Abstract 71: Improving the pH-responsive peptide V3 for pancreatic cancer imaging and identification

Abstract Introduction: Pancreatic cancer treatment with surgical resection or receptor-targeted therapies is complicated by the heavy vasculature of the organ and the heterogeneity of the tumors. Utilization of pH-responsive peptides in tandem with multispectral optoacoustic tomography may address these issues and offer a treatment solution. Although the V3 pH-responsive peptide has demonstrated its ability to target slightly acidic microenvironment, the V3 peptide struggles to identify highly acidic microenvironment like those found around pancreatic cancer cells. To overcome this limitation, we modified the V3 peptide’s original sequence to make the V3-Pro and V3-ProFS variants and then tested the new variants’ abilities to target the more acidic microenvironment that is characteristic of pancreatic cancer. Methods: We designed modifications to the V3 peptide sequence, and the peptide variants were synthesized using the CEM Liberty Blue microwave technology. V3 and the new variants were conjugated to HiLyte Fluor 750 C2 maleimide dye to make the V3-750, V3-Pro-750, and V3-ProFS-750 imaging probes. S2VP10 pancreatic cancer cells were pretreated with 7.4, 6.8, and 6.6 pH media for 30 minutes, and then treated with the peptide imaging probes at 1 micromolar concentration for 1 hour. The cells were then washed with pH-specific PBS and imaged with the Odyssey LiCor near-infrared fluorescence machine. Cells were then scraped for multispectral optoacoustic tomography (MSOT). Scraped cells were loaded into tissue-like phantoms, then imaged with the MSOT software. Results: The V3-Pro-750 and the V3-ProFS-750 treated S2VP10 cells featured significantly higher signal values in the 6.6 pH environment compared to the 7.4 pH environment (p<0.01). Fluorescent images of the V3-Pro-750 and V3-ProFS-750 treated S2VP10 cells featured higher signal values for the 6.6 pH and a larger contrast between 6.6 and 7.4 pHs as compared to fluorescent images of S2VP10 cells treated with V3-750 (p<0.05). MSOT data supported this trend, with the V3-Pro-750 and V3-ProFS-750 treated cells at 6.6 pH displaying the highest signal values and visual contrast. Conclusion: Increased signal values for cells treated with the new V3-Pro-750 and V3-ProFS-750 imaging probes in both fluorescence and MSOT suggest that the modified sequences increased the dynamic range between the 6.6 pH and the 7.4 pH. These results point to the newly designed probes potentially being better suited to identify pancreatic cancer based on its acidic tumor microenvironment. The V3-ProFS-750 is especially appealing because of its increased water solubility and its contrast between the 6.6 and 7.4 pHs, making it promising for the clinical translatability of a pH-responsive peptide suited for targeting pancreatic cancers. Citation Format: Emma Sanderson, Ryan C. Bynum, Tereza Husarova, Lacey R. McNally. Improving the pH-responsive peptide V3 for pancreatic cancer imaging and identification [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 71.