MUC1 and HIF-1alpha Signaling Crosstalk Induces Anabolic Glucose Metabolism to Impart Gemcitabine Resistance to Pancreatic Cancer

Metabolic Subtyping for Novel Personalized Therapies Against Pancreatic Cancer

Through metabolic subtyping, metabolic vulnerabilities can be exploited for developing efficacious treatments. A glycolytic subtype indicates poor survival in patients with pancreatic cancer, whereas a cholesterogenic subtype correlates with better outcomes potentially due to more energy expenditure. Personalized medicine holds great promise for improving therapy outcomes by optimally targeting metabolic pathways.See related article by Karasinska et al., p. 135.

Chemoresistance in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC), generally known as pancreatic cancer (PC), ranks the fourth leading cause of cancer-related deaths in the western world. While the incidence of pancreatic cancer is displaying a rising tendency every year, the mortality rate has not decreased significantly because of late diagnosis, early metastasis, and limited reaction to chemotherapy or radiotherapy. Adjuvant chemotherapy after surgical resection is typically the preferred option to treat early pancreatic cancer. Although 5-fluorouracil/leucovorin with irinotecan and oxaliplatin (FOLFIRINOX) and gemcitabine/nab-paclitaxel can profoundly improve the prognosis of advanced pancreatic cancer, the development of chemoresistance still leads to poor clinical outcomes. Chemoresistance is multifactorial as a result of the interaction among pancreatic cancer cells, cancer stem cells, and the tumor microenvironment. Nevertheless, more pancreatic cancer patients will benefit from precision treatment and targeted drugs. Therefore, we outline new perspectives for enhancing the efficacy of gemcitabine after reviewing the related factors of gemcitabine metabolism, mechanism of action, and chemoresistance.

Altered Gene Expression along the Glycolysis-Cholesterol Synthesis Axis Is Associated with Outcome in Pancreatic Cancer

PURPOSE

Identification of clinically actionable molecular subtypes of pancreatic ductal adenocarcinoma (PDAC) is key to improving patient outcome. Intertumoral metabolic heterogeneity contributes to cancer survival and the balance between distinct metabolic pathways may influence PDAC outcome. We hypothesized that PDAC can be stratified into prognostic metabolic subgroups based on alterations in the expression of genes involved in glycolysis and cholesterol synthesis.

EXPERIMENTAL DESIGN

We performed bioinformatics analysis of genomic, transcriptomic, and clinical data in an integrated cohort of 325 resectable and nonresectable PDAC. The resectable datasets included retrospective The Cancer Genome Atlas (TCGA) and the International Cancer Genome Consortium (ICGC) cohorts. The nonresectable PDAC cohort studies included prospective COMPASS, PanGen, and BC Cancer Personalized OncoGenomics program (POG).

RESULTS

On the basis of the median normalized expression of glycolytic and cholesterogenic genes, four subgroups were identified: quiescent, glycolytic, cholesterogenic, and mixed. Glycolytic tumors were associated with the shortest median survival in resectable (log-rank test P = 0.018) and metastatic settings (log-rank test P = 0.027). Patients with cholesterogenic tumors had the longest median survival. KRAS and MYC-amplified tumors had higher expression of glycolytic genes than tumors with normal or lost copies of the oncogenes (Wilcoxon rank sum test P = 0.015). Glycolytic tumors had the lowest expression of mitochondrial pyruvate carriers MPC1 and MPC2. Glycolytic and cholesterogenic gene expression correlated with the expression of prognostic PDAC subtype classifier genes.

CONCLUSIONS

Metabolic classification specific to glycolytic and cholesterogenic pathways provides novel biological insight into previously established PDAC subtypes and may help develop personalized therapies targeting unique tumor metabolic profiles.See related commentary by Mehla and Singh, p. 6.

