Hongyu Shen1, Liangpeng Li2, Sujin Yang1, Dandan Wang3, Shanliang Zhong4, Jianhua Zhao5, Jinhai Tang6. 1. The Fourth Clinical School of Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China; Department of General Surgery, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China. 2. Department of Thoracic and Cardiovascular Surgery, Nanjing First Hospital, Nanjing Medical University, Changle Road 68, Nanjing 210006, Jiangsu, China. 3. Department of General Surgery, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China. 4. Center of Clinical Laboratory Science, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China. 5. Center of Clinical Laboratory Science, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China. Electronic address: lcjyjhzhao@163.com. 6. The Fourth Clinical School of Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China; Department of General Surgery, Jiangsu Cancer Hospital Affiliated to Nanjing Medical University, Baiziting 42, Nanjing 210009, Jiangsu, China. Electronic address: njmujhtang@163.com.
Abstract
PURPOSE: Acquisition of resistance to adriamycin (ADR) during the treatment of breast cancer is still a major clinical obstacle. MicroRNAs (miRNAs) are a class of short noncoding RNAs which associate with cancer chemoresistance through regulating gene expression by targeting mRNAs. Our previous microarray found that miR-29a may strongly confer the ADR resistance of breast cancer cells. Here, we aim to explore the possible mechanism by which miR-29a affects sensitivity to ADR. METHODS: ADR-resistant MCF-7 breast cancer cell subline (MCF-7/ADR) was successfully established in vitro through a stepwise increase of ADR concentrations in the culture based on parental MCF-7 cell lines (MCF-7/S). We used TargetScan (a wide use of target prediction algorithms) in conjunction with pathway enrichment analyses to predict the mRNAs that were most likely to involve in miR-29a-mediated drug resistance in cancers. We confirmed the effects of miR-29a-mediated ADR resistance through MTT and apoptosis assays, and further investigated the activities of two target genes, PTEN and GSK3β, by RT-qPCR analyses and western blot assays. RESULTS: The expression level of miR-29a in MCF-7/ADR cells was remarkablely higher than in MCF-7/S cells. Further MTT and apoptosis assays revealed that transfection of miR-29a inhibitors into MCF-7/ADR cells resulted in prominent reduction of the drug resistance, in contrast, transfection of miR-29a mimics into MCF-7/S cells obviously increased their drug resistance. Through pathway enrichment analyses for miR-29a, we found that PTEN/AKT/GSK3β signaling pathway may be of importance. RT-qPCR and Western blot results showed that downregulation of miR-29a expression in MCF-7/ADR cells increased PTEN expression levels, resulting in decreased phospho-Akt (p-Akt) and phospho-GSK3β (p-GSK3β) expression. Conversely, upregulation of miR-29a expression in MCF-7/S cells is associated with decreasing PTEN expression and increasing p-Akt and p-GSK3β expression. CONCLUSIONS: PTEN and GSK3β are targeted by miR-29a, and miR-29a may contribute to ADR resistance through inhibition of the PTEN/AKT/GSK3β pathway in breast cancer cells. Thus, miR-29a may be a potential target for the patients who acquired ADR-resistance during the treatment of breast cancer.
PURPOSE: Acquisition of resistance to adriamycin (ADR) during the treatment of breast cancer is still a major clinical obstacle. MicroRNAs (miRNAs) are a class of short noncoding RNAs which associate with cancer chemoresistance through regulating gene expression by targeting mRNAs. Our previous microarray found that miR-29a may strongly confer the ADR resistance of breast cancer cells. Here, we aim to explore the possible mechanism by which miR-29a affects sensitivity to ADR. METHODS: ADR-resistant MCF-7 breast cancer cell subline (MCF-7/ADR) was successfully established in vitro through a stepwise increase of ADR concentrations in the culture based on parental MCF-7 cell lines (MCF-7/S). We used TargetScan (a wide use of target prediction algorithms) in conjunction with pathway enrichment analyses to predict the mRNAs that were most likely to involve in miR-29a-mediated drug resistance in cancers. We confirmed the effects of miR-29a-mediated ADR resistance through MTT and apoptosis assays, and further investigated the activities of two target genes, PTEN and GSK3β, by RT-qPCR analyses and western blot assays. RESULTS: The expression level of miR-29a in MCF-7/ADR cells was remarkablely higher than in MCF-7/S cells. Further MTT and apoptosis assays revealed that transfection of miR-29a inhibitors into MCF-7/ADR cells resulted in prominent reduction of the drug resistance, in contrast, transfection of miR-29a mimics into MCF-7/S cells obviously increased their drug resistance. Through pathway enrichment analyses for miR-29a, we found that PTEN/AKT/GSK3β signaling pathway may be of importance. RT-qPCR and Western blot results showed that downregulation of miR-29a expression in MCF-7/ADR cells increased PTEN expression levels, resulting in decreased phospho-Akt (p-Akt) and phospho-GSK3β (p-GSK3β) expression. Conversely, upregulation of miR-29a expression in MCF-7/S cells is associated with decreasing PTEN expression and increasing p-Akt and p-GSK3β expression. CONCLUSIONS:PTEN and GSK3β are targeted by miR-29a, and miR-29a may contribute to ADR resistance through inhibition of the PTEN/AKT/GSK3β pathway in breast cancer cells. Thus, miR-29a may be a potential target for the patients who acquired ADR-resistance during the treatment of breast cancer.
Authors: Glenn D Hoke; Corrine Ramos; Nicholas N Hoke; Mary C Crossland; Lisa G Shawler; Joseph V Boykin Journal: J Diabetes Res Date: 2016-10-20 Impact factor: 4.011