Abstract: The combination of doxorubicin and paclitaxel is widely used in clinical cancer therapy. Due to enhanced permeation and retention effects of nanomaterials in tumor tissues, nanocarriers with good biocompatibility have been designed to encapsulate doxorubicin/paclitaxel, and used to facilitate delivery of the drugs to achieve better therapeutic outcome. In this study, NMR-based metabonomic analyses were used to study the metabolic profiles in spleen tissues of normal healthy mice and of 4T1 tumor-bearing mice, which were treated with either saline, or doxorubicin/paclitaxel in their free forms, or doxorubicin/paclitaxel encapsulated in nanocarriers. The results demonstrated that treatment with the free forms of doxorubicin/paclitaxel remitted tumor-induced disturbances in gut microbiota, while treatment with nanocarrier-encapsulated doxorubicin/paclitaxel alleviated increased glucose and fumarate metabolism associated with tumor bearing. In contrast, tumor-related splenomegaly and metabolic alterations in amino acids, organic acids, nucleic acids and choline, both attributable to immune responses of the spleen, were not ameliorated by drug treatment. This could also be due to the fact that the treatment period was too short to have any significant effects. This work provided metabolic phenotypical information of the spleen tissues in 4T1 tumor-bearing mice, and helped to understand the metabolic impacts of drug delivery systems on the spleen.

Key words: doxorubicin, paclitaxel, nanocarrier, spleen, metabonomics