Hexokinase 2 dimerization and interaction with voltage-dependent anion channel promoted resistance to cell apoptosis induced by gemcitabine in pancreatic cancer

Gemcitabine (GEM) is the standard chemotherapy drug for pancreatic cancer. Because of widespread drug resistance, the effect is limited. Therefore, it is urgent to reveal the underlying mechanism. Glycolysis is the most remarkable character of tumor aberrant metabolism, which plays vital roles on tumor drug resistance. Hexokinase 2 (HK2), as the key enzyme regulating the first‐step reaction of glycolysis, is overexpressed in many kinds of tumors. The putative role of HK2 resisting GEM therapy was investigated in this study. We found that HK2 was overexpressed in pancreatic cancer and associated with poor prognosis. HK2 knockdown decreased pancreatic cancer cell proliferation, migration viability, and promoted cell apoptosis in vitro. HK2 high expression in pancreatic cancer showed GEM resistance. HK2 knockdown increased the sensitivity of pancreatic cancer cell to GEM, the growth of xenograft tumor with HK2 knockdown was also further decreased with the GEM treatment compared with control in vivo. GEM‐resistant pancreatic cancer showed the increase of HK2 dimer rather than HK2 mRNA or protein. Our study revealed that the ROS derived from GEM promoted HK2 dimerization combining with voltage‐dependent anion channel, which resulted in the resistance to GEM. Meanwhile, our study established a new sight for GEM resistance in pancreatic cancer.

Pluronic block copolymers enhance the anti-myeloma activity of proteasome inhibitors

Proteasome inhibitors (PIs) have markedly improved response rates as well as the survival of multiple myeloma (MM) patients over the past decade and have become an important foundation in the treatment of MM patients. Unfortunately, the majority of patients either relapses or becomes refractory to proteasome inhibition. This report describes that both PI sensitive and resistant MM cells display enhanced sensitivity to PI in the presence of synthetic amphiphilic block copolymers, Pluronics (SP1017). SP1017 effectively overcomes both acquired resistance and tumor microenvironment-mediated resistance to PIs. The combination of bortezomib and SP1017 augments accumulation of ubiquitinated proteins, increases markers of proteotoxic and ER stress, and ultimately induces both the intrinsic and extrinsic drug-induced apoptotic pathways in MM cells. Notably, co-treatment of bortezomib and SP1017 intensifies SP1017-induced disorganization of the Golgi complex and significantly reduces secretion of paraproteins. Using a human MM/SCID mice model, the combination of bortezomib and SP1017 exerted enhanced antitumor efficacy as compared to bortezomib alone, delaying disease progression, but without additional toxicity. Collectively, these findings provide proof of concept for the utility of combining PI with SP1017 and present a new approach to enhance the efficacy of current treatment options for MM patients.

Oridonin overcomes the gemcitabine resistant PANC-1/Gem cells by regulating GST pi and LRP/1 ERK/JNK signalling

Background: Chemotherapy remains a primary treatment method for advanced pancreatic cancer. However, chemotherapy resistance can influence the therapeutic effect of pancreatic cancer. The resistance mechanism of chemotherapeutic agents such as gemcitabine, which is an agent typically used to treat pancreatic cancer, is complicated and can be influenced by genes and the environment. Oridonin is a tetracyclic diterpenoid compound extracted from the traditional Chinese herb Rabdosia labtea. Oridonin may overcome drug resistance in pancreatic cancer, but researching pancreatic cancer drug resistance of chemotherapy by oridonin is not completely understood.

Purpose: The present study aimed to assess the impact of oridonin on multidrug resistance proteins, apoptosis-associated proteins and energy metabolism in gemcitabine-resistant PANC-1 (PANC-1/Gem) pancreatic cancer cells.

