FBW7 (F-box and WD Repeat Domain-Containing 7) Negatively Regulates Glucose Metabolism by Targeting the c-Myc/TXNIP (Thioredoxin-Binding Protein) Axis in Pancreatic Cancer

Abstract Purpose: FBW7 functions as a tumor suppressor by targeting oncoproteins for destruction. We previously reported that the oncogenic mutation of KRAS inhibits the tumor suppressor FBW7 via the Ras–Raf–MEK–ERK pathway, which facilitates the proliferation and survival of pancreatic cancer cells. However, the underlying mechanism by which FBW7 suppresses pancreatic cancer remains unexplored. Here, we sought to elucidate the function of FBW7 in pancreatic cancer glucose metabolism and malignancy. Experimental Design: Combining maximum standardized uptake value (SUVmax), which was obtained preoperatively via a PET/CT scan, with immunohistochemistry staining, we analyzed the correlation between SUVmax and FBW7 expression in pancreatic cancer tissues. The impact of FBW7 on glucose metabolism was further validated in vitro and in vivo. Finally, gene expression profiling was performed to identify core signaling pathways. Results: The expression level of FBW7 was negatively associated with SUVmax in pancreatic cancer patients. FBW7 significantly suppressed glucose metabolism in pancreatic cancer cells in vitro. Using a xenograft model, MicroPET/CT imaging results indicated that FBW7 substantially decreased 18F-fluorodeoxyglucose (18F-FDG) uptake in xenograft tumors. Gene expression profiling data revealed that TXNIP, a negative regulator of metabolic transformation, was a downstream target of FBW7. Mechanistically, we demonstrated that TXNIP was a c-Myc target gene and that FBW7 regulated TXNIP expression in a c-Myc–dependent manner. Conclusions: Our results thus reveal that FBW7 serves as a negative regulator of glucose metabolism through regulation of the c-Myc/TXNIP axis in pancreatic cancer. Clin Cancer Res; 22(15); 3950–60. ©2016 AACR.