Gemcitabine-based chemotherapy is commonly applied for the treatment of breast cancer in a clinical setting. However, acquired resistance to chemotherapy primarily results in treatment failure and eventually culminates in patient mortality. Aberrant expression of microRNAs (miRNAs) has been demonstrated to be implicated in the development of chemoresistance; however, the role of miR-873 in the chemoresistance of breast cancer and its underlying mechanism have not been completely elucidated. Herein, using cell viability assays, the present study demonstrated that overexpression of miR-873 sensitized triple-negative breast cancer (TNBC) cells (MDA-MB-231 and BT549) towards gemcitabine treatment, while inhibition of miR-873 promoted resistance of TNBC cells to gemcitabine exposure. The 3' untranslated region of zinc finger E-box binding homeobox 1 (ZEB1) was predicted as a candidate target of miR-873, and the regulatory association between ZEB1 and miR-873 was validated with a dual luciferase assay. Reverse transcription-quantitative polymerase chain reaction and western blot analysis confirmed that miR-873 mimics reduced ZEB1 at mRNA and protein levels in MDA-MB-231 and BT549 cells. As ZEB1 was previously reported to interact with Yes associated protein (YAP) to promote cancer progression. The present study observed that miR-873 overexpression decreased the expression of YAP target genes AXL receptor tyrosine kinase, connective tissue growth factor and cysteine rich angiogenic inducer 61 at mRNA and protein levels. Additionally, elevation of the ZEB1 level and reduction of the miR-873 level were detected in gemcitabine-resistant MDA-MB-231 (MDA-MB-231GEMr) cells, which were accompanied with stronger proliferative ability, compared with parental cells. Overexpression of miR-873 or ZEB1 knockdown reversed chemoresistance of MDA-MB-231GEMr cells by inducing a notable cell growth arrest upon gemcitabine exposure. In conclusion, the data obtained by the present study demonstrated that the decrease of miR-873 promoted the development of gemcitabine resistance in TNBC via elevation of ZEB1 expression, which indicated that miR-873 may be a promising predictor for gemcitabine sensitivity in patients with TNBC.
Background: Triple-negative breast cancer (TNBC) is a severe disease with a high mortality rate.Metformin has been found to possess anti-tumor properties. Curcumol, an active ingredient extracted from curcuma, exerts the protective effect in TNBC cells through inducing apoptosis. However, the effects of curcumol combined with metformin on the treatment of TNBC have yet to be fully established.Methods: TNBC cells MDA-MB-231 and MDA-MB-468 cells were used in the study. TNBC cells were treated with curcumol and metformin alone or treated with curcumol combined with metformin.Cell viability was determined using Cell Counting Kit-8 (CCK-8) assay. Cell apoptosis was detected using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. The levels of proteins were measured using Western blot. Wound healing assay and Transwell invasion assays were used to determine cell migration and invasion ability, respectively. A xenograft model was established to investigate the tumor growth ability. Immunohistochemistry was performed to determine the expression of Ki-67 and Vascular endothelial growth factor (VEGF).Results: In the study, the administration of curcumol alone had no significant effects on the TNBC cells.However, the anti-proliferation, anti-metastasis, and anti-epithelial-mesenchymal transition (EMT) effects of metformin were enhanced by the addition of curcumol. Further, curcumol reversed TNBC cell proliferation, migration, invasion, and EMT induced by rucaparib, and enhanced the effect of metformin on rucaparibinduced TNBC cells. The combination of curcumol and metformin also suppressed tumor growth, EMT marker expression, and the activation of Wnt2/β-Catenin signaling during in vivo experiments. Conclusions:The combination of curcumol and metformin enhances the anti-tumor effects of metformin on TNBC via inhibiting EMT. Curcumol combined with metformin may hold promise as a therapeutic strategy for TNBC.
Breast cancer is one of the most frequently diagnosed malignancies among women. Triple-negative breast cancer (TNBC) represents a significant challenge for breast oncologists, as the availability of effective therapies for this aggressive disease is limited. The molecular mechanisms underlying TNBC development are not fully understood. Previous studies have demonstrated that microRNAs (miRNAs/miRs) play important roles in the development of various types of cancer, including breast cancer; however, the role of miRNAs in TNBC remains undetermined. The results of the present study revealed that miR-301a-3p may function as an oncogenic miRNA in TNBC. Based on The Cancer Genome Atlas data, miR-301a-3p expression levels were found to be upregulated in breast cancer tissues. Reverse transcription-quantitative PCR analysis demonstrated that the expression levels of miR-301a-3p were upregulated in TNBC tissues compared with non-TNBC tissues, and in MDA-MB-231 cells compared with normal MCF-10A breast cells. miR-301a-3p mimics and inhibitors were subsequently used to overexpress and knock down miR-301a-3p expression, respectively, in MDA-MB-231 cells. Biological functional experiments demonstrated that miR-301a-3p overexpression increased the viability, and the migratory and invasive abilities of MDA-MB-231 cells. By contrast, miR-301a-3p knockdown exerted the opposite effects on MDA-MB-231 cells. Cell apoptosis was negatively regulated by miR-301a-3p. Moreover, overexpression of miR-301a-3p was found to downregulate the expression levels of mesenchyme homeobox 2 (MEOX2). The expression levels of miR-301a-3p were negatively correlated with the expression levels of MEOX2 in clinical tissue specimens from patients with TNBC. Subsequently, the knockdown of MEOX2 expression promoted the viability of MDA-MB-231 cells. In conclusion, the results of the present study suggested that miR-301a-3p may serve as an oncogenic miRNA in TNBC by regulating MEOX2 expression.
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