Mengmeng Lv

Exosomes from Drug-Resistant Breast Cancer Cells Transmit Chemoresistance by a Horizontal Transfer of MicroRNAs

Adriamycin and docetaxel are two agents commonly used in treatment of breast cancer, but their efficacy is often limited by the emergence of chemoresistance. Recent studies indicate that exosomes act as vehicles for exchange of genetic cargo between heterogeneous populations of tumor cells, engendering a transmitted drug resistance for cancer development and progression. However, the specific contribution of breast cancer-derived exosomes is poorly understood. Here we reinforced others report that human breast cancer cell line MCF-7/S could acquire increased survival potential from its resistant variants MCF-7/Adr and MCF-7/Doc. Additionally, exosomes of the latter, A/exo and D/exo, significantly modulated the cell cycle distribution and drug-induced apoptosis with respect to S/exo. Exosomes pre-treated with RNase were unable to regulate cell cycle and apoptosis resistance, suggesting an RNA-dependent manner. Microarray and polymerase chain reaction for the miRNA expression profiles of A/exo, D/exo, and S/exo demonstrated that they loaded selective miRNA patterns. Following A/exo and D/exo transfer to recipient MCF-7/S, the same miRNAs were significantly increased in acquired cells. Target gene prediction and pathway analysis showed the involvement of miR-100, miR-222, and miR-30a in pathways implicated in cancer pathogenesis, membrane vesiculation and therapy failure. Furthermore, D/exo co-culture assays and miRNA mimics transfection experiments indicated that miR-222-rich D/exo could alter target gene expression in MCF-7/S. Our results suggest that drug-resistant breast cancer cells may spread resistance capacity to sensitive ones by releasing exosomes and that such effects could be partly attributed to the intercellular transfer of specific miRNAs.

Exosomes mediate drug resistance transfer in MCF-7 breast cancer cells and a probable mechanism is delivery of P-glycoprotein

Acquired drug resistance is a major obstacle to chemotherapy of cancers. In this study, we aim to investigate the role of exosomes in drug-resistance transfer between breast cancer cells and detect the probable mechanism. A docetaxel-resistant variant of MCF-7 cell line (MCF-7/DOC) was established and then compared with the drug-sensitive variant (MCF-7/S). Exosomes were expelled from the cell supernatant using ultracentrifugation. Drug resistance was assessed by apoptosis assay and MTT examination. Expressions of P-glycoprotein (P-gp) were analyzed by flow cytometry. Stained exosomes were absorbed by receipt cells. MCF-7/S in the presence of exosomes extracted from the supernatant of MCF-7/DOC (DOC/exo) acquired drug resistance, while MCF-7/S exposed to their own exosomes (S/exo) did not. P-gp expression patterns of exosomes were similar as the originated cells. P-gp expression of MCF-7/S increased after incubation with DOC/exo and was affected by the amount of exosomes. Exosomes are effective in transferring drug resistance as well as P-gp from drug-resistant breast cancer cells to sensitive ones. The delivery of P-gp via exosomes may be a mechanism of exosome-mediated drug resistance transfer.

Exosomes from docetaxel-resistant breast cancer cells alter chemosensitivity by delivering microRNAs

Breast cancer (BCa) remains chemo-unresponsive by inevitable progression of resistance to first-line treatment with docetaxel (doc). Emerging studies indicate that exosomes act as mediators of intercellular communication between heterogeneous populations of tumor cells, engendering a transmitted drug resistance for cancer development. Such modulatory effects have been related to the constant shuttle of biologically active molecules including microRNAs (miRNAs). Here, we aimed to investigate the relevance of exosome-mediated miRNA delivery in resistance transmission of BCa subpopulations. Using microarray and polymerase chain reaction, we found that exosomes from doc-resistant BCa cells (D/exo) loaded cellular miRNAs. Following D/exo transfer to the fluorescent sensitive cells (GFP-S), some miRNAs were significantly increased in recipient GFP-S. Target gene prediction and pathway analysis revealed the involvement of the top 20 most abundant miRNAs of D/exo in pathways implicated in therapy failure. Coculture assays showed that miRNA-containing D/exo increased the overall resistance of GFP-S to doc exposure. Moreover, D/exo was able to alter gene expression in GFP-S. Our results open up an intriguing possibility that drug-resistant BCa cells may spread chemoresistance to sensitive ones by releasing exosomes and that the effects could be partly attributed to the intercellular transfer of specific miRNAs.

Roles of caloric restriction, ketogenic diet and intermittent fasting during initiation, progression and metastasis of cancer in animal models: a systematic review and meta-analysis.

Background The role of dietary restriction regimens such as caloric restriction, ketogenic diet and intermittent fasting in development of cancers has been detected via abundant preclinical experiments. However, the conclusions are controversial. We aim to review the relevant animal studies systematically and provide assistance for further clinical studies. Methods Literatures on associations between dietary restriction and cancer published in PubMed in recent twenty years were comprehensively searched. Animal model, tumor type, feeding regimen, study length, sample size, major outcome, conclusion, quality assessment score and the interferential step of cancer were extracted from each eligible study. We analyzed the tumor incidence rates from 21 studies about caloric restriction. Results Fifty-nine studies were involved in our system review. The involved studies explored roles of dietary restriction during initiation, progression and metastasis of cancer. About 90.9% of the relevant studies showed that caloric restriction plays an anti-cancer role, with the pooled OR (95%CI) of 0.20 (0.12, 0.34) relative to controls. Ketogenic diet was also positively associated with cancer, which was indicated by eight of the nine studies. However, 37.5% of the related studies obtained a negative conclusion that intermittent fasting was not significantly preventive against cancer. Conclusions Caloric restriction and ketogenic diet are effective against cancer in animal experiments while the role of intermittent fasting is doubtful and still needs exploration. More clinical experiments are needed and more suitable patterns for humans should be investigated.

