[Retracted] Long non­coding RNA receptor activator of nuclear factor­κB ligand promotes cisplatin resistance in non­small cell lung cancer cells.

[This retracts the article DOI: 10.3892/etm.2021.9949.].

m6A Methyltransferase KIAA1429 Regulates the Cisplatin Sensitivity of Gastric Cancer Cells via Stabilizing FOXM1 mRNA.

Although cisplatin is frequently used to treat gastric cancer, the resistance is the main obstacle for effective treatment. mRNA modification, N6-methyladenosine (m6A), is involved in the tumorigenesis of many types of cancer. As one of the largest m6A methyltransferase complex components, KIAA1429 bridges the catalytic m6A methyltransferase components, such as METTL3. In gastric cancer, KIAA1429 was reported to promote cell proliferation. However, whether KIAA1429 is involved in the resistance of gastric cancer to cisplatin remains unclear. Here, we generated cisplatin resistant gastric cancer cell lines, and compared the m6A content between resistant cells and wild type cells. The m6A content as well as KIAA1429 expression are higher in resistant cells. Interestingly, the expression of KIAA1429 was significantly increased after cisplatin treatment. We then used shRNA to knockdown KIAA1429 and found that resistant cells responded more to cisplatin treatment after KIAA1429 depletion, while overexpression of KIAA1429 decreased the sensitivity. Moreover, we identified a putative p65 binding site on the promoter area of KIAA1429 and ChIP assay confirmed the binding. p65 depletion decreased the expression of KIAA1429. YTHDF1 is the most abundant m6A "reader" that interacts with m6A modified mRNA. Mechanistically, YTHDF1 was recruited to the 3'-untranslated Region (3'-UTR) of transcriptional factor, FOXM1 by KIAA1429 and stabilized FOXM1 mRNA. More importantly, KIAA1429 knockdown increased the sensitivity of resistant cells to cisplatin in vivo. In conclusion, our results demonstrated that KIAA1429 facilitated cisplatin resistance by stabilizing FOXM1 mRNA in gastric cancer cells.

m6A methyltransferase KIAA1429 acts as an oncogenic factor in colorectal cancer by regulating SIRT1 in an m6A-dependent manner.

N6-methyladenosine (m6A) modifications of RNAs are involved in various aspects of colorectal carcinogenesis via regulation of mRNA stability, splicing, and translation. KIAA1429, an m6A methyltransferase, was found deregulated in multiple cancer types. However, its role in colorectal cancer remains elusive. By analyzing TCGA and GEPIA database, we found that KIAA1429 in colorectal cancer was highly expressed. In addition, we used immunohistochemistry, western blotting, and QRT-PCR to detect the expression of KIAA1429 in colorectal cancer samples and cell lines, and we found that KIAA1429 was overexpressed in colorectal cancer sample and cell line. Functionally, silencing of KIAA1429 by shRNA in colorectal cancer cell lines resulted in decreased cell proliferation, colony formation, and migration. On the contrary, overexpression of KIAA1429 increased cell proliferation, colony formation, and migration. Further mechanism analysis demonstrated that KIAA1429 increased the expression of SIRT1 via regulating its mRNA stability in an m6A-dependent manner. More importantly, in vivo experiment showed that depletion of KIAA1429 significantly inhibited colorectal tumor growth. In conclusion, our results suggested that the m6A methyltransferase KIAA1429 promotes the growth and motility of colorectal cancer and could be a potent therapeutic target.

LINC00511 Knockdown Suppresses Resistance to Cisplatin in Lung Adenocarcinoma by Interacting with miR-182-3p and BIRC5.

We studied the role of long intergenic non-protein coding RNA 00,511 (LINC00511) in lung adenocarcinoma (LUAD), with a specific focus on acquired chemoresistance. LINC00511 expression was higher in responders to cisplatin (DDP, another name for cisplantin) than non-responders, in A549/DDP cells than in parental A549 cells and normal human bronchial epithelial cells (16HBE). LINC00511 knockdown decreased the half maximal inhibitory concentration (IC50) value, suppressed A549/DDP cell viability, but induced apoptosis. LINC00511 bound with miR-182 and increased the expression of baculoviral inhibitor of apoptosis protein (IAP) repeat containing 5 (BIRC5). BIRC5 knockdown mimicked the effects of LINC00511 knockdown on the IC50 value, A549/DDP cell viability, and apoptosis. BIRC5 overexpression negated the effects of LINC00511 knockdown on A549/DDP cells. In vivo, LINC00511 knockdown attenuated the tumorigenesis of A549/DDP cells after DDP injection. These results provide a novel LINC00511/miR-182/BIRC5 paradigm to explain the mechanism of acquired DDP resistance.

