CircVMP1 promotes glycolysis and disease progression by upregulating HKDC1 in colorectal cancer.

BACKGROUND: Circular RNAs (circRNAs) have been reported to play important roles in cancers. Here, we characterized circVMP1 (hsa_circ_0006508), an important circRNA which promoted glycolysis and disease progression in colorectal cancer (CRC). In this study, we aimed to explore the mechanism by which circVMP1 regulated tumor glycolysis and its related pathways in promoting CRC cell proliferation and metastasis. METHODS: The expression level of circVMP1 in CRC tissues and adjacent normal tissues was detected using quantitative PCR. In vitro and in vivo functional experiments were used to evaluate the effects of circVMP1 in the regulation of CRC cell proliferation and migration. Mitochondrial stress tests and glycolysis stress tests were conducted to detect the effect of circVMP1 on oxidative phosphorylation and glycolysis. Dual-luciferase reporter and RNA immunoprecipitation assays were used to evaluate the interaction between circVMP1, miR-3167, and HKDC1. RESULTS: We demonstrated that the level of circVMP1 was significantly upregulated in CRC tissues compared with normal tissues. In HCT116 and SW480 cells, overexpression of circVMP1 promoted proliferation, metastasis, and glycolysis. In vivo analysis indicated that circVMP1 accelerated the proliferation of xenograft tumors. As for the mechanism, overexpression of circVMP1 increased the levels of hexokinase domain component 1 (HKDC1) through competitive binding with miR-3167. CONCLUSION: Our study reported that circVMP1 was one of the tumor driver genes that promoted CRC malignant progression and glycolysis by upregulating HKDC1. CircVMP1/miR-3167/HKDC1 was a signaling axis that might be a target for CRC therapy.

Elevated Levels of circRUNX1 in Colorectal Cancer Promote Cell Growth and Metastasis via miR-145-5p/IGF1 Signalling.

BACKGROUND: Emerging evidence suggests that circular RNAs (circRNAs) are vital regulators in a range of cancers. "miRNA sponge" is the most reported role played by circRNAs in many tumors. The insulin-like growth factor (IGF) 1 pathway plays a key role in the development and progression of many cancers, including colorectal cancer (CRC). The aim of the study is to establish the potential clinical value and driving molecular mechanisms of circRNAs in CRC. MATERIALS AND METHODS: Real-time quantitative RT-PCR (qRT-PCR) was performed to measure the circRUNX1 expression in 52 tissue samples from CRC patients. We verified the tumor promotor role of circRUNX1 in cell-based in vitro and in vivo assays. Human growth factor array was used to identify circRUNX1-regulated signaling pathways. We then used a double luciferase reporter assay and RNA fluorescence in situ hybridization to identify the downstream miR-145-5p of circRUNX1. Furthermore, we performed Western blotting and biological function assays to demonstrate if the circRUNX1/miR-145-5p/IGF1 axis is responsible for the proliferation of CRC cells and promotes CRC development. RESULTS: By performing qRT-PCR from CRC tissues and paired adjacent normal mucosa tissues, we identified that circRUNX1 expression was significantly upregulated in CRC tissues and positively related with lymph node metastasis, distant metastasis and advanced tumor-node-metastasis tumor stage in patients. Functionally, circRUNX1 knockdown inhibited cell proliferation and migration and promoted apoptosis, whereas its overexpression exerted opposite effects. In vivo, circRUNX1 promoted tumor growth and metastasis. Mechanically, circRUNX1 shared miRNA response elements with IGF1. circRUNX1 competitively bound to miR-145-5p and prevented miR-145-5p from decreasing the expression of IGF1, which facilitated tumor growth. CONCLUSION: Our studies verified that circRUNX1 functions as a tumor promotor in CRC cells by targeting the miR-145-5p/IGF1 signaling pathway and may have potential use as a prognostic indicator and therapeutic target in CRC patients.

Circular RNA circHUWE1 Is Upregulated and Promotes Cell Proliferation, Migration and Invasion in Colorectal Cancer by Sponging miR-486.

