Preparation and evaluation of (68)Ga-DOTA-hEGF for visualization of EGFR expression in malignant tumors.
Detection of epidermal growth factor receptor (EGFR) overexpression in many carcinomas provides important diagnostic information, which can influence patient management. The use of PET may enable such detection in vivo by a noninvasive procedure with high sensitivity. The aim of this study was to develop a method for preparation of a positron-emitting tracer based on a natural ligand to EGFR, the recombinant human epidermal growth factor (hEGF), and to perform a preclinical evaluation of the tracer.


METHODS
DOTA-hEGF (DOTA is 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid) was prepared by coupling of a N-sulfosuccinimide ester of DOTA to hEGF. The conjugate was labeled with a generator-produced positron-emitting nuclide, (68)Ga (half-life = 68 min), using microwave heating. Binding specificity, affinity, internalization, and retention of (68)Ga-DOTA-hEGF was studied in 2 EGFR-expressing cell lines, U343 glioma cells and A431 cervical carcinoma cells. Biodistribution and microPET visualization studies were performed in BALB/c nu/nu mice bearing A431 carcinoma xenografts.


RESULTS
A 1-min-long microwave-assisted labeling provided radioactivity incorporation of 77% +/- 4%. Both cell lines demonstrated receptor-specific uptake of the conjugate, rapid internalization of the tracer, and good retention of radioactivity. Binding to both cell lines occurred with high affinity, approximately 2 nmol/L. The biodistribution study demonstrated accumulation of radioactivity in xenografts and in EGFR-expressing organs. The microPET imaging study enabled visualization of tumors and demonstrated quick--within 5 min--localization of radioactivity in tumors.


CONCLUSIONS
(68)Ga-DOTA-hEGF has potential for imaging EGFR overexpression in tumors.
Velikyan
Irina
I
Department of Organic Chemistry, Institute of Chemistry, Biomedical Centre, Uppsala University, Uppsala, Sweden.
Sundberg
Asa Liljegren
AL
Lindhe
Orjan
O
Höglund
A Urban
AU
Eriksson
Olof
O
Werner
Eva
E
Carlsson
Jorgen
J
Bergström
Mats
M
Långström
Bengt
B
Tolmachev
Vladimir
V
D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000378:metabolism*; D045744:Cell Line, Tumor; D004353:Drug Evaluation, Preclinical; D004815:Epidermal Growth Factor / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D066246:ErbB Receptors / Q000378:metabolism*; D005240:Feasibility Studies; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D005910:Glioma / Q000000981:diagnostic imaging* / Q000378:metabolism*; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D008657:Metabolic Clearance Rate; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009928:Organ Specificity; D009942:Organometallic Compounds / Q000493:pharmacokinetics*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D014018:Tissue Distribution
C507513:68Ga-DOTA-hEGF; D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; D004815:Epidermal Growth Factor; D066246:ErbB Receptors