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Chemotherapeutic resistance is a major obstacle in the control of advanced breast cancer (BCa). We have previously shown that small extracellular vesicles (sEVs) can transmit adriamycin resistance between BCa cells. Here, we describe that sEV-mediated TGF-β1 intercellular transfer is involved in the drug-resistant transmission. sEVs were isolated and characterized from both sensitive and resistant cells. sEVs derived from the resistant cells were incubated with the sensitive cells and resulted in transmitting the resistant phenotype to the recipient cells. Cytokine antibody microarray revealed that most metastasis-associated cytokines present at the high levels in sEVs from the resistant cells compared with their levels in sEVs from the sensitive cells, particularly TGF-β1 is enriched in sEVs from the resistant cells. The sEV-mediated TGF-β1 intercellular transfer led to increasing Smad2 phosphorylation and improving cell survival by suppressing apoptosis and enhancing cell mobility. Furthermore, sEV-mediated drug-resistant transmission by delivering TGF-β1 was validated using a zebrafish xenograft tumor model. These results elaborated that sEV-mediated TGF-β1 intercellular transfer contributes to adriamycin resistance in BCa., (© 2021 The Authors. Molecular Oncology published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

MircoRNA (miRNA) are a group of small, non-coding, regulatory RNA with an average length of approximately 22 nucleotides, which mostly modulate gene expression post-transcriptionally through complementary binding to the 3'-untranslated region (3'-UTR) of multiple target genes. Emerging evidence has shown that miRNA are frequently dysregulated in a variety of human malignancies. Among them, microRNA-145 (miR-145) has been increasingly identified as a critical suppressor of carcinogenesis and therapeutic resistance. Resistance to tumor therapy is a challenge in cancer treatment due to the daunting range of resistance mechanisms. We reviewed the status quo of recent advancements in the knowledge of the functional role of miR-145 in therapeutic resistance and the tumor microenvironment. It may serve as an innovative biomarker for therapeutic response and cancer prognosis., (© 2020 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.)

Background: The activation of the NF-κB pathway plays a crucial role in the progression of breast cancer (BCa) and also involved in endocrine therapy resistance. On the contrary to the canonical NF-κB pathway, the effect of the noncanonical NF-κB pathway in BCa progression remains elusive., Methods: BCa tumor tissues and the corresponding cell lines were examined to determine the correlation between RelB and the aggressiveness of BCa. RelB was manipulated in BCa cells to examine whether RelB promotes cell proliferation and motility by quantitation of apoptosis, cell cycle, migration, and invasion. RNA-Seq was performed to identify the critical RelB-regulated genes involved in BCa metastasis. Particularly, RelB-regulated MMP1 transcription was verified using luciferase reporter and ChIP assay. Subsequently, the effect of RelB on BCa progression was further validated using BCa mice xenograft models., Results: RelB uniquely expresses at a high level in aggressive BCa tissues, particularly in triple-negative breast cancer (TNBC). RelB promotes BCa cell proliferation through increasing G1/S transition and/or decreasing apoptosis by upregulation of Cyclin D1 and Bcl-2. Additionally, RelB enhances cell mobility by activating EMT. Importantly, RelB upregulates bone metastatic protein MMP1 expression through binding to an NF-κB enhancer element located at the 5'-flanking region. Accordingly, in vivo functional validation confirmed that RelB deficiency impairs tumor growth in nude mice and inhibits lung metastasis in SCID mice. Video abstract.

