Metastasis: Breaching barriers

Targeting intracellular MMPs efficiently inhibits tumor metastasis and angiogenesis

Treatment for metastatic cancer is a great challenge throughout the world. Commonly, directed inhibition of extracellular matrix metalloproteinases (MMPs) secreted by cancer cells can reduce metastasis. Here, a novel nanoplatform (HPMC NPs) assembled from hyaluronic acid (HA)-paclitaxel (PTX) prodrug and marimastat (MATT)/β-casein (CN) complexes was established to cure a 4T1 metastatic cancer model via targeting CD44 and intracellular, rather than extracellular, MMPs.

Methods: HPMC NPs were prepared by assembling the complexes and prodrug under ultrasonic treatment, which the interaction between them was evaluated by förster resonance energy transfer, circular dichroism and fluorescence spectra. The developed nanoplatform was characterized via dynamic light scattering and transmission electron microscopy, and was evaluated in terms of MMP-sensitive release and stability. Subsequently, the cellular uptake, trafficking, and in vitro invasion were studied by flow cytometry, confocal laser microscopy and transwell assay. MMP expression and activity was determined by western blotting and gelatin zymography. Finally, the studies of biodistribution and antitumor efficacy in vivo were performed in a mouse 4T1 tumor breast model, followed by in vivo safety study in normal mouse.

Results: The interaction between the prodrug and complexes is strong with a high affinity, resulting in the assembly of these two components into hybrid nanoparticles (250 nm). Compared with extracellular incubation with MATT, HPMC NP treatment markedly reduced the expression (100%) and activity (50%) of MMPs in 4T1 cells and in the tumor. HPMC NPs exhibited 1.4-fold tumor accumulation, inhibited tumor-growth by >8-fold in volume with efficient apoptosis and proliferation, and suppressed metastasis (>5-fold) and angiogenesis (>3-fold). Overall, HPMC NPs were efficient in metastatic cancer therapy. Conclusions: According to the assembly of polymer prodrug and protein-drug complexes, this study offers a new strategy for constructing nanoparticles for targeted drug delivery, biomedical imaging, and combinatorial treatment. Importantly, via inhibition of intracellular MMPs, metastasis and angiogenesis can be potently blocked, benefiting the rational design of nanomedicine for cancer treatment.