In-vivo efficacy of novel paclitaxel nanoparticles in paclitaxel-resistant human colorectal tumors.

Colloidal carriers have been shown to improve tumor therapy by increased drug delivery into tumor sites resulting directly from the enhanced permeability and retention effect (EPR). However, the clinical outcome of tumor therapy is often limited due to multidrug resistance. Several different types of resistance exist with expression of p-glycoprotein being the most commonly described. Paclitaxel entrapped in emulsifying wax nanoparticles (PX NPs) was shown to overcome drug resistance in a human colon adenocarcinoma cell line (HCT-15). In the present studies, the in-vivo efficacy of PX NPs in a HCT-15 mouse xenograft model was demonstrated. Significant inhibition in tumor growth was observed in mice receiving PX NPs treatment. Additionally, mice dosed with Taxol also demonstrated slower tumor growth; however, the efficacy of the Taxol treatment was shown in the in-vitro HUVEC model to be due to the antiangiogenic effect of paclitaxel. It was concluded that the enhanced efficacy of PX NPs over Taxol in the xenograft model was due to both overcoming paclitaxel resistance and an antiangiogenic effect.