(W1230-02-08) Colorectal Lumen-to-Tumor Delivery of Rectally Administered Ligand-Functionalized Nanoparticles for the Local Treatment of Colorectal Cancer

Purpose: Colorectal cancer (CRC) is the third most common cancer worldwide with a rapidly increasing incidence in many countries. For the treatment of CRC, rectal administration of chemotherapeutic agents has gained much attention since high levels of chemotherapeutics could be easily reached near the CRC tissues located in the surface of colorectum, and free from the concerns about off-target toxicity caused by systemic absorption. However, owing to the rapid clearance after administration and poor drug distribution from the colorectal lumen to the CRC tissues, local chemotherapy by using rectally administered chemotherapeutics has been limited. In this study, we elucidated that rectal administration of the ligand-functionalized nanoparticles could show potent tumor growth inhibition effects via enhanced ligand-mediated lumen-to-tumor uptake. As a model delivery system, paclitaxel (PTX)-loaded, hyaluronic acid (HA)-grafted poly (lactic-co-glycolic acid) nanoparticles (HA-PLGA/PTX NPs) was developed, and selective drug accumulation in CRC tissues and tumor growth inhibition effects of the rectally administered HA-PLGA/PTX NPs were evaluated in an azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced CRC mouse model.

Methods: HA-PLGA was synthesized via carbodiimide-assisted esterification between carboxyl group of PLGA and hydroxyl group of HA, and successful synthesis of HA-PLGA was confirmed by Nuclear Magnetic Resonance (NMR) and Fourier-transform infrared (FT-IR) spectroscopy. HA-PLGA/PTX NPs was fabricated using an oil-in-water emulsion solvent evaporation method. Hydrodynamic particle and zeta potential of the nanoparticles were measured using a zetasizer, and the morphology of the nanoparticles were observed by scanning electron microscopy (SEM). Cytotoxic effects and cellular uptake studies were conducted against HCT-116 CRC cell line. To investigate in vivo distribution after rectal administration of HA-PLGA/PTX NPs, IR780-loaded HA-PLGA NPs were fabricated, and the remaining fluorescence after nanoparticle administration was measured using an in vivo imaging system (IVIS). Tumor penetration of HA-PLGA/PTX NPs was evaluated by measuring penetrated nanoparticles in the CRC tissues after rectal administration of nile red-loaded HA-PLGA NPs using a confocal laser scamming microscopy. Antitumor effects of HA-PLGA/PTX NPs were evaluated in AOM/DSS-induced CRC mouse model by the direct observation of the tumors in colorectum using a colonoscopy.

Results: HA-PLGA/PTX NPs was successfully prepared with 186.3 ± 3.0 nm of mean particle diameter and -19.1 ± 0.5 mV of zeta potential. Around 3.52% of PTX were loaded in the nanoparticles, and PTX was released from the nanoparticles for more than 70 h in a sustained manner. Due to the presence of HA on the surface of HA-PLGA/PTX NPs, the nanoparticles showed rapid cellular uptake and enhanced cytotoxicity in the short-term exposure cytotoxicity test. Rectally administered HA-PLGA/PTX NPs was selectively accumulated in the CRC tissues of AOM/DSS-induced CRC mouse, and internalized nanoparticles stayed in the CRC tissues for more than 24 h. In in vivo tumor penetration test, fluorescence signals from nile red-loaded HA-PLGA NPs were observed not only on the tumor surface but also in the center of the tumor tissue, indicating that the nanoparticles could be distributed deep into the tumor tissues via enhanced penetration provided by strong interactions between HA on the surface of the nanoparticles and CD44 receptor of CRC cells. Resulted from the enhanced colorectal lumen-to-tumor delivery, HA-PLGA/PTX NPs showed potent tumor growth inhibition in AOM/DSS-induced CRC mouse.

Conclusion: In this study, we elucidated that rectal administration of ligand-functionalized nanoparticles could efficiently deliver the chemotherapeutic agents via enhanced ligand-mediated colorectal lumen-to-tumor delivery, followed by the enhanced anticancer effects. As a model drug delivery system, HA-PLGA/PTX NPs were successfully prepared by synthesis of HA-PLGA followed by fabrication of HA-PLGA/PTX NPs. Owing to the strong interactions between HA on the surface of the HA-PLGA/PTX NPs and CD44 receptors overexpressed on the surface of CRC cells, rectally administered HA-PLGA/PTX NPs were selectively accumulated in AOM/DSS-induced CRC tissues and showed limited uptake by the normal tissues. As a result of the enhanced PTX delivery to CRC tissues without systemic absorption, HA-PLGA/PTX NPs showed potent antitumor effects in AOM/DSS-induced CRC mice without any significant off-target toxicity. The results suggest that ligand-mediated colorectal lumen-to-tumor delivery could be a desirable approach for the local treatment of CRC.
Schematic illustration of the suggested mechanism for non-systemic targeted chemotherapy using HA-functionalized nanoparticles via facilitated colorectal lumen-to-tumor delivery.

In vivo distribution of rectally administered HA-PLGA NPs and PLGA NPs in AOM/DSS-induced colorectal cancer (CRC) mice and healthy mice.

In vivo tumor growth inhibition effects of rectally administered PTX formulations via endoscopic assessment.