In vitro and in vivo application of radiolabeled gastrin-releasing peptide receptor ligands in breast cance

Journal of Nuclear Medicine, 2015, Volume: 56, Issue: 5, Pages: 752-757, DOI: 10.2967/jnumed.114.153023

S. U. Dalm, J. W. M. Martens, A. M. Sieuwerts, C. H. M. van Deurzen, S. J. Koelewijn, E. de Blois, T. Maina, B. A. Nock, L. Brunel, J.-A. Fehrentz, J. Martinez, M. de Jong, M. Melis


Breast cancer (BC) consists of multiple subtypes defined by various mol. characteristics, for instance, estrogen receptor (ER) expression.  Methods for visualizing BC include mammog., MR imaging, ultrasound, and nuclear medicine-based methods such as 99mTc-sestamibi and 18F-FDG PET, unfortunately all lacking specificity.  Peptide receptor scintigraphy and peptide receptor radionuclide therapy are successfully applied for imaging and therapy of somatostatin receptor-expressing neuroendocrine tumors using somatostatin receptor radioligands.  On the basis of a similar rationale, radioligands targeting the gastrin-releasing peptide receptor (GRP-R) might offer a specific method for imaging and therapy of BC.  The aim of this study was to explore the application of GRP-R radioligands for imaging and therapy of BC by introducing valid preclin. in vitro and in vivo models.  Methods: GRP-R expression of 50 clin. BC specimens and the correlation with ER expression was studied by in vitro autoradiog. with the GRP-R agonist 111In-AMBA.  GRP-R expression was also analyzed in 9 BC cell lines applying 111In-AMBA internalization assays and quant. reverse transcriptase polymerase chain reaction.  In vitro cytotoxicity of 111Lu-AMBA was detd. on the GRP-R-expressing BC cell line T47D.  SPECT/CT imaging and biodistribution were studied in mice with s.c. and orthotopic ER-pos. T47D and MCF7 xenografts after injection of the GRP-R antagonist 111In-JMV4168.  Results: Most of the human BC specimens (96%) and BC cell lines (6/9) were found to express GRP-R.  GRP-R tumor expression was pos. (P = 0.026, Χ2(4) = 12,911) correlated with ER expression in the human BC specimens.  Treatment of T47D cells with 10-7 M/50 MBq of 111Lu-AMBA resulted in 80% redn. of cells in vitro.  Furthermore, s.c. and orthotopic tumors from both BC cell lines were successfully visualized in vivo by SPECT/CT using 111In-JMV4168; T47D tumors exhibited a higher uptake than MCF7 xenografts.  Conclusion: Targeting GRP-R-expressing BC tumors using GRP-R radioligands is promising for nuclear imaging and therapy, esp. in ER-pos. BC patients.