Precise Oligopeptides Block CCDC25 Interaction with DNA in Neutrophil Extracellular Traps Inhibiting Tumor Metastasis.

Neutrophil extracellular traps (NETs) induce tumor metastasis by riding tumor cells through interaction via the transmembrane protein CCDC25 on the surface of cancer cells. Recently, we applied positively charged polyamino acids to neutralize negatively charged NET-DNA and inhibit tumor metastasis as approved on several metastasis models. To elucidate the exact polymer structures on performance, herein, we precisely synthesized a series of cationic oligopeptides with defined numbers of arginine (R) and glycine (G). The oligopeptides R5, R7, R9, and R5G4 showed much better binding affinity and lower cytotoxicity than R3 and R3G6. From the pull-down assay, the oligoarginines, R5, R7, and R9, inhibited CCDC25 interaction with NET-DNA because of stronger competitive interaction than myeloperoxidase (MPO) and citrullinated histone H3 (H3Cit) in NETs. The subsequent inhibition of cell migration and tumor metastasis in triple-negative breast cancer (TNBC) mouse models demonstrated that R5, R7, and R9 efficiently prevented tumor cell metastasis to the liver and lung. This was corroborated by the distribution of oligoarginines in the liver and lung, which reduced NETs accumulation. Thus, in this study, we screened out oligoarginines with a precise number of units to inhibit TNBC metastasis to distant organs, which may benefit in the decreasing mortality rate because of tumor metastasis. With their low cytotoxicity, oligoarginines represent a major advancement for the clinical treatment of metastatic diseases.