PTEN and neoplasm: It was reported that combined use of miR‐21 inhibitor oligonucleotide (miR‐21i) and 5‐FU delivered by the engineered exosomes could overcome resistance and markedly enhance the drug cytotoxicity in 5‐FU‐resistant HCT‐116/5‐FU cell line by increasing apoptosis, inducing cell cycle arrest, reducing tumor proliferation, and rescuing the decrease of phosphatase and tensin homolog (PTEN) and hMSH2 (regulatory targets of miR‐21) due to the downregulation of miR‐21.34