Promoter methylation of SEPT9 as a potential biomarker for early detection of cervical cancer and its overexpression predicts radioresistance

Abstract

Background: Cervical cancer screening by combined cytology and HPV test has reduced the incidence of cervical cancer, but cytological screening lacks a higher sensitivity while HPV testing possesses a lower specificity. Most patients with invasive cervical cancer are treated with radiotherapy. However, insensitivity to radiotherapy leads to poor efficacy. Methods: Illumina Methylation EPIC 850k Beadchip was used for genomic screening. We detected methylation of SEPT9 and mRNA expression in different cervical tissues by using methylation-specific PCR and qRT-PCR. Then using CCK8, migration assay, and flow cytometry to detect the biological function and irradiation resistance of SEPT9 in vitro and in vivo. Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and co-immunoprecipitation (CoIP) were used to find the interacting gene with SEPT9. Immunostaining of CD206 in cervical cancer and polarization of macrophages (M2) were evaluated by immunofluorescence and WB. The Cancer Genome Atlas (TCGA) database was used for screening the potential miRNAs induced by SEPT9. Results: Hyper-methylation of SEPT9 detects cervical cancer and normal tissues, normal+CIN1 and CIN2+CIN3+cancer with high sensitivity and specificity (AUC = 0.854 and 0.797, respectively, P < 0.001). The mRNA and protein expression of SEPT9 was upregulated in cervical cancer tissues when compared to para-carcinoma tissues. SEPT9 promotes proliferation, invasion, migration, and influences the cell cycle of cervical cancer. SEPT9 interacted with HMGB1-RB axis increases irradiation resistance. Furthermore, SEPT9 mediated miR-375 via the tumor-Associated macrophages (TAMs) polarization, affecting the resistance to radiotherapy in cervical cancer. Conclusions: These findings give us the evidence that SEPT9 methylation could be a biomarker for cervical cancer diagnoses. It promotes tumorigenesis and radioresistance of cervical cancer by targeting HMGB1-RB axis and causes polarization of macrophages by mediating miR-375. We suggest SEPT9 could be a potential screening and therapeutic biomarker for cervical cancer.