MiRNA-۲۱۸ Is Frequently Downregulated in Malignant Breast Tumors: A Footprint of Epstein-Barr Virus Infection

Background & Objective: The role of Epstein-Barr Virus in development of breast cancer is frequently studied. In this regard, miRNAs are among the contributing elements in the molecular pathophysiology of EBV-related diseases. In addition, a growing number of host miRNAs are believed to be implicated in pathogenesis of breast cancer. MiR-۲۱۸ is a tumor suppressive miRNA that is subjected to dysregulation in various EBV-associated cancers. We aimed to investigate the frequency of EBV and its relationship with expression status of tumor suppressive miR-۲۱۸ in breast cancer and adjacent normal tissue.Methods: A total number of ۵۱ fresh malignant breast cancer tissues (cases) and their adjacent normal tissues (controls) were collected. Nested-PCR and RT-qPCR were set to identify EBV frequency and miR-۲۱۸ expression in cases and controls, respectively.Results: Out of all samples, ۶.۸% (۷/۱۰۲) comprising ۱۱.۶% (۶/۵۱) in malignant tissues and ۱.۹% (۱/۵۱) in normal control tissues were positive for EBV (P<۰.۰۵). Quantitative data showed that miR-۲۱۸ was significantly downregulated in malignant tissues compared to control tissues (P<۰.۰۰۰۱). In addition, reduced expression of miR-۲۱۸ was associated with adverse clinical outcomes, metastasis, and higher grades of malignancy. Given the presence of EBV, lower expression of miR-۲۱۸ was observed in breast cancer group in comparison with normal group (P<۰.۰۵). Conclusion: Our results raise the possibility of the relation between EBV infection and miR-۲۱۸ downregulation in breast cancer and propose further investigations in this regard. 

Keywords:

Breast Neoplasm , Epstein Barr virus , Human microRNA۲۱۸