Dan-dan Yu

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.

Exosomes decrease sensitivity of breast cancer cells to adriamycin by delivering microRNAs.

While adriamycin (adr) offers improvement in survival for breast cancer (BCa) patients, unfortunately, drug resistance is almost inevitable. Mounting evidence suggests that exosomes act as a vehicle for genetic cargo and constantly shuttle biologically active molecules including microRNAs (miRNAs) between heterogeneous populations of tumor cells, engendering a resistance-promoting niche for cancer progression. Our recent study showed that exosomes from docetaxel-resistance BCa cells could modulate chemosensitivity by delivering miRNAs. Herein, we expand on our previous finding and explore the relevance of exosome-mediated miRNA delivery in resistance transmission of adr-resistant BCa sublines. We now demonstrated the selective packing of miRNAs within the exosomes (A/exo) derived from adr-resistant BCa cells. The highly expressed miRNAs in A/exo were significantly increased in recipient fluorescent sensitive cells (GFP-S) after A/exo incorporation. Gene ontology analysis of predicted targets showed that the top 30 most abundant miRNAs in A/exo were involved in crucial biological processes. Moreover, A/exo not only loaded miRNAs for its production and release but also carried miRNAs associated with Wnt signaling pathway. Furthermore, A/exo co-culture assays indicated that miRNA-containing A/exo was able to increase the overall resistance of GFP-S to adr exposure and regulate gene levels in GFP-S. Our results reinforce our earlier reports that adr-resistant BCa cells could manipulate a more deleterious microenvironment and transmit resistance capacity through altering gene expressions in sensitive cells by transferring specific miRNAs contained within exosomes.

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.

Aspirin use and risk of breast cancer: Systematic review and meta-analysis of observational studies

Previous studies concerning the association between aspirin use and breast cancer risk yielded inconsistent results. We aimed to investigate the association by meta-analysis. PubMed and EMBASE were searched for relevant studies. We calculated the summary relative risks (RR) and 95% confidence intervals (CI) using random-effects models. Seventeen cohort studies and 15 case–control studies were included. The overall result showed that aspirin use decreased risk of breast cancer (RR, 0.90; 95% CI, 0.85–0.95). However, there was evidence of publication bias and heterogeneity and the association disappeared after correction using the trim-and-fill method. When stratified by study design, a significant benefit for aspirin users was only found in population-based and hospital-based case–control studies but not in cohort or nest case–control studies. Further subgroup analyses showed that aspirin use could decrease risk of in situ breast tumors or hormone receptor–positive tumors and reduce risk of breast cancer in postmenopausal women. Aspirin use may not affect overall risk of breast cancer, but decrease risk of in situ breast tumors or hormone receptor–positive tumors and reduce risk of breast cancer in postmenopausal women. Considering between-study significant heterogeneity and publication bias, confirmation in future studies is also essential. Cancer Epidemiol Biomarkers Prev; 24(11); 1645–55. ©2015 AACR.

MicroRNA-3646 Contributes to Docetaxel Resistance in Human Breast Cancer Cells by GSK-3β/β-Catenin Signaling Pathway

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.

The role of ADAM17 in tumorigenesis and progression of breast cancer.

A disintegrin and metalloproteinase (ADAM) family members are known to process the target membrane-bound molecules through the quick induction of their protease activities under interaction with other molecules, which have diverse roles in tissue morphogenesis and pathophysiological remodeling. Among these, ADAM17 is a membrane-bound protease that sheds the extracellular domain of various receptors or its ligands from the cell membrane and subsequently activates downstream signaling transduction pathways. Importantly, breast cancer remains a mainspring of cancer-induced death in women, and numerous regulatory pathways have been implicated in the formation of breast cancer. Substantial evidence has demonstrated that an obvious increased in ADAM17 cell surface expression has been discovered in breast cancer and was shown to be associated with mammary tumorigenesis, invasiveness, and drug resistance. Over the last decades, it has received more than its share of attention that ADAM17 plays a potential role in breast cancer, including cell proliferation, invasion, angiogenesis, apoptosis, and trastuzumab resistance. In our review, we discuss the mechanisms through which ADAM17 acts on breast cancer tumorigenesis and progression. Thus, this will provide further impetus for exploiting ADAM17 as a new target for breast cancer treatment.

