title: miRNA-520b and miR-520e sensitize breast cancer cells to complement attack via directly targeting 3'UTR of CD46.
abstract: MicroRNAs (miRNAs), non-coding RNAs that function as post-transcriptional gene regulators, play a pivotal role in cancer development. In the present study, we elucidated the roles of miR-520b and miR-520e in breast cancer cells. We examined the expression levels of miR-520b and miR-520e in the immortalized breast cell line, HBL-100, and in three breast cancer cell lines: MCF-7, LM-MCF-7 and MDA-MB-231. We show the expression levels of miR-520b and miR-520e in the breast cancer cell lines were lower than that in the HBL-100 cells. Furthermore, the breast cancer cell lines showed less sensitivity to complement-dependent cytotoxicity (CDC). We found that overexpression of miR-520b and miR-520e increases the sensitivity of the breast cancer cells to CDC, whereas further suppression of miR-520b and miR-520e decreases the sensitivity of the breast cancer cells to CDC. We then demonstrate that miR-520b and miR-520e are able to directly target the 3'untranslated regions (3'UTR) of the membrane-bound complement regulatory protein CD46; suggesting that miR-520b and miR-520e down-regulate CD46 at post-transcriptional level. Enzyme-linked immunosorbent assay (ELISA) showed that overexpression of miR-520b and miR-520e results in the increased expression of C3b, which is mediated by downregulated CD46. These results suggest that miRNA-520b and miR-520e mediated down-regulation of CD46 induces opsonization of cancer cells via an alternative pathway resulting in complement activation. Thus, we conclude that miR-520b and miR-520e contribute to CDC in breast cancer cells via directly targeting the 3'UTR of CD46.
authors.affiliation: Department of Biochemistry, The Key Laboratory of Bioactive Materials, Ministry of Education, Institute for Molecular Biology and Biochemistry, College of Life Sciences, Nankai University, Tianjin, China.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Cui
authors.forename: Yiwen
authors.initials: Y
authors.lastname: Zhang
authors.forename: Nan
authors.initials: N
authors.lastname: Hu
authors.forename: Changliang
authors.initials: C
authors.lastname: Shan
authors.forename: Shuai
authors.initials: S
authors.lastname: Zhang
authors.forename: Weiying
authors.initials: W
authors.lastname: Zhang
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zhang
authors.forename: Lihong
authors.initials: L
authors.lastname: Ye
mesh_terms: D020413:3' Untranslated Regions; D001483:Base Sequence; D001943:Breast Neoplasms / Q000235:genetics* / Q000276:immunology* / Q000378:metabolism; D045744:Cell Line, Tumor; D003179:Complement C3b / Q000096:biosynthesis / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D015536:Down-Regulation; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D051916:Membrane Cofactor Protein / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D035683:MicroRNAs / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D014162:Transfection
chemical_list: D020413:3' Untranslated Regions; D051916:Membrane Cofactor Protein; D035683:MicroRNAs; D003179:Complement C3b