BACKGROUND: Emerging studies have revealed that circular RNAs (circRNAs) correlate with diverse diseases including cancers. However, little is known about the functions of circRNAs in colorectal cancer (CRC). In our previous research, downregulation of hsa_circ_0140388 (circHUEW1) has been detected in CRC tissues through high-throughput sequencing. However, the underlying mechanism by which circHUWE1 regulates the proliferation and apoptosis in CRC has not been investigated. MATERIALS AND METHODS: The levels of circHUWE1 in 58 pairs of CRC tissues and corresponding adjacent healthy tissues were detected by RT-qPCR. In addition, the effects of circHUWE1 on cell proliferation, apoptosis migration and invasion were evaluated by cell proliferation assays, flow cytometry, and transwell assays in HCT116 and SW480 cell lines respectively. Meanwhile, the dual-luciferase reporter system assay was used to explore the interaction between circHUWE1 and miR-486 (hsa-miR-486-5p). RESULTS: In this study, we demonstrate that the expression of circHUEW1 is upregulated in CRC tissues. High expression of circHUEW1 was significantly associated with lymphovascular invasion (P =0.036), lymph node metastasis (P =0.017), distant metastasis (P =0.024), and TNM stage (P =0.009). Moreover, the area under the curve (AUC) of the receiver operating characteristic (ROC) curve was 0.732, which indicated that circHUWE1 could serve as a potential biomarker in the detection of CRC. Silencing circHUWE1 significantly inhibited the proliferation, migration and invasion capacity of CRC cells in vitro. Mechanistically, we demonstrated that circHUWE1 could sponge miR-486 and the downregulation of miR-486 could reverse the cancer suppressive effects caused by silencing circHUWE1. CONCLUSION: In this study, our results revealed that circHUWE1 may be a potential therapeutic target and diagnostic biomarker for CRC.

Human colorectal cancer cells frequently express IgG and display unique Ig repertoire.

BACKGROUND: There is growing evidence proving that many human carcinomas, including colon cancer, can overexpress immunoglobulin (Ig); the non B cancer cell-derived Ig usually displayed unique V(D)J rearrangement pattern that are distinct from B cell-derived Ig. Especially, the cancer-derived Ig plays important roles in cancer initiation, progression, and metastasis. However, it still remains unclear if the colon cancer-derived Ig can display unique V(D)J pattern and sequencing, which can be used as novel target for colon cancer therapy. AIM: To investigate the Ig repertoire features expressed in human colon cancer cells. METHODS: Seven cancerous tissue samples of colon adenocarcinoma and corresponding noncancerous tissue samples were sorted by fluorescence-activated cell sorting using epithelial cell adhesion molecule as a marker for epithelial cells. Ig repertoire sequencing was used to analyze the expression profiles of all 5 classes of Ig heavy chains (IgH) and the Ig repertoire in colon cancer cells and corresponding normal epithelial cells. RESULTS: We found that all 5 IgH classes can be expressed in both colon cancer cells and normal epithelial cells. Surprisingly, unlike the normal colonic epithelial cells that expressed 5 Ig classes, our results suggested that cancer cells most prominently express IgG. Next, we found that the usage of Ig in cancer cells caused the expression of some unique Ig repertoires compared to normal cells. Some VH segments, such as VH3-7, have been used in cancer cells, and VH3-74 was frequently present in normal epithelial cells. Moreover, compared to the normal cell-derived Ig, most cancer cell-derived Ig showed unique VHDJH patterns. Importantly, even if the same VHDJH pattern was seen in cancer cells and normal cells, cancer cell-derived IgH always displayed distinct hypermutation hot points. CONCLUSION: We found that colon cancer cells could frequently express IgG and unique IgH repertoires, which may be involved in carcinogenesis of colon cancer. The unique IgH repertoire has the potential to be used as a novel target in immune therapy for colon cancer.

Circular RNA circVAPA is up-regulated and exerts oncogenic properties by sponging miR-101 in colorectal cancer.

