Trop-2 is a transmembrane signal transducer that can induce cancer growth. Using antibody targeting and N-terminal Edman degradation, we show here that Trop-2 undergoes cleavage in the first thyroglobulin domain loop of its extracellular region, between residues R87 and T88. Molecular modeling indicated that this cleavage induces a profound rearrangement of the Trop-2 structure, which suggested a deep impact on its biological function. No Trop-2 cleavage was detected in normal human tissues, whereas most tumors showed Trop-2 cleavage, including skin, ovary, colon, and breast cancers. Coimmunoprecipitation and mass spectrometry analysis revealed that ADAM10 physically interacts with Trop-2. Immunofluorescence/confocal time-lapse microscopy revealed that the two molecules broadly colocalize at the cell membrane. We show that ADAM10 inhibitors, siRNAs and shRNAs abolish the processing of Trop-2, which indicates that ADAM10 is an effector protease. Proteolysis of Trop-2 at R87-T88 triggered cancer cell growth both in vitro and in vivo. A corresponding role was shown for metastatic spreading of colon cancer, as the R87A-T88A Trop-2 mutant abolished xenotransplant metastatic dissemination. Activatory proteolysis of Trop-2 was recapitulated in primary human breast cancers. Together with the prognostic impact of Trop-2 and ADAM10 on cancers of the skin, ovary, colon, lung, and pancreas, these data indicate a driving role of this activatory cleavage of Trop-2 on malignant progression of tumors.

Trop-2 是一种跨膜信号传感器，可以诱导癌症生长。使用抗体靶向和 N 端 Edman 降解，我们在这里展示了 Trop-2 在其细胞外区域的第一个甲状腺球蛋白结构域环中，在残基 R87 和 T88 之间经历切割。分子模型表明，这种切割引起 Trop-2 结构的深刻重排，这表明对其生物学功能产生了深远的影响。在正常人体组织中未检测到 Trop-2 裂解，而大多数肿瘤显示出 Trop-2 裂解，包括皮肤癌、卵巢癌、结肠癌和乳腺癌。共免疫沉淀和质谱分析表明 ADAM10 与 Trop-2 发生物理相互作用。免疫荧光/共聚焦延时显微镜显示这两种分子在细胞膜上广泛共定位。我们表明 ADAM10 抑制剂，siRNA 和 shRNA 取消了 Trop-2 的加工，这表明 ADAM10 是一种效应蛋白酶。Trop-2 在 R87-T88 的蛋白水解引发癌细胞生长体外和体内。由于 R87A-T88A Trop-2 突变体消除了异种移植转移性传播，因此对结肠癌的转移性扩散显示出相应的作用。Trop-2 的活化蛋白水解在原发性人类乳腺癌中得到了概括。连同 Trop-2 和 ADAM10 对皮肤癌、卵巢癌、结肠癌、肺癌和胰腺癌的预后影响，这些数据表明 Trop-2 的这种激活裂解对肿瘤恶性进展的驱动作用。