Methods: Gemcitabine resistance in PANC-1/Gem cells was induced using a concentration gradient of gemcitabine. Cell Counting Kit-8 assays were used to detect the impact of gemcitabine and oridonin on the proliferation of PANC-1 and PANC-1/Gem cells. Western blot analysis and immunofluorescence were used to detect the expression of multidrug resistance proteins, apoptosis-associated proteins and low-density lipoprotein receptor protein 1 (LRP1) proteins in PANC-1/Gem cells. The effects of gemcitabine and oridonin on PANC-1/Gem cells apoptosis were detected using flow cytometry. Animal xenograft tumor assays were used to detect the effect of gemcitabine and oridonin on pancreatic cancer in vivo. Furthermore, the ATP Assay kit was used to determine the effects of gemcitabine and oridonin on ATP levels in PANC-1/Gem cells. Immunofluorescence assays were used to detect the effects of gemcitabine and oridonin on the expression of low-density lipoprotein receptor protein 1 (LRP1) in PANC-1/Gem cells. In addition, LRP1 expression was knocked down in PANC-1/Gem cells via lentiviral vector-mediated RNA silencing. Clone formation assays and Western blot analysis were used to detect the effect of LRP1 knockdown on the proliferation of PANC-1/Gem cells.

Results: The present results demonstrate that oridonin overcomes PANC-1/Gem cells gemcitabine reistance by regulating GST pi and LRP1/ERK/JNK signaling.

Conclusion: In conclusion, the present study indicated that oridonin could overcome gemcitabine resistance in PANC-1/Gem cells by regulating GST pi and LRP1/ ERK/JNK signaling, inducing cell apoptosis. Therefore, oridonin with gemcitabine may be a promising preoperative treatment for patients who suffer from pancreatic cancer.

Metabolic Regulation of Redox Balance in Cancer

Reactive oxygen species (ROS) are chemically active free radicals produced by partial reduction of oxygen that can activate discrete signaling pathways or disrupt redox homeostasis depending on their concentration. ROS interacts with biomolecules, including DNA, and can cause mutations that can transform normal cells into cancer cells. Furthermore, certain cancer-causing mutations trigger alterations in cellular metabolism that can increase ROS production, resulting in genomic instability, additional DNA mutations, and tumor evolution. To prevent excess ROS-mediated toxicity, cancer-causing mutations concurrently activate pathways that manage this oxidative burden. Hence, an understanding of the metabolic pathways that regulate ROS levels is imperative for devising therapies that target tumor cells. In this review, we summarize the dual role of metabolism as a generator and inhibitor of ROS in cancer and discuss current strategies to target the ROS axis.

Inhibition of GLS suppresses proliferation and promotes apoptosis in prostate cancer

Altered glutamine metabolism is a hallmark of cancer growth, forming the theoretical basis for development of metabolic therapies as cancer treatments. Glutaminase (GLS), a crucial enzyme involved in the regulation of glutamine metabolism, has been reported to play crucial roles in cancer development. However, the precise function of GLS in prostate cancer (PCa) remains unclear. The purpose of the present study was to assess the GLS expression and its clinical significance in PCa. We found that GLS was significantly up-regulated in PCa tissues and cell lines. High expression of GLS was significantly associated with Gleason score (P=0.001) and Tumor stage (P=0.015). Functionally, we silenced GLS in PCa cell lines and revealed that GLS knockdown largely blunted the proliferation of DU145 and PC-3 cells. Mechanistically, we demonstrated that knockdown of GLS induced apoptosis and cell cycle arrest. Moreover, we observed that the expressions of Bax were increased while the levels of cyclinD1 and Bcl-2 were decreased after knockdown of GLS in PCa cells. Importantly, through Western blot analysis, we identified that GLS knockdown dramatically suppressed Wnt/β-catenin pathway. Taken together, GLS is a novel oncogene in PCa and may be a potential treatment target for PCa patients.

Overcoming platinum-acquired resistance in ovarian cancer patient-derived xenografts

Background:

Epithelial ovarian cancer is the most lethal gynecological cancer and the high mortality is due to the frequent presentation at advanced stage, and to primary or acquired resistance to platinum-based therapy.