Circular RNAs (circRNAs) are a novel class of non-coding RNAs with distinct properties and diverse physiological and pathological functions. However, the functions of circRNAs in colorectal cancer (CRC) remain elusive. This study aimed to investigate the functional roles of circVAPA in CRC. High-throughput RNA sequencing was performed in 4 paired CRC tissues, and circVAPA (hsa_circ_0006990), was identified as a potential functional circRNA. Using quantitative real-time polymerase chain reaction (qRT-PCR), circVAPA was found to be up-regulated in CRC patients' tissues and plasma. Furthermore, circVAPA level was associated with unfavorable clinicopathologic features in CRC. The area under curve (AUC) of ROC was 0.724, suggesting that plasma level of circVAPA could serve as a promising biomarker for CRC detection. Sanger sequencing confirmed the back-splice junction sequences of circVAPA. Actinomycin D and RNase R treatments suggested that circVAPA was highly stable compared with its linear counterpart, and qRT-PCR for the circVAPA level in nuclear and cytoplasmic fractions indicated that circVAPA was predominantly localized in the cytoplasm. Gain-of-function and loss-of-function studies in CRC cell lines indicated that circVAPA could promote CRC cell proliferation, migration, invasion, and inhibit apoptosis. miRanda software (v3.3a) was used to predict target miRNAs of circVAPA. Moreover, target miRNAs associated with the KEGG pathway of COLORECTAL CANCER (Entry: map05210; https://www.kegg.jp/) were screened using DIANA-miRPath v.3 platform (Reverse Search module; TarBase v7.0 method). The analyses by miRanda and miRPath suggested that circVAPA could potentially bind to hsa-miR-101-3p (miR-101) associated with the COLORECTAL CANCER pathway. Luciferase reporter assay confirmed a direct interaction between circVAPA and miR-101. Furthermore, circVAPA had no effect on the expression level of miR-101, and miR-101 over-expression had the similar tumor-suppressing effects as circVAPA silencing. The tumor-promoting effect of circVAPA over-expression could be reversed by the up-regulation of miR-101. These data demonstrated that circVAPA promoted CRC progression by sponging miR-101. In conclusion, we have verified that circVAPA is up-regulated in CRC patients' tissues and plasma, and exerts oncogenic properties by sponging miR-101 in CRC. CircVAPA could serve as a promising biomarker and a therapeutic target for CRC.

RNA sequencing reveals the expression profiles of circRNA and indicates that circDDX17 acts as a tumor suppressor in colorectal cancer.

BACKGROUND: Circular RNA (circRNA) is a novel class of noncoding RNAs with functions in various pathophysiological activities. However, the expression profiles and functions of circRNAs in colorectal cancer (CRC) remain largely unknown. METHODS: High-throughput RNA sequencing (RNA-seq) was performed to assess circRNA expression profiles in 4 paired CRC tissues, and significantly dysregulated circRNAs were validated by quantitative real-time polymerase chain reaction (qRT-PCR). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed to predict the potential functions of dysregulated circRNAs. Target miRNAs of circRNAs were predicted using miRanda software, and were further analyzed combining DIANA-miRPath v.3 platform (Reverse Search module) with KEGG pathways of COLORECTAL CANCER and MicroRNAs in cancer (Entry: map05210 and map05206). CircRNA-miRNA interaction networks were constructed using Cytoscape software. Expression levels of a significantly down-regulated circRNA, circDDX17 (hsa_circ_0002211), was detected by qRT-PCR in 60 paired CRC tissues. CircDDX17 was knockdown by siRNA, and the biological functions of circDDX17 were examined in CRC cell lines. RESULTS: Totally 448 differentially expressed circRNAs were identified, including 394 up-regulated and 54 down-regulated circRNAs. qRT-PCR validation confirmed the reliability of the RNA-Seq data. GO and KEGG analyses revealed that these dysregulated circRNAs were potentially implicated in CRC pathogenesis. Analyses by combining miRanda and miRPath softwares with KEGG pathways suggested that the miRNAs targeted by the top 10 dysregulated circRNAs were associated with the KEGG pathways of COLORECTAL CANCER and MicroRNAs in cancer, indicating that circRNA-miRNA interactions might play important functional roles in the initiation and progression of CRC. The results of qRT-PCR for circDDX17 in 60 paired CRC tissues showed that circDDX17 was significantly down-regulated in CRC tissues and associated with unfavorable clinicopathological parameters. In vitro experiments showed that silencing of circDDX17 promoted CRC cell proliferation, migration, invasion, and inhibited apoptosis. CONCLUSIONS: In conclusion, we have identified numerous circRNAs that are dysregulated in CRC tissues compared with adjacent normal mucosa tissues. Bioinformatic analyses suggested that these dysregulated circRNAs might play important functional roles in CRC tumorigenesis. CircDDX17 functions as a tumor suppressor and could serve as a potential biomarker and a therapeutic target for CRC.

Synergistic effect of nitrate-doped TiO2 aerosols on the fast photochemical oxidation of formaldehyde.

