CELF1 elicited a significant antiproliferative effect in HCT-116, Caco-2, and IEC-6 cells, whereas knockdown of CELF1 elicited a significant proproliferative effect. Moreover, cell-cycle assay revealed that ectopic overexpression of CELF1 induced sustained G2 arrest and G1 arrest in HCT-116 and IEC-6 cells, respectively, which could be abolished by p53 silencing. Mechanistically, polysomal profiling and nascent protein analysis revealed that regulation of p53 by CELF1 was mediated through accelerating its protein translation in polysomes. Taken together, our findings revealed a sustained suppression of IEC proliferation evoked by CELF1/p53 axis, which may be a potential therapeutic target for the treatment of TPN-induced villus atrophy.-Yan, J.-K., Zhang, T., Dai, L.-N., Gu, B.-L., Zhu, J., Yan, W.-H., Cai, W., Wang, Y. CELF1/p53 axis: a sustained antiproliferative signal leading to villus atrophy under total parenteral nutrition.

Systems analysis identifies melanoma-enriched pro-oncogenic networks controlled by the RNA binding protein CELF1

Melanomas are well-known for their altered mRNA expression profiles. Yet, the specific contribution of mRNA binding proteins (mRBPs) to melanoma development remains unclear. Here we identify a cluster of melanoma-enriched genes under the control of CUGBP Elav-like family member 1 (CELF1). CELF1 was discovered with a distinct prognostic value in melanoma after mining the genomic landscape of the 692 known mRBPs across different cancer types. Genome-wide transcriptomic, proteomic, and RNA-immunoprecipitation studies, together with loss-of-function analyses in cell lines, and histopathological evaluation in clinical biopsies, revealed an intricate repertoire of CELF1-RNA interactors with minimal overlap with other malignancies. This systems approach uncovered the oncogene DEK as an unexpected target and downstream effector of CELF1. Importantly, CELF1 and DEK were found to represent early-induced melanoma genes and adverse indicators of overall patient survival. These results underscore novel roles of CELF1 in melanoma, illustrating tumor type-restricted functions of RBPs in cancer.

Supplementary choline attenuates olive oil lipid emulsion-induced enterocyte apoptosis through suppression of CELF1/AIF pathway

Enterocyte apoptosis induced by lipid emulsions is a key cause of intestinal atrophy under total parenteral nutrition (TPN) support, and our previous work demonstrated that olive oil lipid emulsion (OOLE) could induce enterocyte apoptosis via CUGBP, Elav‐like family member 1 (CELF1)/ apoptosis‐inducing factor (AIF) pathway. As TPN‐associated complications are partially related to choline deficiency, we aimed to address whether choline supplementation could attenuate OOLE‐induced enterocyte apoptosis. Herein we present evidence that supplementary choline exhibits protective effect against OOLE‐induced enterocyte apoptosis both in vivo and in vitro. In a rat model of TPN, substantial reduction in apoptotic rate along with decreased expression of CELF1 was observed when supplementary choline was added to OOLE. In cultured Caco‐2 cells, supplementary choline attenuated OOLE‐induced apoptosis and mitochondria dysfunction by suppressing CELF1/AIF pathway. Compared to OOLE alone, the expression of CELF1 and AIF was significantly decreased by supplementary choline, whereas the expression of Bcl‐2 was evidently increased. No obvious alterations were observed in Bax expression and caspase‐3 activation. Mechanistically, supplementary choline repressed the expression of CELF1 by increasing the recruitment of CELF1 mRNA to processing bodies, thus resulting in suppression of its protein translation. Taken together, our data suggest that supplementary choline exhibits effective protection against OOLE‐induced enterocyte apoptosis, and thus, it has the potential to be used for the prevention and treatment of TPN‐induced intestinal atrophy.

