Enhanced delivery of liposomes to lung tumor through targeting interleukin-4 receptor on both tumor cells and tumor endothelial cells.

A growing body of evidence suggests that pathological lesions express tissue-specific molecular targets or biomarkers within the tissue. Interleukin-4 receptor (IL-4R) is overexpressed in many types of cancer cells, including lung cancer. Here we investigated the properties of IL-4R-binding peptide-1 (IL4RPep-1), a CRKRLDRNC peptide, and its ability to target the delivery of liposomes to lung tumor. IL4RPep-1 preferentially bound to H226 lung tumor cells which express higher levers of IL-4R compared to H460 lung tumor cells which express less IL-4R. Mutational analysis revealed that C1, R2, and R4 residues of IL4RPep-1 were the key binding determinants. IL4RPep-1-labeled liposomes containing doxorubicin were more efficiently internalized in H226 cells and effectively delivered doxorubicin into the cells compared to unlabeled liposomes. In vivo fluorescence imaging of nude mice subcutaneously xenotransplanted with H226 tumor cells indicated that IL4RPep-1-labeled liposomes accumulate more efficiently in the tumor and inhibit tumor growth more effectively compared to unlabeled liposomes. Interestingly, expression of IL-4R was high in vascular endothelial cells of tumor, while little was detected in vascular endothelial cells of control organs including the liver. IL-4R expression in cultured human vascular endothelial cells was also up-regulated when activated by a pro-inflammatory cytokine tumor necrosis factor-α. Moreover, the up-regulation of IL-4R expression was observed in primary human lung cancer tissues. These results indicate that IL-4R-targeting nanocarriers may be a useful strategy to enhance drug delivery through the recognition of IL-4R in both tumor cells and tumor endothelial cells.

Facilitated intracellular delivery of peptide-guided nanoparticles in tumor tissues.

Macromolecular nanoparticles can extravasate and accumulate within tumor tissues via the passive targeting system, reflecting enhanced permeability and the retention effect. However, the unsatisfactory tumor therapeutic efficacy of the passive-targeting system, attributable to the retention of extravasated nanoparticles in the vicinity of tumor vessels, argues that a new system that facilitates intracellular delivery of nanoparticles within tumors is needed. Here, we developed hydrophobically modified glycol chitosan (HGC) nanoparticles conjugated with interleukin-4 receptor (IL-4R) binding peptides, termed I4R, and tested them in mice bearing IL-4R-positive tumors. These HGC-I4R nanoparticles exhibited enhanced IL-4R-dependent cellular uptake in tumors compared to nonconjugated nanoparticles, leading to better therapeutic and imaging efficacy. We conclude that I4R facilitates and enhances cellular uptake of nanoparticles in tumor tissues. This study suggests that the intracelluar uptake of nanoparticles in tumors is an essential factor to consider in designing nanoparticles for tumor-targeted drug delivery and imaging.

In situ dose amplification by apoptosis-targeted drug delivery.

When tumor cells undergo apoptosis in response to chemotherapy, the levels of apoptotic biomarkers such as histone H1 are increased at the tumor. This would amplify in situ homing signals and thus drug delivery by apoptosis-targeted drugs. To examine this possibility, we prepared apoptosis-targeted liposomes containing doxorubicin by labeling them with the CQRPPR peptide (ApoPep-1) that recognizes apoptotic cells by binding to histone H1. ApoPep-1-labeled liposomes, but not folate-labeled liposomes, inhibited tumor growth in mice more efficiently than untargeted liposomes, although in vitro cytotoxicities of those liposomes were similar. Fluorescence imaging signals at tumor were increased by the homing of ApoPep-1-labeled, fluorescent liposomes, which was correlated with the increase of apoptosis and the amount of doxorubicin at the tumor and, conversely, with the decrease of tumor volume. These results demonstrate that the apoptosis-targeted drug delivery enables in situ dose amplification and, when combined with imaging of apoptosis, provides a real-time monitoring of treatment response for cancer theragnosis.

A novel peptide probe for imaging and targeted delivery of liposomal doxorubicin to lung tumor.

