The docetaxel- and siRNA–MMP-9-loadedpolymeric nanoparticles inhibit migration and viability of breastcancer cells by down-regulation of MMP-9 (inhibition of metastasis)and cellular uptake of docetaxel (apoptosis induction).245 Because MMP-9 induces epithelial-to-mesenchymaltransition via extracellular matrix degradation,246 it is rational to down-regulate MMP-9 to control malignancyand sensitize the cancer cells to chemotherapy.247 Breast cancer cells have been found in the lung due tometastasis. The gene discussed is MMP9; the disease is breast cancer.