Radiopeptide internalisation and externalization assays: cell viability and radioligand integrity.

Various aspects of radiopeptide receptor-mediated cell internalisation and externalization assays were assessed, including the integrity of externalized peptides and the effect of varying the pH and incubation time of the acid wash step (to remove surface receptor-bound ligand) on efficacy and cell viability. The observed intact proportion of externalized peptide was 5-10%, and acid wash buffers with pH 2.8 or below were found to be detrimental to cell viability and integrity, particularly following prolonged incubation times.

Insertion of a lysosomal enzyme cleavage site into the sequence of a radiolabeled neuropeptide influences cell trafficking in vitro and in vivo.

Radiolabeled neuropeptides are widely explored for targeting tumours for either imaging or radiotherapeutic purposes. After binding to their receptors, these peptides are rapidly internalized into lysosomes, where they are degraded by proteolytic enzymes, such as cathepsins. The aim of this study was to investigate the effect of the inclusion of specific cleavage sites for cathepsin B into the peptide sequence.

Targeting of CCK-2 receptor-expressing tumors using a radiolabeled divalent gastrin peptide.

Unlabelled: Gastrin/cholecystokinin subtype 2 receptors (CCK-2Rs) are overexpressed in several tumor types and are, thus, a potential target for peptide receptor radionuclide therapy (PRRT) of cancer. To improve the in vivo performance of CCK-2R binding peptides, we have previously synthesized and screened a series of divalent gastrin peptides for improved biochemical and biologic characteristics. In this study, we explore in more detail the most promising of these compounds and compare its performance with a previously described monomeric peptide.

Hypoxia-targeted over-expression of carboxylesterase as a means of increasing tumour sensitivity to irinotecan (CPT-11).

The induced expression of carboxylesterase (CE) enzymes, which convert the prodrug irinotecan (CPT-11) into its active cytotoxic metabolite SN-38, constitutes a promising strategy for cancer gene therapy. By incorporating hypoxia-responsive elements (HREs) in conjunction with the transgene, expression can be targeted specifically to hypoxic tissues (such as solid tumours), expressing the hypoxia-inducible factor 1 (HIF-1). We have constructed a recombinant adenoviral vector, AdHRE-rCE, encoding the cDNA for the highly efficient rabbit liver CE (rCE), under the control of a HRE derived from the human phosphoglycerate kinase 1 (PGK-1) gene in conjunction with a minimal SV40 promoter.

Engineered expression of the Coxsackie B and adenovirus receptor (CAR) in human dendritic cells enhances recombinant adenovirus-mediated gene transfer.

Dendritic cells (DCs) are key antigen-presenting cells (APCs) that act as central modulators of cellular immune responses. Genetic modification of DCs has considerable therapeutic potential in the treatment of a wide spectrum of diseases, including cancer and persistent viral infection. In this report, we show that pre-treatment of DCs with a recombinant adenovirus encoding the major adenovirus receptor, Coxsackie B and adenovirus receptor (CAR), significantly increased the uptake of recombinant adenoviruses (Ads) by primary immature monocyte-derived DCs.