Assessing intratumor distribution and uptake with MBBG versus MIBG imaging and targeting xenografted PC12-pheochromocytoma cell line.
The heterogeneity of tumor uptake is likely to substantially limit the effectiveness of metaiodobenzylguanidine (MIBG) therapy. This study was done to establish whether metabromobenzylguanidine (MBBG) can target neuroendocrine tumors and to provide intratumor biodistribution and uptake information in comparison to MIBG.


METHODS
MBBG and MIBG tumor uptake and kinetic studies were performed in experimental PC-12 pheochromocytoma grown in nude mice. Intratumor distribution studies were performed using autoradiography and secondary ion mass spectrometry (SIMS) microscopy, because the latter technique can detect and potentially quantify both drugs concomitantly within the same tumor specimen.


RESULTS
MBBG uptake in PC12 tumors was early (2 hr) and intense (80% ID/g). Retention values were similar for both drugs 24 hr postinjection. At the cellular level, MBBG mostly accumulated in the cytosol. At the multicellular level, cells exhibited staining, but in many areas, SIMS images of both drugs were not spatially correlated.


CONCLUSIONS
MBBG targeted experimental pheochromocytoma efficiently with high early uptake values. Bromine-76-MBBG is a promising means of imaging and quantifying tumor uptake with PET. Both drugs were localized in the cytosol, but the correlation between the two distributions, as assessed by the values of the standardized local concentrations, was weak although significant multicellularly.
Clerc
J
J
Equipe de Microscopie Ionique, INSERM, Institut Gustave Roussy, Villejuif, France.
Mardon
K
K
Galons
H
H
Loc'h
C
C
Lumbroso
J
J
Merlet
P
P
Zhu
J
J
Jeusset
J
J
Syrota
A
A
Fragu
P
P
D019797:3-Iodobenzylguanidine; D000818:Animals; D001345:Autoradiography; D001967:Bromine Radioisotopes / Q000493:pharmacokinetics; D001969:Bromobenzenes / Q000493:pharmacokinetics; D006146:Guanidines / Q000493:pharmacokinetics; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D007462:Iodobenzenes / Q000493:pharmacokinetics; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D016716:PC12 Cells; D010673:Pheochromocytoma / Q000000981:diagnostic imaging*; D011877:Radionuclide Imaging; D051381:Rats
D001967:Bromine Radioisotopes; D001969:Bromobenzenes; D006146:Guanidines; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; C083603:3-bromobenzylguanidine; D019797:3-Iodobenzylguanidine