Background:The type I insulin-like growth factor receptor (IGF1R) is a transmembrane tyrosine kinase involved in cancer proliferation, survival, and metastasis.Methods:In this study, we used two different fluorescent technologies (small-molecule fluorophores and quantum dot (QD) nanoparticles) to detect receptor expression and its downregulation by antibodies in vivo.Results:After conjugation with AVE-1642, a humanised anti-IGF1R monoclonal antibody, both QDs (705 nm) or Alexa 680 (small-molecule fluorophore) detected expression and downregulation of IGF1R in vitro. To examine their utility in vivo, either AVE-1642 conjugates were intravenously delivered to mice bearing xenograft tumours of mouse embryo fibroblasts expressing human IGF1R or MCF-7 human breast cancer cells. Quantum dot fluorescence was mainly localised to the reticuloendothelial system in several organs and engulfed by macrophages, with only very small amount of QDs detected in the xenograft tumours. Depletion of macrophages by clodronate liposomes did not alter the nonspecific uptake of QDs. In contrast, AVE-1642-conjugated Alexa 680 solely targeted to xenograft tumour and was able to detect IGF1R downregulation, with little nonspecific targeting to other tissues or organs in mice.Conclusion:Taken together, our data suggest that small-molecule fluorophores, not QDs, are suitable to detect the expression and downregulation of IGF1R in vivo.
Bibliographical noteFunding Information:
We are grateful to James Sentementes (CRI), Drs Ilse Matise, G Eric Bauer, and Deepali Sachdev for their valuable discussion on this project. We thank Colleen Forster for technical assistance with immunofluorescent staining of liver tissue, Dr Qing Zhou for technical assistance in mice operation, Dr Renato Baserga for R cells, and Dr Deepali Sachdev for R-/IGF1R cells. We are grateful to the services from the Masonic Cancer Center Flow Cytometry Shared Resource .We would like to acknowledge the use of confocal microscope made available through an NCRR Shared Instrumentation Grant (no. 1 S10 RR16851). This study was supported by Department of Defense post-doctoral Grant BC050548 (HZ) and R01CA74285 (DY), and Cancer Center Support Grant P30 077598.
- Quantum dots
- Small-molecule fluorophore
- Tumour imaging
- Type IIGF receptor