Tartary Buckwheat Lectin Inhibits The Proliferation Of Colon Cancer Cells By Down-regulation On MiR-21

miRNAs are a kind of single-chain RNAs of 18-25 nucleotides in length and they can negatively regulate the expression of target genes.As a mode of gene regulation,miRNAs play a role at post-transcriptional time.The process of life regulation by miRNAs is widely existed.About one-third of human genes are regulated by miRNAs.Some miRNAs which can suppress the cancer cells are called tumor suppressor miRNAs,while the other which are closely related to the tumorigenesis and tumor development are called oncomiRNAs.More and more molecular studies have shown that miRNAs are maladjusted in many tumor cells,and oncomiRNAs are generally overexpressed,so oncomiRNAs can serve as effective targets for cancer therapy.Tartary Buckwheat Lectin(TBL)which contains ribosome inactiving protein N-glycosidase activity and rutin hydrolase activity is a glycoprotein,and it has anti-proliferation activity towards colon cancer cell.Previous studies have shown that TBL can make miR-135a&b lose the control of suppression of its target gene of APC and increase the APC expression by down-regulating the expression of miR-135a&b.TBL can inhibit colon cancer cells HCT116 by suppressing Wnt/b-catenin signaling pathway.By screening miRNAs difference,we found that TBL could down-regulate or up-regulate the expression of many miRNAs,among which the miR-21 was most down-regulated significantly.miR-21 is a typical oncomiRNA that is up-regulated in all cancer cells.We used miR-21 as a clue and found that PTEN gene was one of the target genes of miR-21 by double luciferase assay and TBL can reduce the suppression of miR-21 to PTEN gene.We found TBL can up-regulate PTEN and its downstream AKT mRNA levels and down-regulate PI3 K p110 subunit mRNA levels by q RT-PCR.After treating with TBL,Western Blot results showed that the protein of PTEN was up-regulated significantly and the protein of AKT was down-regulated.By detecting the cell cycle,we found that TBL can up-regulate G1 phase cell quantity and down-regulate the cell quantity of S phase and G2 phase.We also found that TBL can significantly inhibit the migration capacity of human colorectal cancer cells HCT116.The above results demonstrated that one possible mechanism of TBL which is extracted from Tartary Buckwheat Lectin inhibits human colorectal cancer cells HCT116 is that TBL can up-regulate the gene PTEN through down-regulating the miR-21.By inhibiting PI3K/AKT signaling pathway,TBL blocks cell cycle progression and inhibits migration capacity.This study is valuable for further investigation of mode and mechanism of action of bioactive substances in anti-cancer.