Cellular metabolic responses of PET radiotracers to (188)Re radiation in an MCF7 cell line containing dominant-negative mutant p53.
We investigated the relations between the cell uptakes of metabolic radiotracers and beta-radiation pretreatment using a dominant mutant p53 (p53mt) cell line to evaluate the effects of p53 genes on (18)F labeled positron emission tomography (PET) radiotracer uptakes.


METHODS
pCMV-Neo-Bam (control), which contains a neo-resistance marker, and p53 dominant-negative mutant expression constructs were stably transfected into MCF7 cell line. Cells were plated in 24-well plates at 1.0x10(5) cells for 18 h. Rhenium-188 ((188)Re) (a beta emitter) was added to the medium (3.7, 18.5, 37 MBq) and incubated for 24 h. We performed gamma-counting to determine the cellular uptakes of 2-[(18)F]fluoro-2-deoxy-d-glucose (FDG), o-(2-[(18)F]fluoroethyl)-l-tyrosine (FET) and 2'-[(18)F]fluoro-2'-deoxythymidine (FLT) (370 kBq, 60 min). Cell viabilities were determined by trypan blue staining and flow cytometry.


RESULTS
p53mt cells showed 1.5-2-fold higher FDG uptake than wild-type p53 cells in basal condition, and the difference of FDG uptake was greater after (188)Re treatment (P<.01). FET uptake increased with (188)Re dose without a significant difference between p53 statuses. p53mt cells showed lower FLT uptake than wild-type p53 cells in basal condition, and the difference of FLT uptake was greater after (188)Re treatment. By cell viability testing and FACS analysis, p53mt cells showed lower viability and a larger apoptotic fraction (sub-G1) than wild-type p53 cells after (188)Re treatment.


CONCLUSIONS
We speculate that p53 dysfunction increases glucose and decreases thymidine metabolism in cancer cells and that this may be exaggerated by (188)Re beta-radiation. Our findings suggest that FDG could reflect tumor viability and malignant potential after (188)Re beta-radiation treatment, whereas FLT could be a more useful PET radiotracer for assessing therapeutic response to beta-radiation, especially in cancer cells with an altered function of p53.
Cheon
Gi Jeong
GJ
Laboratory of Nuclear Medicine Research, Korea Institute of Radiological and Medical Sciences, Seoul 139-706, South Korea. larry@kcch.re.kr
Chung
Hye-Kyung
HK
Choi
Jung-A
JA
Lee
Su-Jae
SJ
Ahn
Soon-Hyuk
SH
Lee
Tae-Sup
TS
Choi
Chang Woon
CW
Lim
Sang Moo
SM
D000596:Amino Acids / Q000096:biosynthesis; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D001610:Beta Particles; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002477:Cells / Q000378:metabolism* / Q000528:radiation effects*; D004247:DNA / Q000096:biosynthesis; D005434:Flow Cytometry; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics / Q000494:pharmacology; D016158:Genes, p53 / Q000235:genetics*; D005947:Glucose / Q000096:biosynthesis; D006593:Hexokinase / Q000378:metabolism; D006801:Humans; D049268:Positron-Emission Tomography; D011868:Radioisotopes; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D012211:Rhenium; D014162:Transfection
D000596:Amino Acids; D011868:Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D012211:Rhenium; D004247:DNA; D006593:Hexokinase; D005947:Glucose