Methods:

We developed three new models of ovarian cancer patient-derived xenografts (ovarian PDXs) resistant to cisplatin (cDDP) after multiple in vivo drug treatments. By different and complementary approaches based on integrated metabolomics (both targeted and untargeted mass spectrometry-based techniques), gene expression, and functional assays (Seahorse technology) we analyzed and compared the tumor metabolic profile in each sensitive and their corresponding cDDP-resistant PDXs.

Results:

We found that cDDP-sensitive and -resistant PDXs have a different metabolic asset. In particular, we found, through metabolomic and gene expression approaches, that glycolysis, tricarboxylic acid cycle and urea cycle pathways were deregulated in resistant versus sensitive PDXs. In addition, we observed that oxygen consumption rate and mitochondrial respiration were higher in resistant PDXs than in sensitive PDXs under acute stress conditions. An increased oxidative phosphorylation in cDDP-resistant sublines led us to hypothesize that its interference could be of therapeutic value. Indeed, in vivo treatment of metformin and cDDP was able to partially reverse platinum resistance.

Conclusions:

Our data strongly reinforce the idea that the development of acquired cDDP resistance in ovarian cancer can bring about a rewiring of tumor metabolism, and that this might be exploited therapeutically.

P4HA1/HIF1α feedback loop drives the glycolytic and malignant phenotypes of pancreatic cancer

Hypoxia-inducible factor 1α (HIF1α) activation is profoundly implicated in the initiation and progression of multiple malignant tumors. Prolyl 4-hydroxylase subunit alpha 1 (P4HA1) is the active catalytic component of prolyl 4-hydroxylase and has been reported to promote tumor progression in several cancers. In this study, we revealed that P4HA1 was highly expressed in pancreatic ductal adenocarcinoma (PDAC) and predicted a poor clinical outcome. Notably, elevated expression of P4HA1 in PDAC cells was HIF1α-dependent. Gene set enrichment analysis of The Cancer Genome Atlas (TCGA) cohort demonstrated a close link between P4HA1 expression and glycolysis and hypoxia gene signatures in PDAC. Knockdown of P4HA1 significantly suppressed the glycolytic activity of PDAC cells as revealed by reduced glucose utilization and lactate production. Consistently, there was a close correlation between P4HA1 and glycolysis genes. Moreover, we found that P4HA1 can enhance HIF1α stability, indicating a positive feedback loop between HIF1α and P4HA1 in PDAC. Genetic silencing of P4HA1 significantly inhibited the cell proliferation, chemoresistance, and stemness of PDAC cells. Collectively, our findings identify the P4HA1-HIF1α loop as a critical regulator in glycolysis and oncogenic activities of PDAC and provide a potential target for pancreatic cancer treatment.

Identification of metabolic vulnerabilities of receptor tyrosine kinases-driven cancer

One of the biggest hurdles for the development of metabolism-targeted therapies is to identify the responsive tumor subsets. However, the metabolic vulnerabilities for most human cancers remain unclear. Establishing the link between metabolic signatures and the oncogenic alterations of receptor tyrosine kinases (RTK), the most well-defined cancer genotypes, may precisely direct metabolic intervention to a broad patient population. By integrating metabolomics and transcriptomics, we herein show that oncogenic RTK activation causes distinct metabolic preference. Specifically, EGFR activation branches glycolysis to the serine synthesis for nucleotide biosynthesis and redox homeostasis, whereas FGFR activation recycles lactate to fuel oxidative phosphorylation for energy generation. Genetic alterations of EGFR and FGFR stratify the responsive tumors to pharmacological inhibitors that target serine synthesis and lactate fluxes, respectively. Together, this study provides the molecular link between cancer genotypes and metabolic dependency, providing basis for patient stratification in metabolism-targeted therapies.

