Development of a calcium-sensing receptor molecular imaging agent.
BACKGROUND
Calcium-sensing receptor (CaSR) is expressed by parathyroid cells and thyroid C-cells (from which medullary thyroid carcinoma [MTC] is derived). A molecular imaging agent localizing to the CaSR could improve the detection of parathyroids and MTC preoperatively or intraoperatively. We synthesized a novel compound containing a fluorine residue for potential future labeling and demonstrated that the compound inhibited CaSR function in vitro.


METHODS
We synthesized compound M, a derivative of a known calcilytic compound, Calhex-231. Human embryonic kidney cells transfected with green-fluorescent protein-tagged CaSR or control vector were preincubated with compound M before the addition of calcium. Immunoblotting for total mitogen-activated protein kinase (MAPK: ERK1/2), activated MAPK (phosphorylated ERK1/2), and glyceraldehyde 3-phosphate dehydrogenase was performed.


RESULTS
Synthesis of compound M was confirmed by mass spectrometry. Inhibition of the MAPK signaling pathway by compound M was demonstrated in a dose-dependent manner by a decrease in phosphorylated ERK1/2 with no change in total ERK1/2 levels. Compound M inhibited MAPK signaling slightly better than the parent compound.


CONCLUSIONS
We have developed a novel molecule which demonstrates functional inhibition of CaSR and has a favorable structure for labeling. This compound appears to be appropriate for further development as a molecular imaging tool to enhance the surgical treatment of parathyroid disease and MTC.
Department of Surgery, The Ohio State University, Columbus, OH.
Adlina Mohd
AM
Yusof
Shankaran
S
Kothandaraman
Xiaoli
X
Zhang
Motoyasu
M
Saji
Matthew D
MD
Ringel
Michael F
MF
Tweedle
John E
JE
Phay
D001549:Benzamides / Q000138:chemical synthesis / Q000737:chemistry; D018276:Carcinoma, Medullary / Q000378:metabolism / Q000473:pathology / Q000601:surgery; D018278:Carcinoma, Neuroendocrine; D003514:Cyclohexylamines / Q000138:chemical synthesis / Q000737:chemistry; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D020935:MAP Kinase Signaling System; D013058:Mass Spectrometry; D057054:Molecular Imaging / Q000379:methods*; D010280:Parathyroid Glands / Q000378:metabolism* / Q000473:pathology; D044169:Receptors, Calcium-Sensing / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000601:surgery
D001549:Benzamides; C095550:CASR protein, human; D003514:Cyclohexylamines; C482333:N(1)-(4-chlorobenzoyl)-N(2)-(1-(1-naphthyl)ethyl)-1,2-diaminocyclohexane; D044169:Receptors, Calcium-Sensing; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins