硼中子捕獲治療的優勢在於它是一種二要素結合(binary)系統，即選擇一合適之含硼藥物為腫瘤組織所吸收，再給予中子的照射，由於10B和熱中子的結合產生高線性能量轉移(LET)輻射，若此含硼藥物集中在腫瘤組織，則可利用高LET之輻射能量殺死腫瘤細胞。相對地，若正常組織細胞吸收比例抑低則傷害可降至最低；而αvβ3 integrin是一種與腫瘤血管新生及腫瘤轉移相關的細胞黏著受器(cell adhesion receptor)，其具有Arg-Gly-Asp(RGD)序列之胜肽具有高度的專一結合特性，如能在其RGD胜肽上鍵結了含硼化合物，必能發展出具有潛力的硼中子捕獲治療劑。
在本研究合成的過程中，以4-iodobenzoic acid為起始物，進行保護反應、硼化反應及去保護反應，即得到化合物4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoic acid (TDBA)，以化合物進而行酸基的活化反應，形成NHS-activated ester。上述合成產物皆經由氫核磁共振光譜及碳核磁共振光譜予以鑑定確認。進而將NHS-activated ester分別與mono-RGD 胜肽及dimer-RGD 胜肽進行耦合反應，以高效能液相層析儀(HPLC)分離純化，依滯留時間在14.5分鐘及16.2分鐘分別觀察出硼化mono-RGD胜肽及硼化dimer-RGD胜肽之耦合化合物，以MALDI-TOF-Mass鑑定其分子量分別為885.23 Da及1615.286 Da。

Boron neutron capture therapy (BNCT) is a binary therapy that is to select a suitable boronated drug absorbed by tumor tissue and then to give thermal neutron irradiation. By nuclear reaction of 10B with thermal neutron, high linear energy transfer (LET) radiations including α2+ and 7Li+ can be produced. If the boronated drug is able to concentrate on tumor tissue, the resulted high-LET radiations will kill tumor with sparing of the normal tissue. αvβ3 integrin is an important cell adhesion receptor involved in tumor-induced angiogenesis and tumor metastasis. The high binding specificity to αvβ3 integrins of the peptides containing Arg-Gly-Asp(RGD) residue suggests that the RGD peptides conjugated boronated compound may be developed as a potential BNCT agent.
In this study, using 4-iodobenzoic acid as starting material to proceed via protection, boronation and deprotection, the boronated compound, 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoic acid (TDBA) was obtained. By activation of carboxyl group, the TDBA was converted to NHS-activated ester. The aforementioned products were confirmed by 1H and 13C-NMR. While proceeding coupling reaction in the NHS-activated ester with mono-RGD peptide, or dimer-RGD peptide, high performance liquid chromatography (HPLC) was employed to separate and purify the coupling products, the boronated mono-RGD peptide and boronated dimer-RGD peptide with retention times at 14.5 min or 16.2 min, respectively. The molecular weights identified by MALDI-TOF-Mass for the boronated mono-RGD and the boronated dimmer-RGD are 885.23 Da and 1615.286 Da, respectively.