Therapeutic resistance leading to tumor relapse is a major challenge in breast cancer (BCa) treatment. Numerous factors involved in multiple mechanisms promote the development of tumor chemo/radio-resistance. Cytokines/chemokines are important inflammatory factors and highly related to tumorigenesis, metastasis and tumors responses to treatment. A large number of studies have demonstrated that the network of cytokines activates multiple cell signaling pathways to promote tumor cell survival, proliferation, invasion, and migration. Particularly in BCa, cytokines-enhanced the epithelial-mesenchymal transition (EMT) process plays a pivotal role in the progression of metastatic phenotypes and resistance to the traditional chemo/radio-therapy. Virtually, therapeutic resistance is not entirely determined by tumor cell intrinsic characteristics but also dependent upon synchronized effects by numerous of local microenvironmental factors. Emerging evidence highlighted that exosomes secreted from various types of cells promote intercellular communication by transferring bioactive molecules including miRNAs and cytokines, suggesting that exosomes are essential for sustentation of tumor progression and therapeutic resistance within the tumor microenvironment. In this review, we discuss the mechanisms by which cytokines promote therapeutic resistance of BCa and suggest a potential approach for improving BCa therapeutics by inhibition of exosome function., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Emerging evidence suggests that curcumin can overcome drug resistance to classical chemotherapies, but poor bioavailability and low absorption have limited its clinical use and the mechanisms remain unclear. Also, Adriamycin (Adr) is one of the most active cytotoxic agents in breast cancer; however, the high resistant rate of Adr leads to a poor prognosis., Methods: We utilized encapsulation in liposomes as a strategy to improve the bioavailability of curcumin and demonstrated that liposomal curcumin altered chemosensitivity of Adr-resistant MCF-7 human breast cancer (MCF-7/Adr) by MTT assay. The miRNA and mRNA expression profiles of MCF-7/S, MCF-7/Adr and curcumin-treated MCF-7/Adr cells were analyzed by microarray and further confirmed by real-time PCR. We focused on differentially expressed miR-29b-1-5p to explore the involvement of miR-29b-1-5p in the resistance of Adr. Candidate genes of dysregulated miRNAs were identified by prediction algorithms based on gene expression profiles. Networks of KEGG pathways were organized by the selected dysregulated miRNAs. Moreover, protein-protein interaction (PPI) was utilized to map protein interaction networks of curcumin regulated proteins., Results: We first demonstrated liposomal curcumin could rescue part of Adriamycin resistance in breast cancer and further identified 67 differentially expressed microRNAs among MCF-7/S, MCF-7/Adr and curcumin-treated MCF-7/Adr. The results showed that lower expressed miR-29b-1-5p decreased the IC50 of MCF-7/Adr cells and higher expressed miR-29b-1-5p, weaken the effects of liposomal curcumin to Adr-resistance. Besides, we found that 20 target genes (mRNAs) of each dysregulated miRNA were not only predicted by prediction algorithms, but also differentially expressed in the microarray. The results showed that MAPK, mTOR, PI3K-Akt, AMPK, TNF, Ras signaling pathways and several target genes such as PPARG, RRM2, SRSF1and EPAS1, may associate with drug resistance of breast cancer cells to Adr., Conclusions: We determined that an altered miRNA expression pattern is involved in acquiring resistance to Adr, and that liposomal curcumin could change the resistance to Adr through miRNA signaling pathways in breast cancer MCF-7 cells., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background and Purpose: Acquisition of resistance to adriamycin (ADR) is one of the most important clinical obstacles in the treatment of breast cancer, but the molecular mechanisms underlying sensitivity to ADR remain elusive. In our previous study, through miRNA microarray and experiments, we have emphasized that miR-222 could promote the ADR-resistance in breast cancer cells. The aim of this study was to explore the possible mechanism by which miR-222 affects sensitivity to ADR., Methods: Through pathway enrichment analyses for miR-222, we found that PTEN/Akt/FOXO1 signaling pathway may be of importance. RT-qPCR analyses and western blot assays confirmed the relationship between miR-222 expression and target genes. Immunofluorescence further visually displayed the location of FOXO1. When blocking PTEN/Akt/FOXO1 signaling pathway, we demonstrated the effects of miR-222-mediated ADR resistance by MTT and apoptosis assays., Results: RT-qPCR and Western blot results showed that miR-222 expression was negatively correlated with FOXO1 expression. In addition, the subcellular translocation of FOXO1 due to the altered expression of miR-222 was observed from immunofluorescence. Moreover, upregulation of miR-222 expression in MCF-7/S cells is associated with decreased PTEN expression levels and increased phospho-Akt (p-Akt) expression. Conversely in MCF-7/ADR cells, inhibition of miR-222 resulted in increased PTEN expression and decreased p-Akt expression. For further validation, results of the present study also demonstrated that PTEN/Akt/FOXO1 signaling was responsible for the ADR-resistance of breast cancer cells since LY294002, an inhibitor of Akt signaling, partially increased the sensitivity of MCF-7/S cells to ADR. More importantly, we postulated that high expression of miR-222 is closely related to poor overall survival by TCGA database validation., Conclusions: Taken together, these data elucidated that miR-222 mediated ADR-resistance of breast cancer cells partly through regulation of PTEN/Akt/FOXO1 signaling pathway and inhibition of miR-222 may improve the prognosis of breast cancer patients., (Copyright © 2016 Elsevier B.V. All rights reserved.)