Cancer subtypes may have distinct metabolic vulnerabilities that can be exploited for therapeutic interventions. Here, the authors show that in lung cancer, genetic activation of distinct oncogenic receptor tyrosine kinases results in unique metabolic liabilities and, in particular, EGFR aberrant cancers rely on the serine biosynthetic pathway while FGFR aberrant cancers rely on glycolysis.

Evaluating the Metabolic Alterations in Pancreatic Cancer

Metabolic reprograming is an established hallmark of cancer cells. Pancreatic cancer cells, by virtue of the underlying oncogenic drivers, demonstrate metabolic reprograming to sustain growth, invasiveness, and therapy resistance. The increased demands of the growing tumor cells alter the metabolic and signaling pathways to meet the growing nutrient requirements. Investigating the metabolic vulnerabilities of tumor cells can help in developing effective therapeutics to target pancreatic cancer. In this chapter, we explain in detail the methods to evaluate the metabolic changes occurring in the tumor. This includes the glucose/glutamine uptake assays and the measurement of reactive oxygen species, extracellular acidification rate, and oxygen consumption rate in the tumor cells. All these physiological assays help in understanding the metabolic nature of the tumor.

Macrophage-Released Pyrimidines Inhibit Gemcitabine Therapy in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDA) is characterized by abundant infiltration of tumor-associated macrophages (TAMs). TAMs have been reported to drive resistance to gemcitabine, a frontline chemotherapy in PDA, though the mechanism of this resistance remains unclear. Profiling metabolite exchange, we demonstrate that macrophages programmed by PDA cells release a spectrum of pyrimidine species. These include deoxycytidine, which inhibits gemcitabine through molecular competition at the level of drug uptake and metabolism. Accordingly, genetic or pharmacological depletion of TAMs in murine models of PDA sensitizes these tumors to gemcitabine. Consistent with this, patients with low macrophage burden demonstrate superior response to gemcitabine treatment. Together, these findings provide insights into the role of macrophages in pancreatic cancer therapy and have potential to inform the design of future treatments. Additionally, we report that pyrimidine release is a general function of alternatively activated macrophage cells, suggesting an unknown physiological role of pyrimidine exchange by immune cells.

Combining Hyperpolarized Real-Time Metabolic Imaging and NMR Spectroscopy To Identify Metabolic Biomarkers in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is a deadly cancer that progresses without any symptom, and oftentimes, it is detected at an advanced stage. The lack of prior symptoms and effective treatments have created a knowledge gap in the management of this lethal disease. This issue can be addressed by developing novel noninvasive imaging-based biomarkers in PDAC. We explored in vivo hyperpolarized (HP) ¹³C MRS of pyruvate to lactate conversion and ex vivo ¹H NMR spectroscopy in a panel of well-annotated patient-derived PDAC xenograft (PDXs) model and investigated the correlation between aberrant glycolytic metabolism and aggressiveness of the tumor. Real-time metabolic imaging data demonstrate the immediate intracellular conversion of HP ¹³C pyruvate to lactate after intravenous injection interrogating upregulated lactate dehydrogenase (LDH) activity in aggressive PDXs. Total ex vivo lactate measurement by ¹H NMR spectroscopy showed a direct correlation with in vivo dynamic pyruvate-to-lactate conversion and demonstrated the potential of dynamic metabolic flux as a biomarker of total lactate concentration and aggressiveness of the tumor. Furthermore, the metabolite concentrations were very distinct among all four tumor types analyzed in this study. Overexpression of LDH-A and hypoxia-inducible factor (HIF-1α) plays a significant role in the conversion kinetics of HP pyruvate-to-lactate in tumors. Collectively, these data identified aberrant metabolic characteristics of pancreatic cancer PDXs and could potentially delineate metabolic targets for therapeutic intervention. Metabolic imaging with HP pyruvate and NMR metabolomics may enable identification and classification of aggressive subtypes of patient-derived xenografts. Translation of this real-time metabolic technique to the clinic may have the potential to improve the management of patients at high risk of developing pancreatic diseases.

