P-glycoprotein targeted photodynamic therapy of chemoresistant tumors using recombinant Fab fragment conjugates

Biomater Sci. 2018 Oct 24;6(11):3063-3074. doi: 10.1039/c8bm00844b.


P-glycoprotein (Pgp) has been considered as a major cause of cancer multidrug resistance; however, clinical solutions to overcome this drug resistance do not exist despite the tremendous endeavors. The lack of cancer specificity is a main reason for clinical failure of conventional approaches. Targeted photodynamic therapy (PDT) is highly cancer specific by combining antibody targeting and locoregional light irradiation. We aimed to develop Pgp-targeted PDT using antibody-photosensitizer conjugates made of a recombinant Fab fragment. We prepared the photosensitizer conjugates by expressing a recombinant Fab fragment and specifically linking IR700-maleimide at the C-terminal of the Fab heavy chain. In vitro studies showed that the Fab conjugates specifically bind to Pgp. Their phototoxicity was comparable to full antibody conjugates when assayed with conventional 2-D cell culture, but they outperformed the full antibody conjugates in a 3-D tumor spheroid model. In a mouse xenograft model of chemoresistant tumors, Fab conjugates showed Pgp specific delivery to chemoresistant tumors. Upon irradiation with near-infrared light, they caused rapid tumor shrinkage and significantly prolonged the survival of tumor-bearing mice. Compared to the full antibody conjugates, Fab conjugates took a shorter time to reach peak tumor levels and achieved a more homogeneous tumor distribution. This allows light irradiation to be initiated at a shorter time interval after the conjugate injection, and thus may facilitate clinical translation. We conclude that our targeted PDT approach provides a highly cancer-specific approach to combat chemoresistant tumors, and that the conjugates made of recombinant antibody fragments are superior to full antibody conjugates for targeted PDT.

MeSH terms

  • 3T3 Cells
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism*
  • Animals
  • Antibodies / chemistry*
  • Antibodies / therapeutic use
  • Antineoplastic Agents / chemistry*
  • Antineoplastic Agents / therapeutic use
  • Cell Survival / drug effects
  • Combined Modality Therapy / methods
  • Drug Resistance, Multiple
  • Drug Resistance, Neoplasm*
  • Female
  • Heterografts
  • Humans
  • Immunoglobulin Fab Fragments / chemistry*
  • Immunoglobulin Fab Fragments / therapeutic use
  • Mice
  • Mice, Inbred BALB C
  • Mice, Nude
  • Neoplasms / diagnostic imaging
  • Neoplasms / pathology
  • Neoplasms / therapy
  • Photochemotherapy / methods*
  • Photosensitizing Agents / chemistry
  • Photosensitizing Agents / therapeutic use
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / therapeutic use
  • Spheroids, Cellular / drug effects
  • Spheroids, Cellular / pathology
  • Tissue Distribution


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Antibodies
  • Antineoplastic Agents
  • Immunoglobulin Fab Fragments
  • Photosensitizing Agents
  • Recombinant Proteins