1. Saha G. B., Fundamentals of nuclear pharmacy. 4th ed. Springer. 1997
2. Hom R. K., Katzenellenbogen J. A., Techetium-99m-labeled receptor-specificsmall-molecule radiopharmaceticals: recent developments and encouraging results. Nuclear Medicine and Biology. 1997; 24, 485-498
3. Couturier O., Supiot S., Cancer radioimmunotherapy with alpha-emitting nuclides. Eur J Nucl Med Mol Imaging. 2005; 32, 601-614
4. Thomas E., Yttrium-90 zevalin radioimmunotherapy for patients with relapsed B-cell non-Hodgkin’s lymphoma (IDEC-Y2B8) Witzig 2001:259-266
5. Diane E., Eric D., Antibody-targeted radiation cancer therapy. Nature Reviews 2004; 3, 488-498
6. Albert H. S., Wemer T., Beverly A. B., Feng-guang R., Rolf F. B., Iwona M. C., Gerald W. J., The Chemistry of Neutron Capture Therapy. Chem. Rev. 1998; 98, 1515-1562
7. Locher G. L., Biological effects and therapeutic possibilities of neutrons. Am. J Roentgenol. Radium Ther. 1936; 36, 1-13
8. Jaid M., Brownell G. L., Sweet W. H., The possible use of neutron-capture isotopes such as boron-10 in the treatment of neoplasms. II. Computation of the radiation energy and estimates of effects in normal and neoplastic brain. J. Clin. Invest. 1952; 31, 603-610
9. Sweet W. H., The use of nuclear disintegrations in the diagnosis and treatment of brain tumor. N. Engl. J. Med. 1951; 245, 875-878
10. Sweet W. H., Javid M., The possible use of neutron-capturing isotopes such as boron-10 in the treatment of neoplasms. I. Intracranial tumor. J. Neurosurg. 1952; 9, 200-209
11. Srivastava R. R., Kabalka G. W., Syntheses of 1-amino-3-[2-(7-(2-hydroxyethyl)-1,7-dicarba-closo-dodecaboran(12)-1-yl)ethyl]cyclobutanecarboxylic acid and its nido-analogue: Potential BNCT agents. J. Org. Chem. 1997; 62, 8730–8734
12. Hawthorne M. F., New horizons for therapy based on the boron neutron capture reaction. Mol. Med. Today. 1998; 4, 174–181
13. Villiant J.F., Schaffer P., A new approach for the synthesis of isonitrile carborane derivatives: Ligands for metal based boron neutron capture therapy (BNCT) and boron neutron capture synovectomy (BNCS) agents. J. Inorg. Biochem. 2001; 85, 43–51
14. Liao T.K., Pondrebarac E.H., Cheng C.C., Boron-substituted pyrimidines. J. Am. Chem. Soc. 1964; 86, 1869–1870
15. Schinazi R.F., Prusoff W.H., Synthesis and properties of boron and silicon. Tetrahedron Lett. 1978; 50, 4981–4984
16. Schinazi R.F., Prusoff W.H., Synthesis of 5-(dihydroxyboroyl)-2'-deoxyuridine and relatived boron-containing pyrimidines. J. Org. Chem. 1985; 50, 841–847
17. Soloway A.H., Correlation of drug penetration of brain and chemical structure. Science 1958; 128, 1572–1573
18. Malan C., Morin C., Synthesis of 4-borono-L-phenylalanine. Synlett. 1996; 167–168
19. Kirihata M., Morimoto T., Ichimoto I., Takagki M., An efficient synthesis of p-boronophenylalanine and its homologs by the reaction of ethyl isocyanoacetate with a p-formylbenzeneboronic acid derivative. In: Mishima Y. editor. Cancer Neutron Capture Therapy. New York: Plenum Press; 1996. p 99–104
20. Kiger W.S., III, Palmer M.R., Riley K.J., Zamenhol R.G., Busse P.M., A pharmacokinetic model for the concentration of 10B in blood after boronophenylalanine-fructose administration in humans. Radiat. Res. 2001; 155, 611–618
21. Nemoto H., Cai J., Asao N., Iwamoto S., Yamamoto Y., Synthesis and biological properties of water-soluble p-boronophenylalanine derivatives. Relationship between water solubility, cytotoxicity, and cellular uptake. J. Med. Chem. 1995; 38, 1673–167
22. Hartman T., Carlsson J., Radiation dose heterogeneity in receptor and antigen mediated boron neutron capture therapy. Radiother Oncol. 1994; 31, 61–75
23. Gabel D., Foster S., Fairchild R.G., The monte carlo simulation of the biological effect of the 10B(n,α)7Li reaction in cells and tissue and its implication for boron neutron capture therapy. Radiat. Res. 1987; 111, 14–25
24. Corder A., Whittaker A.R.D., Kelly D.P., Carolan M., Meriaty H., Allen B.J., Martin R.F., Evaluation of a 10B-labeled DNA ligand. In: Soloway A.H., Barth R.F., Carpenter D.E., editors. Adv Neutron Capture Ther [Proc Int Symp]. 5th edn. New York: Plenum Press; 1993. p 377–381
25. Tjarks W., Gabel D., Boron-containing thiouracil derivatives for neutron-capture therapy of melanoma. J. Med. Chem. 1991; 34, 315–319
26. Soloway A.H., Wright R.L., Messer J.R., Evaluation of boron compounds for use in neutron-capture therapy of brain tumors. I. Animal investigations. J. Pharmacol. Exp. Ther. 1961; 134, 117–122
27. Soloway A.H., Hatanaka H., Davis M.A., Penetration of brain and brain tumor. VII. Tumor-binding sulfhydryl boron compounds. J. Med. Chem. 1967; 10, 714–717