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., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Exosomes have been shown to transmit drug resistance through delivering miRNAs. We aimed to explore their roles in breast cancer. Three resistant sublines were established by exposing parental MDA-MB-231 cell line to docetaxel, epirubicin and vinorelbine, respectively. Preneoadjuvant chemotherapy biopsies and paired surgically-resected specimens embedded in paraffin from 23 breast cancer patients were collected. MiRNA expression profiles of the cell lines and their exosomes were evaluated using microarray. The result showed that most miRNAs in exosomes had a lower expression level than that in cells, however, some miRNAs expressed higher in exosomes than in cells, suggesting a number of miRNAs is concentrated in exosomes. Among the dysregulated miRNAs, 22 miRNAs were consistently up-regulated in exosomes and their cells of origin. We further found that 12 of the 22 miRNAs were significantly up-regulated after preneoadjuvant chemotherapy. Further study of the role of these 12 miRNAs in acquisition of drug resistance is needed to clarify their contribution to chemoresistance.

Acquisition of resistance to docetaxel (Doc) is one of the most important problems in treatment of breast cancer patients, but the underlying mechanisms are still not fully understood. In present study, Doc-resistant MDA-MB-231 and MCF-7 breast cancer cell lines (MDA-MB-231/Doc and MCF-7/Doc) were successfully established in vitro by gradually increasing Doc concentration on the basis of parental MDA-MB-231 and MCF-7 cell lines (MDA-MB-231/S and MCF-7/S). The potential miRNAs relevant to the Doc resistance were screened by miRNA microarray. We selected 5 upregulated miRNAs (has-miR-3646, has-miR-3658, has-miR-4438, has-miR-1246, and has-miR-574-3p) from the results of microarray for RT-qPCR validation. The results showed that expression level of miR-3646 in MDA-MB-231/Doc cells was significantly higher than in MDA-MB-231/S cells. Compared to MCF-7/S cells, miR-3646 expression was up-regulated in MCF-7/Doc cells. Further studies revealed that transfection of miR-3646 mimics into MDA-MB-231/S or MCF-7/S cells remarkably increased their drug resistance, in contrast, transfection of miR-3646 inhibitors into MDA-MB-231/Doc or MCF-7/Doc cells resulted in significant reduction of the drug resistance. By the pathway enrichment analyses for miR-3646, we found that GSK-3β/β-catenin signaling pathway was a significant pathway, in which GSK-3β was an essential member. RT-qPCR and Western blot results demonstrated that miR-3646 could regulate GSK-3β mRNA and protein expressions. Furthermore, a marked increase of both nuclear and cytoplasmic β-catenin expressions (with phosphorylated-β-catenin decrease) was observed in MDA-MB-231/Doc cells compared with MDA-MB-231/S cells, and their expression were positively related to miR-3646 and negatively correlated with GSK-3β. Taken together, our results suggest that miR-3646-mediated Doc resistance of breast cancer cells maybe, at least in part, through suppressing expression of GSK-3β and resultantly activating GSK-3β/β-catenin signaling pathway.