Inhibition of CUG-binding protein 1 and activation of caspases are critically involved in piperazine derivative BK10007S induced apoptosis in hepatocellular carcinoma cells

Though piperazine derivative BK10007S was known to induce apoptosis in pancreatic cancer xenograft model as a T-type CaV3.1 a1G isoform calcium channel blocker, its underlying antitumor mechanism still remains unclear so far. Thus, in the present study, the antitumor mechanism of BK10007S was elucidated in hepatocellular carcinoma cells (HCCs). Herein, BK10007S showed significant cytotoxicity by 3-[4,5-2-yl]-2,5-diphenyltetra-zolium bromide (MTT) assay and anti-proliferative effects by colony formation assay in HepG2 and SK-Hep1 cells. Also, apoptotic bodies and terminal deoxynucleotidyl transferase (TdT) dUTP Nick End Labeling (TUNEL) positive cells were observed in BK10007S treated HepG2 and SK-Hep1 cells by 4',6-diamidino-2-phenylinodole (DAPI) staining and TUNEL assay, respectively. Consistently, BK10007S increased sub G₁ population in HepG2 and SK-Hep1 cells by cell cycle analysis. Furthermore, Western blotting revealed that BK10007S activated the caspase cascades (caspase 8, 9 and 3), cleaved poly (ADP-ribose) polymerase (PARP), and downregulated the expression of cyclin D1, survivin and for CUG-binding protein 1 (CUGBP1 or CELF1) in HepG2 and SK-Hep1 cells. Conversely, overexpression of CUGBP1 reduced cleavages of PARP and caspase 3, cytotoxicity and subG₁ population in BK10007S treated HepG2 cells. Overall, these findings provide scientific evidences that BK10007S induces apoptosis via inhibition of CUGBP1 and activation of caspases in hepatocellular carcinomas as a potent anticancer candidate.

Olive Oil-Supplemented Lipid Emulsion Induces CELF1 Expression and Promotes Apoptosis in Caco-2 Cells

Background and Aims: Parenterally-administered lipid emulsion (LE) is a key cause of enterocyte apoptosis under total parenteral nutrition, yet the pathogenesis has not been fully understood. CUGBP, Elav-like family member 1 (CELF1) has been recently identified as a crucial modulator of apoptosis, and thus this study sought to investigate its role in the LE-induced apoptosis in vitro. Methods: Caco-2 cells were used as an in vitro model. The cells were treated with varying LEs derived from soybean oil, olive oil or fish oil, and changes in the apoptosis and CELF1 expression were assessed. Rescue study was performed using transient knockdown of CELF1 with specific siRNA prior to LE treatment. Regulation of CELF1 by LE treatment was studied using quantitative real-time PCR and Western blotting. Results: All the LEs up-regulated CELF1expression and induced apoptosis, but only olive oil-supplemented lipid emulsion (OOLE)-induced apoptosis was attenuated by depletion of CELF1. Up-regulation of apoptosis-inducing factor (AIF) was involved in OOLE-induced CELF1 dependent apoptosis. The protein expression of CELF1 was up-regulated by OOLE in a dose- and time-dependent manner, but the mRNA expression of CELF1 was unchanged. Analysis by polysomal profiling and nascent protein synthesis revealed that the regulation of CELF1 by OOLE treatment was mediated by directly accelerating its protein translation. Conclusion: OOLE-induces apoptosis in Caco-2 cells partially through up-regulation of CELF1.

Tumor necrosis factor superfamily member 13 is a novel biomarker for diagnosis and prognosis and promotes cancer cell proliferation in laryngeal squamous cell carcinoma

