Study On A Novel Small Cyclic Peptides For Tumor Therapy

Aim: To get novel cyclic peptide derived from P5 peptide that has been obtained by our group previously.Then we evaluated it by detecting its stability,anti-tumor activity and molecular mechanism in vitro and in vivo.Methods: Firstly,we synthesized and cyclized the P5 peptide by using two L-cysteines or D-cysteines at the both terminus to form disulfide bind,which named LcP5 or DcP5 respectively.After affinity detection,we found DcP5 has higher affinity.So we used DcP5 to perform the following studies.Half life time of DcP5 in vivo was detected by ELISA.Anti-tumor bioactivities were investigated by cell proliferation assay in vitro and xenograft tumor mouse model in vivo.The toxicity of DcP5 was assessed by xenograft tumor mouse organs state and blood elements.We also explored the molecular mechanism by detecting the affinities of DcP5 bind to other trosine kinase receptor(RTK)members and key proteins' phosphorylation in some associated signal pathway.Results: Compared with LcP5,DcP5 has higher affinity in ITC assay.ELISA showed DcP5 has longer half life time than P5 peptide in vivo.Being Similar with P5,DcP5 also can inhibit tumor growth in dose-dependend way in vitro and in vivo,and they both have well effect in accordance.Detection of blood elements and investigation of organ state suggested that DcP5 have low side effect in vivo.In molecular mechanism studies,ITC assays showed DcP5 could bind to FGFR3,FGFR4,PDGFRa,PDGFRb,HGFR2,HER2,VEGFR2,IGF1 R,etc,which they have different affinities.Indirect immunofluorescence test showed DcP5 could bind to FGFR2 expressed on the DU145 cell surface visibly.Western Blot showed DcP5 could decrease the phosphorylations of FGFRs protein,both AKT and ERK pathways and so on.Conclusion: Compared with P5 linear peptide,DcP5 cyclic peptide has the same anti-tumor bioactivity,higher affinity,and more stability.So DcP5 is the novel potential small cyclic peptide to develop for tumor therapy prospectively.