Characterization and evaluation of two novel fluorescent sigma-2 receptor ligands as proliferation probes.
We synthesized and characterized two novel fluorescent sigma-2 receptor selective ligands, SW120 and SW116, and evaluated these ligands as potential probes for imaging cell proliferation. Both ligands are highly selective for sigma-2 receptors versus sigma-1 receptors. SW120 and SW116 were internalized into MDA-MB-435 cells, and 50% of the maximum fluorescent intensity was reached in 11 and 24 minutes, respectively. In vitro studies showed that 50% of SW120 or SW116 washed out of cells in 1 hour. The internalization of SW120 was reduced ≈30% by phenylarsine oxide, an inhibitor of endocytosis, suggesting that sigma-2 ligands are internalized, in part, by an endocytotic pathway. Subcellular localization studies using confocal and two-photon microscopy showed that SW120 and SW116 partially colocalized with fluorescent markers of mitochondria, endoplasmic reticulum, lysosomes, and the plasma membrane, suggesting that sigma-2 receptors localized to the cytoplasmic organelles and plasma membrane. SW120 did not colocalize with the nuclear dye 4',6-diamidino-2-phenylindole. In vivo studies showed that the uptake of SW120 in solid tumors and peripheral blood mononuclear cells of mice positively correlated with the expression level of the cell proliferation marker Ki-67, suggesting that sigma-2 fluorescent probes may be used to image cell proliferation in mice.
Department of Radiology, Washington University School of Medicine, St. Louis, MO, USA.
Chenbo
C
Zeng
Suwanna
S
Vangveravong
Lynne A
LA
Jones
Krzysztof
K
Hyrc
Katherine C
KC
Chang
Jinbin
J
Xu
Justin M
JM
Rothfuss
Mark P
MP
Goldberg
Richard S
RS
Hotchkiss
Robert H
RH
Mach
D000818:Animals; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D058948:Cell Tracking / Q000379:methods*; D005260:Female; D005456:Fluorescent Dyes / Q000737:chemistry* / Q000493:pharmacokinetics; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008024:Ligands; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D036641:Microscopy, Fluorescence, Multiphoton; D015336:Molecular Probe Techniques; D009374:Neoplasms, Experimental / Q000378:metabolism; D017480:Receptors, sigma / Q000378:metabolism*
D005456:Fluorescent Dyes; D008024:Ligands; D017480:Receptors, sigma; C106107:sigma-2 receptor