Long Non-Coding RNA ZFAS1 Promotes Colorectal Cancer Tumorigenesis And Development Through DDX21/POLR1B Regulatory Axis

Objective: Increasing evidence supports long non-coding RNA-ZFAS1 as master protein regulators involved in a variety of human cancer initiation and development.However,the molecular mechanism underlying the regulation function is not fully understood in colorectal cancer(CRC)and remain to be elucidated.Methods: The dysregulated expression profiling of lncRNAs-mRNAs and the enrichment network of correlations and co-expression target genes were assessed by the Genechip microarray dataset.In this included paired of CRC tissues and matched tumor-adjacent controls(n=157),lncRNA-ZFAS1 were determined by in situ hybridization(ISH),meanwhile,DEAD-boxDDX21 and POLR1 B were detected by immunohistochemistry(IHC).These indicators were randomly detected and identified by RT-PCR and qPCR assays upon at least 20 pairs of the CRC tissues.The biological functions of the indicators were investigated using in vitro and in vivo studies including MTT assay,Trans-well method,apoptosis analysis,immunofluorescence(IF)assay,Western Blot method,and the xenograft mice models.The molecular mechanisms were explored by bioinformatics analysis,RNA fluorescence ISH,RNA pull-down assay.Results: Here,we uncovered a previously unreported molecular mechanism linking nucleolar RNA helicase DDX21 regulated by lncRNA-ZFAS1 in control of POLR1 B dependent transcription manner in CRC development and progression.Specifically,LncRNA ZFAS1 exerts its functions as an oncogene and was confirmed significantly upregulated accompanied by elevated DDX21,POLR1 B expression in CRC cells and tissues,which further closely associated with poor clinical outcomes in this included cohort.Furthermore,ZFAS1 knockdown dramatically suppressed CRC cell proliferation,invasion,migration,and increased cell apoptosis,which were contrary to the effect caused by ZFAS1 up-regulation.Notably,we further revealed that the inhibitory effect caused by ZFAS1 knockdown could be reversed by DDX21 overexpression in CRC cells and xenograft mice tumors.Mechanistically,our research for the first time reported that ZFAS1 could directly recruit DDX21 protein by harboring the specific motif(AAGA or CAGA).Finally,POLR1 B was identified as the downstream target gene of DDX21 regulated by ZFAS1,which was also up-regulated in CRC cells and tissues and closely related to poor prognosis.Therefore,our results illustrated that ZFAS1 promoted POLR1 B expression via direct binding DDX21 protein,subsequently contributed to tumorigenesis and progression in CRC cells and tissues.Conclusions:The novel ZFAS1/DDX21/POLR1 B signaling regulation axis in CRC may provide new biomarkers and targets for the early treatment and prognostic evaluation of CRC.