Targeted therapy for lymphoma with peptides

Techniques for Molecular Imaging Probe Design

Molecular imaging allows clinicians to visualize disease-specific molecules, thereby providing relevant information in the diagnosis and treatment of patients. With advances in genomics and proteomics and underlying mechanisms of disease pathology, the number of targets identified has significantly outpaced the number of developed molecular imaging probes. There has been a concerted effort to bridge this gap with multidisciplinary efforts in chemistry, proteomics, physics, material science, and biology—all essential to progress in molecular imaging probe development. In this review, we discuss target selection, screening techniques, and probe optimization with the aim of developing clinically relevant molecularly targeted imaging agents.

Cytophobic surface modification of microfluidic arrays for in situ parallel peptide synthesis and cell adhesion assays

A combination of PEG-based surface passivation techniques and spatially addressable SPPS (solid-phase peptide synthesis) was used to demonstrate a highly specific cell-peptide adhesion assay on a microfluidic platform. The surface of a silicon-glass microchip was modified to form a mixed self-assembled monolayer that presented PEG moieties interspersed with reactive amino terminals. The PEG provided biomolecular inertness and the reactive amino groups were used for consequent peptide synthesis. The cytophobicity of the surface was characterized by on-chip fluorescent binding assays and was found to be resistant to nonspecific attachment of cells and proteins. An integrated system for parallel peptide synthesis on this reactive amino surface was developed using photogenerated acid chemistry and digital microlithography. A constant synthesis efficiency of >98% was observed for up to 7mer peptides. To demonstrate specific cell adhesion on these synthetic peptide arrays, variations of a 7mer cell binding peptide that binds to murine B lymphoma cells were synthesized. Sequence-specific binding was observed on incubation with fluorescently labeled, intact murine B lymphoma cells, and key residues for binding were identified by deletional analysis.

A mimotope peptide-based anti-cancer vaccine selected by BAT monoclonal antibody

Combinatorial phage display peptide libraries are employed to identify small molecules which bind with high affinity to receptor molecules and which mimic the interaction with natural ligands. We used a synthetic combinatory phage display peptide library to screen for peptides that bind BAT monoclonal antibody, an immune modulatory and anti-tumor antibody, to serve as the basis for an anti-cancer vaccine. Two distinct mimotopes, peptides A and B, were isolated, with repeated Proline, Arginine, and Isoleucine amino acids. Mimotope binding was determined by direct binding and by inhibition of BAT binding to the peptide bound phages and to Daudi cells. Immunization of mice with the peptides induced cellular and humoral responses. Cellular response was manifested by significant increase in cytolitic activity. Humoral response was manifested by production of specific antibodies. Serum purified IgG fraction contained anti-peptide antibodies that identified BAT binding mimotopes and competed with BAT binding on Daudi cells. These "BAT like" antibodies exhibited similar immune stimulatory properties to BAT. Immunization of mice with the peptides prevented tumor growth. These finding are the basis for the development of an anti-cancer vaccine.

Treatment of terminal peritoneal carcinomatosis by a transducible p53-activating peptide

Advanced-stage peritoneal carcinomatosis is resistant to current chemotherapy treatment and, in the case of metastatic ovarian cancer, results in a devastating 15%–20% survival rate. Therapeutics that restore genes inactivated during oncogenesis are predicted to be more potent and specific than current therapies. Experiments with viral vectors have demonstrated the theoretical utility of expressing the p53 tumor suppressor gene in cancer cells. However, clinically useful alternative approaches for introducing p53 activity into cancer cells are clearly needed. It has been hypothesized that direct reactivation of endogenous p53 protein in cancer cells will be therapeutically beneficial, but few tests of this hypothesis have been carried out in vivo. We report that a transducible D-isomer RI-TATp53C′ peptide activates the p53 protein in cancer cells, but not normal cells. RI-TATp53C′ peptide treatment of preclinical terminal peritoneal carcinomatosis and peritoneal lymphoma models results in significant increases in lifespan (greater than 6-fold) and the generation of disease-free animals. These proof-of-concept observations show that specific activation of endogenous p53 activity by a macromolecular agent is therapeutically effective in preclinical models of terminal human malignancy. Our results suggest that TAT-mediated transduction may be a useful strategy for the therapeutic delivery of large tumor suppressor molecules to malignant cells in vivo.

