Combination Chemotherapy of L1210 Tumors in Mice with Pretubulysin and Methotrexate Lipo-Oligomer Nanoparticles.

ABSTRACT

In the current study, nanoparticles containing the antimetabolite drug methotrexate (MTX) and the novel tubulin-binding drug pretubulysin (PT) were developed for combination chemotherapy. Polyelectrolyte complexes were formed based on ∼20 nm cationic nanomicelles of lipo-oligomer 454 with the anionic MTX at the molar ratio of 31, resulting in spherical nanoparticles with sizes of 150 nm (454 MTX). Particle formation in the presence of PT, which also interacts with 454, resulted in coloaded micelle complexes (454 PT+MTX) of 170 nm as demonstrated by transmission electron microscopy and dynamic light scattering measurements. Both drugs were incorporated to a high extent (∼85% for MTX, ∼70% for PT). Nanoparticles were stable in up to 20% serum and physiological NaCl solution. Cellular internalization of 454 PT+MTX into L1210 leukemia and KB cervix carcinoma cells was determined by confocal light scattering microscopy. The antitumor activity of the drug combination PT+MTX in both cell lines was strongly increased by drug formulation with 454 with IC50 values of PT+MTX decreasing 11-fold from 0.22 nM to 19 pM on L1210 cells and 6-fold from 2.8 to 0.48 nM on KB cervix carcinoma cells. Systemic treatment of NMRI nu/nu mice bearing subcutaneous L1210 tumors with 454 PT+MTX nanoparticles resulted in a more effective delay of tumor growth in comparison to the free drug combination of PT+MTX without 454. Importantly, nanoparticle formulation of PT+MTX with 454 increased the survival of mice by more than 100% compared to that of the buffer treated group and more than 40% compared to that of the free drug group.