Design Of Anti-Tumor Targeting Peptides And Study On Its Mechanism

For a long time,cancer has caused many deaths each year.Traditional methods of cancer treatment, such as radiotherapy, chemotherapy and traditional anti-cancer drugs, have made great progress, but there are still serious side effects on human body.Therefore, in recent years, many scientists have focused on the research of anticancer drugs with less adverse reactions, high activity, and low possibility to result in drug resistantce. However, anticancer peptides(ACPs) also has some deficiencies, in which two main points are frequently referred to. Firstly, it is easy to be hydrolyzed by protease in blood or be absorbed by endothelial system.These resulting in poor stability. Secondary, ACPs have poor selectivity and are easy to produce toxic side effects on the human body's normal cells. The design of the ACPs has an important influence on the anti-tumor activity, stability and selectivity of ACPs. Through the design of amino acid in sequence, we can screen out the ACPs with excellent antitumor activity peptides. On the basis of the parent drug design, we added target fragment to the anticancer peptide in order to enhance its targeting ability and improve its stability.In this paper, we constructed a series of IL peptides to study the mechanism of anticancer peptide ZXR-2. I-L residue pairs play an important role in the anti-tumor activity of the peptides. In ZXR-2, ZXR-3 and IL peptides, I-L pairs are similar to the leucine zipper structure. Leucine and isoleucine are hydrophobic amino acids, at a difference of seven residues. When peptide interact with membrane, the isoleucine and leucine are conducive to peptide aggregation and role in cancer cell membrane. MTT cytotoxicity test verified that the I-L amino acid had an important effect on cytotoxicity of peptides. According to KI fluorescence quenching experiments and the measurement of peptide-induced pressure changes of lipid membranes, we determined that the peptide ZXR-2 could insert into lipid membranes from C-terminal and the insertion depth was at the W11 residue. Through the study on the mode of action of the antitumor peptide, we had deeper understanding about the mechanism of ACPs on cancer cells.LA-2 (CRGDKGPDCGKAFRRFLGALFKALSHLL), a peptide target the prostate cancer is composed of three parts:targeting peptide segment, connecting sigment and functional sigment. CRGDKGPDC is the targeting peptide segment., which targeted integrin ?v?3. Connecting peptide sequence is GKAFRR, which be cleaved by human kallikrein 2 (hk2) and release the parent drug which have anticancer activity. Using scanning electron microscope and transmission electron microscope, we found that the peptide LA-2 could forme micelles in water environment. The critical micelle concentration was determined by LB membrane analyzer. According to the serum stability and protease hydrolysis assays, self-assembled peptide LA-2 was more stable than PTP-7b and PTP-7r. Hydrolysis of peptide LA-2 by hK2 was detected by MALDI-TOF and the peptides PTP-7b and and PTP-7r were released. The MTT experiment showed that LA-2 had selectivity to prostate cancer cell and have lower cytotoxicity on other cancer cell and human normal cells. Through the study on antitumor peptide, deepen the understanding of the mechanism of peptide on cancer cell. The antitumor peptide LA-2, with multiple targeting, and good serum stability, may have great potential in the treatment of cancer.