Metabolomics facilitates the discrimination of the specific anti-cancer effects of free- and polymer-conjugated doxorubicin in breast cancer models

Metabolomics is becoming a relevant tool for understanding the molecular mechanisms
involved in the response to new drug delivery systems. The applicability of this experimental
approach to cell cultures and animal models makes metabolomics a useful tool for establishing
direct connections between in vitro and in vivo data, thus providing a reliable platform for the
characterization of chemotherapeutic agents. Herein, we used metabolomic profiles based on
nuclear magnetic resonance (NMR) spectroscopy to evaluate the biochemical pathways involved in
the response to a chemotherapeutic anthracycline drug (Doxorubicin, Dox) and an N-(2-
hydroxypropyl) methacrylamide (HPMA) copolymer-conjugated form (HPMA-Dox) in an in vitro
cell culture model and an in vivo orthotopic breast cancer model. We also used protein expression
and flow cytometry studies to obtain a better coverage of the biochemical alterations associated
with the administration of these compounds. The overall analysis revealed that polymer conjugation
leads to increased apoptosis, reduced glycolysis, and reduced levels of phospholipids when
compared to the free chemotherapeutic drug. Our results represent a first step in the application of
integrated in vitro and in vivo metabolomic studies to the evaluation of drug delivery systems.