Purine Nucleoside Phosphorylase Targeted by Annexin V to Breast Cancer Vasculature for Enzyme Prodrug Therapy

Conceived and designed the experiments: JJK OD RGH. Performed the experiments: JJK OD. Analyzed the data: JJK OD RGH. Wrote the paper: JJK OD RGH.Background and PurposeThe targeting of therapeutics is a promising approach for the development of new cancer treatments that seek to reduce the devastating side effects caused by the systemic administration of current drugs. This study evaluates a fusion protein developed as an enzyme prodrug therapy targeted to the tumor vasculature. Cytotoxicity would be localized to the site of the tumor using a protein fusion of purine nucleoside phosphorylase (PNP) and annexin V. Annexin V acts as the tumor-targeting component of the fusion protein as it has been shown to bind to phosphatidylserine expressed externally on cancer cells and the endothelial cells of the tumor vasculature, but not normal vascular endothelial cells. The enzymatic component of the fusion, PNP, converts the FDA-approved cancer therapeutic, fludarabine, into a more cytotoxic form. The purpose of this study is to determine if this system has a good potential as a targeted therapy for breast cancer.MethodsA fusion of E. coli purine nucleoside phosphorylase and human annexin V was produced in E. coli and purified. Using human breast cancer cell lines MCF-7 and MDA-MB-231 and non-confluent human endothelial cells grown in vitro, the binding strength of the fusion protein and the cytotoxicity of the enzyme prodrug system were determined. Endothelial cells that are not confluent expose phosphatidylserine and therefore mimic the tumor vasculature.ResultsThe purified recombinant fusion protein had good enzymatic activity and strong binding to the three cell lines. There was significant cell killing (p<0.001) by the enzyme prodrug treatment for all three cell lines, with greater than 80% cytotoxicity obtained after 6 days of treatment.ConclusionThese results suggest that this treatment could be useful as a targeted therapy for breast cancer.Yeshttp://www.plosone.org/static/editorial#pee

Valorizzazione e incentivazione del capitale umano negli intermediari finanziari

Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 , Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Effect of macrophage depletion on viral DNA rebound following antiretroviral therapy in a murine model of AIDS (MAIDS)

In the attempt to eradicate HIV-1 infection, a strategy to eliminate macrophages, one of themost important cellular reservoirs in sustaining virus replication during HAART, could be of great benefit in the suppression of viral rebound. Aware of the ability of clodronate to cause macrophage depletion, the effect of the administration of clodronate encapsulated in erythrocytes on disease progression and on viral rebound was evaluated in a murine model of AIDS (MAIDS). One group of LP-BM5 retroviral complex-infected C57BL/6 mice received oral administrations of azidothymidine and dideoxyinosine daily for 12 weeks; two other groups received in addition, either clodronate-loaded erythrocytes or free clodronate at 7–10 day intervals. At the end of the treatment, the three groups maintained parameters characterizing disease progression similar to those of uninfected mice and showed a significantly lower level of BM5d DNA than infected mice in all organs and cells tested. To assess the viral rebound, some animals were left for an additional 4 month period without any treatment. After this time, the BM5d DNA content in blood leukocytes increased in all groups, but the group having received clodronate-loaded erythrocytes, in addition to transcriptase inhibitors, showed a significant delay in viral rebound

Macrophage depletion induced by clodronate-loaded erythrocytes.

Given the important role of macrophages in various disorders, the transient and organ specific suppression of their functions may benefit some patients. Until now, liposome-encapsulated bisphosphonate clodronate has been extensively proposed to this end. In this paper, we demonstrate that erythrocytes loaded with clodronate can also be effective in macrophage depletion. Here, clodronate was encapsulated in erythrocytes through hypotonic dialysis, isotonic resealing and reannealing to final concentrations of 4.1 +/- 0.4 and 10.1 +/- 0.8 micromol/ml of human and murine erythrocytes, respectively. The ability of clodronate-loaded erythrocytes to deplete macrophages was evaluated both in vitro and in vivo. In vitro studies on human macrophages showed that a single administration of engineered erythrocytes was able to reduce cell adherence capacity in a time-dependent manner, reaching 50 +/- 4% reduction, 13 days post treatment. The administration of loaded erythrocytes to cultures of murine peritoneal macrophages was able to reduce macrophage adhesion 67 +/- 3%, 48 h post treatment. In vivo, the ability of clodronate-loaded erythrocytes to deplete macrophages was evaluated both in Swiss and C57BL/6 mice. Swiss mice received 125 microg of clodronate through erythrocytes and 6 days post treatment 69 +/- 7% reduction in the number of adherent peritoneal macrophages and 75 +/- 5% reduction in number of spleen macrophages were observed. C57BL/6 mice received 220 microg clodronate by RBC and 3 and 8 days post treatment 65 +/- 7% reduction in the number of spleen macrophages and the complete depletion of liver macrophages were obtained. In summary, our results indicate that clodronate selectively targeted to the phagocytic cells by a single administration of engineered erythrocytes is able to deplete macrophages, even if not completely. The transient suppression of macrophage functions through clodronate-loaded erythrocytes can be used in many biomedical phenomena and research applications

Targeting nucleotide dimers containing antiviral nucleosides

Among the antiviral agents developed for the treatment of human viral infections, nucleoside analogs represent the largest group. However, much remains to do to improve their pharmacokinetic properties, to increase their efficacy, to reduce the selection of drug-resistent strains and to reduce their toxic side effects. Towards this end many nucleotide dimers have been synthesized in the last years in several laboratories. Such compounds have several advantages compared to the administration of nucleoside analogs as single drugs: 1) can act as prodrugs for a slow delivery of monomers in circulation; 2) can be encapsulated into autologous erythrocytes to perform as bioreactors converting a non diffusible dimer into a diffusible nucleoside analog to be released in circulation; 3) can be targeted to macrophages by proper drug targeting systems; 4) can overcome the limiting phosphorylating activities of several infectable cell types; 5) can have the advantage of a combination therapy with the administration of a single compound. In this review, dimers developed in our laboratory will be reported. In particular, the heterodinucleotide AZTpPMPA and the homodinucleotide Bis-PMEA are shown to be able to act as prodrugs when administered to mice releasing the single monomer in circulation. The homodinucleotide AZTp2AZT and the dimer AZTp2EMB once encapsulated in human erythrocytes are converted by erythrocyte enzymes into diffusible nucleosides and slowly released from the carrier cells. The dimers AZTp2AZT, AZTp2ACV, ACVpPMPA, AZTpPMPA and Bis-PMEA were targeted to macrophages where a very effective protection against virus replications was obtained. Thus, nucleotide dimers could be used as effective prodrugs for drug delivery in the treatment of viral infections improving the pharmacokinetic of single moieties and can be efficiently targeted to selected cell types with intracellular release of a phosphorylated (active) nucleoside