MMP9 and breast cancer: Jiang et al. designed a sequential delivery strategy for synergistic breast cancer treatment: combretastatin A4 nanoparticles (a vascular disrupting agent) disrupted neovascularization and exacerbated tumor hypoxia, upregulating MMP-9 and subsequently triggering MMP-9-activated doxorubicin-loaded nanoparticles to enhance chemotherapy targeting [145].