CircSMARCC1 Promotes Prostate Cancer Progression By Inducing TAM Recruitment And M2 Polarization Through The MiR-1322/CCL20/CCR6 Axis

BackgroundCircular RNAs(circRNAs)have been shown to mediate the infiltration of tumorassociated macrophages(TAMs)and are closely related to the occurrence and progression of various cancers.However,the regulation of TAMs by circRNAs in prostate cancer(PCa)remains uncertain.MethodsUsing circRNA sequencing,the expression patterns of circRNAs in the plasma of patients with PCa and patients with benign prostatic hyperplasia(BPH)were studied,and we identified a series of circRNAs that were differentially expressed in PCa.CircSMARCC1 expression levels were detected in PCa tissues and cell lines by fluorescence in situ hybridization(FISH)and quantitative real-time PCR(qRT-PCR).The oncogenic role of circSMARCC1 in tumor proliferation and metastasis of PCa was investigated through a series of in vitro and in vivo functional experiments.The relationship between the gene expression of circSMARCCl and clinicopathological parameters of PCa was investigated.Subsequently,the activation of the PI3K/Akt pathway following altered expression of circSMARCCl was determined by Western blot.We revealed the potential mechanism of role of circSMARCC 1/miR-1322/CCL20 signalling axis on PCa progression by bioinformatics analysis,RNA pull down,and dual luciferase reporter gene assay.In addition,co-culture systems were used to determine the interactions between prostate cancer cells and macrophages.qRT-PCR technology,flow cytometry antibody detection and Western blot analysis were used to explore the phenotypic changes of TAM after co-culture.Finally,conditioned medium from prostate cancer cells overexpressing or knocking down circSMARCCl was used as an inducer to explore its effect on TAM migration and recruitment.ResultsThe expression of circSMARCCl was significantly increased in human PCa cell lines,plasma and tissues.Moreover,the expression of circSMARCCl was positively correlated with the Gleason score of PCa patients.Overexpression of circSMARCCl promoted PCa cell proliferation,migration,invasion and epithelial mesenchymal transition(EMT)in vitro,and in vivo experiments also demonstrated the ability of circSMARCC1 to promote tumour growth and metastasis.However,knockdown of circSMARCC1 led to the opposite result.Bioinformatic analysis,RNA pull down,and dual luciferase reporter gene assays revealed a potential regulatory mechanism of the circSMARCC1/miR-1322/CCL20 axis on PCa malignant progression.Further,we found that the circSMARCC1/miR-1322/CCL20 axis activated the PI3K-Akt pathway to upregulate the expression of p-AKT473 and p-AKT308.In addition,we demonstrated by co-culture system that circSMARCCl was able to recruit TAMs infiltration in the tumour microenvironment and induce TAM to undergo M2-type polarisation,which in turn promoted the malignant progression of PCa.ConclusioncircSMARCCl promotes PCa proliferation and metastasis by upregulating the secretion of chemokine CCL20 through sponging miR-1322 and activating the PI3K/Akt signaling pathway.In addition,circSMARCCl promotes PCa progression by targeting CCL20/CCR6 signaling to induce TAMs recruitment and M2 polarization in the tumor microenvironment.