In Vitro and In Vivo Application of Radiolabeled Gastrin-Releasing Peptide Receptor Ligands in Breast Cancer

Abstract

Breast cancer (BC) consists of multiple subtypes defined by various molecular characteristics, for instance, estrogen receptor (ER) expression. Methods for visualizing BC include mammography, MR imaging, ultrasound, and nuclear medicine-based methods such as 99m Tcsestamibi and 18 F-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 preclinical in vitro and in vivo models. Methods: GRP-R expression of 50 clinical BC specimens and the correlation with ER expression was studied by in vitro autoradiography with the GRP-R agonist 111 In-AMBA. GRP-R expression was also analyzed in 9 BC cell lines applying 111 In-AMBA internalization assays and quantitative reverse transcriptase polymerase chain reaction. In vitro cytotoxicity of 177 Lu-AMBA was determined on the GRP-Rexpressing BC cell line T47D. SPECT/CT imaging and biodistribution were studied in mice with subcutaneous and orthotopic ER-positive T47D and MCF7 xenografts after injection of the GRP-R antagonist 111 In-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 positively (P 5 0.026, χ 2 (4) 5 12,911) correlated with ER expression in the human BC specimens. Treatment of T47D cells with 10 −7 M/50 MBq of 177 Lu-AMBA resulted in 80% reduction of cells in vitro. Furthermore, subcutaneous and orthotopic tumors from both BC cell lines were successfully visualized in vivo by SPECT/CT using 111 In-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, especially in ER-positive BC patients.

Clinical Relevance of Targeting the Gastrin-Releasing Peptide Receptor, Somatostatin Receptor 2, or Chemokine C-X-C Motif Receptor 4 in Breast Cancer for Imaging and Therapy

“…Results showed that high-density GRPR expression was observed in 50 of 77 tumors, compared with 14 of 77 tumors with high-density SSTR2 expression. Similarly, in our previous work we found homogeneous GRPR expression in 56% of the breast cancer specimens analyzed (30), whereas homogeneous SSTR2 expression was seen in 29% only (SU Dalm, CHM van Deurzen, M Melis, M de Jong, unpublished data, 2014).…”

Bombesin related peptides/receptors and their promising therapeutic roles in cancer imaging, targeting and treatment

“…In breast-cancers, 38–96% possess GRPR and 0–50% NMBR,BRS-3[23,26, 111•,112,113]]. A number of studies report GRPR-activation stimulates breast-cancer cell-lines, the migration of tumor in vitr o cells[114]; their growth: and that GRPR-overexpression enhances cell-invasiveness[113].…”

“…In breast-cancers the expression of GRPR correlates positively(p=0.026) with estrogen-receptor-expression[111•]. …”

177Lu-Dendrimer Conjugated to Folate and Bombesin with Gold Nanoparticles in the Dendritic Cavity: A Potential Theranostic Radiopharmaceutical

“…Clinical studies 2 Journal of Nanomaterials in women using radio-bombesin derivatives have shown successful radionuclide imaging of breast tumors [7][8][9][10]. In particular, the GRPR is highly expressed in T47D human breast cells, and that is the reason why these cells have been used as tumor models to evaluate new bombesin probes [6,[11][12][13].…”

“…Overexpression of gastrin-releasing peptide receptors (GRPR) is present in 96% of breast cancer tissues [6]. Different bombesin analogues with high affinity for GRPR have been evaluated in preclinical studies for receptor-specific imaging and therapy [5].…”