Jinhai Tang

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.

Statin use and mortality in cancer patients: Systematic review and meta-analysis of observational studies.

BACKGROUND Previous studies have examined the effect of statin use on the mortality in cancer patients, but the results are inconsistent. A meta-analysis was performed to assess the association with all available studies. METHODS Relevant studies were identified by searching PubMed and EMBASE to April 2015. We calculated the summary hazard ratios (HRs) and 95% confidence intervals (CIs) using random-effects models. We estimated combined HRs associated with defined increments of statin use, using random-effects meta-analysis and dose-response meta-regression models. RESULTS Thirty-nine cohort studies and two case-control studies involving 990,649 participants were included. The results showed that patients who used statins after diagnosis had a HR of 0.81 (95% CI: 0.72-0.91) for all-cause mortality compared to non-users. Those who used statin after diagnosis (vs. non-users) had a HR of 0.77 (95% CI: 0.66-0.88) for cancer-specific mortality. Prediagnostic exposure to statin was associated with both all-cause mortality (HR=0.79, 95% CI: 0.74-0.85) and cancer-specific mortality (HR=0.69, 95% CI: 0.60-0.79). Stratifying by cancer type, the three largest cancer-type subgroups were colorectal, prostate and breast cancer and all showed a benefit from statin use. HRs per 365 defined daily doses increment were 0.80 (95% CI: 0.69-0.92) for all-cause mortality and 0.77 (95% CI: 0.67-0.89) for cancer-specific mortality. A 1year increment in duration only conferred a borderline decreased risk of death. CONCLUSIONS In conclusion, the average effect of statin use, both postdiagnosis and prediagnosis, is beneficial for overall survival and cancer-specific survival.

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.

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.

MTHFR polymorphisms, dietary folate intake and breast cancer risk in Chinese women.

To evaluate the relationship between dietary folate intake and genetic polymorphisms of 5,10-methylenetetrahydrofolate reductase (MTHFR) with reference to breast cancer risk, we conducted a case–control study with 669 cases and 682 population-based controls in the Jiangsu Province of China. MTHFR C677T and A1298C genotypes were identified using PCR–RFLP (restrictrion fragment length polymorphism) methods. Dietary folate intake was assessed using an 83-item food frequency questionnaire. Odds ratios (ORs) were estimated with an unconditional logistic model. The frequencies of MTHFR C677T C/C, C/T and T/T genotypes were 32.37, 48.88 and 18.75% in cases and 37.66, 48.24 and 14.10% in controls, respectively. The difference in distribution was significant (χ2=6.616, P=0.037), the T/T genotype being associated with an elevated OR (adjusted for age, menopausal status, body mass index (BMI), income, work intensity and status of smoking and drinking) for breast cancer (1.62, 95% confidence interval (95% CI): 1.14–2.30). The frequencies of MTHFR A1298C A/A, A/C and C/C were 71.47, 27.08 and 1.44% in cases and 68.11, 30.13 and 1.76% in controls, respectively, with no significant differences being found (χ2=1.716, P=0.424). A significant inverse relationship was observed between folate intake and breast cancer risk. Compared with the lowest tertile of folate intake, the adjusted OR for breast cancer in the top tertile was 0.70 (95% CI: 0.53–0.92). However, no significant interaction was observed between folate intake and the MTHFR C677T polymorphism. Among individuals with the MTHFR A1298C A/A genotype, adjusted ORs for breast cancer were 0.89 (0.62–1.27) and 1.69 (1.20–2.36) for the second to the third tertile of folate intake compared with the highest folate intake group (tread test, P=0.0008). The findings of this study suggest that MTHFR genetic polymorphisms and dietary intake of folate may modify susceptibility to breast cancer.

MiR-139-5p: promising biomarker for cancer

MicroRNAs (miRNAs) were reported to be associated with cancer progression and carcinogenesis. MiRNAs are small, highly conserved, small non-coding RNA molecules, consisting of 18–25 nucleotides that control gene expression at the post-transcription level. By binding to complementary binding sites within the 3′ untranslated region (3′UTR) of target messenger RNAs (mRNAs), inhibiting translation or promoting degradation of mRNAs. MicroRNAs not only play an important part in regulating gene expression but also controlling diverse physiological and pathological processes. Similarly, several studies have demonstrated that miRNAs have been involved in regulating various biological processes, including apoptosis, proliferation, cellular differentiation, metabolism, signal transduction, and carcinogenesis. MiRNA-139, which is located in 11q13.4 and has anti-oncogenic and antimetastatic activity in humans, meanwhile, was identified to be downregulated in previous studies. However, based on the pathogenetic relationship between cancer and the role of miR-139-5p in tumorigenesis, we consider that miR-139-5p may be the candidates to serve as promising biomarkers with sufficient sensitivity and specificity for the diagnosis of cancer in a clinical setting; moreover, it would offer a new safe and effective way in further molecular targeting cancer treatment, as well as improving overall survival of patients.

Expression of the PXR gene in various types of cancer and drug resistance

Pregnane X receptor (PXR) is a member of the nuclear receptor superfamily of ligand-regulated transcription factors. PXR is a key xenobiotic receptor that regulates the expression of genes implicated in drug metabolism, detoxification and clearance, including drug metabolizing enzymes and transporters, suggesting that it is significant in the drug resistance of cancer cells. PXR is expressed in a wide range of tissues in the human body. Studies have demonstrated that PXR is expressed in a variety of tumor types, correlating not only with drug resistance but also with the cell proliferation, apoptosis and prognosis of cancer. The purpose of the present review is to provide a comprehensive review of PXR and its potential roles in multidrug resistance and the biological characteristics of PXR-positive tumors.

MiR-139-5p inhibits the biological function of breast cancer cells by targeting Notch1 and mediates chemosensitivity to docetaxel

OBJECTIVES MiRNA-139 is located at 11q13.4 and it has anti-oncogenic and antimetastatic activity in humans. However, its role in controlling apoptosis, invasion and metastasis and the development of chemosensitivity to docetaxel in breast cancer cells are not fully understood. The aim of this study was to research the biological function of miR-139-5p and the efficacy of chemosensitivity to docetaxel. METHODS MiR-139-5p expression in MCF-7, MCF-7/Doc cells and in selected breast cancer tissue samples was confirmed by real-time PCR; cell viability was analyzed by Cell Counting Kit-8 assay; apoptosis and cell cycle were analyzed by flow cytometry; control of metastasis and invasion of breast cancer cells was measured by transwell assay; expression of Notch1 was measured by western blot; a luciferase reporter vector was constructed to identify the miR-139-5p target gene. RESULTS MiR-139-5p was significantly down-regulated in breast cancer cells. MiR-139-5p inhibits the viability of breast cancer cells. MiR-139-5p induces apoptosis, causes cell cycle arrest in S phase, inhibits migration and invasion in breast cancer cells, however, MiR-139-5p play the opposite role in docetaxel-induced breast cancer cells. CONCLUSIONS MiR-139-5p not only attenuated the development of breast cancer cells but also mediated drug-resistance by regulating the expression of the downstream target gene Notch1.

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.