PTEN and neoplasm: In the present study, engineered exosomes were employed to co-deliver 5-FU and miR-21i into HCT-1165FR cells which showed that while co-delivering miR-21i could increase the sensitivity of 5-FU on HCT-1165FR cells by rescuing the expression of hMSH2 and PTEN, and the combination therapy with 5-FU and miR-21i yielded a significantly enhanced antitumor efficacy compared with the single-agent treatment, as reflected in the decrease in tumor cell proliferation in vitro (Fig. 3e), tumor sizes (Fig. 5c) and tumor weights (Fig. 5d) in vivo.