The uptake of formaldehyde (HCHO) on mineral dust affects its budget as well as particle properties, yet the process has not yet been fully investigate. Here, TiO2 and nitrate-doped TiO2 aerosols were used as proxies for mineral dust, and the uptake of HCHO was explored in a chamber under both dark and illuminated conditions. The uptake loss of HCHO on UV-illuminated aerosols is 2-9 times faster than its gaseous photolysis in our experimental system. The uptake coefficient in the range of 0.43-1.68 × 10-7 is 1-2 orders of magnitude higher than previous reports on model mineral dust particles. The reaction rate exhibits a Langmuir-Hinshelwood-type dependence on nitrate content and relative humidity, suggesting the competitive role of nitrate salts, water vapor and HCHO on the TiO2 surface. The reaction produces carbon dioxide as the main product and gaseous formic acid as an important intermediate. The hydroxyl radical produced on illuminated TiO2 primarily drives the fast oxidation of HCHO. The nitrate radical arising from the TiO2-catalyzed photoreaction of nitrate synergistically promotes the oxidation process. This study suggests a novel oxidation route for HCHO in the atmosphere, taking into account high abundance of both mineral dust and anthropogenic TiO2 aerosols.

Long noncoding RNA HIT000218960 promotes papillary thyroid cancer oncogenesis and tumor progression by upregulating the expression of high mobility group AT-hook 2 (HMGA2) gene.

Accumulating evidence suggests that long noncoding RNAs (lncRNAs) play an important role in oncogenesis and tumor progression. However, our knowledge of lncRNAs in thyroid cancer is still limited. To explore the crucial lncRNAs involved in oncogenesis of papillary thyroid cancer (PTC), we acquired data of differentially expressed lncRNAs between PTC tissues and paired adjacent noncancerous thyroid tissues through lncRNA microarray. In the microarray data, we observed that a newly identified lncRNA, HIT000218960, was significantly upregulated in PTC tissues and associated with a well-known oncogene, high mobility group AT-hook 2 (HMGA2) gene. Both in normal thyroid tissues and PTC tissues, the expression of HIT000218960 was significantly positively correlated with that of HMGA2 mRNA. Knockdown of HIT000218960 in PTC cells resulted in downregulation of HMGA2. In addition, functional assays indicated that inhibition of HIT000218960 in PTC cells suppressed cell proliferation, colony formation, migration and invasion in vitro. Increased HIT000218960 expression in PTC tissues was obviously correlated with lymph node metastasis and multifocality, as well as TNM stage. Those findings suggest that HIT000218960 might acts as a tumor promoter through regulating the expression of HMGA2.

Downregulation of miR-199b is associated with distant metastasis in colorectal cancer via activation of SIRT1 and inhibition of CREB/KISS1 signaling.

The progression of distant metastasis cascade is a multistep and complicated process, frequently leading to a poor prognosis in cancer patients. Recently, growing evidence has indicated that deregulation of microRNAs (miRNAs) contributes to tumorigenesis and tumor progression in colorectal cancer (CRC). In the present study, by comparing the miRNA expression profiles of CRC tissues and corresponding hepatic metastasis tissues, we established the downregulation of miR-199b in CRC metastasis tissues. The decrease in miR-199b expression was significantly correlated to late TNM stage and distant metastasis. Moreover, Kaplan-Meier curves showed that CRC patients with high expression level of miR-199b had a longer median survival. Functional assays results indicated that the restoration of miR-199b considerably reduced cell invasion and migration in vitro and in vivo, and increased the sensitivity to 5-FU and oxaliplatin. Further dual-luciferase reporter gene assays revealed that SIRT1 was the direct target of miR-199b in CRC. The expression of miR-199b was inversely correlated with SIRT1 in CRC specimens. SIRT1 knockdown produced effects on biological behavior that were similar to those of miR-199b overexpression. Furthermore, through Human Tumor Metastasis PCR Array we discovered KISS1 was one of the downstream targets of SIRT1. Silencing of SIRT1 upregulated KISS1 expression by enhancing the acetylation of the transcription factor CREB. The latter was further activated via binding to the promoter of KISS1 to induce transcription. Thus, we concluded that miR-199b regulates SIRT1/CREB/KISS1 signaling pathway and might serve as a prognosis marker or a novel therapeutic target for patients with CRC.