28. http://www.osaka-med.ac.jp/deps/neu/omcBNCT/BNCT_E/BNCT_E1.html
29. Risau W., Mechanisms of angiogenesis. Nature. 1999; 386, 671-67
30. Folkman J., Clinical applications of research on angiogenesis. N Engl J Med. 1995; 333, 1757-1763
31. Kerbel R., Folkman J. Clinical translation of angiogenesis inhibitors. Nat. Rev. Cancer. 2002；2, 727-39.
32. Tucker G. C. αv integrin inhibitors and cancer therapy. Curr. Opin. Investig. Drugs. 2003；4, 722-31.
33. Jain R. K. Normalization of tumor vasculature: an emerging concept in antiangiogenic therapy. Science. 2005； 307, 58-62.
34. Brooks P. C., Montgomery A. M. P., Rosenfeld M. Integrin αvβ3 antagonists promote tumor regression by inducing apoptosis of angiogenic blood vessels. Cell. 1994; 79, 1157-1164
35. Bischoff J. Approaches to studying cell adhesion molecules in angiogenesis. Trends Cell Biol. 1995; 5, 69-73
36. Folkman J. Tumor angiogenesis: Therapeutic implications. N Engl J Med. 1971; 285, 1182-118
37. Hanahan D., Weinberg R. A., The hallmarks of cancer. Cell. 2000; 100, 7-70
38. Haubner R., Weber W. A., Radiotracer-based strategies to image angiogenesis. QJ Nucl. Med. 2003；47, 189-199
39. Frenette P. S., Wagner D. D., Molecular medicine：Adhesion molecules-partⅠ. N Engl J Med. 1996；334, 1526-1529
40. Horwitz A. F., Hunter T., Cell adhesion：Integrating circuitry. Trends Cell Biol. 1996；6, 460-461
41. Aplin A. E., Signal transduction and signal modulation by cell adhesion receptors：The role of integrin, cadherins, immunoglobulin-cell adhesion molecules, and selectins. Pharmacol. Rev. 1998；50, 197-263
42. Tamku J. W., Fonda D., Structure of integrin, a glycoprotein involved in the transmembrane linkage between fibronectin and actin. Cell. 1986；46, 271-282
43. Brooks P. C., Clark R. A., Cheresh D. A., Requirement of vascular integrin αVβ3 for angiogenesis. Science. 1994；264, 596-571
44. Kumar. C. C., Integrin αVβ3 as a therapeutic target for blocking tumor-induced angiogenesis. Curr. Drug Targets. 2003；4, 123-131.
45. Newham P., Analysis of ligand-induced and ligand-attenuated epitopes on the leukocyte integrin α4β1：VCAM-1, mucosal addressin cell adhesion molecule-1, and fibronectin induce distinct conformational change. J. Immunol. 1998；160, 4508-4517
46. Peyman A., RGD mimetics containing a central hydantoin scaffold：αvβ3 vs αⅡβ3 selectivity requirements. Bioorg. Med. Chem. Lett. 2000；10, 179-182
47. Plow E. F., Ligand binding to integrins. J. Biol. Chem. 2000；275, 21785-21788
48. Parise L. V., Integrin αⅡbβ3 signaling in platelet adhesion and aggregation. Curr. Opin. Cell Biol. 1999；11, 597-601
49. Ruoslahti E., The Walter Herbert Lecture. Control of cell motility and tumour invasion by extracellular matrix interactions, Br. J. Cancer. 1992; 66, 239–242
50. Hynes R.O., Integrins: versatility, modulation, and signaling in cell adhesion, Cell. 1992; 69, 11–25
51. Albelda S. M., Mette S. A., Elder D. E., Stewart R., Damjanovich L., Herlyn M., Buck C. A., Integrin distribution in malignant melanoma: association of the beta 3 subunit with tumor progression, Cancer Res. 1990; 50, 6757–6764