Long non-coding RNA receptor activator of nuclear factor-κ B ligand promotes cisplatin resistance in non-small cell lung cancer cells.

Non-small cell lung cancer (NSCLC) is a common malignancy associated with poor clinical outcomes and high mortality rate. The association between NSCLC development and long non-coding RNA (lncRNA) expression remains to be elucidated. The current study investigated the role of a novel lncRNA, receptor activator of nuclear factor-κ B ligand (RANKL), in the resistance of NSCLC to chemotherapy. RANKL expression was assessed via reverse transcription-quantitative PCR, cell death rate was evaluated using flow cytometry and sensitivity of cisplatin (DDP)-resistant A549/DDP cells to chemotherapy was determined using the Cell Counting Kit-8 assay. Western blotting was performed to quantify p53 protein levels. Compared with matched A549 cells, A549/DDP cells exhibited significant upregulation of RANKL expression. Sensitivity of A549/DDP cells to DDP was restored following RANKL knockdown. A549 cells overexpressing RANKL exhibited notably impaired DDP sensitivity compared with controls. Conversely, downregulated RANKL expression triggered cell death and inhibited cell migration via p53 stimulation and phosphatidylinositol 3-kinase/protein kinase B pathway suppression. The current findings indicate that RANKL contributes to DDP resistance in NSCLC and may represent a novel therapeutic target in this malignancy.

lncRNA CCAT2 promotes radiotherapy resistance for human esophageal carcinoma cells via the miR­145/p70S6K1 and p53 pathway.

The long non­coding RNA colon cancer­associated transcript 2 (CCAT2) is abnormally expressed in various types of malignant tumor tissues and considered to be an oncogene, including for esophageal cancer (EC). Radiotherapy is an important and widely used cancer treatment. However, some patients with EC do not respond to radiotherapy. This study was designed to investigate effects of CCAT2 expression on radiotherapy dynamics for EC cells and to explore underlying molecular mechanisms. Reverse transcription­quantitative PCR was used to measure CCAT2 expression in EC tissues, normal esophageal mucosa, EC cells and normal human esophageal epithelial cells. TUNEL assays were used to assess the effect of CCAT2 on X­ray­induced apoptosis of EC cells. Protein expression was detected by western blot. CCAT2 was highly expressed in EC tissues and EC cells, and was negatively associated with radiotherapy efficacy in patients with EC. In vitro, knockdown of CCAT2 enhanced radiosensitivity of EC cells and promoted apoptosis by increasing Bax/Bcl2 and active­caspase 3/caspase 3 following X­ray treatment. In addition, CCAT2 negatively regulated miR­145 and P70 ribosomal protein S6 kinase 1 (p70S6K1) expression, and inhibited phosphorylation of Akt, ERK and p70S6K1 in EC cells. After X­ray treatment, CCAT2 negatively regulated protein levels of p53, P21 and c­Myc. These results showed that CCAT2 promoted the radiotherapy resistance of EC cells via negative regulation of the miR­145/p70S6K1 and the p53 signaling pathways and associated elements may be potential targets for improving the sensitivity of EC radiotherapy.

Miltirone-induced apoptosis in cisplatin-resistant lung cancer cells through upregulation of p53 signaling pathways.

The active ingredients of natural plants are important sources of antitumor agents. Miltirone is a major effective ingredient in traditional Chinese medicine and it is considered to have anti-infection and immunosuppressive activities. Clinically, it is often used for the treatment of arthritis and immune diseases. The effect of miltirone on cisplatin-resistant lung cancer cells has not been investigated to date. The present study aimed to examine the anticancer effect of miltirone in cisplatin-resistant lung cancer cells. Treatment with miltirone suppressed cell viability and induced apoptosis in HCC827 and A549 platinum-resistant lung cancer cells. It was also revealed that miltirone increased caspase-3/8 activity as well as B-cell lymphoma 2-associated X-protein, apoptosis-inducing factor (AIF), p53 and poly(ADP-ribose) polymerase (PARP) protein expression, whereas it inhibited mitochondrial reactive oxygen species (ROS) generation and matrix metalloproteinase (MMP)-2/9 protein expression in HCC827 and A549 platinum-resistant lung cancer cells. The results of the present study demonstrated that miltirone induces apoptosis in cisplatin-resistant lung cancer cells through ROS-p53, AIF, PARP and MMP2/9 signaling pathways.

Expression and significance of RRBP1 in esophageal carcinoma.