Type Iγ phosphatidylinositol phosphate kinase promotes tumor growth by facilitating Warburg effect in colorectal cancer

BACKGROUND

Emerging evidence suggests that metabolic alterations are a hallmark of cancer cells and contribute to tumor initiation and development. Cancer cells primarily utilize aerobic glycolysis (the Warburg effect) to produce energy and support anabolic growth. The type Iγ phosphatidylinositol phosphate kinase (PIPKIγ) is profoundly implicated in tumorigenesis, however, little is known about its role in reprogrammed energy metabolism.

METHODS

Loss- and gain-of-function studies were applied to determine the oncogenic roles of PIPKIγ in colorectal cancer. Transcriptome analysis, real-time qPCR, immunohistochemical staining, Western blotting, and metabolic analysis were carried out to uncover the cellular mechanism of PIPKIγ.

FINDINGS

In this study, we showed that PIPKIγ was frequently upregulated in colorectal cancer and predicted a poor prognosis. Genetic silencing of pan-PIPKIγ suppressed cell proliferation and aerobic glycolysis of colorectal cancer. In contrast, the opposite effects were observed by overexpression of PIPKIγ_i2. Importantly, PIPKIγ-induced prolific effect was largely glycolysis-dependent. Mechanistically, PIPKIγ facilitated activation of PI3K/Akt/mTOR signaling pathways to upregulate c-Myc and HIF1α levels, which regulate expression of glycolytic enzymes to enhance glycolysis. Moreover, pharmacological inhibition by PIPKIγ activity with the specific inhibitor UNC3230 significantly inhibited colorectal cancer glycolysis and tumor growth.

INTERPRETATION

Our findings reveal a new regulatory role of PIPKIγ in Warburg effect and provide a key contributor in colorectal cancer metabolism with potential therapeutic potentials. FUND: National Key Research and Development Program of China, Outstanding Clinical Discipline Project of Shanghai Pudong, Natural Science Foundation of China, and Science and Technology Commission of Shanghai Municipality.

HNF1A inhibition induces the resistance of pancreatic cancer cells to gemcitabine by targeting ABCB1

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with poor prognosis, and gemcitabine-based chemotherapy remains an effective option for the majority of PDAC patients. Hepatocyte nuclear factor 1α (HNF1A) is a tumor-suppressor in PDAC, but its role in gemcitabine chemoresistance of PDAC has not been clarified.

METHODS

The function of HNF1A in gemcitabine was detected by overexpression and knockdown of HNF1A in vitro and in vitro. The regulatory network between HNF1A and ABCB1 was further demonstrated by luciferase assays, deletion/mutation reporter construct assays and CHIP assays.

FINDINGS

Here, we found that HNF1A expression is significantly associated with gemcitabine sensitivity in PDAC cell lines. Moreover, we identified that HNF1A overexpression enhanced gemcitabine sensitivity of PDAC both in vitro and in vitro, while inhibition of HNF1A had the opposite effect. Furthermore, by inhibiting and overexpressing HNF1A, we revealed that HNF1A regulates the expression of MDR genes (ABCB1 and ABCC1) in PDAC cells. Mechanistically, we demonstrated that HNF1A regulates ABCB1 expression through binding to its specific promoter region and suppressing its transcription levels. Finally, the survival analyses revealed the clinical value of HNF1A in stratification of gemcitabine sensitive pancreatic cancer patients.

INTERPRETATION

Our study paved the road for finding novel treatment combinations using conventional cytotoxic agents with functional restoration of the HNF1A protein, individualized treatment through HNF1A staining and improvement of the prognosis of PDAC patients. FUND: National Natural Science Foundations of China and National Natural Science Foundation of Guangdong Province.