52. Stromblad S., Cheresh D. A., Integrins, angiogenesis and vascular cell survival, Chem. Biol. 1996; 3, 881–885
53. Brooks P. C., Clark R. A., Cheresh D. A., Requirement of vascular integrin avb3 for angiogenesis, Science. 1994; 264, 569–571
54. Ruoslahti E., Pierschbacher M. D., New perspectives in cell adhesion: RGD and integrins, Science. 1987; 238, 491–497
55. Chen X., Conti P. S., Moats R. A., In vivo near-infrared fluorescence imaging of integrin αVβ3 in brain tumor xenografts. Cancer Res. 2004；64, 8009-8014
56. Chen X., Park R., Tohme M., Shahinian A. H., Bading J. R., Conti P. S., MicroPET and autoradiographic imaging of breast cancer αV integrin expression using 18F- and 64Cu-labeled RGD peptide. Bioconjug. Chem. 2004；15, 41-49
57. Chen X., Liu S., Hou Y., Tohme M., Park R., BadingJ. R., Conti P. S., MicroPET imaging of breast cancer αV integrin expression with 64Cu-labeled dimeric RGD peptides. Mol. Imaging Bio. 2004；6, 350-359
58. Chen X., Hou Y., Tohme M., Park R., Khankaldyyan V., Gonzales-Gomez I., Bading J. R., Laug W. E., Conti, P. S., Pegylated Arg-Gly-Asp peptide: 64Cu labeling and PET imaging of brain tumor αVβ3-integrin expression. J. Nucl. Med. 2004；45, 1776-1783
59. Chen X., Park R., Shahinian A. H., Tohme M., Khankaldyyan V., Bozorgzadeh M. H., Bading J. R., Moats R. A., Laug W. E., Conti P. S., 18F labeled RGD peptide: initial evaluation for imaging brain tumor angiogenesis. Nucl. Med. Biol. 2004；31, 179-189
60. Chen X., Park R., Hou Y., Khankaldyyan V., Gonzales-Gomez I., Tohme M., Bading J. R., Laug W. E., Conti P. S., MicroPET imaging of brain tumor angiogenesis with 18F-labeled PEGylated RGD peptide. Eur. J. Nucl. Med. Mol. Imaging, 2004；31, 1081-1089
61. Chen X., Park R., Shahinian A. H., Bading J. R., Conti P. S., Pharmacokinetics and tumor retention of 125I-labeled RGD peptide are
improved by PEGylation. Nucl. Med. Biol. 2004；31, 11-19
62. Chen X., Sievers E., Hou Y., Park R., Tohme M., Bart R., Bremner R., Bading J. R., Conti P. S., Integrin αvβ3-targeted imaging of lung cancer. Neoplasia 2005；7, 271-279
63. Chen X., Plasencia C., Hou Y., Neamati N., Synthesis and biological evaluation of dimeric RGD peptide-paclitaxel conjugate as a model for integrin-targeted drug delivery. J. Med. Chem. 2005；48,1098-1106
64. Chen X., Tohme M., Park R., Hou Y., Bading J. R., Conti P. S., Micro-PET imaging of αVβ3-integrin expression with 18F-labeled dimeric RGD peptide. Mol. Imaging 2004；3, 96-104
65. Ma D., Zhu W., Formation of arylboronates by a CuI-catalyzed coupling reaction of pinacolborane with aryl iodides at room temperature. Org. Lett. 2006 ; 8, 261-263
66. Strazzolini P., Misuri N., Polese P., Efficient cleavage of carboxylic tert-butyl and 1-adamantyl esters, and N-Boc-amines using H2SO4 in CH2Cl2. Tetrahedron Lett. 2005; 46, 2075-2078
67. Koziorowski J., Henssen C., Weinreich R., A new convent route to radioiodinated N-succinimidyl 3- and 4-iodobenzoate, two reagents for radioiodination of proteins. Appl. Radioat. Isot. 1998 ; 49, 955-959
68. http://chem.ch.huji.ac.il/~eugeniik/edc.htm
69. Liu S., Edwards D. S., 99mTc-labeled small peptides as diagnostic radiopharmaceuticals. Chem. Revs. 1999 ; 99, 2235-2268