Chemotherapy-elicited exosomal miR-378a-3p and miR-378d promote breast cancer stemness and chemoresistance via the activation of EZH2/STAT3 signaling

Abstract

Background Not all breast cancer (BC) patients who receive neoadjuvant chemotherapy achieve a pathologic complete response (pCR), but the reasons for this are unknown. Previous studies have shown that exosomes produced in the tumor microenvironment in response to chemotherapy promote a chemotherapy-resistant phenotype in tumors. However, the role of BC chemotherapy-elicited exosomes in regulating chemoresistance is poorly understood. Methods Using commercial kits, serum exosomes were extracted from patients before neoadjuvant chemotherapy, after one cycle of chemotherapy and after four cycles of chemotherapy consisting of doxorubicin (DOX) and paclitaxel (PTX). Their miRNAs were sequenced, and the correlation between the sequencing results and chemotherapy effects was further verified by RT-qPCR using patient serum exosomes. Cell Counting Kit-8 (CCK-8) was used to detect chemosensitivity. Stemness was assessed by CD44+/CD24- population analysis and mammosphere formation assays. Chromatin immunoprecipitation (ChIP) experiments were performed to verify the binding of signal transducer and activator of transcription 3 (STAT3) to the promoter of miRNAs. Results Here, we provide clinical evidence that chemotherapy-elicited exosomal miR-378a-3p and miR-378d are closely related to the chemotherapy response and that exosomes produced by BC cells after stimulation with DOX or PTX deliver miR-378a-3p and miR-378d to neighboring cells to activate WNT and NOTCH stemness pathways and induce drug resistance by targeting Dickkopf 3 (DKK3) and NUMB. In addition, STAT3, which is enhanced by zeste homolog 2 (EZH2), bound to the promoter regions of miR-378a-3p and miR-378d, thereby increasing their expression in exosomes. More importantly, chemotherapeutic agents combined with the EZH2 inhibitor tazemetostat reversed chemotherapy-elicited exosome-induced drug resistance in a nude mouse tumor xenograft model. Conclusion This study revealed a novel mechanism of acquired chemoresistance whereby chemotherapy activates the EZH2/STAT3 axis in BC cells, which then secrete chemotherapy-elicited exosomes enriched in miR-378a-3p and miR-378d. These exosomes are absorbed by chemotherapy-surviving BC cells, leading to activation of the WNT and NOTCH stem cell pathways via the targeting of DKK3 and NUMB and subsequently resulting in drug resistance. Therefore, blocking this adaptive mechanism during chemotherapy may reduce the development of chemotherapy resistance and maximize the therapeutic effect.

Exosomal miRNA profiles of triple‑negative breast cancer in neoadjuvant treatment

“…Patients with a complete response to therapy were more likely to have lower levels of miR-21 compared to those with stable disease, although this finding did not reach statistical significance (P= 0.060). Another study by Yang et al (32). provided clinical evidence that chemotherapy-elicited exosomal miR-378a-3p and miR-378d were related to chemotherapy response via the EZH2/STAT3 axis.…”

Eribulin and Paclitaxel Differentially Alter Extracellular Vesicles and Their Cargo from Triple-Negative Breast Cancer Cells

“…Additionally, paclitaxel and nocodozale increased survivin, a protein implicated in chemoresistance, in EVs from MDA-MB-231 cells [ 57 ]. Recent studies show that paclitaxel and doxorubicin chemotherapy increased the levels of EV miRNAs associated with chemoresistance in patients and in preclinical models [ 60 ]. These results show that paclitaxel can impact EV cargo that may contribute to drug resistance.…”

Hypoxia-Induced Intracellular and Extracellular Heat Shock Protein gp96 Increases Paclitaxel-Resistance and Facilitates Immune Evasion in Breast Cancer

“…Thus, it becomes necessary and meaningful to delve into the molecular mechanisms by which BC cells transform from paclitaxel-sensitive BC (PS-BC) cells into the paclitaxel-resistant BC (PR-BC) cells. In recent studies, it draws our attention that cancer cells derived exosomes play critical role in regulating paclitaxel-resistance in BC ( 6 , 7 ). Specifically, data from Pederson et al.…”