Targeted delivery of imaging agents and therapeutics to tumors would provide early detection and increased therapeutic efficacy against cancer. Here we have screened a phage-displayed peptide library to identify peptides that selectively bind to lung tumor cells. Evaluation of individual phage clones after screening revealed that a phage clone displaying the CSNIDARAC peptide bound to H460 lung tumor cells at higher extent than other phage clones. The synthetic CSNIDARAC peptide strongly bound to H460 cells and was efficiently internalized into the cells, while little binding of a control peptide was seen. It also preferentially bound to other lung tumor cell lines as compared to cells of different tumor types. In vivo imaging of lung tumor was achieved by homing of fluorescence dye-labeled CSNIDARAC peptide to the tumor after intravenous injection into mice. Ex vivo imaging and microscopic analysis of isolated organs further demonstrated the targeting of CSNIDARAC peptide to tumor. The CSNIDARAC peptide-targeted and doxorubicin-loaded liposomes inhibited the tumor growth more efficiently than untargeted liposomes or free doxorubicin. In vivo imaging of fluorescence dye-labeled liposomes demonstrated selective homing of the CSNIDARAC-liposomes to tumor. In the same context, higher levels of doxorubicin and apoptosis in tumor tissue were observed when treated with the targeted liposomes than untargeted liposomes or free doxorubicin. These results suggest that the CSNIDARAC peptide is a promising targeting probe that is able to direct imaging agents and therapeutics to lung tumor.

In vivo imaging of tumor apoptosis using histone H1-targeting peptide.

In vivo imaging of apoptosis could allow monitoring of tumor response to cancer treatments such as chemotherapy. Using phage display, we identified the CQRPPR peptide, named ApoPep-1(Apoptosis-targeting Peptide-1), that was able to home to apoptotic and necrotic cells in tumor tissue. ApoPep-1 also bound to apoptotic and necrotic cells in culture, while only little binding to live cells was observed. Its binding to apoptotic cells was not dependent on calcium ion and not competed by annexin V. The receptor for ApoPep-1 was identified to be histone H1 that was exposed on the surface of apoptotic cells. In necrotic cells, ApoPep-1 entered the cells and bound to histone H1 in the nucleus. The imaging signals produced during monitoring of tumor apoptosis in response to chemotherapy was enhanced by the homing of a fluorescent dye- or radioisotope-labeled ApoPep-1 to tumor treated with anti-cancer drugs, whereas its uptake of the liver and lung was minimal. These results suggest that ApoPep-1 holds great promise as a probe for in vivo imaging of apoptosis, while histone H1 is a unique molecular signature for this purpose.

Phage display selection of peptides that home to atherosclerotic plaques: IL-4 receptor as a candidate target in atherosclerosis.

Imaging or drug delivery tools for atherosclerosis based on the plaque biology are still insufficient. Here, we attempted to identify peptides that selectively home to atherosclerotic plaques using phage display. A phage library containing random peptides was ex vivo screened for binding to human atheroma tissues. After three to four rounds of selection, the DNA inserts of phage clones wer sequenced. A peptide sequence, CRKRLDRNC, was the most frequently occurring one. Intravenously injected phage displaying the CRKRLDRNC peptide was observed to home to atherosclerotic aortic tissues of low-density lipoprotein receptor-deficient (Ldlr-/-) mice at higher levels than to normal aortic tissues of wild-type mice. Moreover, a fluorescein- or radioisotope-conjugated synthetic CRKRLDRNC peptide, but not a control peptide, homed in vivo to atherosclerotic plaques in Ldlr(-/-) mice, while homing of the peptide to other organs such as brain was minimal. The homing peptide co-localized with endothelial cells, macrophages and smooth muscle cells a mouse and human atherosclerotic plaques. Homology search revealed that the CRKRLDRNC peptide shares a motif of interleukin-receptor (IL-4) that is critical for binding to its receptor. The peptide indeed co-localized with IL-4 receptor (IL-4R) at atherosclerotic plaques. Moreover, the peptide bound to cultured cells expressing IL-4R on the cell surface and the binding was inhibited by the knock-down of IL-4R. These results show that the CRKRLDRNC peptide homes to atherosclerotic plaques through binding to IL-4R as its target and may be a useful tool for selective drug delivery and molecular imaging of atherosclerosis.