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Tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) is considered an attractive anticancer agent due to its tumor cell–specific cytotoxicity. However, its low stability, solubility, unexpected side effects, and weak pharmacokinetic profiles restrict its successful clinical application. To develop efficient TRAIL-based anticancer biotherapeutics, a new version of trimeric TRAIL was constructed by incorporating trimer-forming zipper sequences (HZ-TRAIL), and then NH2-terminal–specific PEGylation was done to produce PEGylated TRAIL (PEG-HZ-TRAIL). The biological, physicochemical, and pharmaceutical characteristics of PEG-HZ-TRAIL were then investigated using various in vitro and in vivo experiments, including a cell-based cytotoxicity test, a solubility test, pharmacokinetic analysis, and antitumor efficacy evaluations. Although slight activity loss occurred after PEGylation, PEG-HZ-TRAIL showed excellent tumor cell–specific cytotoxic effects via apoptotic pathways with negligible normal cell toxicity. The stability and pharmacokinetic problems of HZ-TRAIL were successfully overcome by PEGylation. Furthermore, in vivo antitumor tests revealed that PEG-HZ-TRAIL treatment enhanced therapeutic potentials compared with HZ-TRAIL in tumor xenograft animal models, and these enhancements were attributed to its better pharmacokinetic properties and tumor-targeting performance. These findings show that PEG-HZ-TRAIL administration provides an effective antitumor treatment, which exhibits superior tumor targeting and better inhibits tumor growth, and suggest that PEG-HZ-TRAIL should be considered a potential candidate for antitumor biotherapy.

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Cathepsin B and matrix metalloproteinase (MMP) play key roles in tumor progression by controlled degradation of extracellular matrix. Consequently, these proteases have been attracted in cancer research, and many imaging probes utilizing these proteases have been developed. Our groups developed cathepsin B and MMP imaging nanoprobes based on polymer nanoparticle platform. Both cathepsin B and MMP imaging probes used near-infrared fluorescence (NIRF) dye and dark-quencher to for high sensitivity, and protease-sensitive peptide sequence in each probe authorized high specificity of the probes. We compared the bioactivities of cathepsin B and MMP sensitive probes in cancer-related environments to investigate the biological property of the probes. As a result, cathepsin B probe showed fluorescence recovery after the probe entered the cytoplasm. This property could be useful to evaluate the cytoplasmic targeted delivery by using probe-conjugated nanoparticles in vivo. On the other hand, MMP probe was superior in specificity in vivo and tissue study. This comparative study will provide precise information about peptide-based optical probes, and allow their proper application to cancer diagnosis.