The roles of glucose metabolic reprogramming in chemo- and radio-resistance

Reprogramming of cancer metabolism is a newly recognized hallmark of malignancy. The aberrant glucose metabolism is associated with dramatically increased bioenergetics, biosynthetic, and redox demands, which is vital to maintain rapid cell proliferation, tumor progression, and resistance to chemotherapy and radiation. When the glucose metabolism of cancer is rewiring, the characters of cancer will also occur corresponding changes to regulate the chemo- and radio-resistance of cancer. The procedure is involved in the alteration of many activities, such as the aberrant DNA repairing, enhanced autophagy, oxygen-deficient environment, and increasing exosomes secretions, etc. Targeting altered metabolic pathways related with the glucose metabolism has become a promising anti-cancer strategy. This review summarizes recent progress in our understanding of glucose metabolism in chemo- and radio-resistance malignancy, and highlights potential molecular targets and their inhibitors for cancer treatment.

Therapeutic targeting of glutaminolysis as an essential strategy to combat cancer

Metabolic reprogramming in cancer targets glutamine metabolism as a key mechanism to provide energy, biosynthetic precursors and redox requirements to allow the massive proliferation of tumor cells. Glutamine is also a signaling molecule involved in essential pathways regulated by oncogenes and tumor suppressor factors. Glutaminase isoenzymes are critical proteins to control glutaminolysis, a key metabolic pathway for cell proliferation and survival that directs neoplasms' fate. Adaptive glutamine metabolism can be altered by different metabolic therapies, including the use of specific allosteric inhibitors of glutaminase that can evoke synergistic effects for the therapy of cancer patients. We also review other clinical applications of in vivo assessment of glutaminolysis by metabolomic approaches, including diagnosis and monitoring of cancer.

Leflunomide Synergizes with Gemcitabine in Growth Inhibition of PC Cells and Impairs c-Myc Signaling through PIM Kinase Targeting

The immunosuppressive agent leflunomide has been used in the treatment of over 300,000 patients with rheumatoid arthritis. Its active metabolite, teriflunomide (Ter), directly inhibits dihydroorotate dehydrogenase (DHODH), an enzyme involved in nucleoside synthesis. We report that Ter not only shows in vitro anti-proliferative activity in pancreatic cancer (PC) cells as a single agent but also synergizes with the chemotherapeutic gemcitabine (Gem) in growth inhibition of PC cells. The growth-inhibitory effects of Ter are not solely caused by inhibition of DHODH. Through a kinase screening approach, we identified the PIM-3 serine-threonine kinase as a novel direct target. Subsequent dose-response kinase assays showed that Ter directly inhibited all three PIM family members, with the highest activities against PIM-3 and -1. The PIM-3 kinase was the PIM family member most often associated with PC oncogenesis and was also the kinase inhibited the most by Ter among more than 600 kinases investigated. Ter in PC cells induced changes in phosphorylation and expression of PIM downstream targets, consistent with the effects achieved by overexpression or downregulation of PIM-3. Finally, pharmacological inhibition of PIM proteins not only diminished PC cell proliferation, but also small-molecule pan-PIM and PIM-3 inhibitors synergized with Gem in growth inhibition of PC cells.

Metabolic enzyme PDK3 forms a positive feedback loop with transcription factor HSF1 to drive chemoresistance

Background & Aims: Dysregulation of metabolism plays an important role in the development and progression of cancers, while the underlying mechanisms remain largely unknown. This study aims to explore the regulation and relevance of glycolysis in chemoresistance of gastric cancer.

Methods: Biochemical differences between chemoresistant and chemosensitive cancer cells were determined by metabolism profiling, microarray gene expression, PCR or western blotting. Cancer cell growth in vitro or in vivo were analyzed by viability, apoptosis and nude mice assay. Immunoprecipation was used to explore the interaction of proteins with other proteins or DNAs.

