當腫瘤細胞表現涉及細胞遷移和細胞貼附之內皮細胞相關基因時，可以形成類似血管新生的血管網絡通道，這種現象被稱之為血管生成擬態(vascular mimicry, VM)。並且臨床數據指出腫瘤形成VM的程度和病人的存活率呈負相關性。凝血酶調節素(thrombomodulin, TM) 是一種具有五個功能區域的內皮細胞穿膜醣蛋白，除內皮細胞、巨噬細胞、表皮細胞外，也表達於多種腫瘤細胞，且不同的腫瘤細胞表達量亦有所差異。許多文獻已證實， TM與肌動蛋白 (F-actin)調控細胞骨架及FAK活性有密切關連性，並影響血管新生的發生。但TM與VM的相關性則尚待釐清。故此，我們利用體外黑色素腫瘤細胞模式及實驗小鼠動物模式來探討TM於VM形成中所扮演的角色。首先，利用低血清環境或小分子干擾核糖核酸 (siRNA)降低TM表現，結果顯示黑色素腫瘤細胞VM的形成受到顯著地抑制。相反地，過度表達TM的黑色素腫瘤細胞，其細胞的遷移及VM的形成則明顯的增加，而此現象受FAK的活性所調控。此外，TM過度表達在黑色素腫瘤細胞會促進細胞與細胞外基質 (ECM)的相互作用，並增加FAK和Src的磷酸化，而活化與細胞貼附相關的訊息傳遞路徑。接著，我們進一步探討TM功能區域對VM形成的重要性。結果說明，TM若要促進VM的形成，cytoplasmic domain和lectin-like domain是不可缺少的，其中cytoplasmic domain和ezrin結合調控細胞的遷移及VM的形成。最後，我們探討重組TM蛋白 (rTMD1)抑制黑色素腫瘤生長及VM形成的相關性。在細胞實驗中，rTMD1可以抑制黑色素腫瘤細胞形成VM，但不影響細胞的增生。在動物實驗中，給予rTMD1治療，可以抑制免疫缺陷小鼠 (NOD-SCID mice)體內黑色素腫瘤的生長。經由以上的研究結果，我們更清楚地了解TM在黑色素腫瘤形成VM過程中扮演重要的角色，並期望能對未來臨床抑制腫瘤進展提供新的治療方向。

Tumor cells that express endothelium-associated genes involving in cell migration and adhesion could form vessel-like channels independent of angiogenesis. This phenomenon is called vascular mimicry (VM) and is adversely associated with the survival of cancer patients. Thrombomodulin (TM), an endothelial transmembrane glycoprotein consisting 5 functional domains, is differentially expressed in various tumor cells. Since TM has been demonstrated to regulate angiogenesis through its association with F-actin cytoskeleton and focal adhesion kinase activity. In this study, we study molecular mechanism of TM in melanoma VM formation. The results showed that reduction of TM expression either by serum starvation or siRNA led to decrease of melanoma VM on Matrigel, indicating TM contributes to VM. On the other hand, overexpression of TM but not TM mutants increased melanoma migration and VM, while suppressed by inhibition of focal adhesion kinase. In addition, TM was associated with activation of FAK and Src, suggesting its role in cell adhesion and migration. Moreover, TM connection to ezrin was essential for TM-mediated cell migration and VM activity in melanoma cells. Excitingly, treatment of recombinant TM protein significantly inhibited melanoma VM formation in vitro and tumor growth in vivo. In summary, our study unravels a novel mechanism of TM in melanoma VM. Importantly, interfering with TM may have a potential to suppress tumor progression.

1. Hujanen, Roosa, et al. "Vasculogenic mimicry: a promising prognosticator in head and neck squamous cell carcinoma and esophageal cancer? a systematic review and meta-analysis." Cells 9.2 (2020): 507.
2. Viallard, Claire, and Bruno Larrivée. "Tumor angiogenesis and vascular normalization: alternative therapeutic targets." Angiogenesis 20.4 (2017): 409-426.
3. Carmeliet, Peter, and Rakesh K. Jain. "Molecular mechanisms and clinical applications of angiogenesis." Nature 473.7347 (2011): 298-307.
4. Ramjiawan, Rakesh R., Arjan W. Griffioen, and Dan G. Duda. "Anti-angiogenesis for cancer revisited: Is there a role for combinations with immunotherapy? ." Angiogenesis 20.2 (2017): 185-204.
