Increasing potency and safety of anticancer drugs through sortilin receptor-mediated cancer therapy: A new targeted approach for the treatment of ovarian cancer.

Abstract

e17068 Background: The development of personalized therapies against ovarian cancer remains highly challenging in current modern oncology. One strategy to achieve greater selectivity and better anticancer drug delivery into cancer cells is to conjugate cytotoxic agents to specific peptide ligands that selectively target receptors abundantly and/or exclusively expressed on these cells. Increased expression of Sortilin, a scavenging receptor, has been clinically observed in invasive ovarian cancer biopsies, and correlated with tumor grades. In light of this, we developed a peptide conjugation platform and a new Sortilin receptor-mediated vectorization strategy to increase cell targeting selectivity and cell delivery efficacy of anticancer agents. Methods: As a proof-of-concept, Doxorubicin was conjugated to a Sortilin binding peptide (KA-peptide). In vitro, intracellular delivery of the Doxorubicin-KA-peptide conjugate (DoxKA) was assessed in ES-2 and SKOV-3 ovarian cancer cell line models using flow cytometry and fluorescent microscopy. Sortilin gene silencing was performed with specific siRNA. DoxKA efficacy and safety were evaluated in vivo using ES-2 (CD1 nude mice) and SKOV-3 (athymic mice) subcutaneous xenograft models. Results: Uptake of DoxKA was observed in both Sortilin-positive ovarian cancer cell lines tested and was reduced when Sortilin expression was specifically silenced or upon competition with the Sortilin ligands Neurotensin and Progranulin. Results indicate that the uptake of DoxKA occurs via Sortilin-mediated endocytosis in contrast to simple diffusion for Doxorubicin. DoxKA was found to bypass the P-glycoprotein (P-gp) efflux pump in MDCK-MDR1 cells overexpressing P-gp as the uptake of DoxKA was unaffected by the P-gp inhibitor Cyclosporin A. In vivo, DoxKA showed lower potential side effects than Doxorubicin alone did, with decreased accumulation in healthy tissues such as heart and ovary. DoxKA caused a more potent inhibition of human ovarian tumor xenografts growth in mice and was better tolerated (absence of leukopenia and neutropenia) than the unconjugated Doxorubicin at an equivalent dose. Conclusions: These results strongly support the future clinical use of this platform to generate novel personalized therapeutics with specific targeting of Sortilin-positive tumors in the next stage of development in phase 1 clinical trial.