Recently, Yingyuad et al. described new PEGylated siRNA-nanoparticles activated by human leukocyte elastase (HLE) or matrix metalloproteinase-2 (MMP-2), both present in the extracellular spaces of tumor in order to promote invasion and metastasis of cancerous cells via degradation of basement membrane and extracellular matrix barrier. The gene discussed is MMP2; the disease is neoplasm.