Vinorelbine (NVB) is one of the most active cytotoxic agents in breast cancer, especially metastatic breast cancer. However, breast cancer patients who are treated with the drug often develop resistance to it and some other drugs. Recently studies have shown that microRNAs (miRNAs) play an important role in drug resistance. In present study, miRNA expression profiles of breast cancer cells MDA-MB-231/S and its NVB-resistant variant MDA-MB-231/NVB cells were analyzed using microarray and the results were confirmed by real-time quantitative polymerase chain reaction. Bioinformatic analyses were carried out to predict gene targets of the dysregulated miRNAs and to analyze their potential roles in the development of drug resistance. Here, 123 differentially expressed miRNAs were identified in the resistant subline compared to MDA-MB-231/S. Networks of KEGG pathways, Gene Ontology (GO) terms, and protein-protein interaction (PPI) of 17 specific selected dysregulated miRNAs were constructed. The results showed that MAPK, mTOR, Wnt, and TGF-beta signaling pathways and several target genes such as CCND1, GRB2 and NT5E may associate with drug resistance of breast cancer cells to NVB. In summary, this study demonstrates that altered miRNA expression pattern is involved in acquiring resistance to NVB in breast cancer MDA-MB-231 cells. All these analysis results provided us a comprehensive view of the function of differential expression miRNAs related to drug resistance of breast cancer and may be helpful for the further study., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Objective: To study the effect of miR-342-3p on the chemotherapy sensitivity in triple-negative breast cancer (TNBC)., Methods: Tissue samples were collected from January 2011 to August 2013 samples in Jiangsu Cancer Hospital from a total of 32 triple-negative breast cancer patients with preoperative chemotherapy, with 5 cases of complete response (CR) and 27 cases of partial response (PR). We detected miR-342-3p expression of TNBC with RT-PCR. We transfected has-miR-342-3p mimic and inhibitor into breast cancer cell lines MDA-MB-231 by lipofection transfection and set up negative control mim-NC and inhi-NC. Group of mimic, mim-NC, inhibitor and inhi-NC were cultivated with 2 μmol /L paclitaxel, cisplatin or 4 μmol/L doxorubicin for 48 h. The cell growth rates were measured by CCK8 reagent kit, and the cell apoptosis rate by flow cytometry., Results: The expressions of miRNA-342-3p in TNBC tissue of CR were higher than those of PR. The cell growth rates of mimic were lower and cell apoptosis rates were higher than those of min- NC after cultivating with paclitaxel or cisplatin for 48 h, with significant difference (P<0.05). The cell growth rates of inhibitor were higher and cell apoptosis rates lower than those of inhi-NC after cultivating with paclitaxel or cisplatin 48 h, with significant difference (P<0.05). The cell growth and cell apoptosis rates of mimic and inhibitor had no difference with those of mim-NC and inhi- NC after cultivating with doxorubicin 48 h (P>0.05)., Conclusion: TNBC with high expression of miR-342-3p are more sensitive to chemotherapy. miRNA-342-3p may regulate the sensitivity of breast cancer cell line MDA-MB-231 to chemotherapy drugs paclitaxel and cisplatin, but can not affect the chemotherapy sensitivity of doxorubicin.

Objective: To explore whether docetaxel-resistant cells (MCF-7/Doc) and doxorubicin-resistant cells (MCF-7/ADM) can secrete Exosomes and their potential role in cell-cell drug-resistance transfer., Methods: Exosomes were extracted from the cell culture supernatants of MCF-7/Doc and MCF-7/ADM cells by fractionation ultracentrifugation, and were identified by transmission electron microscopy and Western blot analysis. GFP-MCF-7/S, a breast cancer parental sensitive cell line stably expressing green fluorescent protein (GFP), was constructed by recombinant lentiviral vector with GFP. Then the resistance experiment of cells and the experiment of resistance transfer by exosomes were designed to observe the phenomenon of cell-to-cell drug-resistance transfer., Results: Similar to the breast cancer parental sensitive cells (MCF-7/S), the breast cancer resistant sublines could secrete exosomes, which exhibited round or elliptic shape ranging from 30 to 100 nm in diameter with intact membrane, and only expressed the protein marker of exosomes, Tsg101, did not express the endoplasmic reticulum marker calnexin. After MCF-7/S, MCF-7/DOC and MCF-7/ADM cells we cocultured with GFP-MCF-7/S cells for 72 h, there were no significant differences in the expression of fluorescence-labeled cells among the four groups. When treated by the drug ADM or DOC for 24 hours, the MCF-7/DOC+GFP-MCF-7/S group was in favor of a significant higher survival rate of fluorescence-labeled cells compared with the MCF-7/S+GFP-MCF-7/S group (65.5% vs. 25.5%, P < 0.001), and so did the MCF-7/ADM+GFP-MCF-7/S group (53.6% vs. 25.4%, P < 0.001). The exosomes extracted from MCF-7/S, MCF-7/DOC and MCF-7/ADM cells were cultured with the GFP-MCF-7/S cells for 48 h. Among these groups, no significant differences in the expression of fluorescence-labeled cells were found. After treated by the drug ADM or DOC for 24 hours, the exosomes extracted from MCF-7/DOC+GFP-MCF-7/S group was associated with a significant higher survival rate of fluorescence-labeled cells compared with the exosomes extracted from MCF-7/S+GFP-MCF-7/S group (59.9% vs. 32.4%, P < 0.001), and so did the exosomes extracted from the MCF-7/ADM)+GFP-MCF-7/S group (58.3% vs. 27.2%, P < 0.001)., Conclusion: Our results suggest that drug-resistance can be transferred between breast cancer cells, and exosomes are probably the transporter of the drug resistance.

Objectives: 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., Methods: 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., Results: 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., Conclusions: 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., (© 2013 S. Karger AG, Basel.)