F-box and WD repeat domain-containing 7 (FBW7) is the substrate recognition component of the Skp1-Cul1-F-box (SCF) ubiquitin ligase complex and functions as a major tumor suppressor by targeting various oncoproteins for degradation. Genomic deletion or mutation of FBW7 has frequently been identified in many human cancers but not in pancreatic ductal adenocarcinoma. Thus it is important to know how the tumor suppressive function of FBW7 is impaired in pancreatic cancer. In this study, we first observed that low FBW7 expression correlated significantly with ERK activation in pancreatic cancer clinical samples, primarily due to KRAS mutations in pancreatic cancer. We further showed that ERK directly interacted with FBW7 and phosphorylated FBW7 at Thr205, which sequentially promoted FBW7 ubiquitination and proteasomal degradation. Furthermore, the phospho-deficient T205A FBW7 mutant is resistant to ERK activation and could significantly suppress pancreatic cancer cell proliferation and tumorigenesis. These results collectively demonstrate how the oncogenic KRAS mutation inhibits the tumor suppressor FBW7, thus revealing an important function of KRAS mutations in promoting pancreatic cancer progression.

FBW7 functions as a tumor suppressor by targeting oncoproteins for degradation. Our previous study found FBW7 was low expressed in pancreatic cancer due to sustained activation of Ras-Raf-MEK-ERK pathway, which destabilized FBW7 by phosphorylating at Thr205. MicroPET/CT imaging results revealed that FBW7 substantially decreased 18F-fluorodeoxyglucose uptake in xenograft tumors. Mechanistically, FBW7 inhibited glucose metabolism via c-Myc/TXNIP axis. But in these studies, we observed FBW7 down-regulated genes were widely involved in redox reaction and lipid metabolism. Here we reanalyzed previous gene expression profiling and conducted targeted cell metabolites analysis. Results revealed that FBW7 regulated lipid peroxidation and promoted ferroptosis, a non-apoptotic form of cell death. Mechanistically, we found FBW7 inhibited the expression of stearoyl-CoA desaturase (SCD1) via inhibiting nuclear receptor subfamily 4 group A member 1 (NR4A1). SCD1 was reported to inhibit both ferroptosis and apoptosis, which was consistent with the function of FBW7 and NR4A1, another FBW7 down-regulated gene in the gene expression profiling. Moreover, FBW7 potentiated cytotoxic effect of gemcitabine via activating ferroptosis and apoptosis. Combination ferroptosis inducers and apoptosis activators could also significantly potentiated cytotoxic effect of gemcitabine in pancreatic cancer. Therefore, our findings might provide new strategies for the comprehensive treatment of pancreatic cancer.

Long non-coding RNAs (lncRNAs) are frequently dysregulated in multiple malignancies, demonstrating their potential oncogenic or tumor-suppressive roles in tumorigenesis. Herein, we reported the identification of a novel lncRNA, linc00665 (ENST00000590622), which was markedly upregulated in lung adenocarcinoma (LUAD) tissues and might serve as an independent predictor for poor prognosis. Functional assays indicated that linc00665 reinforced LUAD cell proliferation and metastasis in vitro and in vivo. Mechanistically, transcription factor SP1 induced the transcription of linc00665 in LUAD cells, which exerted its oncogenic role by functioning as competing endogenous RNA (ceRNA) for miR-98 and subsequently activating downstream AKR1B10-ERK signaling pathway. Together, our study elucidates oncogenic roles of linc00665–miR98–AKR1B10 axis in LUAD tumorigenesis, which may serve as potential diagnostic biomarkers and therapeutic targets.

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Pancreatic ductal adenocarcinoma (PDAC) is among the most devastating human malignancies. The poor clinical outcome in PDAC is partly attributed to a growth-permissive tumor microenvironment. In the PDAC microenvironment, the stroma is characterized by the development of extensive fibrosis, with stromal components outnumbering pancreatic cancer cells. Each of the components within the stroma has a distinct role in conferring chemoresistance to PDAC, and intrinsic chemoresistance has further worsened this pessimistic prognosis. The nucleoside analog gemcitabine (GEM) is usually the recommended first-line chemotherapeutic agent for PDAC patients and is given alone or in combination with other agents. The mechanisms of intrinsic resistance to GEM are an active area of ongoing research. This review highlights the important role the complex structure of stroma in PDAC plays in the intrinsic resistance to GEM and discusses whether antistroma therapy improves the efficacy of GEM. The addition of antistroma therapy combined with GEM is expected to be a novel therapeutic strategy with significant survival benefits for PDAC patients.

