Fluorescence Imaging of Tumors with “Smart” pH-Activatable Targeted Probes

  • Daisuke Asanuma
  • Hisataka Kobayashi
  • Tetsuo Nagano
  • Yasuteru Urano
Part of the Methods in Molecular Biology™ book series (MIMB, volume 574)


One goal of molecular imaging is to establish a widely applicable technique for specific detection of tumors with minimal background originated from non-target tissues. In this study, a “smart” activatable strategy for specific tumor imaging is proposed in which pH-activatable targeted probes specifically detect tumors after binding to the target cell surface proteins, internalization, and eventual acidic pH activation within the acidic organelles. We successfully visualized submillimeter-sized tumors using this strategy in two different tumor mouse models. Since the design of pH-activatable targeted probes can be applied to any target molecules on the cell surface that are to be internalized after ligand binding, this imaging strategy can afford a general and powerful method to diagnose and monitor the target tumors.


Optical tumor imaging fluorescence molecular probes pH receptor-mediated endocytosis 


  1. 1.
    Hengerer, A., Wunder, A., Wagenaar, D. J., Vija, A. H., Shah, M., and Grimm, J. (2005) From genomics to clinical molecular imaging. Proceedings of the IEEE 93, 819–828.Google Scholar
  2. 2.
    Krohn, K. A., O’Sullivan, F., Crowley, J., Eary, J. F., Linden, H. M., Link, J. M., Mankoff, D. A., Muzi, M., Rajendran, J. G., Spence, A. M., and Swanson, K. R. (2007) Challenges in clinical studies with multiple imaging probes. Nucl Med Biol 34, 879–885.PubMedCrossRefGoogle Scholar
  3. 3.
    Becker, A., Hessenius, C., Licha, K., Ebert, B., Sukowski, U., Semmler, W., Wiedenmann, B., and Grotzinger, C. (2001) Receptor-targeted optical imaging of tumors with near-infrared fluorescent ligands. Nat Biotechnol 19, 327–331.PubMedCrossRefGoogle Scholar
  4. 4.
    Moon, W. K., Lin, Y., O’Loughlin, T., Tang, Y., Kim, D. -E., Weissleder, R., and Tung, C. -H. (2003) Enhanced tumor detection using a folate receptor-targeted near-infrared fluorochrome conjugate. Bioconjug Chem 14, 539–545.PubMedCrossRefGoogle Scholar
  5. 5.
    Weissleder, R., Tung, C. -H., Mahmood, U., and Bogdanov, A. (1999) In vivo imaging of tumors with protease-activated near-infrared fluorescent probes. Nat Biotechnol 17, 375–378.PubMedCrossRefGoogle Scholar
  6. 6.
    Bremer, C., Tung, C. -H., and Weissleder, R. (2001) In vivo molecular target assessment of matrix metalloproteinase inhibition. Nat Med 7, 743–748.PubMedCrossRefGoogle Scholar
  7. 7.
    Hama, Y., Urano, Y., Koyama, Y., Kamiya, M., Bernardo, M., Paik, R. S., Shin, I. S., Paik, C. H., Choyke, P. L., and Kobayashi, H. (2007) A target cell-specific activatable fluorescence probe for in vivo molecular imaging of cancer based on a self-quenched avidin-rhodamine conjugate. Cancer Res 67, 2791–2799.PubMedCrossRefGoogle Scholar
  8. 8.
    Kamiya, M., Kobayashi, H., Hama, Y., Koyama, Y., Bernardo, M., Nagano, T., Choyke, P. L., and Urano, Y. (2007) An enzymatically activated fluorescence probe for targeted tumor imaging. J Am Chem Soc 129, 3918–3929.PubMedCrossRefGoogle Scholar
  9. 9.
    Hama, Y., Urano, Y., Koyama, Y., Choyke, P. L., and Kobayashi, H. (2006) Targeted optical imaging of cancer cells using lectin-binding BODIPY conjugated avidin. Biochem Biophys Res Commun 348, 807–813.PubMedCrossRefGoogle Scholar
  10. 10.
    Austin, C. D., De Maziere, A. M., Pisacane, P. I., van Dijk, S. M., Eigenbrot, C., Sliwkowski, M. X., Klumperman, J., and Scheller, R. H. (2004) Endocytosis and sorting of ErbB2 and the site of action of cancer therapeutics trastuzumab and geldanamycin. Mol Biol Cell 15, 5268–5282.PubMedCrossRefGoogle Scholar
  11. 11.
    Hongyan Li, Z. M. Q. (2002) Transferrin/transferrin receptor-mediated drug delivery. Med Res Rev 22, 225–250.PubMedCrossRefGoogle Scholar
  12. 12.
    Konan, Y. N., Gurny, R., and Allemann, E. (2002) State of the art in the delivery of photosensitizers for photodynamic therapy. J Photochem Photobiol 66, 89–106.CrossRefGoogle Scholar
  13. 13.
    Atobe, K., Ishida, T., Ishida, E., Hashimoto, K., Kobayashi, H., Yasuda, J., Aoki, T., Obata, K. -I., Kikuchi, H., Akita, H., Asai, T., Harashima, H., Oku, N., and Kiwada, H. (2007) In vitro efficacy of a sterically stabilized immunoliposomes targeted to membrane type 1 matrix metalloproteinase (MT1-MMP). Biol Pharm Bull 30, 972–978.PubMedCrossRefGoogle Scholar
  14. 14.
    Urano, Y., Asanuma, D., Hama, Y., Koyama, Y., Barrett, T., Kamiya, M., Nagano, T., Watanabe, T., Hasegawa, A., Choyke, P. L., and Kobayashi, H. (2009). Selective molecular imaging of viable cancer cells with pH-activatable fluorescence probes. Nat Med 15(1): 104–109.PubMedCrossRefGoogle Scholar

Copyright information

© Humana Press, a part of Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Daisuke Asanuma
    • 1
  • Hisataka Kobayashi
    • 2
  • Tetsuo Nagano
    • 1
  • Yasuteru Urano
    • 2
  1. 1.Graduate School of Pharmaceutical Sciences, The University of TokyoTokyoJapan
  2. 2.Molecular Imaging Program, National Cancer Institute, National Institute of Health, Center for Cancer ResearchBethesdaUSA

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