TY - JOUR T1 - Regulation of Uptake of <sup>18</sup>F-FDG by a Follicular Human Thyroid Cancer Cell Line with Mutation-Activated K-Ras JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1364 LP - 1370 DO - 10.2967/jnumed.109.062331 VL - 50 IS - 8 AU - Olaf Prante AU - Simone Maschauer AU - Valerie Fremont AU - Julia Reinfelder AU - Robert Stoehr AU - Mariusz Szkudlinski AU - Bruce Weintraub AU - Arndt Hartmann AU - Torsten Kuwert Y1 - 2009/08/01 UR - http://jnm.snmjournals.org/content/50/8/1364.abstract N2 - Dedifferentiation of thyroid carcinoma is accompanied by increased accumulation of the PET tracer 18F-FDG. The molecular mechanisms responsible for this phenomenon are poorly understood. Therefore, we studied the regulation of 18F-FDG uptake by the human follicular thyroid carcinoma cell line ML-1 and the as-yet-unknown oncogene expression of that cell line. The data obtained in ML-1 were compared with those of a well-differentiated thyroid cell line of rat origin (FRTL-5). Methods: The expression of the thyroid-stimulating hormone (TSH) receptor was investigated by immunocytochemistry, and the expression of the glucose transporters (GLUTs) was determined by Western blotting. Mutation analysis of ML-1 was performed for K-ras codons 12 and 13. The effect of TSH on intracellular cAMP levels was determined by a competitive enzyme immunoassay. Cells were incubated with 18F-FDG (0.5–1.0 MBq/mL) for 1 h, and tracer uptake was related to protein concentration. The effects of bovine TSH, the cAMP analog (Bu)2cAMP, and the phosphatidylinositol-3-kinase (PI3-kinase) inhibitor LY294002 on 18F-FDG uptake were investigated. Results: The TSH receptor was present in both cell lines. FRTL-5 clearly expressed GLUT-1 and also GLUT-4. In ML-1 only, the expression of GLUT-3 was detected. TSH and (Bu)2cAMP had a significant effect on 18F-FDG uptake or GLUT-1 expression in FRTL-5, but not in ML-1 cells. PI3-kinase inhibition by LY294002 downregulated 18F-FDG uptake in FRTL-5 by 58% ± 9% (n = 6) and in ML-1 by 26% ± 5% (n = 42, both P &lt; 0.05). Mutation analysis of ML-1 cells revealed a Gly12Ser point mutation at codon 12 of the K-ras gene. Conclusion: 18F-FDG uptake in the thyroid carcinoma cell line ML-1 is no longer regulated by TSH or cAMP or mediated by GLUT-1. However, in this cell line, this variable is still governed to some extent by PI3-kinase located downstream to the constitutively active K-ras in the Ras-PI3-kinase-Akt pathway. These data suggest that increases in 18F-FDG uptake in thyroid carcinomas observed in vivo by PET may reflect activation of intracellular signal transduction cascades by oncogenes. ER -