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Abstract：
The integrin αvβ6 is an antigen expressed at low levels in healthy tissue but upregulated during tumorigenesis, which makes it a promising target for cancer imaging and therapy. A20FMDV2 is a 20-mer peptide derived from the foot-and-mouth disease virus that exhibits nanomolar and selective affinity for αvβ6 versus other integrins. Despite this selectivity, A20FMDV2 has had limited success in imaging and treating αvβ6+ tumors in vivo because of its poor serum stability. Here, we explore the cyclization and modification of the A20FMDV2 peptide to improve its serum stability without sacrificing its affinity and specificity for αvβ6. Using cysteine amino acid substitutions and cyclization by perfluoroarylation with decafluorobiphenyl, we synthesized six cyclized A20FMDV2 variants and discovered that two retained binding to αvβ6 with modestly improved serum stability. Further d-amino acid substitutions and C-terminal sequence optimization outside the cyclized region greatly prolonged peptide serum stability without reducing binding affinity. While the cyclized A20FMDV2 variants exhibited increased nonspecific integrin binding compared with the original peptide, additional modifications with the non-natural amino acids citrulline, hydroxyproline, and d-alanine were found to restore binding specificity, with some modifications leading to greater αvβ6 integrin selectivity than the original A20FMDV2 peptide. The peptide modifications detailed herein greatly improve the potential of utilizing A20FMDV2 to target αvβ6 in vivo, expanding opportunities for cancer targeting and therapy.
摘要：
整合素αvβ6是一种在健康组织中低水平表达但在肿瘤发生过程中上调的抗原。这使得它成为癌症成像和治疗的有希望的目标。A20FMDV2是源自口蹄疫病毒的20聚体肽,其表现出对αvβ6相对于其他整联蛋白的纳摩尔和选择性亲和力。尽管有这种选择性,A20FMDV2在体内成像和治疗αvβ6+肿瘤方面具有有限的成功,因为其血清稳定性差。这里,我们探索了A20FMDV2肽的环化和修饰，以提高其血清稳定性，而不牺牲其对αvβ6的亲和力和特异性。使用半胱氨酸氨基酸取代并通过十氟联苯的全氟芳基化进行环化，我们合成了六个环化的A20FMDV2变体，发现两个保留了与αvβ6的结合，血清稳定性略有改善。环化区域外的进一步的d-氨基酸取代和C-末端序列优化大大延长了肽血清稳定性而不降低结合亲和力。与原始肽相比，环化的A20FMDV2变体显示出增加的非特异性整合素结合，使用非天然氨基酸瓜氨酸进行额外修饰，羟脯氨酸,和d-丙氨酸被发现恢复结合特异性，一些修饰导致比原始A20FMDV2肽更高的αvβ6整联蛋白选择性。本文详述的肽修饰大大提高了利用A20FMDV2在体内靶向αvβ6的潜力。扩大癌症靶向和治疗的机会。
