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Hypoxia-induced activity loss of a photo-responsive microtubule inhibitor azobenzene combretastatin A4

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The conformation-dependent activity of azobenzene combretastatin A4 (Azo-CA4) provides a unique approach to reduce the side-effects of chemotherapy, due to the light-triggered conformation transition of its azobenzene moiety. Under hypoxic tumor microenvironment, however, the high expression of azoreductase can reduce azobenzene to aniline. It was postulated that the Azo-CA4 might be degraded under hypoxia, resulting in the decrease of its anti-tumor activity. The aim of this study was to verify such hypothesis in HeLa cells in vitro. The quantitative drug concentration analysis shows the ratio-metric formation of degradation end-products, confirming the bioreduction of Azo-CA4. The tubulin staining study indicates that Azo-CA4 loses the potency of switching off microtubule dynamics under hypoxia. Furthermore, the cell cycle analysis shows that the ability of Azo-CA4 to induce mitotic arrest is lost at low oxygen content. Therefore, the cytotoxicity of Azo-CA4 is compromised under hypoxia. In contrast, combretastatin A4 as a positive control maintains the potency to inhibit tubulin polymerization and break down the nuclei irrespective of light irradiation and oxygen level. This work highlights the influence of hypoxic tumor microenvironment on the anti-tumor potency of Azo-CA4, which should be considered during the early stage of designing translational Azo-CA4 delivery systems.

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  1. 1.

    Mollman J E. Cisplatin neurotoxicity. New England Journal of Medicine, 1990, 322(2): 126–127

  2. 2.

    Singal P K, Iliskovic N. Doxorubicin-induced cardiomyopathy. New England Journal of Medicine, 1998, 339(13): 900–905

  3. 3.

    Bae Y H, Park K. Targeted drug delivery to tumors: Myths, reality and possibility. Journal of Controlled Release, 2011, 153(3): 198–205

  4. 4.

    Lu D, Tao R, Wang Z. Carbon-based materials for photodynamic therapy: A mini-review. Frontiers of Chemical Science and Engineering, 2019, 13(2): 310–323

  5. 5.

    Kwon I K, Lee S C, Han B, Park K. Analysis on the current status of targeted drug delivery to tumors. Journal of Controlled Release, 2012, 164(2): 108–114

  6. 6.

    Wilhelm S, Tavares A J, Dai Q, Ohta S, Audet J, Dvorak H F, Chan W C W. Analysis of nanoparticle delivery to tumours. Nature Reviews. Materials, 2016, 1(5): 1–12

  7. 7.

    Hu Q, Bomba H N, Gu Z. Engineering platelet-mimicking drug delivery vehicles. Frontiers of Chemical Science and Engineering, 2017, 11(4): 624–632

  8. 8.

    Xin K, Li M, Lu D, Meng X, Deng J, Kong D, Ding D, Wang Z, Zhao Y. Bioinspired coordination micelles integrating high stability, triggered cargo release, and magnetic resonance imaging. ACS Applied Materials & Interfaces, 2017, 9(1): 80–91

  9. 9.

    Hu Q, Sun W, Wang C, Gu Z. Recent advances of cocktail chemotherapy by combination drug delivery systems. Advanced Drug Delivery Reviews, 2016, 98: 19–34

  10. 10.

    Webster R M. Combination therapies in oncology. Nature Reviews. Drug Discovery, 2016, 15(2): 81–82

  11. 11.

    Doroshow J H, Simon R M. On the design of combination cancer therapy. Cell, 2017, 171(7): 1476–1478

  12. 12.

    Li H, Li M, Chen C, Fan A, Kong D, Wang Z, Zhao Y. On-demand combinational delivery of curcumin and doxorubicin via a pH-labile micellar nanocarrier. International Journal of Pharmaceutics, 2015, 495(1): 572–578

  13. 13.

    Maeda H. Toward a full understanding of the EPR effect in primary and metastatic tumors as well as issues related to its heterogeneity. Advanced Drug Delivery Reviews, 2015, 91: 3–6

  14. 14.

    Peer D, Karp J M, Hong S, Farokhzad O C, Margalit R, Langer R. Nanocarriers as an emerging platform for cancer therapy. Nature Nanotechnology, 2007, 2(12): 751–760

  15. 15.

    Zhang P, Ye J, Liu E, Sun J, Zhang S J, Lee J, Gong J, He H, Yang V C. Aptamer-coded DNA nanoparticles for targeted doxorubicin delivery using pH-sensitive spacer. Frontiers of Chemical Science and Engineering, 2017, 11(4): 529–536

  16. 16.

