MicroRNA-34a modulates chemosensitivity of breast cancer cells to adriamycin by targeting Notch1.

MicroRNA-34a (miR-34a) as a tumor suppressor has been reported in many other studies. However, its role in modulating the sensitivity of breast cancer cells to adriamycin (ADR) remains unclear. The aim of this study is to evaluate the role of miR-34a in the sensitivity of breast cancer cells to ADR. The role of miR-34a in breast cancer cells was detected using MTT assay, flow cytometry assay, real-time PCR and Western blot, etc. The association of miR-34a and Notch1 was analyzed by dual-luciferase reporter assay and Notch1-siRNA technology. Real-time PCR assay was performed to test the expression of miR-34a and Notch1 in 38 selective breast cancer tissue samples. Ectopic overexpression of miR-34a could sensitize MCF-7 breast cancer cells to ADR. MiR-34a mimic could inhibit the luciferase activity of the construct containing wild-type 3' UTR of Notch1 in MCF-7/ADR cells. Notch1-siRNA could partially reverse the effect of miR-34a inhibitor in inducing chemoresistance of MCF-7 cells to ADR. Further, there was an inverse association between Notch1 and miR-34a expression in breast cancer. Dysregulation of miR-34a plays critical roles in the acquired ADR resistance of breast cancer, at least in part via targeting Notch1.

Li XJ ，Ji MH ，Zhong SL ，Zha QB ，Xu JJ ，Zhao JH ，Tang JH ... -  《-》

[miR-34a may regulate sensitivity of breast cancer cells to adriamycin via targeting Notch1].

Li X ，Zhao J ，Tang J 《-》

MicroRNA-21 modulates chemosensitivity of breast cancer cells to doxorubicin by targeting PTEN.

Ovexpression of microRNA-21 (miR-21) is found in various human cancers. Our aim is to investigate the association of miR-21 expression with the sensitivity of breast cancer cells to doxorubicin (ADR). The half maximal inhibitory concentration (IC(50)) value of ADR in resistant MCF-7/ADR or parental MCF-7 cells was determined by MTT assay. TaqMan RT-PCR or Western blot assay was performed to detect the expression of mature miR-21 and tumor suppressor gene (PTEN) protein. MCF-7 or MCF-7/ADR cell line was transfected with miR-21mimic or inhibitor. The IC(50) value of ADR was determined. Flow cytometry and TUNEL assays were performed to analyze apoptosis. The activity of caspase-3 was analyzed. The IC(50) of ADR in MCF-7 and MCF-7/ADR cells was 0.21 ± 0.05 and 16.5 ± 0.08 μmol/L, respectively. We showed that upregulation of miR-21 in MCF-7/ADR cells was concurrent with downregulation of PTEN protein. MiR-21 mimic or inhibitor could obviously affect the sensitivity of breast cancer cells to ADR. Moreover, miR-21 inhibitor could enhance caspase-3-dependent apoptosis in MCF-7/ADR cells. Overexpression of PTEN could mimic the same effects of miR-21 inhibitor in MCF-7/ADR cells and PTEN-siRNA could increase the resistance of MCF-7 cells to ADR. MiR-21 inhibitor could increase PTEN protein expression and the luciferase activity of a PTEN 3' untranslated region-based reporter construct in MCF-7/ADR cells. PTEN-siRNA could partially reverse the increased chemosensitivity of MCF-7/ADR cells induced by miR-21 inhibitor. Dysregulation of miR-21 plays critical roles in the ADR resistance of breast cancer, at least in part via targeting PTEN.

Wang ZX ，Lu BB ，Wang H ，Cheng ZX ，Yin YM ... -  《-》

Exosomes regulate doxorubicin resistance in breast cancer via miR-34a-5p/NOTCH1.

Breast cancer (BRCA) is the most common cancer among women. Adriamycin (ADR), also known as doxorubicin (Dox), is a commonly used chemotherapeutic agent for BRCA patients, however, the susceptibility of tumor cells to develop resistance to Dox has severely limited its clinical use. One new promising therapeutic target for breast cancer patients is exosomes. The objective of this study was to investigate the role of exosomes in regulating Dox resistance in BRCA. In this study, the exosomes from both types of cells were extracted by differential centrifugation. The effect of exosomes on drug resistance was assessed by laser confocal microscopy, MTT assay, and qRT-PCR. The miRNA was transfected into cells using Lipofectamine 2000, which was then evaluated for downstream genes and changes in drug resistance. Exosomes from MCF-7 cells (MCF-7/exo) and MCF-7/ADR cells (ADR/exo) were effectively extracted in this study. The ADR/exo was able to endocytose MCF-7 cells and make them considerably more resistant to Dox. Moreover, we observed a significant difference in miR-34a-5p expression in MCF-7/ADR and ADR/exo compared to MCF-7 and MCF-7/exo. Among the miR-34a-5p target genes, NOTCH1 displayed a clear change with a negative correlation. In addition, when miR-34a-5p expression was elevated in MCF-7/ADR cells, the expression of miR-34a-5p in ADR/exo was also enhanced alongside NOTCH1, implying that exosomes may carry miRNA into and out of cells and perform their function. In conclusion, exosomes can influence Dox resistance in breast cancer cells by regulating miR-34a-5p/NOTCH1. These findings provide novel insights for research into the causes of tumor resistance and the enhancement of chemotherapy efficacy in breast cancer.

Chen NN ，Zhou KF ，Miao Z ，Chen YX ，Cui JX ，Su SW ... -  《-》

The function role of miR-181a in chemosensitivity to adriamycin by targeting Bcl-2 in low-invasive breast cancer cells.

miR-181a is involved in immunity, metabolism, tumor suppression or carcinogenesis reported by many other studies. However, its role in the development of chemosensitivity to adriamycin in low-invasive breast cancer cells remains unclear. The aim of this study is to define the function role of miR-181a in promoting the efficacy of adriamycin-based neoadjuvant chemotherapy. Cell survival analysis was detected by Cell Counting Kit-8 assay. Apoptotic cells were quantitatively detected using FITC Annexin V apoptosis Detection Kit I. Bcl-2 protein expression was measured by western blot. Luciferase reporter vector with the putative BCL-2 3' untranslated region (3'UTR) was constructed to explore whether BCL-2 was a direct target gene of miR-181a. Real-time PCR was performed to test the expression of miR-181a and Bcl-2 in the selected breast cancer tissue samples. The down-regulation of miR-181a decreased adriamycin-induced apoptosis in MCF-7 cells. Transfected with miR-181a mimic in cells resulted in the decreased expression of Bcl-2. The alteration of miR-181a expression did not significantly affect the chemosensitivity to adriamycin in MCF-7 and MCF-7/ADR cells with genetic knockout of Bcl-2. miR-181a may suppress Bcl-2 expression by forming imperfect base pairing with the 3'UTR of Bcl-2 gene such that a negative relationship between miR-181a and Bcl-2 in MCF-7 and MCF-7/ADR cells is observed. At least in part, the detection of miR-181a may direct the clinical medication in patients with neoadjuvant chemotherapy because of miR-181a enhanced adriamycin-induced apoptosis via targeting Bcl-2.

Zhu Y ，Wu J ，Li S ，Ma R ，Cao H ，Ji M ，Jing C ，Tang J ... -  《-》