Targeting the cancer stroma with a fibroblast activation protein-activated promelittin protoxin.
Targeting the cancer stroma with a fibroblast activation protein-activated promelittin protoxin.
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DOI：
10.1158/1535-7163.mct-08-1170
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发表时间：
2009-05
影响因子：
5.7
通讯作者：
Denmeade SR
中科院分区：
文献类型：
--
作者：
LeBeau AM;Brennen WN;Aggarwal S;Denmeade SR
成纤维细胞激活蛋白-α是一种膜结合的丝氨酸蛋白酶，表达于大多数人类上皮性肿瘤的反应性间质成纤维细胞表面，而在正常组织中不表达。FAP是一种后脯氨酸肽酶，不同于其他二肽基脯氨酸肽酶，如二脯氨酸肽酶4，它还具有明胶酶和胶原酶内肽酶活性。因此，FAP是一个潜在的泛肿瘤靶点，其酶活性可以被用来激活前药物和前毒素。为了评价FAP作为肿瘤特异性靶点，通过对蜂毒素原结构域的修饰，构建了FAP选择性多肽原毒素。蜂毒素是一种26个氨基酸的两亲性细胞溶解多肽，是常见的欧洲蜜蜂毒液中的主要有毒成分。蜂毒素是以proelittin的形式合成的，含有一个22个氨基酸的NH2末端前结构域，富含脯氨酸和丙氨酸。在这项研究中，含有截短的蜂毒素原结构域序列的多肽在红细胞上进行测试，以确定抑制细胞溶解活性的最佳原结构域长度。一旦优化，就产生了修饰的proelittin多肽，其中先前鉴定的FAP底物序列被引入到原结构域中。FAP能有效地激活FAP，并选择性地对表达FAP的细胞株产生毒性作用，其IC50值与蜂毒素的IC50值相近。瘤内注射FAP激活的原毒素对人乳腺癌和前列腺癌异种移植瘤有显著的溶解和生长抑制作用，对宿主动物的毒性最小。
Fibroblast-Activation Protein-α (FAP) is a membrane-bound serine protease that is expressed on the surface of reactive stromal fibroblasts present within the majority of human epithelial tumors but is not expressed by normal tissues. FAP is a postprolyl peptidase that differs from other dipeptidyl prolyl peptidases such as di-prolylpeptidase 4 in that it also has gelatinase and collagenase endopeptidase activity. Therefore, FAP represents a potential pan-tumor target whose enzymatic activity can be exploited for the intratumoral activation of prodrugs and protoxins. To evaluate FAP as a tumor-specific target, putative FAP-selective peptide protoxins were constructed through modification of the prodomain of melittin, a 26 amino acid amphipathic cytolytic peptide that is the main toxic component in the venom of the common European honeybee Apis milefera. Melittin is synthesized as promelittin, containing a 22 amino acid NH2-terminal prodomain rich in the amino acids proline and alanine. In this study, peptides containing truncated melittin prodomain sequences were tested on erythrocytes to determine the optimal prodomain length for inhibiting cytolytic activity. Once optimized, modified promelittin peptides were generated in which previously identified FAP substrate sequences were introduced into the prodomain. Peptide protoxins were identified that were efficiently activated by FAP and selectively toxic to FAP-expressing cell lines with an IC50 value in the low micromolar range that is similar to melittin. Intratumoral injection of an FAP-activated protoxin produced significant lysis and growth inhibition of human breast and prostate cancer xenografts with minimal toxicity to the host animal.