Purpose: Circular RNAs (circRNAs), a novel class of noncoding RNAs, have recently drawn lots of attention in the pathogenesis of human cancers. However, the role of circRNAs in cancer cells epithelial-mesenchymal transition (EMT) remains unclear. In this study, we aimed to identify novel circRNAs that regulate urothelial carcinoma of the bladder (UCB) cells' EMT and explored their regulatory mechanisms and clinical significance in UCBs. Experimental Design: We first screened circRNA expression profiles using a circRNA microarray in paired UCB and normal tissues, and then studied the clinical significance of an upregulated circRNA, circPRMT5, in a large cohort of patients with UCB. We further investigated the functions and underlying mechanisms of circPRMT5 in UCB cells' EMT. Moreover, we evaluated the regulation effect of circPRMT5 on miR-30c, and its target genes, SNAIL1 and E-cadherin, in two independent cohorts from our institute and The Cancer Genome Atlas (TCGA). Results: We demonstrated that upregulated expression of circPRMT5 was positively associated with advanced clinical stage and worse survival in patients with UCB. We further revealed that circPRMT5 promoted UCB cell's EMT via sponging miR-30c. Clinical analysis from two independent UCB cohorts showed that the circPRMT5/miR-30c/SNAIL1/E-cadherin pathway was essential in supporting UCB progression. Importantly, we identified that circPRMT5 was upregulated in serum and urine exosomes from patients with UCB, and significantly correlated with tumor metastasis. Conclusions: CircPRMT5 exerts critical roles in promoting UCB cells' EMT and/or aggressiveness and is a prognostic biomarker of the disease, suggesting that circPRMT5 may serve as an exploitable therapeutic target for patients with UCB.

Background: Metastasis causes the vast majority of colorectal carcinoma (CRC)-related deaths. However, little is known about the specific traits and underlying mechanisms of metastasis-initiating cells in primary CRC. And whether or not circular RNAs (circRNAs) take part in this particular event remain not adequately stated yet. Methods: A screening method based on Transwell assay was first applied to build CRC subgroups with different metastatic potential. High throughput RNA sequencing was used to find out novel metastatic drivers in CRC metastasis-initiating step. A series of in vitro and in vivo assays were further applied to elucidate the functions and underlying molecular mechanisms of circRNAs in CRC metastasis. Results: A circRNA consisting of exon 8-11 of LONP2, termed as circLONP2, was upregulated in metastasisinitiating CRC subgroups. Aberrant higher expression of circLONP2 was observed in primary CRC tissues with established metastasis, and along the invasive margin in metastatic site. High expression of circLONP2 predicted unfavorable overall survival. Functional studies revealed that circLONP2 could enhance the invasiveness of CRC cells in vitro, and targeting circLONP2 through anti-sense oligonucleotide (ASO) dramatically reduced the penetrance of metastasis to foreign organs in vivo. Mechanically, circLONP2 directly interacted with and promoted the processing of primary microRNA-17 (pri-miR-17), through recruiting DiGeorge syndrome critical region gene 8 (DGCR8) and Drosha complex in DDX1-dependent manner. Meanwhile, upregulated mature miR-17-5p could be assembled into exosomes and internalized by neighboring cells to enhance their aggressiveness.

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Chromobox homolog 8 (CBX8), also known as human polycomb 8, is a repressor that maintains the transcriptionally repressive state in various cellular genes, and has been reported to promote tumorigenesis. In the present study, we examined CBX8 expression in eight pairs of muscle invasive bladder cancer tissues and adjacent non‐tumor tissues, and found that CBX8 was frequently upregulated in muscle invasive bladder cancer tissues when compared to adjacent non‐tumor tissues. Analysis showed that high expression of CBX8 in 152 muscle invasive bladder cancer specimens was associated with progression of the T, N, and M stages (P = 0.004, 0.005, <0.001, respectively). Furthermore, Kaplan–Meier survival analysis and log–rank test showed that muscle invasive bladder cancer patients with high CBX8 expression had a poor rate of overall survival (P < 0.001) and 5‐year recurrence‐free survival (P < 0.001) compared to patients with low CBX8 expression. High CBX8 expression predicted poor overall survival and 5‐year recurrence‐free survival in T and N stages of muscle invasive bladder cancer patients. Moreover, knockdown of CBX8 inhibited cell proliferation of urothelial carcinoma of the bladder both in vitro and in vivo. In addition, CBX8 depletion resulted in cell cycle delay of urothelial carcinoma cells of the bladder at the G2/M phase by the p53 pathway. The data suggest that high expression of CBX8 plays a critical oncogenic role in aggressiveness of urothelial carcinoma cells of the bladder through promoting cancer cell proliferation by repressing the p53 pathway, and CBX8 could be used as a novel predictor for muscle invasive bladder cancer patients.

Kinesin family member C1 (KIFC1) is implicated in the clustering of multiple centrosomes to maintain tumor survival and is thought to be an oncogene in several kinds of cancers. In our experiments, we first performed bioinformatics analysis to investigate the expression levels of KIFC1 in bladder cancer (BC) specimens and normal bladder epitheliums and then, using our samples, verified findings by quantitative real‐time PCR and western blotting assays. All data showed that KIFC1 was significantly upregulated in BC specimens at both the mRNA and protein levels. Immunohistochemical studies in a cohort of 152 paraffin‐embedded BC tissues displayed that upregulated expression of KIFC1 clearly correlated with pT status (P = .014) and recurrent status (P = .002). Kaplan‐Meier survival analysis and log‐rank test indicated that patients with BC with high KIFC1 expression had both shorter cancer‐specific survival (P < .001) and recurrence‐free survival time (P < .001) than those with low KIFC1 expression. Furthermore, ectopic downregulation of KIFC1 weakened BC cell proliferation and migration both in vitro and in vivo, whereas upregulation of KIFC1 enhanced this in vitro. Overexpression of KIFC1 phosphorylated GSK3β and promoted Snail through activating AKT (protein kinase B0) to induce proliferation and epithelial–mesenchymal transition (EMT) and, therefore, substantially promoted BC migration and metastasis. Our study revealed an oncogenic role for KIFC1 to promote BC cell proliferation and EMT via Akt/GSK3β signaling; KIFC1 might be a promising prognostic biomarker as well as a therapeutic target for BC.