A unique squalenoylated and nonpegylateddoxorubicin nanomedicine with systemiclong-circulating properties and anticancer activity

Abstract

We identified that the chemical linkage of the anticancer drugdoxorubicin onto squalene, a natural lipid precursor of the choles-terol's biosynthesis, led to the formation of squalenoyl doxorubicin(SQ-Dox) nanoassemblies of 130-nm mean diameter, with an original "loop-train" structure. This unique nanomedicine demonstrates:(/) high drug payload, (//) decreased toxicity of the coupled anticancer compound, (/;';') improved therapeutic response, (/V)use ofbiocompatible transporter material, and (v) ease of preparation,all criteria that are not combined in the currently available nano-drugs. Cell culture viability tests and apoptosis assays showed thatSQ-Dox nanoassemblies displayed comparable antiproliferative andcytotoxic effects than the native doxorubicin because of the highactivity of apoptotic mediators, such as caspase-3 and poly(ADP-ribose) polymerase. In vivo experiments have shown that the SQ-Dox nanomedicine dramatically improved the anticancer efficacy,compared with free doxorubicin. Particularly, the M109 lung tumorsthat did not respond to doxorubicin treatment were found inhibitedby 90% when treated with SQ-Dox nanoassemblies. SQ-Dox nano-assembly-treated MiaPaCa-2 pancreatic tumor xenografts in micedecreased by 95% compared with the tumors in the saline-treatedmice, which was significantly higher than the 29% reduction achievedby native doxorubicin. Concerning toxicity, SQ-Dox nanoassem-blies showed a fivefold higher maximum-tolerated dose than thefree drug, and moreover, the cardiotoxicity study has evidencedthat SQ-Dox nanoassemblies did not cause any myocardial lesions,such as those induced by the free doxorubicin treatment. Takentogether, these findings demonstrate that SQ-Dox nanoassembliesmake tumor cells more sensitive to doxorubicin and reduce thecardiac toxicity, thus providing a remarkable improvement in thedrug's therapeutic index.