    Mura S, Nicolas J, Couvreur P. Stimuli-responsive nanocarriers for drug delivery. Nature Materials, 2013, 12(11): 991–1003

  17. 17.

    Torchilin V P. Multifunctional, stimuli-sensitive nanoparticulate systems for drug delivery. Nature Reviews. Drug Discovery, 2014, 13(11): 813–827

  18. 18.

    Li X, Gao M, Xin K, Zhang L, Ding D, Kong D, Wang Z, Shi Y, Kiessling F, Lammers T, Cheng J, Zhao Y. Singlet oxygen-responsive micelles for enhanced photodynamic therapy. Journal of Controlled Release, 2017, 260: 12–21

  19. 19.

    Tao R, Gao M, Liu F, Guo X, Fan A, Ding D, Kong D, Wang Z, Zhao Y. Alleviating the liver toxicity of chemotherapy via pH-responsive hepatoprotective prodrug micelles. ACS Applied Materials & Interfaces, 2018, 10(26): 21836–21846

  20. 20.

    Gao J, Li J, Geng W C, Chen F Y, Duan X, Zheng Z, Ding D, Guo D S. Biomarker displacement activation: A general host-guest strategy for targeted phototheranostics in vivo. Journal of the American Chemical Society, 2018, 140(14): 4945–4953

  21. 21.

    He H, Sun L, Ye J, Liu E, Chen S, Liang Q, Shin M C, Yang V C. Enzyme-triggered, cell penetrating peptide-mediated delivery of anti-tumor agents. Journal of Controlled Release, 2016, 240: 67–76

  22. 22.

    Chen C, Zhao J, Gao M, Meng X, Fan A, Wang Z, Zhao Y. Photo-triggered micelles: Simultaneous activation and release of micro-tubule inhibitors for on-demand chemotherapy. Biomaterials Science, 2018, 6(3): 511–518

  23. 23.

    Liu Y, Liu Y, Bu W, Cheng C, Zuo C, Xiao Q, Sun Y, Ni D, Zhang C, Liu J, Shi J. Hypoxia induced by upconversion-based photo-dynamic therapy: Towards highly effective synergistic bioreductive therapy in tumors. Angewandte Chemie International Edition, 2015, 54(28): 8105–8109

  24. 24.

    Borowiak M, Nahaboo W, Reynders M, Nekolla K, Jalinot P, Hasserodt J, Rehberg M, Delattre M, Zahler S, Vollmar A, Trauner D, Thorn-Seshold O. Photoswitchable inhibitors of microtubule dynamics optically control mitosis and cell death. Cell, 2015, 162(2): 403–411

  25. 25.

    Engdahl A J, Torres E A, Lock S E, Engdahl T B, Mertz P S, Streu C N. Synthesis, characterization, and bioactivity of the photoisomerizable tubulin polymerization inhibitor azo-combretastatin A4. Organic Letters, 2015, 17(18): 4546–4549

  26. 26.

    Sheldon J E, Dcona M M, Lyons C E, Hackett J C, Hartman M C. Photoswitchable anticancer activity via trans-cis isomerization of a combretastatin A-4 analog. Organic & Biomolecular Chemistry, 2016, 14(1): 40–49

  27. 27.

    Rastogi S K, Zhao Z, Barrett S L, Shelton S D, Zafferani M, Anderson H E, Blumenthal M O, Jones L R, Wang L, Li X, Streu C N, Du L, Brittain W J. Photoresponsive azo-combretastatin A-4 analogues. European Journal of Medicinal Chemistry, 2018, 143: 1–7

  28. 28.

    Muroyama A, Lechler T. Microtubule organization, dynamics and functions in differentiated cells. Development, 2017, 144(17): 3012–3021

  29. 29.

    Castle B T, Odde D J. Optical control of microtubule dynamics in time and space. Cell, 2015, 162(2): 243–245

  30. 30.

    Perche F, Biswas S, Wang T, Zhu L, Torchilin V P. Hypoxia-targeted siRNA delivery. Angewandte Chemie International Edition, 2014, 53(13): 3362–3366

  31. 31.

    Li J, Meng X, Deng J, Lu D, Zhang X, Chen Y, Zhu J, Fan A, Ding D, Kong D, Wang Z, Zhao Y. Multifunctional micelles dually responsive to hypoxia and singlet oxygen: Enhanced photodynamic therapy via interactively triggered photosensitizer delivery. ACS Applied Materials & Interfaces, 2018, 10(20): 17117–17128

  32. 32.

    Hanahan D, Weinberg R A. Hallmarks of cancer: The next generation. Cell, 2011, 144(5): 646–674

  33. 33.

