Liver-Specific Nanoparticle-Mediated Delivery and MMP-Triggered Release of Veratridine to Effectively Target Metastatic Colorectal Cancer.

BACKGROUND: Despite considerable advances to improve colorectal cancer (CRC) survival over the last decade, therapeutic challenges remain due to the rapid metastatic dissemination of primary tumors. This study revealed the apoptotic and anti-growth mechanism of VTD, a previously used anti-hypertensive supplement, can elevate UBXN2A, a known tumor suppressor protein in CRC, and simultaneously enhance intrinsic and extrinsic apoptosis in metastatic cancer cells. METHODS AND RESULTS: An AOM/DSS mouse model of CRC showed that UBXN2A haplosufficient (UBXN2A +/-) mice treated with VTD had less tumor burden than mice with the full UBXN2A gene treated with vehicle. We have previously shown that casein-coated mesoporous silica nanoparticles (MSNs) offer an effective local delivery of drugs at tumor sites. Our findings demonstrate that the high rate of extracellular release of matrix metalloproteinases (MMPs), particularly MMP-7, by metastatic colon cancer cells, triggers the release of VTD from casein-coated mesoporous MSNs. This shows the "Zip Code" mechanism for the local enrichment of VTD at the tumor sites. After in vitro drug release verification, two independent mouse experiments, a xenograft and a splenolepatic metastatic mouse model of CRC, were used to evaluate the therapeutic efficacy of VTD-loaded and casein-coated carboxylated mesoporous silica nanoparticles, MSN-COOH/VTD/CAS (VTD, 0.2 mg/kg). Animal experiments revealed that MSN-COOH/VTD/CAS (VTD, 0.2 mg/kg) slows down the progress of tumors. Mass spectrometry (MS) revealed improved pharmacokinetics (PK) profile as MSN-COOH/VTD/CAS had less VTD accumulation in non-cancerous organs compared to pure VTD. We further improved nanoparticle targeting and drug release by shifting to calcium-based particles (CBPs). The engineered CBPs demonstrated higher drug-releasing performance. Without the MMPs trigger, MSNs show slow and continuous "drug leak" over longer period of time whereas CCSMPs stops leakage within an hour. Additionally, CBPs showed higher sensitivity to MMP-7 than MMP-9, enhancing the targetability of CBPs for CRC metastatic tumors with excessive extracellular MMP-7. CONCLUSIONS: This study introduces a new platform utilizing nanoparticle-based site-specific delivery of a plant-based anti-metastatic molecule, veratridine, with enhanced safety and therapeutic efficacy for the treatment of metastatic CRC.