ABSTRACT
Most primary breast cancers express estrogen receptor α and can be treated via endocrine therapy using anti-estrogens such as tamoxifen; however, acquired endocrine resistance is a critical issue. To identify tamoxifen response-related microRNAs (miRNAs) in breast cancer, MCF-7 cells infected with a lentiviral miRNA library were treated with 4-hydroxytamoxifen (OHT) or vehicle for 4 weeks, and the amounts of individual miRNA precursors that had integrated into the genome were evaluated by microarray. Compared to the vehicle-treated cells, 5 'dropout' miRNAs, which were downregulated in OHT-treated cells, and 6 'retained' miRNAs, which were upregulated in OHT-treated cells, were identified. Of the dropout miRNAs, we found that miR-574-3p expression was downregulated in clinical breast cancer tissues as compared with their paired adjacent tissues. In addition, anti-miR-574-3p reversed tamoxifen-mediated suppression of MCF-7 cell growth. Clathrin heavy chain (CLTC) was identified as a miR-574-3p target gene by in silico algorithms and luciferase reporter assay using the 3' untranslated region of CLTC mRNA. Interestingly, loss and gain of miR-574-3p function in MCF-7 cells causes CLTC to be upregulated and downregulated, respectively. These results suggest that functional screening mediated by miRNA libraries can provide new insights into the genes essential for tamoxifen response in breast cancer.
Subject(s)
Antineoplastic Agents, Hormonal/toxicity , Down-Regulation/drug effects , MicroRNAs/metabolism , Tamoxifen/analogs & derivatives , Up-Regulation/drug effects , 3' Untranslated Regions , Algorithms , Base Sequence , Binding Sites , Breast Neoplasms/genetics , Breast Neoplasms/pathology , Cell Proliferation/drug effects , Clathrin/antagonists & inhibitors , Clathrin/genetics , Clathrin/metabolism , Female , Gene Library , Humans , MCF-7 Cells , MicroRNAs/antagonists & inhibitors , MicroRNAs/genetics , Oligonucleotides, Antisense/metabolism , RNA Interference , RNA, Messenger/metabolism , RNA, Small Interfering/metabolism , Sequence Alignment , Tamoxifen/toxicityABSTRACT
This manuscript is a brief discussion of the developments of the technology and concepts that led to modern procedures of radiotracer guided surgery of sentinel nodes (SNs) for breast cancer. The past section highlights some of the contributions by key persons involved with SN methods. The present section describes the magnitude of types of published material to date. The future section describes the major international trials and some important technical challenges yet to be solved.
