Supplementary Figure Legend - PDF file 60K, Supplementary Figure S1: top panel: MCF-7 cells were transiently transfected with control of ER-alpha siRNA. RNA was extracted 48 hours after transfected and the level of ATM mRNA was measured by RT-PCR. Bottom panel: Expression of ATM mRNA in MCF-7 cells by Real-time PCR. Expression levels were normalized by GAPDH. Error bars represent mean SD calculated from 3 parallel experiments. Supplemental Figure S2: Predicted consequential pairing of target region of ATM (top) and miRNA (bottom) of MiRNAs 18a, 106a and 101. Supplemental Figure S3: MDA-MB-231 cells were co-transfected with a luciferase reporter plasmid along with miRNA-18a or miRNA 106a. Relative luciferase activities representing ATM 3'UTR and pMirTarget vector are presented. Shown are averages of triplicate samples and standard deviations. Student t tests were used to analyze the data. Supplemental Figure S4: MiRNAs 18a and 106a are under-expressed in ER negative breast cancer tissues. In situ hybridization was conducted in 296 cases of breast cancer tissues probing miRNAs 18a and 106a. Shown are representative images of miRNA 18a and 106 expressions
ARTICLE ABSTRACT
Purpose: Estrogen receptor α (ERα) is an essential element regulating mammary gland development and it contributes to breast cancer development and progression. Most of the ER-negative breast cancers display more aggressive clinical behaviors and are resistant to antiestrogen therapies. In addition, many ER-negative tumors show insensitivity to many chemotherapeutic drugs and radiotherapy, although mechanisms underlying this phenotype are less clear.Experimental Design: We conducted immunohistochemistry on 296 cases of breast cancer tissues using a variety of antibodies. On the basis of the clinical data, we conducted siRNA knockdown to study the role of ERα on ATM expression in breast cancer cell lines. Furthermore, we used antisense oligonucleotides against micro RNAs (miRNA) or miRNA overexpression plasmids to study the role of miR-18a and -106a on ATM expression. Finally we used in situ hybridization to assess miR-18a and -106a expression in breast cancer tissues.Results: We found that in ER-negative breast cancer tissues, expression of the ATM kinase, a critical DNA damage-response protein, is aberrantly upregulated. We also found that the locoregional recurrence rate after radiotherapy positively correlates with ATM expression. On the cellular level, we showed that ERα, but not ERβ, negatively regulates ATM expression. Furthermore, we identified that ERα activates miR-18a and -106a to downregulate ATM expression. We also showed that miR-18a and -106a were significantly underexpressed in ER-negative breast cancer tissues.Conclusions: We reveal a novel mechanism involving ERα and miR-18a and -106a regulation of ATM in breast cancer. Clin Cancer Res; 19(18); 4994–5002. ©2013 AACR.
