Study On The Process And Mechanism Of Exocrine - Mediated MicroRNAs Transmission In Breast Cancer Resistance

PARTIExosomes from drug-resistant breast cancer cells transmit chemoresistance by a horizontal transfer of microRNAsDocetaxel and adriamycin 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 other’s report that human breast cancer cell line MCF-7/S could acquire increased survival potential from its resistant variants MCF-7/Doc and MCF-7/Adr. Additionally, exosomes of the latter, D/exo and A/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 microRNA expression profiles of D/exo,A/exo,and S/exo demonstrated that they loaded selective microRNA patterns. Following D/exo and A/exo transfer to recipient MCF-7/S, the same microRNAs 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 microRNA 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 microRNAs.PART IIExosomes decrease sensitivity of breast cancer cells to adriamycin by delivering microRNAsWhile adriamycin offers improvement in survival for breast cancer 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 between heterogeneous populations of tumor cells, engendering a resistance-promoting niche for cancer progression.Our recent study showed that exosomes from docetaxel-resistance breast cancer cells could modulate chemosensitivity by delivering microRNAs. Herein, we expand on our previous finding and explore the relevance of exosome-mediated microRNA delivery in resistance transmission of adriamycin-resistant breast cancer sublines. We now demonstrated the selective packing of microRNAs within the exosomes (A/exo) derived from adriamycin-resistant breast cancer cells. The highly expressed microRNAs 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 microRNAs in A/exo were involved in crucial biological processes. Moreover, A/exo not only loaded microRNAs for its production and release but also carried microRNAs associated with Wnt signaling pathway. Furthermore, A/exo co-culture assays indicated that microRNA-containing A/exo was able to increase the overall resistance of GFP-S to adriamycin exposure and regulate gene levels in GFP-S.Our results reinforce our earlier reports that adriamycin-resistant breast cancer cells could manipulate a more deleterious microenvironment and transmit resistance capacity through altering gene expressions in sensitive cells by transferring specific microRNAs contained within exosomes.