Engineered exosomes for targeted co-delivery of miR-21 inhibitor and chemotherapeutics to reverse drug resistance in colon cancer

TLDR

5‑Fluorouracil resistance limits colorectal cancer therapy, and miRNAs have emerged as modulators capable of reversing this resistance by targeting key signaling pathways. This study investigates whether engineered exosomes can safely co‑deliver 5‑FU and a miR‑21 inhibitor to Her2‑expressing colorectal cancer cells to overcome drug resistance. Engineered exosomes were purified from donor cells, loaded with 5‑FU and miR‑21i by electroporation, and introduced into the 5‑FU‑resistant HCT‑1165FR cell line. Co‑delivery of 5‑FU and miR‑21i via engineered exosomes markedly enhanced uptake, suppressed miR‑21, induced cell‑cycle arrest, apoptosis, restored PTEN/hMSH2, and reduced tumor growth in 5‑FU‑resistant CRC cells and xenografts, thereby reversing resistance and improving cytotoxicity compared with single agents.

Abstract

5-Fluorouracil (5-FU) has been commonly prescribed for patients with colorectal cancer (CRC), but resistance to 5-FU is one of the main reasons for failure in CRC. Recently, microRNAs (miRNAs) have been established as a means of reversing the dilemma by regulating signaling pathways involved in initiation and progression of CRC. However, how to safely and effectively deliver miRNA to target cells becomes a main challenge.In this study, Engineered exosomes were exploited to simultaneously deliver an anticancer drug 5-FU and miR-21 inhibitor oligonucleotide (miR-21i) to Her2 expressing cancer cells. Purified engineered exosomes from the donor cells loaded with 5-FU and miR-21i via electroporation to introduce into 5-FU-resistant colorectal cancer cell line HCT-1165FR. Furthermore, systematic administration of 5-FU and miR-21i loaded exosomes in tumor bearing mice indicated a significantly anti-tumor effect. The results showed that the engineered exosome-based 5-FU and miR-21i co-delivery system could efficiently facilitate cellular uptake and significantly down-regulate miR-21 expression in 5-FU resistant HCT-1165FR cell lines. Consequently, the down-regulation of miR-21 induced cell cycle arrest, reduced tumor proliferation, increased apoptosis and rescued PTEN and hMSH2 expressions, regulatory targets of miR-21. Of particular importance was the significant reduction in tumor growth in a mouse model of colon cancer with systematic administration of the targeting miR-21i. More excitedly, the combinational delivery of miR-21i and 5-FU with the engineered exosomes effectively reverse drug resistance and significantly enhanced the cytotoxicity in 5-FU-resistant colon cancer cells, compared with the single treatment with either miR-21i or 5-FU.The strategy for co-delivering the functional small RNA and anticancer drug by exosomes foreshadows a potential approach to reverse the drug resistance in CRC and thus to enhance the efficacy of the cancer treatment.