Microtubule-Associated Protein 9 Is a Potential Tumor Suppressor That Is Inactivated by Methylation in Cervical Cancer

Cervical cancer is a malignant disease that seriously affects women’s health, and the cause of cervical cancer is complex. Microtubule-associated protein 9 (MAP9) localizes to the mitotic spindle and it plays an important role in spindle assembly and centrosome integrity maintenance. The expression and function of MAP9 is unclear in cervical cancer. This study aims to explore the relationship between DNA methylation of MAP9 and cervical cancer, and the function of MAP9 in cervical cancer. qRT-PCR was used to detect the transcriptional expression of MAP9 in cervical cancer tissues and cell lines. The methylation status of MAP9 promoter was determined by bisulfite sequencing PCR (BSP). The DNA methyltransferase inhibitor, 5-Aza-CdR, was used to inhibit the activity of methyltransferase. Then, the cell proliferation was performed by CCK-8 assay after the transfection of MAP9 plasmids. Furthermore, the cell cycle and apoptosis were performed by flow cytometry. It was found that MAP9 was down-regulated both in cervical cancer tissues and cell lines. The promoter and the first exon region of MAP9 was hypermethylated and its mRNA expression could be restored after the treatment of 5-Aza-CdR. Ectopic expression of MAP9 could inhibit cell proliferation and cell cycle, without effecting the cell apoptosis. The low expression of MAP9 in cervical cancer dues to its hypermethylation and acts a potential tumor suppressor gene. MAP9 might be a novel biomarker in cervical cancer.