OBJECTIVE: This study was to investigate the expression and clinical significance of RRBP1 in esophageal carcinoma. MATERIALS AND METHODS: RRBP1 expression was detected in 120 esophageal carcinoma and matched adjacent normal tissues, and the relationship of RRBP1 with clinicopathological characteristics and prognosis was analyzed. RESULTS: RRBP1 was highly expressed in esophageal carcinoma tissues compared with matched adjacent normal tissues (P<0.05). Moreover, RRBP1 expression was associated with T stage, lymph node metastasis, and TNM stage in esophageal carcinoma (P<0.05). Survival analysis revealed that RRBP1, T stage, lymph node metastasis, and TNM stage were significantly associated with patients' prognosis. CONCLUSION: RRBP1 is highly expressed in esophageal carcinoma and can serve as a potential biomarker to predict patients' prognosis.

MiR-214 inhibits the proliferation and invasion of esophageal squamous cell carcinoma cells by targeting CDC25B.

BACKGROUND: Dysregulation of microRNA(miRNAs) expression was reported in human esophageal squamous cell carcinoma (ESCC). MiR-214 has been found to acts as a tumor suppressor in some tumors including ESCC. The objective of the study was to investigate the functional effect of miR-214 on the regulation of human ESCC progression. METHODS: The expression levels of miR-214 in 57 paired human ESCC tissues and adjacent normal tissues were examined by qRT-PCR. The capacities of cell proliferation and invasion were determined after up-regulation or down-regulation of miR-214 by performing cell viability assay, colony formation assay and transwell assay. Dual luciferase assays, Western blot analysis and qRT-PCR assay were used to demonstrate the association between CDC25B and miR-214. Western blot analysis assessed relative CDC25B protein expression. RESULTS: We observed that miR-214 expression exhibited a frequent down-regulation in ESCC tissues and cells, compared to adjacent normal tissues and cells, respectively. Furthermore, up-regulation of miR-214 significantly inhibited cell proliferation and colony formation and cell invasion capacities in Eca9706 and Eca109 cells. However, down-regulation of miR-214 exhibited an opposite effects. Dual luciferase assays showed that CDC25B was identified as a direct target of miR-214. Meanwhile, up-regulation of miR-214 decreased CDC25B expression, whereas, down-regulation of miR-214 increased the CDC25B expression in Eca9706 and Eca109 cells. Moreover, we demonstrated that miR-214 inhibited Eca9706 and Eca109 cells proliferation and invasion through CDC25B. CONCLUSION: Our results indicate that miR-214 function as a tumor suppressor and may be potential therapeutic target for ESCC.

Tough and Thermosensitive Poly(N-isopropylacrylamide)/Graphene Oxide Hydrogels with Macroscopically Oriented Liquid Crystalline Structures.

Bulk graphene oxide (GO) nanocomposite materials with macroscopically oriented GO liquid crystalline (LC) structures exhibit interesting anisotropic properties, but their facile preparations remain challenging. This work reports for the first time the facile preparation of poly(N-isopropylacrylamide) (PNIPAM)/GO nanocomposite hydrogels with macroscopically oriented LC structures with the assistance of a flow field induced by vacuum degassing and the in situ polymerization accelerated by GO. The hydrogel prepared with a GO concentration of 5.0 mg mL(-1) exhibits macroscopically aligned LC structures, which endow the gels with anisotropic optical, mechanical properties, and dimensional changes during the phase transition. The hydrogels show dramatically enhanced tensile mechanical properties and phase transition rates. The oriented LC structures are not damaged during the phase transition of the PNIPAM/GO hydrogels, and hence their LC behavior undergoes reversible change. Moreover, highly oriented LC structures can also be formed when the gels are elongated, even for the gels which do not have macroscopically oriented LC structures. Very impressively, the oriented LC structures in the hydrogels can be permanently maintained by drying the gel samples elongated to and then kept at a constant tensile strain. The thermosensitive nature of PNIPAM and the angle-dependent nature of the macroscopically aligned GO LC structures allow the practical applications of the PNIPAM/GO hydrogels as optical switches, soft sensors, and actuators and so on.

Radical Chain Polymerization Catalyzed by Graphene Oxide and Cooperative Hydrogen Bonding.

