A novel peptide CP29L, selected from the phage displayed cyclic random heptapeptide library, demonstrates its potent inhibitory effects to liver cancer HCCLM3 cells by targeting FOXM1.

FOXM1 is the "Achilles' heel" of cancers and hence the potential therapeutic target for anticancer drug discovery. In this work, we selected high affinity peptides against the protein of human DNA binding domain of FOXM1 (FOXM1-DBD) from the disulfide-constrained, phage displayed random cyclic heptapeptide library Ph.D.-C7C. We obtained a novel peptide, 9 R-CP29L, which was identified to be a potent anticancer peptide with IC₅₀ values of 9.0 and 11.1 μM at 24 h for HCCLM3 and MD-MBA-231 cells respectively. Molecular docking, CETSA, ITC and immunoblot assays demonstrated that 9 R-CP29L can potentially specifically bind to FOXM1-DBD with a K_d value of 1.25 μM and reduced the expression of FOXM1. In addition, Annexin V/PI flow cytometry, AO/EB staining, PI flow cytometry, clone formation and Transwell assays revealed that 9 R-CP29L also induced cell apoptosis and cell cycle arrest while inhibited the proliferation and migration of HCCLM3 cells. The findings were further supported by the results of qRT-PCR and immunoblot assays for the associated gene (CMYC, CDC25B, BAX, CASPASE3 and MMP2, etc) expression in HCCLM3 cells. Finally, in vivo experiment showed that 9 R-CP29 significantly reduced the tumor growth and downregulated the expression of FOXM1 in HCCLM3 xenograft nude mouse models. Taking together, our work provides a novel FOXM1 targeted peptide which has potential in both anticancer drug development and scientific researches.