5. Maniotis, Andrew J., et al. "Vascular channel formation by human melanoma cells in vivo and in vitro: vasculogenic mimicry." The American journal of pathology 155.3 (1999): 739-752.
6. Hendrix, Mary JC, et al. "Molecular plasticity of human melanoma cells." Oncogene 22.20 (2003): 3070-3075.
7. Seftor, Elisabeth A., et al. "Expression of multiple molecular phenotypes by aggressive melanoma tumor cells: role in vasculogenic mimicry." Critical reviews in oncology/hematology 44.1 (2002): 17-27.
8. Seftor, Richard EB, et al. "Tumor cell vasculogenic mimicry: from controversy to therapeutic promise." The American journal of pathology 181.4 (2012): 1115-1125.
9. Fernández-Cortés, Mónica, Daniel Delgado-Bellido, and F. Javier Oliver. "Vasculogenic mimicry: become an endothelial cell “but not so much”." Frontiers in oncology 9 (2019): 803.
10. Liu, Y., et al. "IGFBP2 promotes vasculogenic mimicry formation via regulating CD144 and MMP2 expression in glioma." Oncogene 38.11 (2019): 1815-1831.
11. Zhao, Bing, et al. "Thrombin is a therapeutic target for non-small-cell lung cancer to inhibit vasculogenic mimicry formation." Signal transduction and targeted therapy 5.1 (2020): 1-12.
12. Delgado-Bellido, Daniel, et al. "Vasculogenic mimicry signaling revisited: focus on non-vascular VE-cadherin." Molecular cancer 16.1 (2017): 1-14.
13. Hsu, Yun-Yan, et al. "Thrombomodulin promotes focal adhesion kinase activation and contributes to angiogenesis by binding to fibronectin." Oncotarget 7.42 (2016): 68122.
14. Mitra, Satyajit K., Daniel A. Hanson, and David D. Schlaepfer. "Focal adhesion kinase: in command and control of cell motility." Nature reviews Molecular cell biology 6.1 (2005): 56-68.
15. Mitra, Satyajit K., and David D. Schlaepfer. "Integrin-regulated FAK–Src signaling in normal and cancer cells." Current opinion in cell biology 18.5 (2006): 516-523.
16. Kuo, Cheng-Hsiang, et al. "VEGF-induced endothelial podosomes via ROCK2-dependent thrombomodulin expression initiate sprouting angiogenesis." Arteriosclerosis, thrombosis, and vascular biology 41.5 (2021): 1657-1671.
17. Kuo, Cheng-Hsiang, et al. "The recombinant lectin-like domain of thrombomodulin inhibits angiogenesis through interaction with Lewis Y antigen." Blood, The Journal of the American Society of Hematology 119.5 (2012): 1302-1313.
18. Borah, Supriya, Dileep Vasudevan, and Rajeeb K. Swain. "C type lectin family XIV members and angiogenesis." Oncology letters 18.4 (2019): 3954-3962.
19. Loghmani, Houra, and Edward M. Conway. "Exploring traditional and nontraditional roles for thrombomodulin." Blood, The Journal of the American Society of Hematology 132.2 (2018): 148-158.
20. Huang, Huey-Chun, et al. "Thrombomodulin-mediated cell adhesion: involvement of its lectin-like domain." Journal of Biological Chemistry 278.47 (2003): 46750-46759.
21. Ito, Takashi, et al. "Thrombomodulin in disseminated intravascular coagulation and other critical conditions—a multi-faceted anticoagulant protein with therapeutic potential." Critical Care 23.1 (2019): 1-11.
22. Hsu, Yun‐Yan, et al. "Thrombomodulin is an ezrin‐interacting protein that controls epithelial morphology and promotes collective cell migration." The FASEB Journal 26.8 (2012): 3440-3452.
23. Chen, Po‐Ku, et al. "Thrombomodulin functions as a plasminogen receptor to modulate angiogenesis." The FASEB Journal 27.11 (2013): 4520-4531.
24. Cho, Chia-Fong, et al. "Human plasminogen kringle 1–5 inhibits angiogenesis and induces thrombomodulin degradation in a protein kinase A-dependent manner." Journal of molecular and cellular cardiology 63 (2013): 79-88.
25. Munoz-Chapuli, R., A. R. Quesada, and M. Angel Medina. "Angiogenesis and signal transduction in endothelial cells." Cellular and Molecular Life Sciences CMLS 61.17 (2004): 2224-2243.
