Kaempferol is a flavonoid found in various foods and they have multiple uses, especially it has an anti tumor activity (37) and also demonstrated that to be an effective role in inhibiting cell growth and proliferation in various cancer and also induce cancer cells cytotoxicity (39, 40). Kaempferol inhibits migration and invasion, reduce MMP2 expression and their enzyme activity and also inhibits the ERK1/2 phosphorylation in SCC4 (human tongue squamous cell carcinoma) cells (41).
The previous study demonstrated that Kaempferol is a potential agent for HCC treatment through its antitumor properties and also inhibit the Hep3B cell proliferation (42-45). Kaempferol has been identified as a potential growth suppressor in a cancer cell lines. It modulates the expressions of apoptotic and cell survival important gene expression in HeLa cervical cancer cell. Kaempferol effectively induced the apoptosis of HeLa cells via the up-regulation of p53, p21, casppase3, caspase9, Bax and PTEN and downregulation of PI3K, AKT and Bcl-2 genes (46). In this study, we also showed that Kaempferol inhibit BCL2L12 expression and induced cellular apoptosis via enhancing the p53 expression in Huh7 cells.
p53 is a well-known tumor suppressor protein and play an important role in G1 and G2 checkpoints and it works by activating p21 and Kaempferol modify a number of upstream regulators of p21 and enhance the phosphorylation of p53 (47). p21 is a very important checkpoint gene in the cell cycle, and it is also regulated by the transcription of p53 (48). pRb phosphorylation is the main target of the regulation G1/S progression by p53 and P21Cip1 makes it difficult to identify other possible pathways, independent of pRb. The activation of cyclin kinase inhibitors p21Cip1 and p16INK4A can therefore inhibit pRb and other pocket proteins phosphorylation and prevent E2F transcriptional activity leading to very efficient cells cycle arrest in control cells (49). In our study, Kaempferol effectively inhibit both G1 and G2 phase regulation by enhancing the p53 expression.
BCL2L12 interacts with p53 and inhibit the capacity of its binding process with their target genes. Thus, BCL2L12 suppress the p53 transcription levels after genotoxic stress and inhibit DNA damage-induced apoptosis (50) and cell cycle arrest activities by downregulation of p53 (18). The Bcl-2 family members are a key regulator of apoptosis. BCL2L12 one of the member of Bcl2 family and it contains several evolutionarily conserved p53-binding sites also act as a potent inhibitor of caspase activation and pro-apoptotic activities (51).
BCL2L12 neutralizes the transactivational activity of the p53 by inhibiting the binding of p53 to certain target promoters and attenuated p53-mediated induction of selected target genes, including the cell cycle inhibitor p21 and the proapoptotic proteins Bax. Bcl2L12 mediated neutralization of p53 activity and inhibited DNA damage-induced apoptosis in glioma cells (52). Our subsequent data also showed that BCL2L12 protein expression were down-regulated whilst p53 and their target proteins p21, pRb, Caspase 3, PTEN and MMP9 expression were gradually upregulated in Kaempferol-treated Huh-7 cells.