Identification of a decapeptide with the binding reactivity for tumor-associated TAG72 antigen from a phage displayed library

Retargeting adenoviruses for therapeutic applications and vaccines

Adenoviruses (Ads) are robust vectors for therapeutic applications and vaccines, but their use can be limited by differences in their in vitro and in vivo pharmacologies. This review emphasizes that there is not just one Ad, but a whole virome of diverse viruses that can be used as therapeutics. It discusses that true vector targeting involves not only retargeting viruses, but importantly also detargeting the viruses from off-target cells.

A new TAG-72 cancer marker peptide identified by phage display

Radiolabeled peptides as markers of cancer targets have demonstrated their value in diagnostic imaging and radiotherapy. The 16 mer f88-4/Cys6 phage display library was applied to affinity purified TAG-72 and three consensus peptides were identified: VHHSCTKLTHCCQNWH (A2-13), GGVSCMQTSPVCENNL (A2-6) and TKRDCSAQNYGCQKAI (A2-11). The A2-13 and A2-6 phages showed the highest percent binding to LS-174T cells by flow cytometry and were 3-fold higher than a control phage, while fluorescence microscopy showed that both A2-6 and A2-13 phages bound to the LS-174T cell membrane. However, only the A2-6 phage demonstrated specificity by low binding to the TAG-72 negative cell HT-29. Furthermore, the synthesized free A2-6 peptide demonstrated specific binding to LS-174T cells by flow cytometry and by immunohistochemical staining of xenograft tumor compared to normal colon. These data indicate that the A2-6 peptide is specific for the TAG-72 cancer target.

Evidence of specificity of radiolabeled phage display peptides for the TAG-72 antigen

The TAG-72 glycoprotein is highly expressed in many tumor types and has been considered a target for tumor imaging. In this work, we used the f88-4/Cys6 phage library of constrained 16 mer peptides to select those that demonstrate binding to TAG-72. Three consensus peptides were identified: NPGTCKD-KWIECLLNG (clone A); NLIWCRKEFARCTSDM (clone B); and LKNYCRKCSNRCTPTG (clone C). The phage of clones containing these peptides were radiolabeled with technetium-99m (99mTC) at 90% radiochemical purity and were incubated with TAG-72-positive LS174T colon cancer cells. The phage of clones A and B bound significantly higher by 4.5-fold and 1.5-fold than that of a nonspecific control phage. The 99mTc-labeled phage of clones A, B, and control were also administered intravenously to mice with LS-174T tumors. The accumulation of phages from clone A showed a slightly statistically higher accumulation in the tumor (0.51% ID/g), compared to phages of clone B and control phage (0.28% and 0.29% ID/g; p=0.049 for both). In conclusion, the peptide expressed by clone A phage showed evidence of significant specific binding when presented as the radiolabeled phage to tumor in vivo and especially in vitro with cells and solid tumor. The results suggest that this peptide when free of the phage may have potential for the imaging and possibly radiotherapy of TAG-72-expressing cancers.

Point-of-care biosensor systems for cancer diagnostics/prognostics

With the growing number of fatalities resulting from the 100 or so cancer-related diseases, new enabling tools are required to provide extensive molecular profiles of patients to guide the clinician in making viable diagnosis and prognosis. Unfortunately with cancer-related diseases, there is not one molecular marker that can provide sufficient information to assist the clinician in making effective prognoses or even diagnoses. Indeed, large panels of markers must typically be evaluated that cut across several different classes (mutations in certain gene fragments--DNA; over/under-expression of gene activity as monitored by messenger RNAs; the amount of proteins present in serum or circulating tumor cells). The classical biosensor format (dipstick approach for monitoring the presence of a single element) is viewed as a valuable tool in many bioassays, but possesses numerous limitations in cancer due primarily to the single element nature of these sensing platforms. As such, if biosensors are to become valuable tools in the arsenal of the clinician to manage cancer patients, new formats are required. This review seeks to provide an overview of the current thinking on molecular profiling for diagnosis and prognosis of cancers and also, provide insight into the current state-of-the-art in the biosensor field and new strategies that must be considered to bring this important technology into the cancer field.

Phage display for target-based antibacterial drug discovery

Increasing bacterial drug resistance and hard-to-eradicate opportunistic infections have created a need for new antibiotics. Sequencing of microbial genomes has yielded many new potential targets for antibacterial drug discovery. However, little is known about the biochemical activities of many of these targets, making it difficult to develop HTS assays for them. Peptides isolated by phage display can be used as 'surrogate ligands' in competition assays for screening of targets of unknown function with small-molecule libraries. These screening assays can be adapted into a variety of high-throughput formats, including those based on radioactive, luminescence or fluorescence detection.

Molecular addresses in blood vessels as targets for therapy

We have isolated several organ- and tumor-homing peptides by using in vivo phage display. This technology involves the screening of peptide libraries in a living animal. The peptides that result from such a selection home to specific organs or tissues because they recognize molecular 'addresses', receptors that are differentially expressed in vascular beds. Targeted delivery of chemotherapeutics, pro-apoptotic peptides and cytokines to tumors using these peptides improved therapeutic efficacy in animal models. Translation of this technology into clinical applications will form the basis for targeting therapeutic and imaging agents in the context of cancer and other diseases.