26. Van Hinsbergh, Victor WM, Marten A. Engelse, and Paul HA Quax. "Pericellular proteases in angiogenesis and vasculogenesis." Arteriosclerosis, thrombosis, and vascular biology 26.4 (2006): 716-728.
27. Hess, Angela R., et al. "Phosphoinositide 3-kinase regulates membrane Type 1-matrix metalloproteinase (MMP) and MMP-2 activity during melanoma cell vasculogenic mimicry." Cancer research 63.16 (2003): 4757-4762.
28. Soares, Michael J., et al. "Adaptive mechanisms controlling uterine spiral artery remodeling during the establishment of pregnancy." The International journal of developmental biology 58 (2014): 247.
29. Sato, Yukiyasu. "Endovascular trophoblast and spiral artery remodeling." Molecular and cellular endocrinology 503 (2020): 110699.
30. Apps, R., et al. "Genome-wide expression profile of first trimester villous and extravillous human trophoblast cells." Placenta 32.1 (2011): 33-43.
31. Rai, Anshita, and James C. Cross. "Development of the hemochorial maternal vascular spaces in the placenta through endothelial and vasculogenic mimicry." Developmental biology 387.2 (2014): 131-141.
32. Wei, Xiaoxu, et al. "Mechanisms of vasculogenic mimicry in hypoxic tumor microenvironments." Molecular Cancer 20.1 (2021): 1-18.
33. Kirschmann, Dawn A., et al. "Molecular pathways: vasculogenic mimicry in tumor cells: diagnostic and therapeutic implications." Clinical cancer research 18.10 (2012): 2726-2732.
34. Conway, Edward M. "Thrombomodulin and its role in inflammation." Seminars in immunopathology. Vol. 34. No. 1. Springer-Verlag, 2012.
35. Shi, Chung-Sheng, et al. "Evidence of human thrombomodulin domain as a novel angiogenic factor." Circulation 111.13 (2005): 1627-1636.
36. Kao, Yuan-Chung, et al. "Downregulation of thrombomodulin, a novel target of Snail, induces tumorigenesis through epithelial-mesenchymal transition." Molecular and cellular biology 30.20 (2010): 4767-4785.
37. Chang, Yu-Jia, et al. "Thrombomodulin influences the survival of patients with non-metastatic colorectal cancer through epithelial-to-mesenchymal transition (EMT)." PLoS One 11.8 (2016): e0160550.
38. Yang, Y., B. J. Cheng, and S. Lu. "Thrombomodulin regulates doxorubicin sensitivity through epithelial-mesenchymal transition in non-small cell lung cancer." Eur Rev Med Pharmacol Sci 21.1 (2017): 95-101.
39. Shirai, Yoshihiro, et al. "Recombinant thrombomodulin suppresses tumor growth of pancreatic cancer by blocking thrombin-induced PAR1 and NF-κB activation." Surgery 161.6 (2017): 1675-1682.
40. Amada, En, et al. "The antitumor effect of a soluble recombinant human thrombomodulin as growth suppression against gastrointestinal tumor in murine peritonitis model." (2017): 1681-1681.
41. Khan, Kabir A., et al. "C‐type lectin domain group 14 proteins in vascular biology, cancer and inflammation." The FEBS journal 286.17 (2019): 3299-3332.
42. Hanly, A. M., et al. "Thrombomodulin: tumour biology and prognostic implications." European Journal of Surgical Oncology (EJSO) 31.3 (2005): 217-220.
43. Suzuki, Koji, et al. "Structure and expression of human thrombomodulin, a thrombin receptor on endothelium acting as a cofactor for protein C activation." The EMBO journal 6.7 (1987): 1891-1897.
44. Sun, Baocun, et al. "Hypoxia influences vasculogenic mimicry channel formation and tumor invasion-related protein expression in melanoma." Cancer letters 249.2 (2007): 188-197.
45. Hernández de la Cruz, Olga N., et al. "Regulation Networks Driving Vasculogenic Mimicry in Solid Tumors." Frontiers in oncology 9 (2020): 1419.
46. Eelen, Guy, et al. "Basic and therapeutic aspects of angiogenesis updated." Circulation research 127.2 (2020): 310-329.
47. Poullet, Patrick, et al. "Ezrin interacts with focal adhesion kinase and induces its activation independently of cell-matrix adhesion." Journal of Biological Chemistry 276.40 (2001): 37686-37691.
48. Frame, Margaret C., et al. "The FERM domain: organizing the structure and function of FAK." Nature reviews Molecular cell biology 11.11 (2010): 802-814.