Cancer stem cells (CSCs) are resistant to chemo- and radio-therapy, and can survive to regenerate new tumors. This is an important reason why various anti-cancer therapies often fail to completely control tumors, although they kill and eliminate the bulk of cancer cells. In this study, we determined whether or not adenine nucleotide translocator-2 (ANT2) suppression could also be effective in inducing cell death of breast cancer stem-like cells. A sub-population (SP; CD44+/CD24-) of breast cancer cells has been reported to have stem/progenitor cell properties. We utilized the adeno-ANT2 shRNA virus to inhibit ANT2 expression and then observed the treatment effect in a SP of breast cancer cell line. In this study, MCF7, MDA-MB-231 cells, and breast epithelial cells (MCF10A) mesenchymally-transdifferentiated through E-cadherin knockdown were used. ANT2 expression was high in both stem-like cells and non-stem-like cells of MCF7 and MDA-MB-231 cells, and was induced and up-regulated by mesenchymal transdifferentiation in MCF10A cells (MCF10AEMT). Knockdown of ANT2 by adeno-shRNA virus efficiently induced apoptotic cell death in the stem-like cells of MCF7 and MDA-MB-231 cells, and MCF10AEMT. Stem-like cells of MCF7 and MDA-MB-231, and MCF10AEMT cells exhibited increased drug (doxorubicin) resistance, and expressed a multi-drug resistant related molecule, ABCG2, at a high level. Adeno-ANT2 shRNA virus markedly sensitized the stem-like cells of MCF7 and MDA-MB-231, and the MCF10AEMT cells to doxorubicin, which was accompanied by down-regulation of ABCG2. Our results suggest that ANT2 suppression by adeno-shRNA virus is an effective strategy to induce cell death and increase the chemosensitivity of stem-like cells in breast cancer.
ATP-Binding Cassette Transporters/*genetics/metabolism ; Adenine Nucleotide Translocator 2/antagonists & inhibitors/genetics ; Adenoviridae/*genetics ; Antineoplastic Agents/pharmacology ; Apoptosis/drug effects/genetics ; Breast Neoplasms ; Cadherins/antagonists & inhibitors/genetics ; Cell Line, Tumor ; Cell Survival/drug effects/genetics ; Cell Transdifferentiation/drug effects ; Doxorubicin/pharmacology ; Drug Resistance, Neoplasm/drug effects/*genetics ; Epithelial-Mesenchymal Transition/drug effects ; Female ; Gene Expression Regulation, Neoplastic/drug effects ; Gene Knockdown Techniques ; Humans ; Neoplasm Proteins/*genetics/metabolism ; Neoplastic Stem Cells/drug effects/*metabolism/pathology ; RNA, Small Interfering/*genetics ; Signal Transduction/drug effects