The enrichment of CD44 in exosomes from breast cancer cells treated with doxorubicin promotes chemoresistance

Abstract Background: Exosomes have been shown to be associated with chemotherapy resistance transmission between cancer cells. However, the cargo and function of exosomes changed in response to doxorubicin remains unclear. Methods: We compared proteome profiles of exosomes extracted from the supernatant of MCF-7(S/Exo) and MCF-7/ADR(A/Exo) cells. We confirmed the differential expression of the candidate target-exosomic-CD44 by immune gold staining and western blot. We further studied the changes of chemosensitivity and CD44 expression in MCF-7 cells co-incubated with A/Exo. We analyzed the levels of exosomal CD44 from patient plasma, and compared the sensitivity and specificity of exosomic CD44 and plasma CD44 on diagnosis of chemoresistance. We modified the MCF-7-derived exosomes loaded with siRNA against CD44 to observe the effects of targeting reduced CD44 expression in lumimal A breast cancer cells. Results: DOX increased the exosomes release from MCF-7/ADR cells and the exosomes mediated proteins intercellular transfer in breast cancer chemoresistance regulation. The candidate target of CD44 in A/Exo was much higher than in S/Exo and the increase levels of exosomic CD44 (21.65-fold) was much higher than cellular CD44 (6.55-fold). The same results were obtained in clinical samples. Exosome-siRNA targeted CD44 (Exos-siCD44) could efficiently targeted to silence its expression. When co-cultured on Exos-siCD44, breast cancer cells exhibited reduced cell proliferation and enhanced susceptibility to DOX and the same phenomenon was observed in mice. Conclusion：Drug-resistant breast cancer cells spread resistance capacity to sensitive ones by releasing exosomes to transfer proteins in intercellular.