TY - JOUR
T1 - Localization of CaSR antagonists in CaSR-expressing medullary thyroid cancer
AU - Ding, Haiming
AU - Yusof, Adlina Mohd
AU - Kothandaraman, Shankaran
AU - Saji, Motoyasu
AU - Wang, Chaojie
AU - Kumar, Krishan
AU - Milum, Keisha
AU - Carleton, Michelle
AU - Pan, Xueliang
AU - Ringel, Matthew D.
AU - Tweedle, Michael F.
AU - Phay, John E.
PY - 2013/11/1
Y1 - 2013/11/1
N2 - Objective: Image-based localization of medullary thyroid cancer (MTC) and parathyroid glands would improve the surgical outcomes of these diseases. MTC and parathyroid glands express high levels of calcium-sensing receptor (CaSR). The aim of this study was to prove the concept that CaSR antagonists specifically localize to CaSR-expressing tumors in vivo. Design: We synthesized two isomers of a known CaSR calcilytic, Calhex 231, and four new analogs, which have a favorable structure for labeling. Their antagonistic activity was determined using immunoblots demonstrating decreased ERK1/2 phosphorylation after calcium stimulation in human embryonic kidney cells overexpressing CaSR. Compound 9 was further radiolabeled with 125I and evaluated in nude mice with and without heterotransplanted xenografts of MTC cell lines, TT and MZ-CRC-1, that do and do not express CaSR, respectively. Results: Two newly synthesized compounds, 9 and 11, exhibited better antagonistic activity than Calhex 231. The half-life of 125I-compound 9 in nude mice without xenografts was 9.9 hours. A biodistribution study in nude mice bearing both tumors demonstrated that the uptake of radioactivity in TT tumors was higher than in MZ-CRC-1 tumors at 24 hours: 0.39 ± 0.24 vs 0.18 ± 0.12 percentage of injected dose per gram of tissue (%ID/g) (P = .002), with a ratio of 2.25 ± 0.62. Tumor-to-background ratios for TT tumors, but not MZ-CRC-1 tumors, increased with time. Tumorto- blood values increased from 2.02 ± 0.52 at 1 hour to 3.29 ± 0.98 at 24 hour (P = .015) for TT tumors, and 1.7 ± 0.56 at 1 hour to 1.48 ± 0.33 at 24 hour (P = .36) for MZ-CRC-1 tumors. Conclusions:OurnewCaSRantagonists specifically inhibitCaSRfunction in vitro, preferentially localize to CaSR-expressing tumors in vivo, and therefore have the potential to serve as scaffolds for further development as imaging pharmaceuticals.
AB - Objective: Image-based localization of medullary thyroid cancer (MTC) and parathyroid glands would improve the surgical outcomes of these diseases. MTC and parathyroid glands express high levels of calcium-sensing receptor (CaSR). The aim of this study was to prove the concept that CaSR antagonists specifically localize to CaSR-expressing tumors in vivo. Design: We synthesized two isomers of a known CaSR calcilytic, Calhex 231, and four new analogs, which have a favorable structure for labeling. Their antagonistic activity was determined using immunoblots demonstrating decreased ERK1/2 phosphorylation after calcium stimulation in human embryonic kidney cells overexpressing CaSR. Compound 9 was further radiolabeled with 125I and evaluated in nude mice with and without heterotransplanted xenografts of MTC cell lines, TT and MZ-CRC-1, that do and do not express CaSR, respectively. Results: Two newly synthesized compounds, 9 and 11, exhibited better antagonistic activity than Calhex 231. The half-life of 125I-compound 9 in nude mice without xenografts was 9.9 hours. A biodistribution study in nude mice bearing both tumors demonstrated that the uptake of radioactivity in TT tumors was higher than in MZ-CRC-1 tumors at 24 hours: 0.39 ± 0.24 vs 0.18 ± 0.12 percentage of injected dose per gram of tissue (%ID/g) (P = .002), with a ratio of 2.25 ± 0.62. Tumor-to-background ratios for TT tumors, but not MZ-CRC-1 tumors, increased with time. Tumorto- blood values increased from 2.02 ± 0.52 at 1 hour to 3.29 ± 0.98 at 24 hour (P = .015) for TT tumors, and 1.7 ± 0.56 at 1 hour to 1.48 ± 0.33 at 24 hour (P = .36) for MZ-CRC-1 tumors. Conclusions:OurnewCaSRantagonists specifically inhibitCaSRfunction in vitro, preferentially localize to CaSR-expressing tumors in vivo, and therefore have the potential to serve as scaffolds for further development as imaging pharmaceuticals.
UR - http://www.scopus.com/inward/record.url?scp=84887499775&partnerID=8YFLogxK
U2 - 10.1210/jc.2013-1756
DO - 10.1210/jc.2013-1756
M3 - Article
C2 - 24030941
AN - SCOPUS:84887499775
SN - 0021-972X
VL - 98
SP - E1722-E1729
JO - Journal of Clinical Endocrinology and Metabolism
JF - Journal of Clinical Endocrinology and Metabolism
IS - 11
ER -