The Synthesis of Glutamine-Functionalized Block Polymer and Its Application in Triple-Negative Breast Cancer Treatment

Abstract

Triple-negative breast cancer (TNBC) is a highly malignant tumor. At present, there are still no targeted drugs for TNBC. Clinical chemotherapeutic drugs, such as doxorubicin (DOX), have the characteristic of nontargeted distribution in treatment of TNBC, causing severe side effects. Therefore, new target treatment strategies for TNBC are of urgent need. It was speculated that glutamine could be a potential target because it is in high demand by TNBC. In this study, we found that the transporter for glutamine, ASCT2 (solute carrier family 1 member 5 (SLC1A5)), is highly expressed in TNBC by analysis of data from The Cancer Genome Atlas (TCGA) and experiments in vitro. Based on this, glutamine was grafted onto a polymeric drug carrier in order to develop a tumor-targeting drug delivery system for treatment of TNBC. Firstly, pH-responsive glutamine-PEG5000-b-PAE10000 (Gln-PEG-b-PAE) copolymers were synthesized using Fmoc-PEG5000-b-PAE10000 (Fmoc-PEG-b-PAE) copolymers. Then, Gln-PEG-b-PAE@DOX micelles were prepared by loading DOX to Gln-PEG-b-PAE copolymer using a solvent casting technology. In vitro, Gln-PEG-b-PAE@DOX micelles exhibited pH-dependent micellization-decellularization behavior; namely, they can rapidly release DOX in acidic environment of pH 6.0 but release very slowly in physiological condition. Moreover, glutamine competition experiment showed that Gln-PEG-b-PAE@DOX micelles had the ability to target MDA-MB-231 cells. Compared to free DOX, Gln-PEG-b-PAE@DOX micelles had significantly greater cytotoxic effect and antiproliferative activity against MDA-MB-231 cells. In vivo, compared to free DOX and mPEG-b-PAE@DOX micelles, Gln-PEG-b-PAE@DOX micelles significantly inhibited tumor growth in tumor-bearing mice. Therefore, Gln-PEG-b-PAE@DOX micelles, as a tumor-targeting drug delivery system, may provide a new method for the treatment of TNBC.