MMP2 and cancer: Yao et al. [130,131] synthesized a series of analogues of polyethylene glycol-MMP2-cleavable peptide–phosphatidylethanolamine (PEG-pp-PE) copolymers and revealed the relationship between their chemical structure and the activity against P-gp-induced drug efflux in multidrug-resistant cancer cells (MDR) [130,131].