Mesothelin-Binding Peptide Inhibits Cell Migration and Enables Targeted Delivery of a Mitochondrial-Membrane-Damaging Peptide to Pancreatic Tumors

Mesothelin (MSLN) is up-regulated in many tumors, including pancreatic tumors, making it a promising therapeutic target. We used a phage-displayed peptide library to identify an MSLN-binding peptide. CTILWSLTC, synthesized in cyclic form (MSLNpep), was selected from the library. MSLNpep bound preferentially to MSLN-high versus MSLN-low cells, internalized efficiently, and bound recombinant MSLN more strongly than a control peptide. MSLNpep treatment reduced migration and invasion in MSLN-high tumor cells. To enable targeted cytotoxicity, we generated chimeras linking MSLNpep to L-form or D-form mitochondrial-membrane-damaging peptides (MSLNpep-KLA and MSLNpep-kla, respectively). MSLNpep-kla—and, to a lesser extent, MSLNpep-KLA—exhibited selective cytotoxicity toward MSLN-high versus MSLN-low cells. Systemic MSLNpep-kla, but not MSLNpep-KLA, suppressed orthotopic pancreatic tumor growth, increased survival, and produced no detectable hepatic or renal toxicity in mice. MSLNpep-kla also induced cytotoxicity in patient-derived pancreatic cancer organoids proportionate to MSLN expression. Analysis of a public single-cell RNA-sequencing dataset of human pancreatic cancer tissues revealed that MSLN was predominantly expressed in malignant ductal cells while showing negligible expression in normal ductal cells and stromal cells. These findings demonstrate that MSLNpep inhibits tumor-cell migration and enables targeted delivery of therapeutic payloads to MSLN-high pancreatic tumors, supporting its use as a peptide ligand for cancer therapy.