    Rankin E B, Giaccia A J. Hypoxic control of metastasis. Science, 2016, 352(6282): 175–180

  34. 34.

    Tang J, Huang C, Shu J, Zheng J, Ma D, Li J, Yang R. Azoreductase and target simultaneously activated fluorescent monitoring for cytochrome c release under hypoxia. Analytical Chemistry, 2018, 90(9): 5865–5872

  35. 35.

    Wang L, Huang X, Wang B, Zhao J, Guo X, Wang Z, Zhao Y. Mechanistic insight into the singlet oxygen-triggered expansion of hypoxia-responsive polymeric micelles. Biomaterials Science, 2018, 6(7): 1712–1716

  36. 36.

    Li M, Gao M, Fu Y, Chen C, Meng X, Fan A, Kong D, Wang Z, Zhao Y. Acetal-linked polymeric prodrug micelles for enhanced curcumin delivery. Colloids and Surfaces. B, Biointerfaces, 2016, 140: 11–18

  37. 37.

    Beharry A A, Woolley G A. Azobenzene photoswitches for biomolecules. Chemical Society Reviews, 2011, 40(8): 4422–4437

  38. 38.

    Piao W, Hanaoka K, Fujisawa T, Takeuchi S, Komatsu T, Ueno T, Terai T, Tahara T, Nagano T, Urano Y. Development of an azo-based photosensitizer activated under mild hypoxia for photodynamic therapy. Journal of the American Chemical Society, 2017, 139(39): 13713–13719

  39. 39.

    Verwilst P, Han J, Lee J, Mun S, Kang H G, Kim J S. Reconsidering azobenzene as a component of small-molecule hypoxia-mediated cancer drugs: A theranostic case study. Biomaterials, 2017, 115: 104–114

  40. 40.

    Dong M, Babalhavaeji A, Samanta S, Beharry A A, Woolley G A. Red-shifting azobenzene photoswitches for in vivo use. Accounts of Chemical Research, 2015, 48(10): 2662–2670

  41. 41.

    Wu S, Butt H J. Near-infrared-sensitive materials based on upconverting nanoparticles. Advanced Materials, 2016, 28(6): 1208–1226

  42. 42.

    Bandara H M, Friss T R, Enriquez M M, Isley W, Incarvito C, Frank H A, Gascon J, Burdette S C. Proof for the concerted inversion mechanism in the trans-cis isomerization of azobenzene using hydrogen bonding to induce isomer locking. Journal of Organic Chemistry, 2010, 75(14): 4817–4827

  43. 43.

    Aliprandi A, Mauro M, De Cola L. Controlling and imaging biomimetic self-assembly. Nature Chemistry, 2016, 8(1): 10–15

  44. 44.

    Meng L, Cheng Y, Gan S, Zhang Z, Tong X, Xu L, Jiang X, Zhu Y, Wu J, Yuan A, Hu Y. Facile deposition of manganese dioxide to albumin-bound paclitaxel nanoparticles for modulation of hypoxic tumor microenvironment to improve chemoradiation therapy. Molecular Pharmaceutics, 2018, 15(2): 447–457

  45. 45.

    Sheng Y, Nesbitt H, Callan B, Taylor M A, Love M, McHale A P, Callan J F. Oxygen generating nanoparticles for improved photodynamic therapy of hypoxic tumours. Journal of Controlled Release, 2017, 264: 333–340

  46. 46.

    Cheng Y, Cheng H, Jiang C, Qiu X, Wang K, Huan W, Yuan A, Wu J, Hu Y. Perfluorocarbon nanoparticles enhance reactive oxygen levels and tumour growth inhibition in photodynamic therapy. Nature Communications, 2015, 6(1): 8785

  47. 47.

    Kolemen S, Ozdemir T, Lee D, Kim G M, Karatas T, Yoon J, Akkaya E U. Remote-controlled release of singlet oxygen by the plasmonic heating of endoperoxide-modified gold nanorods: Towards a paradigm change in photodynamic therapy. Angewandte Chemie International Edition, 2016, 55(11): 3606–3610

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The work was financially supported by the National Natural Science Foundation of China (Grant No. 21650110447).

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Correspondence to Yanjun Zhao or Zheng Wang.

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An, Y., Chen, C., Zhu, J. et al. Hypoxia-induced activity loss of a photo-responsive microtubule inhibitor azobenzene combretastatin A4. Front. Chem. Sci. Eng. (2019). https://doi.org/10.1007/s11705-019-1864-6

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  • hypoxia
  • microtubule inhibitor
  • drug delivery
  • azo-combretastatin A4
  • photo-responsive