Regulation of 18F-FDG accumulation in colorectal cancer cells with mutated KRAS

Masayoshi Iwamoto, Kenji Kawada, Yuji Nakamoto, Yoshiro Itatani, Susumu Inamoto, Kosuke Toda, Hiroyuki Kimura, Takehiko Sasazuki, Senji Shirasawa, Hiroaki Okuyama, Masahiro Inoue, Suguru Hasegawa, Kaori Togashi, Yoshiharu Sakai

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Abstract

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.

Original languageEnglish
Pages (from-to)2038-2044
Number of pages7
JournalJournal of Nuclear Medicine
Volume55
Issue number12
DOIs
Publication statusPublished - Dec 1 2014

All Science Journal Classification (ASJC) codes

  • Radiology Nuclear Medicine and imaging

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    Iwamoto, M., Kawada, K., Nakamoto, Y., Itatani, Y., Inamoto, S., Toda, K., Kimura, H., Sasazuki, T., Shirasawa, S., Okuyama, H., Inoue, M., Hasegawa, S., Togashi, K., & Sakai, Y. (2014). Regulation of 18F-FDG accumulation in colorectal cancer cells with mutated KRAS. Journal of Nuclear Medicine, 55(12), 2038-2044. https://doi.org/10.2967/jnumed.114.142927