Assessing a Targeted Heptapeptide as a Molecular Imaging Agent for Colorectal Cancer Screening

Overview

Objectives/Goals The heptapeptide VRPMPLQ was previously isolated as a targeting ligand for early-stage colon adenomas and subsequently validated in vivo in a pilot trial involving 30 patients undergoing colonoscopy. In our present work, we undertook to examine the peptide's performance in vitro as a first step to develop the molecular imaging strategy. Methods/Materials We employed the M13 bacteriophage clone from which the peptide was isolated; using this phage as a vehicle, we performed a variety of assays to evaluate binding to an established colon cancer cell line (HT-29 colon adenocarcinoma cell line). Methods included ELISA-based assays, fluorescence microscopy, and flow cytometry. Results After exhausting the available analytic techniques, we found through a series of troubleshooting tests that the phage displayed the wrong peptide sequences due to frameshift mutations in the phage genome. We were finally able to isolate a small sample with the correct DNA sequence and determined that a short (5-hour) replication time produces a stable phage sample. Conclusions/Discussion The challenges encountered in working with the phage system illustrate the need for a positive control; establishing this positive control phage library is currently in progress. We have developed a detailed plan to interrogate the in vitro properties of the heptapeptide VRPMPLQ to gain a full understanding of the peptide's behavior and we hope to present these results in the future.

Competition history

• CSEF 2013 Biochemistry/ Molecular Biology · Entry S0517

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