Chemotherapy is one of the primary treatments for malignant tumors. However, the acquired drug resistance hinders clinical efficacy and leads to treatment failure in most patients. Exosomes are cell-derived vesicles with a diameter of 30–150 nm carrying and delivering substances such as DNAs, RNAs, lipids, and proteins for cellular communication in tumor development. Circular RNAs (circRNAs) present covalently closed-loop RNA structures, which regulate tumor cell proliferation, apoptosis, and metastasis by controlling different genes and signaling pathways. CircRNAs are abundant and stably expressed in exosomes. Recent studies have shown that they play critical roles in chemotherapy resistance in various cancers. In this review, we summarized the origin of exosomes and discussed the regulation mechanism of exosomal circRNAs in cancer drug resistance.

tumor microenvironment

RNA exonuclease or ribonuclease

Extracellular vesicles

multivesicular bodies

next generation sequencing

internal ribosome entry site

epithelial-mesenchymal transition

transarterial chemoembolization

cancer-associated fibroblasts

non-small cell lung cancer

progression-free survival

myeloid-derived suppressor cells

Exosome

Circular RNA (circRNA)

Chemotherapy resistance

Cancer

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