Circ＿NSD1 Is Upregulated In Colorectal Cancer And Promotes Colorectal Cancer Cell Proliferation,Migration,and Invasion By Regulating MiR-140-5p/IGFBP5 Expression

Colorectal cancer(CRC)is one of the malignant tumors with high morbidity and mortality worldwide,and its pathogenesis involves many factors such as environment,lifestyle,and genetics.Among the diagnosed CRC patients,quite a few have metastasized,and the patients with metastatic CRC have a poor prognosis and low survival rate.Therefore,to find effective biomarkers for the diagnosis of CRC and new therapeutic targets for advanced and recurrent CRC,it is necessary to further explore and elucidate the molecular mechanisms of CRC occurrence and metastasis.Circular RNA(circRNA)is a new type of non-coding RNA molecules with covalent closed-loop structure.CircRNA is more stable than linear RNA,and plays a critical role via regulating target gene expression,changing protein activity,and translating protein.The development of high-throughput RNA sequencing and bioinformatics tools has deeply explored the distribution and function of circRNAs in the human body.Studies have found that circRNAs have cell-specific,tissue-specific,and time-specific expression patterns,and the sequences are in at the same time,circRNA can be detected in liquid biopsy samples such as plasma,saliva,and urine,which shows that circRNA has a strong potential as a diagnostic and prognostic biomarker.CircRNA is not only significantly associated with cardiovascular diseases,nervous system diseases,and autoimmune diseases,but also play an important regulatory role in cancer-related processes such as tumorigenesis and progression.Studies have shown that circRNA is involved in the process of CRC occurrence,metastasis,and drug resistance,and circRNA has been proven to play a role in regulating various signaling pathways in the occurrence and development of CRC.circRNA plays in different mechanisms according to its localization in the cytoplasm or nucleus.Among them,circRNA located in the cytoplasm mainly acts as a microRNA(miRNA)sponge in a way that competitively binds with endogenous RNA(ceRNA)to affect the expression of target genes,which is currently the most widely studied mechanism of circRNA in cancer progression.In this project,human CRC tissues and cell lines were mainly selected.The effects of circ＿NSD1(hsa＿circ＿0075158)on biological behaviors of CRC cells and the underlying molecular mechanisms were studied through the in vitro experiments,and the expression of circ＿NSD1 in CRC tissues and the relationship between circ＿NSD1expression and CRC development and progression were further examined.Objective: To explore the expression and clinical significance of circ＿NSD1 in CRC,and the effects of circ＿NSD1 on the proliferation,migration,and invasion of CRC cells by regulating microRNA-140-5p(miR-140)/insulin-like growth factor binding protein 5(IGFBP5)expressions.Methods: qRT-PCR was used to detect the mRNA expression levels of circ＿NSD1,miR-140,and IGFBP5 in CRC cells and tissues,CRC cell lines DLD-1 and LoVo were treated with actinomycin D,and the mRNA stability of circ＿NSD1 was determined.The expression of circ＿NSD1 was knocked down by small interfering RNA(siRNA)transfection,and the proliferation,migration,and invasion abilities of CRC cells were detected by CCK-8 assay,scratch healing assay,and Transwell chamber assay(including Matrigel).Results: The expression of circ＿NSD1 was significantly increased in CRC cells(P < 0.01)and tissues(P < 0.0001),and the up-regulation of circ＿NSD1 was closely associated with the advanced stage of TNM stage(P = 0.004),lymph node metastasis(P = 0.0005)and distant metastasis(P = 0.01)were significantly correlated;the expression of miR-140 was significantly reduced in CRC cells(P < 0.001)and tissues(P < 0.001),and downregulation of miR-140 was associated with advanced TNM stage(P = 0.0255)and lymph node metastasis(P = 0.0054)significantly correlated with poor differentiation(P =0.0152).The expression of IGFBP5 mRNA was significantly increased in CRC tissues(P = 0.0012),and the up-regulation of IGFBP5 mRNA was correlated with advanced TNM stage(P = 0.0003),lymph node metastasis(P = 0.0036),distant metastasis(P=0.0410),and poor differentiation(P = 0.0064)were significantly correlated.In CRC tissues,there were significant negative correlations between circ＿NSD1 and miR-140 and between miR-140 and IGFBP5 mRNA expression(r =-0.4603,P = 0.0092;r = 0.4955,P = 0.0046).circ＿NSD1 had the characteristics of circular RNA,and the half-life of circ＿NSD1 was significantly longer than that of linear NSD1 mRNA.Knockdown of circ＿NSD1 could significantly inhibit the proliferation,migration,and invasion of CRC cells,while downregulation of miR-140 could partially reverse this inhibitory effect.Conclusion: circ＿NSD1 is a stable circRNA molecule,and the increased expression of circ＿NSD1 may be related to the occurrence,invasion,progression,and metastasis of CRC.circ＿NSD1 may promote the proliferation,migration,and invasion of CRC cells by down-regulating miR-140 and then up-regulating the expression of IGFBP5.circ＿NSD1 It may become a new potential target for the diagnosis and treatment of CRC.