BACKGROUND Increasing evidence indicates that angiogenesis plays an important role in tumor progression. The function of cathepsin L (CTSL), an endosomal proteolytic enzyme, in promoting tumor metastasis is well recognized. The mechanisms by which CTSL has promoted the angiogenesis of gastric cancer (GC), however, remains unclear. METHODS The nuclear expression levels of CTSL were assessed in GC samples. The effects of CTSL on GC angiogenesis were determined by endothelial tube formation analysis, HUVEC migration assay, and chick embryo chorioallantoic membrane (CAM) assay. The involvement of the CDP/Cux/VEGF-D pathway was analyzed by angiogenesis antibody array, Western blot, co-immunoprecipitation (Co-IP) and dual-luciferase reporter assay. RESULTS In this study, we found that the nuclear CTSL expression level in GC was significantly higher than that in adjacent nontumor gastric tissues and was a potential important clinical prognostic factor. Loss- and gain-of-function assays indicated that CTSL promotes the tubular formation and migration of HUVEC cells in vitro. The CAM assay also showed that CTSL promotes angiogenesis of GC in vivo. Mechanistic analysis demonstrated that CTSL can proteolytically process CDP/Cux and produce the physiologically relevant p110 isoform, which stably binds to VEGF-D and promotes the transcription of VEGF-D, thus contributing to the angiogenesis of GC. CONCLUSION The findings of the present study suggested that CTSL plays a constructive role in the regulation of angiogenesis in human GC and could be a potential therapeutic target for GC.

中文翻译：

---

Cathepsin L 通过调节人胃癌中的 CDP/Cux/VEGF-D 通路促进血管生成。

背景越来越多的证据表明血管生成在肿瘤进展中起重要作用。组织蛋白酶 L (CTSL) 是一种内体蛋白水解酶，其促进肿瘤转移的功能已得到广泛认可。然而，CTSL 促进胃癌 (GC) 血管生成的机制仍不清楚。方法 在 GC 样本中评估 CTSL 的核表达水平。CTSL 对 GC 血管生成的影响通过内皮管形成分析、HUVEC 迁移测定和鸡胚绒毛尿囊膜 (CAM) 测定来确定。通过血管生成抗体阵列、蛋白质印迹、免疫共沉淀 (Co-IP) 和双荧光素酶报告基因测定分析 CDP/Cux/VEGF-D 通路的参与。结果 在这项研究中，我们发现 GC 中的核 CTSL 表达水平显着高于邻近的非肿瘤胃组织，并且是潜在的重要临床预后因素。功能丧失和功能获得测定表明 CTSL 在体外促进 HUVEC 细胞的管状形成和迁移。CAM 测定还表明 CTSL 在体内促进 GC 的血管生成。机理分析表明，CTSL 可以蛋白水解处理 CDP/Cux 并产生生理相关的 p110 亚型，它稳定地结合 VEGF-D 并促进 VEGF-D 的转录，从而促进 GC 的血管生成。结论 本研究的结果表明，CTSL 在人类 GC 血管生成的调节中发挥建设性作用，可能成为 GC 的潜在治疗靶点。