Inhibitory effect of paclitaxel and rapamycin individual and dual drug-loaded polymeric micelles in the angiogenic cascade.

Angiogenesis is an essential process for disease progression in many solid tumors. There are several major cascade events in the angiogenic process that can be targeted to inhibit new blood vessel formation in the tumor tissue. The purpose of this work is to evaluate the inhibitory effect of paclitaxel (PTX) and rapamycin (RAP) as individual and in dual drug-loaded poly(ethylene glycol)-block-poly(d,l-lactic acid) (PEG-b-PLA) micelles on the angiogenic cascade processes of proliferation, migration, and tube formation. PEG-b-PLA PTX and/or RAP micelles were formed and characterized for size and drug loading. Sizes of individual and dual drug micelles were below 40 nm. PEG-b-PLA micelles significantly enhanced the aqueous solubility of PTX 1.80 mg/mL and RAP 1.60 mg/mL. The PTX-RAP dual drug PEG-b-PLA micelles were able to load PTX and RAP at 1.60 mg/mL for both drugs. Cell proliferation, apoptosis, tubule formation, and migration studies were performed in human umbilical vein endothelial cells (HUVEC). PTX and RAP in DMSO inhibited HUVEC proliferation with IC50 values of 0.82 ± 0.02 and 13 829 ± 681 nM, respectively, while the combination of both drugs in DMSO produced synergistic inhibition. PTX and RAP individual micelles had IC50 values of 6.3 ± 1.1 and 14 051 ± 821 nM, respectively. PTX and dual drug micelles had a synergistic inhibition effect on HUVEC proliferation through the induction of apoptosis via caspase 3/7 activity. In vitro tube formation assay demonstrated significant inhibition of tube formation upon treatment with dual drug micelles as compared to individual PTX or RAP micelles. Migration studies in HUVEC have shown that individual PTX micelles inhibited cell migration at 1 nM, while RAP micelles did not show any inhibitory effect on cell migration. Interestingly, the presence of RAP in the dual drug micelles was able to initiate the inhibition of the migration of HUVEC at 0.1 nM concentration of PTX. These results indicate that PTX-RAP dual drug micelles have antiangiogenic effects in vitro mediated through three major events in the angiogenic process and have strong potential for further development as antiangiogenic chemotherapy.