Amirkhosravi A, Meyer T, Warnes G, Amaya M, Malik Z, Biggerstaff J P, Siddiqui F A, Sherman P, Francis J L
Cell Biology, Hemostasis and Thrombosis Research Unit, Walt Disney Memorial Cancer Institute at Florida Hospital, Orlando 32804, USA.
Thromb Haemost. 1998 Oct;80(4):598-602.
Tissue factor (TF), the membrane glycoprotein that initiates blood coagulation, is constitutively expressed by many tumor cells and is implicated in peri-tumor fibrin deposition and hypercoagulability in cancer. Upregulation of tumor TF correlates with enhanced metastatic potential. Furthermore, TF has been colocalized with VEGF in breast cancer, specially at sites of early angiogenesis. There are no data on the effect of hypoxia on tumor cell TF expression. Since hypoxia is known to stimulate VEGF production, we studied whether this also induces tumor cell TF expression. Confluent monolayers of A375 melanoma, MCF-7 breast carcinoma and A549 lung carcinoma were cultured in either 95% air, 5% CO2 (normoxic) or 95% N2, 5% CO2 (hypoxic; 25-30 mmHg) for 24 h. Procoagulant activity (PCA) was measured by amidolytic and clotting assays, surface TF antigen by flow cytometry, early apoptosis by annexin V binding and VEGF levels in culture supernatants by ELISA. Hypoxia significantly increased tumor cell PCA in all three cell lines tested and TF antigen on A375 cells was increased four-fold (P <0.05). Pentoxifylline (PTX), a methylxanthine derivative, significantly inhibited the hypoxia-induced increase in PCA as well as VEGF release in all three cell lines tested. In A375 cells, PTX significantly inhibited TF antigen expression by both normoxic and hypoxic cells. Hypoxia induced a slight (5%) but not significant, increase in early apoptosis. Intravenous injection of hypoxic A375 cells into nude rats produced more pronounced thrombocytopenia (n = 5, P <0.01) and more lung metastases (n = 3, P <0.05) compared to normoxic cells. We conclude that hypoxia increases TF expression by malignant cells which enhances tumor cell-platelet binding and hematogenous metastasis. Hypoxia-induced upregulation of TF appears to parallel that of VEGF, although the mechanism remains unclear.
组织因子（TF）是启动血液凝固的膜糖蛋白，许多肿瘤细胞都组成性表达该蛋白，且与肿瘤周围纤维蛋白沉积以及癌症中的高凝状态有关。肿瘤TF的上调与转移潜能增强相关。此外，在乳腺癌中，TF已被证明与血管内皮生长因子（VEGF）共定位，特别是在早期血管生成部位。目前尚无关于缺氧对肿瘤细胞TF表达影响的数据。由于已知缺氧会刺激VEGF产生，我们研究了这是否也会诱导肿瘤细胞TF表达。将A375黑色素瘤、MCF - 7乳腺癌和A549肺癌的汇合单层细胞分别在95%空气、5%二氧化碳（常氧）或95%氮气、5%二氧化碳（缺氧；25 - 30 mmHg）条件下培养24小时。通过酰胺水解和凝血试验测量促凝活性（PCA），通过流式细胞术检测表面TF抗原，通过膜联蛋白V结合检测早期凋亡，并通过酶联免疫吸附测定（ELISA）检测培养上清液中的VEGF水平。缺氧显著增加了所有三种测试细胞系中的肿瘤细胞PCA，A375细胞上的TF抗原增加了四倍（P <0.05）。己酮可可碱（PTX），一种甲基黄嘌呤衍生物，在所有三种测试细胞系中均显著抑制缺氧诱导的PCA增加以及VEGF释放。在A375细胞中，PTX显著抑制常氧和缺氧细胞的TF抗原表达。缺氧诱导早期凋亡轻微（5%）但不显著增加。与常氧细胞相比，将缺氧的A375细胞静脉注射到裸鼠体内会导致更明显的血小板减少（n = 5，P <0.01）和更多的肺转移（n = 3，P <0.05）。我们得出结论，缺氧会增加恶性细胞的TF表达，从而增强肿瘤细胞与血小板的结合以及血行转移。缺氧诱导的TF上调似乎与VEGF的上调平行，尽管其机制尚不清楚。