Tumor necrosis factor superfamily member 13 (TNFSF13) modulates cell proliferation and apoptosis and participates in the pathogenesis of solid tumors, but its role in laryngeal cancer development is not clearly defined. In order to investigate whether TNFSF13 can be used as a biomarker for diagnosis and prognosis in laryngeal squamous cell carcinoma (LSCC) and the role of TNFSF13 in laryngeal cancer carcinogenesis, we conducted immunohistochemistry and ELISA assays to evaluate the expression level of TNFSF13 in laryngeal cancer patients and the contrast. We also conducted experiments on the functional study of TNFSF13 in vitro. We found that the expression levels of TNFSF13, ki-67, and NF-κB p65 in LSCC tumor tissues were higher than those in vocal polyp and para-carcinoma tissues. The Spearman rank correlation analysis showed that the expression of TNFSF13 had a positive correlation with the expression of ki-67 and NF-κB p65. Cox regression analysis and Kaplan-Meier plots confirmed the expression level of TNFSF13 was a prognostic factor for LSCC. Moreover, the serum TNFSF13 level was significantly higher in LSCC patients than in the controls, and the serum expression level of TNFSF13 can distinguish LSCC from healthy people, precancerosis, or laryngeal benign tumor. In addition, functional study of TNFSF13 in vitro revealed that knockdown of TNFSF13 inhibited cell proliferation by inducing G1 phase cell cycle arrest in Hep-2 cells. In conclusion, TNFSF13 may be a potential novel molecular target for diagnosis and prognosis in human LSCC, and therapies that target TNFSF13 may have clinical significance for the treatment of LSCC.

CELF1 is Up-Regulated in Glioma and Promotes Glioma Cell Proliferation by Suppression of CDKN1B

BACKGROUND

As a member of the CELF family, CELF1 (CUG-binding protein 1, CUGBP1) is involved in cardiac and embryonic development, skeletal muscle differentiation and mammary epithelial cell proliferation. CELF1 is also observed in many kinds of cancer and may play a great role in tumorigenesis and deterioration. However, the expression and mechanism of its function in human glioma remain unclear.

METHODS

We examined CELF1 expression in 62 glioma patients by immunohistochemistry and Western blot. The association between the expression of CELF1 protein and clinicopathological characteristics was analysed using SPSS 17.0. Survival analyses were performed using the Kaplan-Meier method. Small-interfering RNA was utilised to specifically knockdown CELF1 mRNA in U87 and U251 cells. Cell proliferation, cell cycle and cell apoptosis were tested by Cell Counting Kit-8 and flow cytometry. The expression of cell cycle-related gene CDKN1B was investigated by Western blot. The interactions between CELF1 and CDKN1B were detected with immune co-precipitation. Subcutaneous tumour models were used to study the effect of CELF1 on the growth of glioma cells in vivo.

RESULTS

Our results showed that CELF1 protein was frequently up-regulated in human glioma tissues. The expression level of this protein was positively correlated with glioma World Health Organisation grade and inversely correlated with patient survival (P < 0.05). Knockdown of CELF1 inhibited the glioma cell cycle process and proliferation potential, possibly by down-regulating its target, CDKN1B protein.

CONCLUSIONS

Results indicated that CELF1 may be a novel independent prognostic predictor of survival for glioma patients. It may promote glioma cell proliferation and cell cycle process during glioma carcinogenesis.

Knockdown of immature colon carcinoma transcript-1 inhibits proliferation of glioblastoma multiforme cells through Gap 2/mitotic phase arrest

“Glioblastoma multiforme” (GBM) is the frequent form of malignant glioma. Immature colon carcinoma transcript-1 (ICT1) is essential for cell vitality and mitochondrial function and has been recognized in several human cancers. In the study reported here, we attempted to evaluate the functional role of ICT1 in GBM cells. Lentivirus-mediated RNA interference (RNAi) was applied to silence ICT1 expression in human GBM cell lines U251 and U87. Cell proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and colony-formation assays. Cell-cycle progression was determined by flow cytometry with propidium iodide staining. The results revealed that lentivirus-mediated short hairpin RNA (shRNA) can specifically suppress the expression of ICT1 in U251 and U87 cells. Functional investigations proved for the first time, as far as we are aware, that ICT1 knockdown significantly inhibited the proliferation of both cell lines. Moreover, the cell cycle of U251 cells was arrested at Gap 2 (G2)/mitotic (M) phase after ICT1 knockdown, with a concomitant accumulation of cells in the Sub-Gap 1 (G1) phase. This study highlights the crucial role of ICT1 in promoting GBM cell proliferation, and provides a foundation for further study into the clinical potential of lentivirus-mediated silencing of ICT1 for GBM therapy.