A novel peptide, 9R-P201, strongly inhibits the viability, proliferation and migration of liver cancer HepG2 cells and induces apoptosis by down-regulation of FoxM1 expression.

Overexpression of FoxM1 was closely related to the proliferation, metastasis, chemo-resistance and poor prognosis of various cancers. FoxM1 was regarded as the Achilles' heel of cancer and a potential target for anti-cancer drug discovery. We previously obtained several high affinity peptides from the phage random library against the DNA binding domain of FoxM1c (FoxM1c-DBD) protein. Here in this paper, we found that 9R-P201, one of the novel peptides, showed stronger inhibition to HepG2 cancer cells than those of DU145, HUVEC and L-02 cells with an IC of 43.6µg/ml (13.1µM). The peptide was highly effective to liver cancer cells with an IC for L-02 cells of 2855.9µg/ml. We confirmed that 9R-P201 aggregated in the cell nucleus and the expression of FoxM1 was significantly down-regulated at both transcriptional and translational levels in HepG2 cells, leading to the suppression of cell proliferation, migration, angiogenesis, and induction of apoptosis. Whole genomic RNA sequencing analysis revealed that 357 genes were significantly and differentially expressed, most of them were enriched in cancer-associated biological processes. Finally, treatment of HepG2 xenografts with 9R-P201 resulted in growth inhibition and down-regulation of foxM1 expression in tumors. Collectively, our findings suggested that 9R-P201 could strongly inhibit the viability, proliferation and migration of liver cancer HepG2 cells and induce apoptosis by down-regulation of FoxM1 and regulation of related gene expression in signal transduction passways. Thus, 9R-P201 holds great potential as a lead anti-cancer drug targeting FoxM1.