177Lu-Bombesin-PLGA (paclitaxel): A targeted controlled-release nanomedicine for bimodal therapy of breast cancer

Abstract

The gastrin-releasing peptide receptor (GRPr) is overexpressed in>75% of breast cancers. 177Lu-Bombesin (177Lu-BN) has demonstrated the ability to target GRPr and facilitate efficient delivery of therapeutic radiation doses to malignant cells. Poly(D,L‑lactide‑co‑glycolide) acid (PLGA) nanoparticles can work as smart drug controlled- release systems activated through pH changes. Considering that paclitaxel (PTX) is a first-line drug for cancer treatment, this work aimed to synthesize and chemically characterize a novel polymeric PTX-loaded nanosystem with grafted 177Lu-BN and to evaluate its performance as a targeted controlled-release nanomedicine for concomitant radiotherapy and chemotherapy of breast cancer. PLGA(PTX) nanoparticles were synthesized using the single emulsification-solvent evaporation method with PVA as a stabilizer in the presence of PTX. Thereafter, the activation of PLGA carboxylic groups for BN attachment through the Lys1-amine group was performed. Results of the chemical characterization by FT-IR, DLS, HPLC and SEM/TEM demonstrated the successful synthesis of BN-PLGA(PTX) with a hydrodynamic diameter of 163.54 +- 33.25 nm. The entrapment efficiency of paclitaxel was 92.8 +- 3.6%. The nanosystem showed an adequate controlled release of the anticancer drug, which increased significantly due to the pH change from neutral (pH=7.4) to acidic conditions (pH=5.3). After labeling with 177Lu and purification by ultrafiltration, 177Lu-BN-PLGA(PTX) was obtained with a radiochemical purity of 99 +- 1%. In vitro and in vivo studies using MDA-MB-231 breast cancer cells (GRPr-positive) demonstrated a 177Lu-BNPLGA( PTX) specific uptake and a significantly higher cytotoxic effect for the radiolabeled nanosystem than the unlabeled BN-PLGA(PTX) nanoparticles. Using a pulmonary micrometastasis MDA-MB-231 model, the added value of 177Lu-BN-PLGA(PTX) for tumor imaging was confirmed. The 177Lu-BN-PLGA(PTX) nanomedicine is suitable as a targeted paclitaxel delivery system with concomitant radiotherapeutic effect for the treatment of GRPr-positive breast cancer.