Graphene oxide (GO) is effective in catalyzing a wide variety of organic reactions and a few types of polymerization reactions. No radical chain polymerizations catalyzed by GO have been reported. In this article, we probe the catalytic role and acceleration effect of GO for self-initiated radical chain polymerizations of acrylic acid (AA) in the presence of GO and a pre-existing polymer, poly(N-vinylpyrrolidone) (PVP), from a calorimetric perspective. Gelation experiments and DSC studies show that GO can function as a catalyst to accelerate the radical chain polymerization of AA. Isothermal polymerization kinetic data shows that the addition of GO diminishes the induction periods and increases the polymerization rates, as indicated by the much enhanced overall kinetic rate constants and lowered activation energies. The catalytic effect of GO for the polymerization of AA is attributed to the acidity of GO and the hydrogen bonding interactions between GO and monomer molecules and/or polymers.

Up-regulation of microRNA-302a inhibited the proliferation and invasion of colorectal cancer cells by regulation of the MAPK and PI3K/Akt signaling pathways.

Aberrant expression of microRNA-302a (miR-302a) has been frequently reported in some cancers excluding colorectal cancer (CRC). However, the role of miR-302a in CRC has not been reported. In this paper, we examined the effect of miR-302a overexpression on proliferation and invasion in CRC cells. The mRNA level of miR-302a in CRC cell lines was determined by real-time PCR. The miR-302a mimic was transiently transfected into CRC cells using Lipofectamine™ 2000 reagent. Subsequently, cell proliferation and invasion were assessed by MTT and Transwell assays. Western blot and ELISA assay were used to detect the expressions and secretions of matrix metalloproteinases (MMPs). Moreover, the expressions of epithelial marker, mesenchymal markers and transcription factors were also determined by Western blot. In addition, the effects of miR-302a overexpression on the MAPK and PI3K/Akt signaling pathways were investigated by Western blot. Our results showed that the mRNA level of miR-302a was remarkably decreased in CRC cell lines compared with normal colon epithelium cells. Up-regulation of miR-302a inhibited the proliferation and invasion of CRC cells. The expressions and secretions of MMP-9 and -2 were evidently reduced by increasing miR-302a. Besides, we found a decrease of ß-catenin, fibronection, vimentin, Snail, Slug, ZEB1 and ZEB2 expressions and an increase of E-cadherin expression. We also found that miR-302a overexpression might decrease the phosphorylation of Erk1/2 and Akt. Altogether, our results indicated that miR-302a overexpression was shown to inhibit proliferation and invasion of CRC cells by reducing the expressions of related proteins through suppressing the MAPK and PI3K/Akt signaling pathways.

Strong fluorescence of poly(N-vinylpyrrolidone) and its oxidized hydrolyzate.

Discovering fluorescence of existing compounds, which are generally regarded as non-fluorescent, is of important academic and technical significance. This article reports the fluorescence of common compounds containing pyrrolidone ring(s) and their oxidized hydrolyzates. Poly(N-vinylpyrrolidone) (PVP), polymerized from a very weak fluorescent monomer N-vinyl-2-pyrrolidone (NVP), exhibits strong intrinsic fluorescence. Moreover, the fluorescence of its "hydrolyzate" is dramatically enhanced by about 1000 times. The "hydrolyzate" of N-methyl-pyrrolidone (NMP) also exhibits significantly enhanced fluorescence. By studying the chemical structures and fluorescence of the hydrolyzates, the enhanced fluorescence is attributed to the formation of secondary amine oxide. The much stronger fluorescence of the polymers compared to the corresponding small molecular compounds is ascribed to the "aggregation-induced emission" (AIE) effect of the luminophores. PVP and its oxidized hydrolyzate also show some phenomena different to the common AIE effect. The fluorescence of PVP and its oxidized hydrolyzate shows stimuli response to metal ions and pH values. This study introduces novel fluorescent materials for various potential applications.

Liquid crystalline behavior of graphene oxide in the formation and deformation of tough nanocomposite hydrogels.

In this paper, we report the formation and transformation of graphene oxide (GO) liquid crystalline (LC) structures in the synthesis and deformation of tough GO nanocomposite hydrogels. GO aqueous dispersions form a nematic LC phase, while the addition of poly(N-vinylpyrrolidone) (PVP) and acrylamide (AAm), which are capable of forming hydrogen bonding with GO nanosheets, shifts the isotropic/nematic transition to a lower volume fraction of GO and enhances the formation of nematic droplets. During the gelation process, a phase separation of the polymers and GO nanosheets is accompanied by the directional assembly of GO nanosheets, forming large LC tactoids with a radial GO configuration. The shape of the large tactoids evolves from a sphere to a toroid as the tactoids increase in size. Interestingly, during cyclic uniaxial tensile deformation a reversible LC transition is observed in the very tough hydrogels. The isolated birefringent domains and the LC domains in the tactoids in the gels are highly oriented under a high tensile strain.