β-Blocker use and mortality in cancer patients: systematic review and meta-analysis of observational studies.

A number of epidemiologic studies have attempted to link the use of &bgr; blockers to mortality in cancer patients, but their findings have been inconclusive. A meta-analysis was carried out to derive a more precise estimation. Relevant studies were identified by searching PubMed and EMBASE to May 2015. We calculated the summary hazard ratios (HRs) and 95% confidence intervals (CIs) using random-effects models. Twenty cohort studies and four case–control studies involving 76 538 participants were included. The overall results showed that patients who used &bgr; blockers after diagnosis had an HR of 0.89 (95% CI 0.81–0.98) for all-cause mortality compared with nonusers. Those who used &bgr; blockers after diagnosis (vs. nonusers) had an HR of 0.89 (95% CI 0.79–0.99) for cancer-specific mortality. Prediagnostic use of &bgr; blockers showed no beneficial effect on all-cause mortality or cancer-specific mortality. Stratifying by cancer type, only breast cancer patients who used &bgr; blockers after diagnosis had a prolonged overall survival. A linear but nonsignificant trend was found between postdiagnostic &bgr;-blocker use and mortality of cancer patients. In conclusion, the average effect of &bgr;-blocker use after diagnosis but not before diagnosis is beneficial for the survival of cancer patients.

Perioperative propofol-paravertebral anesthesia decreases the metastasis and progression of breast cancer

Propofol-paravertebral anesthesia (PPA) is a unique combination of paravertebral nerve blocks (PVBs) and propofol that regulates the cellular microenvironment during surgical period. Growing evidence points to its ability to attenuate perioperative immunosuppression of cancers. Abundant studies show that cancer patients who undergo perioperative PPA exhibit less recurrence as well as metastasis. Breast cancer remains a leading cause of cancer-induced death in women. Over the last decades, increasing concerns have been put on the promotional role of PPA in the prognosis of breast cancer patients. Among them, PPA participates in several bioprocesses in the development of breast cancer, including inhibiting hypoxia-inducible factor (HIF) activity, elevating serum concentration of nitric oxide index (NOx), depression of the neuroepithelial cell transforming gene 1 (NET1) signal pathway, blocking the nuclear factor kappa B (NF-κB) pathway following an decreased expression of matrix metalloproteinase (MMP), increasing NK cytotoxicity, and affecting transforming growth factor (TGF)-β-targeted ras and HER2/neu gene pathways. In this review, we discuss the effect of PPA on breast cancer metastasis and progression. This will provide an alteration pattern of surgical anesthesia technique in breast cancer patients with poor prognosis.

Circular RNA hsa_circ_0072995 promotes breast cancer cell migration and invasion through sponge for miR-30c-2-3p.

AIM To study the role of hsa_circ_0072995 in regulating the invasion and migration of breast cancer cells. MATERIALS & METHODS Hsa_circ_0072995 expression was confirmed by quantitative real-time PCR; evaluating the migration and invasion of breast cancer cells through transwell assay; predicating circRNA/microRNAs interaction using the miRanda and RNAhybrid software; identifying the relationship between hsa_circ_0072995 and miR-30c-2-3p by luciferase activity assay; detecting the location of hsa_circ_0072995 by Fluorescence in situ hybridization assay. RESULTS Hsa_circ_0072995 was significantly upregulated in MDA-MB-231 cells compared with MCF-7 cells. Hsa_circ_0072995 regulated the invasion and migration of breast cancer cells. Hsa_circ_0072995 existed in the nucleus and cytoplasm, and the proportion of the two was roughly equal. Hsa_circ_0072995 bound to miR-30c-2-3p. Overexpression of miR-30c-2-3p inhibited breast cancer cells migration and invasion. Low expression of miR-30c-2-3p was correlated with poor overall survival by The Cancer Genome Atlas database. CONCLUSION Hsa_circ_0072995 may be a novel biomarker for breast cancer, and may function in metastasis of breast cancer.