To establish a patient-derived xenograft model of colorectal cancer (CRC-PDX) and evaluate the safety and anti-tumor efficacy of an ultrasound (US)-mediated triptolide (TPL)-loaded exosome delivery system in vivo.

Tumor tissues were retrospectively collected from 100 CRC patients who underwent surgical treatment in Chenzhou First People's Hospital from March 2024 to March 2025 for the establishment of CRC-PDX models. Among these, the CRC-PDX model derived from one patient with advanced malignant CRC was passaged to the F3 generation. TPL was loaded into exosomes (sEVs) isolated from human umbilical cord mesenchymal stem cells (huc-MSCs) via electroporation to prepare TPL@sEVs, which were characterized by Western Blot and high-performance liquid chromatography. F3-generation model nude mice were randomly divided into 6 groups (n=6): control (PBS), sEVs, US+sEVs, TPL@sEVs, US+TPL@sEVs, and 5-Fu groups. The safety and anti-tumor effects of the delivery system were evaluated after administration via tail vein injection.

A total of 100 CRC patients were included in this study. The tumor formation rate of the P0-generation CRC-PDX models was 62% (57/92). Primary tumor location, TNM stage, and preoperative carcino-embryonic antigen level were identified as influencing factors for tumor formation (P<0.05). The F3-generation CRC-PDX tumor tissues were highly consistent with the primary tumor in terms of cell structure and protein expressions of hypoxia-inducible factor-1α (HIF-1α)/Nuclear factor κB (NF-κB)/Ki-67. Characterization results confirmed that the successful preparation of TPL@sEVs with a drug loading capacity of (12.77± 1.65)%. Safety assessment of the delivery system showed that only nude mice in the 5-Fu group exhibited mild diarrhea and transient anorexia, with significantly lower liver and spleen coefficients than those in the control group (P<0.05). The TPL@sEVs group showed significant abnormalities in liver and kidney function indicators (such as ALT, AST, and CRE) compared with the control group (P<0.05), while these indicators in the US+TPL@sEVs group were significantly improved compared with the TPL@sEVs group (P<0.05). Anti-tumor efficacy assessment revealed that compared with the control group, all treatment groups showed significantly reduced tumor volume and weight (P<0.05), with the US+TPL@sEVs group exhibiting the best inhibitory effect. Immunohistochemical results indicated that compared with the control group, all treatment groups showed a certain degree of downregulation in the protein expressions of HIF-1α/NF-κB/Ki-67. Specifically, the US+TPL@sEVs group had a significantly stronger inhibitory effect on the protein expressions of HIF-1α/NF-κB than the 5-Fu group (P<0.05), while there was no significant difference in the inhibitory effect on Ki-67 protein expression between the US+TPL@sEVs group and the 5-Fu group (P>0.05).

The US-mediated TPL-loaded exosome targeted delivery system can significantly reduce the toxic and side effects of TPL and enhance the anti-tumor activity against the CRC-PDX model, making it a promising targeted therapeutic strategy for colorectal cancer.