ObjectivePancreatic ductal adenocarcinoma (PDAC) is the most aggressive type of GI tumour, and it possesses deregulated cellular energetics. Although recent advances in PDAC biology have led to the discovery of recurrent genetic mutations in Kras, TP53 and SMAD4, which are related to this disease, clinical application of the molecular phenotype of PDAC remains challenging.DesignWe combined molecular imaging technology (positron emission tomography/CT) and immunohistochemistry to evaluate the correlation between the maximum standardised uptake value and SMAD4 expression and examined the effect of SMAD4 on glycolysis through in vitro and in vivo experiments. Furthermore, we identified the effect of SMAD4 on metabolic reprogramming by metabolomics and glucose metabolism gene expression analyses. Dual luciferase reporter assays and chromatin immunoprecipitation were performed to identify whether SMAD4 functioned as a transcription factor for phosphoglycerate kinase 1 (PGK1) in PDAC cells. Proliferative and metastatic assays were performed to examine the effect of PGK1 on the malignant behaviour of PDAC.ResultsWe provide compelling evidence that the glycolytic enzyme PGK1 is repressed by transforming growth factor-β/SMAD4. Loss of SMAD4 induces PGK1 upregulation in PDAC, which enhances glycolysis and aggressive tumour behaviour. Notably, in SMAD4-negative PDAC, nuclear PGK1 preferentially drives cell metastasis via mitochondrial oxidative phosphorylation induction, whereas cytoplasmic PGK1 preferentially supports proliferation by functioning as a glycolytic enzyme. The PDAC progression pattern and distinct PGK1 localisation combine to predict overall survival and disease-free survival.ConclusionPGK1 is a decisive oncogene in patients with SMAD4-negative PDAC and can be a target for the development of a therapeutic strategy for SMAD4-negative PDAC.

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Background The epigenetic factor protein arginine methyltransferase 5 (PRMT5) has been reported to play vital roles in a wide range of cellular processes, such as gene transcription, genomic organization, differentiation and cell cycle control. However, its role in pancreatic cancer remains unclear. Our study aimed to investigate the roles of PRMT5 in pancreatic cancer prognosis and progression and to explore the underlying molecular mechanism. Methods Real-time PCR, immunohistochemistry and analysis of a dataset from The Cancer Genome Atlas (TCGA) were performed to study the expression of PRMT5 at the mRNA and protein levels in pancreatic cancer. Cell proliferation assays, including cell viability, colony formation ability and subcutaneous mouse model assays, were utilized to confirm the role of PRMT5 in cell proliferation and tumorigenesis. A Seahorse extracellular flux analyzer, a glucose uptake kit, a lactate level measurement kit and the measurement of 18 F-FDG (fluorodeoxyglucose) uptake by PET/CT (positron emission tomography/computed tomography) imaging were used to verify the role of PRMT5 in aerobic glycolysis, which sustains cell proliferation. The regulatory effect of PRMT5 on cMyc, a master regulator of oncogenesis and aerobic glycolysis, was explored by quantitative PCR and protein stability measurements. Results PRMT5 expression was significantly upregulated in pancreatic cancer tissues compared with that in adjacent normal tissues. Clinically, elevated expression of PRMT5 was positively correlated with worse overall survival in pancreatic cancer patients. Silencing PRMT5 expression inhibited the proliferation of pancreatic cancer cells both in vitro and in vivo. Moreover, PRMT5 regulated aerobic glycolysis in vitro in cell lines, in vivo in pancreatic cancer patients and in a xenograft mouse model used to measure 18F-FDG uptake. We found that mechanistically, PRMT5 posttranslationally regulated cMyc stability via F-box/WD repeat-containing protein 7 (FBW7), an E3 ubiquitin ligase that controls cMyc degradation. Moreover, PRMT5 epigenetically regulated the expression of FBW7 in pancreatic cancer cells. Conclusions The present study demonstrated that PRMT5 epigenetically silenced the expression of the tumor suppressor FBW7, leading to increased cMyc levels and the subsequent enhancement of the proliferation of and aerobic glycolysis in pancreatic cancer cells. The PRMT5/FBW7/cMyc axis could be a potential therapeutic target for the treatment of pancreatic cancer. Electronic supplementary material The online version of this article (10.1186/s12964-019-0344-4) contains supplementary material, which is available to authorized users.