Specific activiation of the tumor suppressor protein p53, using a transducible p53 C-terminal peptide, dramatically increases survival in a mouse model of peritoneal carcinomatosis. This peptide offers therapeutic potential for tumors in which p53 is mutated

Combinatorial peptide library methods for immunobiology research

The field of combinatorial peptide chemistry has emerged as a powerful tool in the study of many biological systems. This review focuses on combinatorial peptide library methodology, which includes biological library methods, spatially addressable parallel library methods, library methods requiring deconvolution, the "one-bead one-compound" library method, and affinity chromatography selection method. These peptide libraries have successfully been employed to study a vast array of cell surface receptors, as well as have been useful in identifying protein kinase substrates and inhibitors. In recent immunobiological applications, peptide libraries have proven monumental in the definition of MHC anchor residues, in lymphocyte epitope mapping, and in the development of peptide vaccines. Peptides identified from such libraries, when presented in a chemical microarray format, may prove useful in immunodiagnostics. Combinatorial peptide libraries offer a high-throughput approach to study limitless biological targets. Peptides discovered from such studies may be therapeutically and diagnostically useful agents.

Therapeutic cancer targeting peptides

Antitumor monoclonal antibodies have shown clinical promise as cancer cell surface targeting agents. More tumor targeting antibodies are likely to be approved by the FDA in the next few years. However, there are two major limitations in antibody-targeted therapy: large size and nonspecific uptake of the antibody molecules by the liver and the reticuloendothelial system. These result in poor tumor penetration of antibody pharmaceuticals and dose-limiting toxicity to the liver and bone marrow. Peptides are excellent alternative targeting agents for human cancers, and they may alleviate some of the problems with antibody targeting. In the last decade, several investigators have successfully used combinatorial library methods to discover cell surface binding peptides that may be useful for cancer targeting. The phage-display library technique and the "one-bead one-compound" combinatorial library method are the two approaches that have been used. Cancer cell surface receptors or endothelial cell surface receptors of the neovasculature are the two popular therapeutic targets for cancer. Results from preclinical studies with some peptides are encouraging in their targeting potential.

From combinatorial chemistry to chemical microarray

Combinatorial chemistry was first applied to the generation of peptide arrays in 1984. Since then, the field of combinatorial chemistry has evolved rapidly into a new discipline. There is a great need for the development of methods to examine the proteome functionally at a global level. Using many of the techniques and instruments developed for DNA microarrays, chemical microarray methods have advanced significantly in the past three years. High-density chemical microarrays can now be synthesized in situ on glass slides or be printed through covalent linkage or non-specific adsorption to the surface of the solid-support with fully automatic arrayers. Microfabrication methods enable one to generate arrays of microsensors at the end of optical fibers or arrays of microwells on a flat surface. In conjunction with the one-bead one-compound combinatorial library method, chemical microarrays have proven to be very useful in lead identification and optimization. High-throughput protein expression systems, robust high-density protein, peptide and small-molecule microarray systems, and automatic mass spectrometers are critical tools for the field of functional proteomics.

Peptide and small molecule microarray for high throughput cell adhesion and functional assays

A novel class of chemical microchips consisting of glass microscope slides was prepared for the covalent attachment of small molecule ligands and peptides through site-specific oxime bond or thiazolidine ring ligation reaction. Commercially available microscope slides were thoroughly cleaned and derivatized with (3-aminopropyl)triethoxysilane (APTES). The amino slides were then converted to glyoxylyl derivatives via two different routes: (1) coupling of Fmoc-Ser followed by deprotection and oxidation, or (2) coupling with protected glyoxylic acid and final deprotection with HCl. Biotin or peptide ligands derivatized at the carboxyl terminus with a 4,7,10-trioxa-1,13-tridecanediamine succinimic acid linker and an amino-oxy group or a 1,2-amino-thiol group (e.g., cysteine with a free N(alpha)-amino group) were printed onto these slides using a DNA microarray spotter. After chemical ligation, the microarray of immobilized ligands was analyzed with three different biological assays: (1) protein-binding assay with fluorescence detection, (2) functional phosphorylation assay using [gamma(33)P]-ATP and specific protein kinase to label peptide substrate spots, and (3) adhesion assay with intact cells. In the cell adhesion assay, not only can we determine the binding specificity of the peptide against different cell lines, we can also determine functional cell signaling of attached cells using immunofluorescence techniques in situ on the microchip. This chemical microchip system enables us to rapidly analyze the functional properties of numerous ligands that we have identified from the "one-bead one-compound" combinatorial library method.