Targeting aggressive prostate cancer-associated CD44v6 using phage display selected peptides

Area of Science:

• Oncology
• Biotechnology
• Molecular Biology

Background:

• Aggressive prostate cancer (PCa) requires novel biomarkers, particularly those linked to cancer stem cells (CSCs).
• CD44v6, an alternative splice variant of CD44, is implicated as a CSC biomarker correlating with advanced PCa.
• Targeting CD44v6 presents a potential strategy for developing theranostic agents for aggressive PCa.

Purpose of the Study:

• To identify and characterize phage display selected peptides targeting CD44v6 for potential theranostic applications in aggressive PCa.
• To evaluate the binding affinity and specificity of the identified peptide (PFT) to CD44v6.
• To assess the potential of PFT as a diagnostic and therapeutic agent for advanced PCa.

Main Methods:

• Phage display selection was employed to identify peptides binding to a CD44v6-derived peptide.
• The synthesized peptide (PFT) was characterized for binding affinity (Kd) to CD44v6 using biochemical assays.
• Human PCa cell lines, including a novel CSC-like variant (v6A3) with enriched CD44v6, were used for binding studies.
• Immunohistofluorescence on PCa tissue microarrays (TMA) was performed to assess PFT's diagnostic accuracy in clinical samples.

Main Results:

• A 15-amino acid peptide, PFT, was identified with specific binding to CD44v6 (Kd = 743.4 nM).
• PFT demonstrated preferential binding to CD44v6-overexpressing aggressive PCa cells (v6A3) compared to parental cells.
• Immunohistofluorescence studies confirmed PFT's high accuracy in detecting CD44v6-positive aggressive PCa cells, with increased positivity in late-stage, metastatic, and high-grade tumors.

Conclusions:

• Phage display successfully identified peptides, including PFT, that specifically target CD44v6 overexpressed on PCa cells.
• Peptide PFT exhibits potential as a theranostic agent for advanced prostate cancer, aiding in diagnosis and therapy.
• This study highlights CD44v6 as a valuable target for developing novel strategies against aggressive PCa.