Exosomes in development, metastasis and drug resistance of breast cancer

Transport through the cell membrane can be divided into active, passive and vesicular types (exosomes). Exosomes are nano‐sized vesicles released by a variety of cells. Emerging evidence shows that exosomes play a critical role in cancers. Exosomes mediate communication between stroma and cancer cells through the transfer of nucleic acid and proteins. It is demonstrated that the contents and the quantity of exosomes will change after occurrence of cancers. Over the last decade, growing attention has been paid to the role of exosomes in the development of breast cancer, the most life‐threatening cancer in women. Breast cancer could induce salivary glands to secret specific exosomes, which could be used as biomarkers in the diagnosis of early breast cancer. Exosome‐delivered nucleic acid and proteins partly facilitate the tumorigenesis, metastasis and resistance of breast cancer. Exosomes could also transmit anti‐cancer drugs outside breast cancer cells, therefore leading to drug resistance. However, exosomes are effective tools for transportation of anti‐cancer drugs with lower immunogenicity and toxicity. This is a promising way to establish a drug delivery system.

MicroRNAs delivered by extracellular vesicles: an emerging resistance mechanism for breast cancer

Resistance to chemotherapy and endocrine therapy as well as targeted drugs is a major problem in treatment of breast cancer. Over the last decades, emerging studies have revealed that extracellular vesicles, which are chronically released by breast cancer cells and surrounding stromal cells, influence the action of most commonly used therapeutics. Such modulatory effects have been related to the transport of biologically active molecules including proteins and functional microRNAs. In this review, we highlight recent studies regarding extracellular vesicle-mediated microRNA delivery in formatting drug resistance. We also suggest the use of extracellular vesicles as a promising method in antiresistance treatment.

Down-regulation of miRNA-452 is associated with adriamycin-resistance in breast cancer cells.

Adriamycin (ADR) is an important chemotherapeutic agent frequently used in treatment of breast cancer. However, resistance to ADR results in treatment failure in many patients. Recent studies have indicated that microRNAs (miRNAs) may play an important role in such drug-resistance. In the present study, microRNA-452 (miR-452) was found to be significantly down-regulated in adriamycin-resistant MCF-7 cells (MCF-7/ADR) compared with the parental MCF-7 cells by miRNA microarray and real-time quantitative PCR (RT-qPCR). MiR-452 mimics and inhibitors partially changed the adriamycin-resistance of breast cancer cells, as also confirmed by apoptosis assay. In exploring the potential mechanisms of miR-452 in the adriamycin-resistance of breast cancer cells, bioinformatics analysis, RT-qPCR and Western blotting showed that dysregulation of miR-452 played an important role in the acquired adriamycin-resistance of breast cancer, maybe at least in part via targeting insulin-like growth factor-1 receptor (IGF-1R).

Exosomes from adriamycin-resistant breast cancer cells transmit drug resistance partly by delivering miR-222

Breast cancer (BCa) is one of the major deadly cancers in women. However, treatment of BCa is still hindered by the acquired-drug resistance. It is increasingly reported that exosomes take part in the development, metastasis, and drug resistance of BCa. However, the specific role of exosomes in drug resistance of BCa is poorly understood. In this study, we investigate whether exosomes transmit drug resistance through delivering miR-222. We established an adriamycin-resistant variant of Michigan Cancer Foundation-7 (MCF-7) breast cancer cell line (MCF-7/Adr) from a drug-sensitive variant (MCF-7/S). Exosomes were isolated from cell supernatant by ultracentrifugation. Cell viability was assessed by MTT assay and apoptosis assay. Individual miR-222 molecules in BCa cells were detected by fluorescence in situ hybridization (FISH). Then, FISH was combined with locked nucleic acid probes and enzyme-labeled fluorescence (LNA-ELF-FISH). Individual miR-222 could be detected as bright photostable fluorescent spots and then the quantity of miR-222 per cell could be counted. Stained exosomes were taken in by the receipt cells. MCF-7/S acquired drug resistance after co-culture with exosomes from MCF-7/Adr (A/exo) but did not after co-culture with exosomes from MCF-7/S (S/exo). The quantity of miR-222 in A/exo-treated MCF-7/S was significantly greater than in S/exo-treated MCF-7/S. MCF-7/S transfected with miR-222 mimics acquired adriamycin resistance while MCF-7/S transfected with miR-222 inhibitors lost resistance. In conclusion, exosomes are effective in transmitting drug resistance and the delivery of miR-222 via exosomes may be a mechanism.

Role of miR-155 in drug resistance of breast cancer

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expressions at posttranscriptional level. Growing evidence points to their significant role in the acquisition of drug resistance in cancers. Studies show that miRNAs are often aberrantly expressed in human cancer cells which are associated with tumorigenesis, metastasis, invasiveness, and drug resistance. Breast cancer is the leading cause of cancer-induced death in women. Over the last decades, increasing attention has been paid to the effects of miRNAs on the development of breast cancer drug resistance. Among them, miR-155 takes part in a sequence of bioprocesses that contribute to the development of such drug resistance, including repression of FOXO3a, enhancement of epithelial-to-mesenchymal transition (EMT) and mitogen-activated protein kinase (MAPK) signaling, reduction of RhoA, and affecting the length of telomeres. In this review, we discuss the role of miR-155 in the acquisition of breast cancer drug resistance. This will provide a new way in antiresistance treatment of drug-resistant breast cancer.

MicroRNA expression profiles of drug-resistance breast cancer cells and their exosomes

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.