Paclitaxel (PTX) is an essential component of the first-line treatment in breast cancer (BC). However, the conventional PTX formulation currently used has been associated with many dose-limiting toxicities. mTOR inhibitors, such as everolimus (EVER), were found to increase sensitivity to PTX in BC. Importantly, administering PTX and EVER at a synergistic ratio could allow for reducing the dose and toxicities of PTX. BC tumors co-expressing HER2 and EGFR were shown to have poor prognosis and reduced survival compared to other BC subtypes. Therefore, this research aims to develop a dual-targeted polymeric nanoparticle (NP) formulation encapsulating PTX and EVER at the synergistic molar ratio to improve cytotoxicity and cellular uptake in BC cells co-expressing HER2 and EGFR.
The combination of PTX and EVER was evaluated in BC cells and the optimal synergistic ratio was defined. PTX+EVER-loaded NP formulation was successfully prepared. Antibody Fab fragments specific to HER2 and EGFR were prepared by digestion of Trastuzumab (TmAb) and Panitumumab (PmAb), respectively. The cytotoxicity and cellular uptake of untargted-NPs, TmAb(Fab)-NPs, and TmAb(Fab)-PmAb(Fab)-NPs were studies in SKBR3 (HER2 +++/EFGR ++) and MCF-7 (HER2-/EGFR+) BC cells.
The optimal synergistic ratio of PTX and EVER combination was defined at 1:0.5, exhibiting synergy in six BC cell lines. PTX+EVER-loaded NPs were spherical with less than 100 nm in diameter, had a total drug loading of 9% (wt%), and exhibited sustained drug release
Co-encapsulation of PTX and EVER in HER2-EGFR targeted polymeric NPs can lead to a significant increase in the cytotoxicity and cellular uptake in BC cells co-expressing HER2 and EGFR relative to untargeted and HER2-targeted NPs. These data show high potential for a dual-targeted NP formulation of PTX and EVER combination to improve tumor growth inhibition and reduce PTX dose-limiting toxicities in BC tumors co-expressing HER2 and EGFR in vivo.
Leslie Dan Faculty of Pharmacy, University of Toronto
Canadian Institutes of Health Research (CIHR)
All authors have declared no conflicts of interest.