Page 13 - Y. Vascular biology

N-Terminal modification of the tetrapeptide RLYE, a VEGFR-2 antagonist, improves
anti-tumor activity by increasing its stability against serum peptidases.
Department ofMolecular andCellular Biochemistry, School ofMedicine, KangwonNational University, Chuncheon,Gangwon-do,200-702,
South Korea

ABSTRACT

The tetrapeptide Arg-Leu-Tyr-Glu (RLYE), a vascular endothelial growth factor (VEGF) receptor-2 antagonist, has
been used previously either alone or in combination with chemotherapeutic drugs for treating colorectal cancer in
a mouse model. We analyzed the half-life of the peptide and found that due to degradation by
aminopeptidases B and N, it had a short half-life of 1.2 h in the serum. Therefore, to increase the stability and
potency of the peptide, we designed the modified peptide, N-terminally acetylated RLYE (Ac-RLYE), which had
a strongly stabilized half-life of 8.8 h in serum compared with the original parent peptide. The IC 50 value of Ac-
RLYE for VEGF-A-induced endothelial cell migration decreased to approximately 37.1 pM from 89.1
pM for the parent peptide. These findings provide evidence that the N-terminal acetylation augments the
therapeutic effect of RLYE in solid tumors via inhibition of tumor angiogenesis, improvement of tumor vessel integrity
and normalization, and enhancement of delivery and efficacy of the co-administered chemotherapeutic drugs.
RESULTS

Fig. 2. Degradation of RLYE in serum Fig. 3. N-terminal modification of
Fig. 1. RLYE is degraded by a heat- is blocked by inhibitors of RLYE increases stability and anti-
labile serum factor. aminopeptidases B and N. angiogenic activity in serum.

Fig. 4. Ac-RLYE and R (D) LYE inhibit Fig. 5. Ac-RLYE improves tumor Fig. 6. Ac-RLYE improves
tumor angiogenesis and growth. vessel normalization. chemosensitivity of tumors.
CONCLUSION

We previously demonstrated that the tetrapeptide RLYE effectively suppressed
tumor neovascularization by blocking the interaction between VEGF-A and
VEGFR-2, resulting in inhibition of tumor growth and metastasis in a tumor-
bearing mouse model (Baek et al., 2015; Baek et al., 2017). However, we
found that RLYE was unstable and readily degraded with a half-life of
approximately 1.2 h when incubated in human serum. This short half-life was
due to serum aminopeptidases B and N, which cleave the N-terminal Arg
residue of the peptide. As demonstrated by clinical evidence that anti-
angiogenic agents show anti-tumor activity mostly in combination with
chemotherapeutics (Sengupta et al., 2015; Margonis et al., 2017), our findings
Fig. 7. Ac-RLYE attenuates strongly suggest that Ac-RLYE could be used as a potential drug for anti-
polarization of TAMs to M2 angiogenic tumor therapy or in combination with chemotherapy.
phenotype.
Contact information tskim0602@naver.cxom