Identification and characterization of novel peptide binders against platinum resistant epithelial ovarian cancer

Background: Acquirement of Platinum-resistance leads to recurrence and poor survival outcomes in epithelial ovarian cancer (EOC) patients with inadequate second-line treatment options. Moreover, the current therapeutic strategies lack the precision to target the chemoresistant cells in vivo limiting treatment efficacy. Identification and validation of unique targeting moieties are critical to develop effective therapeutic strategies for this dreadful disease. Methods: Phage Display peptide library screening, ELISA and FACS were used to identify novel peptide binders using platinum resistant EOC cells (both intrinsic and acquired). MTT, cell cycle analysis, confocal microscopy, scratch assay and adhesion assays used to delineate the peptide properties. Clinical relevance was determined using primary tumor cells derived from high grade serous ovarian cancer (HGSOC) patients and subsequent PDX models. In-silico analysis and molecular docking were employed to identify the putative receptor/s. Results: Two novel heptapeptides (A and B) exhibiting higher binding capabilities to platinum-resistant cells were identified by phage peptide display screening and further validated using multiple EOC cell lines, primary cells isolated from malignant ascites of high-grade serous ovarian cancer patients, and patient-derived xenograft (PDX) models. Peptide A showed ~2-fold increased binding in intrinsically cisplatin-resistant cells (TOV112D, OVCAR3) while peptide B demonstrated ~3 fold higher binding to A2780 Ptres cells compared to platinum-sensitive A2780 cells. Peptide A showed a 5-fold increased binding in chemoresistant patient-derived cells and a 3-fold higher binding towards chemoresistant PDX models compared to chemonaïve counterparts, suggesting the presence of unique surface receptor(s) enriched in resistant populations. Peptide A did not induce toxicity, cell cycle alteration or proliferation but reduced adhesion and invasion of the resistant cells. Intraperitoneal injection of peptide A led to reduced secondary metastasis in platinum-resistant PDX mice. In silico docking identified GPCR proteins, particularly Endothelin Type A/B receptors (ETAR/ETBR), as putative receptors for peptide A. Functional characterization and receptor identification for peptide B are in progress. Conclusions: With higher affinity towards platinum-resistant cells and ability to impede adhesion, these novel peptide/s have promising potential to be developed as scaffolds for imaging or as therapeutic conjugates for the targeted treatment of platinum-resistant ovarian cancer cells.