Design of a dendrimer with a matrix metalloproteinase-responsive fluorescence probe and a tumor-homing peptide for metastatic tumor cell imaging in the lymph node

Fluorescence imaging is a noninvasive technique for cancer diagnosis. Dendrimers are regularly branched macromolecules with highly controllable size and structure that are a potent multifunctional nanoparticle. Anionic-terminal polyamidoamine (PAMAM) dendrimers were previously found to be accumulated in the lymph node, which is one of the main routes of tumor metastasis. In this study, we designed and synthesized a dendrimeric imaging probe for lymph node-resident tumor cell imaging. A matrix metalloproteinase-2 (MMP-2)-responsive fluorescence peptide probe and a tumor-homing peptide were conjugated to the carboxy-terminal dendrimer. The dendrimeric imaging probe treatment showed fluorescence signals inside some tumor cells (e.g., human fibrosarcoma HT-1080 and breast cancer 4T1 cells), depending on the MMP activity, but not in macrophage-like RAW264 cells.

Homing Peptides for Cancer Therapy

Tumor-homing peptides are widely used for improving tumor selectivity of anticancer drugs and imaging agents. The goal is to increase tumor uptake and reduce accumulation at nontarget sites. Here, we describe current approaches for tumor-homing peptide identification and validation, and provide comprehensive overview of classes of tumor-homing peptides undergoing preclinical and clinical development. We focus on unique mechanistic features and applications of a recently discovered class of tumor-homing peptides, tumor-penetrating C-end Rule (CendR) peptides, that can be used for tissue penetrative targeting of extravascular tumor tissue. Finally, we discuss unanswered questions and future directions in the field of development of peptide-guided smart drugs and imaging agents.

Enhancing the circulating half-life and the antitumor effects of a tumor-selective cytotoxic peptide by exploiting endogenous serum albumin as a drug carrier

The elevated expression of bombesin receptors in many of the deadliest cancers has attracted special interest in developing bombesin-directed agents for tumor imaging and therapy. Previously, we constructed the chimeric peptide BB28 by fusing bombesin to a mitochondria-disrupting peptide. BB28 selectively induced the apoptosis of various tumor cells in vitro and showed promising in vivo antitumor effects. In general, a short circulating half-life limits the in vivo effect of peptides. To prolong the half-life of BB28, here, we generated the novel peptide ABB28 by fusing an albumin-binding domain (ABD) to the N-terminus of BB28. ABB28 exhibited much higher binding affinity for albumin than BB28, and this modification extended the peptide half-life from several minutes to 2 h. Optical imaging revealed that ABB28 accumulated in xenografted tumors within 1h post-injection and persisted at an evident level for up to 24 h. ABB28 exerted stronger tumor-suppressive effects than BB28. Significant differences in the tumor volumes (P<0.001) and the tumor weights (P=0.002) were observed between ABB28- and BB28-treated mice. Moreover, ABB28 exhibited tumor suppression comparable to that of PEGylated 5K-BB28 in vivo. These results suggest that half-life extension via ABD fusion represents a useful strategy for optimizing bombesin-directed pharmaceuticals for cancer-targeted therapy.