Circular RNA circRHOBTB3 represses metastasis by regulating the HuR-mediated mRNA stability of PTBP1 in colorectal cancer

Abstract

Background: Tumor metastasis of colorectal cancer (CRC) is the main cause of death in most patients and the major difficulty in comprehensive CRC treatment. Circular RNAs (circRNAs) affect many biological functions in solid tumors. However, their mechanisms in CRC metastasis remain unclear. Methods: RNA sequencing (RNA-seq) and quantitative real-time PCR were performed to screen differentially expressed circRNAs between CRC tissues and adjacent normal tissues. CCK-8, cell migration and wound healing assays were performed to determine the functions of circRHOBTB3 in cell proliferation and metastasis. RNA pulldown and RNA immunoprecipitation assays were performed to verify the interaction between circRHOBTB3 and the HuR (ELAVL1) protein. Further RNA-seq and rescue experiments were applied to search for the downstream target. We also conducted a mouse xenograft model to elucidate the effect of circRHOBTB3 on cancer metastasis in vivo . Results: We identified circRHOBTB3 which is markedly downregulated in CRC tissues and cell lines. Furthermore, lower circRHOBTB3 levels were significantly associated with advanced clinical stages and greater risk of metastases. Overexpression of circRHOBTB3 suppresses tumor metastasis in CRC cells. Mechanistically, circRHOBTB3 binds to HuR, which is a ubiquitously expressed and functional RNA-binding protein (RBP) in CRC development, and promotes β-Trcp1-mediated ubiquitination of HuR. Normally, HuR binds to the 3'UTR of target mRNAs to facilitate their stabilization, whereas the interaction between circRHOBTB3 and HuR degrades HuR to reduce the expression level of the downstream target PTBP1. Furthermore, overexpressed circRHOBTB3 suppresses lung metastases in vivo , and this effect can be partly reversed by PTBP1 overexpression. In addition, the transcription of circRHOBTB3 can be improved by both FUS and ADARB2 in CRC cells. Conclusions: Our findings indicate that circRHOBTB3 exerts suppressive effects on CRC aggressiveness through the HuR/PTBP1 axis.

Oncogenic circTICRR suppresses autophagy via binding to HuR protein and stabilizing GLUD1 mRNA in cervical cancer

“…As HuR is crucial for mRNA stability [ 27 ] and plays an oncogenic role in cancers [ 28 , 29 ], and GLUD1 mRNA and protein levels were down-regulated by HuR knockdown in this study (Fig. 5G, H ), we further explored the stability of GLUD1 mRNA by HuR knockdown followed by ACTD treatment, and found that the stability of GLUD1 mRNA was decreased in the SiHa and CaSki cells with HuR knockdown, compared with control cells (Fig.…”

Comprehensive analysis of a ceRNA network associated with TP53 mutations in liver hepatocellular carcinoma

“…Functioning as the only mRNA in our network, PTBP1 demonstrated the strongest correlation with immune cell in ltrations and chemoresistance. With the ability to control almost all steps of messenger RNA metabolism and processing 50 , the elevation of PTBP1 caused an adverse effect in glioblastoma 51 and colorectal cancer 52 . In HCC, relationships between PTBP1 up-regulation and tumor growth 50 , tumor invasion as well as metastasis 53 were uncovered.…”

Roles of Embryonic Lethal Abnormal Vision-Like RNA Binding Proteins in Cancer and Beyond

“…The class of circRNAs includes closed circular ncRNA molecules that are not easily degraded and have been shown to regulate the progression of various diseases ( Li et al, 2015 ). For example, circRHOBTB3 is expressed at relatively low levels in hepatocellular carcinoma, and it has been reported that over-expression of circRHOBTB3 can lead to degradation of ELAVL1 and thus inhibition of the expression of the ELAVL1 target gene PTBP1 ( Chen et al, 2021b ). ELAVL1 also interacts competitively with circDLC1 to negatively regulate the expression of the gene encoding matrix metalloproteinase 1 ( Liu et al, 2021 ); this mechanism occurs in a similar manner with regard to circPPM1F and its target gene PPM1F ( Zhang et al, 2020 ) and circPABPN1 and its target gene ATG16L1 ( Li et al, 2020 ).…”