TY - JOUR T1 - Regulation of <sup>18</sup>F-FDG Accumulation in Colorectal Cancer Cells with Mutated <em>KRAS</em> JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 2038 LP - 2044 DO - 10.2967/jnumed.114.142927 VL - 55 IS - 12 AU - Masayoshi Iwamoto AU - Kenji Kawada AU - Yuji Nakamoto AU - Yoshiro Itatani AU - Susumu Inamoto AU - Kosuke Toda AU - Hiroyuki Kimura AU - Takehiko Sasazuki AU - Senji Shirasawa AU - Hiroaki Okuyama AU - Masahiro Inoue AU - Suguru Hasegawa AU - Kaori Togashi AU - Yoshiharu Sakai Y1 - 2014/12/01 UR - http://jnm.snmjournals.org/content/55/12/2038.abstract N2 - KRAS gene mutations occur in approximately 40% of colorectal cancers (CRCs) and are associated with resistance to anti–epidermal growth factor receptor antibody therapy. We previously demonstrated that 18F-FDG accumulation in PET was significantly higher in CRCs with mutated KRAS than in those with wild-type KRAS in a clinical setting. Here, we investigated the mechanisms by which mutated KRAS increased 18F-FDG accumulation. Methods: Using paired isogenic human CRC cell lines that differ only in the mutational status of the KRAS gene, we measured 18F-FDG accumulation in these cells in vitro and in vivo. We also investigated the roles of proteins that have a function in 18F-FDG accumulation. Finally, we examined the relationship among mutated KRAS, hypoxia-inducible factor 1α (HIF-1α), and maximum standardized uptake value with 51 clinical CRC samples. Results: In the in vitro experiments, 18F-FDG accumulation was significantly higher in KRAS-mutant cells than in wild-type controls under normoxic conditions. The expression levels of glucose transporter 1 (GLUT1) and hexokinase type 2 (HK2) were higher in KRAS-mutant cells, and 18F-FDG accumulation was decreased by knockdown of GLUT1. Hypoxic induction of HIF-1α was higher in KRAS-mutant cells than in wild-type controls; in turn, elevated HIF-1α resulted in higher GLUT1 expression and 18F-FDG accumulation. In addition, HIF-1α knockdown decreased 18F-FDG accumulation under hypoxic conditions only in the KRAS-mutant cells. Small-animal PET scans showed in vivo 18F-FDG accumulation to be significantly higher in xenografts with mutated KRAS than in those with wild-type KRAS. The immunohistochemistry of these xenograft tumors showed that staining of GLUT1 was consistent with that of HIF-1α and pimonidazole. In a retrospective analysis of clinical samples, KRAS mutation exhibited a significantly positive correlation with expressions of GLUT1 and HIF-1α and with maximum standardized uptake value. Conclusion: Mutated KRAS caused higher 18F-FDG accumulation possibly by upregulation of GLUT1; moreover, HIF-1α additively increased 18F-FDG accumulation in hypoxic lesions. 18F-FDG PET might be useful for predicting the KRAS status noninvasively. ER -