Abstract A31: A novel melanoma-derived cyclic decapeptide dimer mediates restoration of contact inhibition of growth and reversal of the malignant phenotype

Knowledge of the molecular basis for contact inhibition of growth, an in vitro property differentiating benign from malignant cells and correlated with in vivo growth control, could provide new targets for reestablishing control of malignant cell proliferation. We previously reported a soluble Contact Inhibitory Factor (CIF) in culture medium from a revertant contact inhibited melanoma cell line that restored contact-, serum-, and anchorage-dependent growth control to melanoma cells, closely linked to reversal of multiple malignant properties and whose contact inhibitory effects extended to a wide spectrum of other cancers. We now report identification, purification, and synthesis of the molecule, CIF, responsible for restoring contact inhibition: a structurally novel cyclic decapeptide dimer. Its discovery has both clinical and theoretical implications. Availability of CIF should not only facilitate evaluation of its therapeutic potential but also may provide the key to its target and the sequence of molecular events linking contact inhibition to broad phenotypic reversal. CIF may be the ligand for a widely distributed contact inhibitory checkpoint, one that is defective in cancer cells but pharmacologically correctible by CIF, and controlling replication at a single locus, potentially simplifying treatment. CIF is the first cell-derived peptide that restores contact inhibition of growth to melanoma and a wide spectrum of other cancers, with an obligatory link in melanoma to reversal of multiple aspects of the malignant phenotype. It suggests the possibility of an alternative approach to treatment of intractable melanoma and other cancers: broad-spectrum, endogenous peptide-based control of malignancy through phenotypic reversal that tilts the biologic balance to favor host recapture of control over tumor. Citation Format: Martin Rosenberg, Jennifer R. Bethard, Linda Aronoff, George Lipkin. A novel melanoma-derived cyclic decapeptide dimer mediates restoration of contact inhibition of growth and reversal of the malignant phenotype [abstract]. In: Proceedings of the AACR Special Conference on Melanoma: From Biology to Target; 2019 Jan 15-18; Houston, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(19 Suppl):Abstract nr A31.