Results: By metabolic and gene expression profiling, we found that pyruvate dehydrogenase kinase 3 (PDK3) was highly expressed to promote glycolysis in chemoresistant cancer cells. Its genetic or chemical inhibition reverted chemoresistance in vitro and in vivo. It was transcriptionally regulated by transcription factor HSF1 (Heat shock factor 1). Interestingly, PDK3 can localize in the nucleus and interact with HSF1 to disrupt its phosphorylation by GSK3β. Since HSF1 was subjected to FBXW7-catalyzed polyubiquitination in a phosphorylation-dependent manner, PDK3 prevented HSF1 from proteasomal degradation. Thus, metabolic enzyme PDK3 and transcription factor HSF1 forms a positive feedback loop to promote glycolysis. As a result, inhibition of HSF1 impaired enhanced glycolysis and reverted chemoresistance both in vitro and in vivo.

Conclusions: PDK3 forms a positive feedback loop with HSF1 to drive glycolysis in chemoresistance. Targeting this mitonuclear communication may represent a novel approach to overcome chemoresistance.

Aquaporin-3 deficiency slows cyst enlargement in experimental mouse models of autosomal dominant polycystic kidney disease

Human autosomal dominant polycystic kidney disease (ADPKD) is characterized by bilateral renal cysts that lead to a decline in kidney function. Previous studies reported aquaporin (AQP)-3 expression in cysts derived from collecting ducts in ADPKD. To study the role of AQP3 in cyst development, we generated 2 polycystic kidney disease (PKD) mouse models: kidney-specific Pkd1 knockout mice and inducible Pkd1 knockout mice, each without and with AQP3 deletion. In both models, kidney sizes and cyst indexes were significantly reduced in AQP3-null PKD mice compared with AQP3-expressing PKD mice, with the difference seen mainly in collecting duct cysts. AQP3-deficient kidneys showed significantly reduced ATP content, increased phosphorylated (p)-AMPK, and decreased p-ERK and p-mammalian target of rapamycin (mTOR). In a matrix-grown Madin-Darby canine kidney cyst model, AQP3 expression promoted cyst enlargement and was associated with increased expression of hypoxia-inducible factor 1-α and glucose transporter 1 and increased glucose uptake. Our data suggest that the slowed renal cyst enlargement in AQP3 deficiency involves impaired energy metabolism in the kidney through AMPK and mTOR signaling and impaired cellular glucose uptake. These findings implicate AQP3 as a novel determinant of renal cyst enlargement and hence a potential drug target in ADPKD.-Wang, W., Geng, X., Lei, L., Jia, Y., Li, Y., Zhou, H., Verkman, A. S., Yang, B. Aquaporin-3 deficiency slows cyst enlargement in experimental mouse models of autosomal dominant polycystic kidney disease.

LW6 enhances chemosensitivity to gemcitabine and inhibits autophagic flux in pancreatic cancer

•

LW6 inhibits proliferation and induces cell death in pancreatic cancer cells.

•

LW6 improves the anti-proliferation efficacy of gemcitabine.

•

LW6 enhances gemcitabine-induced cell death.

•

LW6 in combination with gemcitabine decreases tumor weight.

•

LW6 inhibits autophagic flux.

The efficacy of gemcitabine therapy is often insufficient for the treatment of pancreatic cancer. The current study demonstrated that LW6, a chemical inhibitor of hypoxia-inducible factor 1α, is a promising drug for enhancing the chemosensitivity to gemcitabine. LW6 monotherapy and the combination therapy of LW6 plus gemcitabine significantly inhibited cell proliferation and enhanced cell death in pancreatic cancer cells. This combination therapy also significantly reduced the tumor weight in a syngeneic orthotopic pancreatic carcinoma model without causing toxic side effects. In addition, this study provides insight into the mechanism of how LW6 interferes with the pathophysiology of pancreatic cancer. The results revealed that LW6 inhibited autophagic flux, which is defined by the accumulation of microtubule-associated protein 1 light chain 3 (LC3) and p62/SQSTM1. Moreover, these results were verified by the analysis of a tandem RFP-GFP-tagged LC3 protein. Thence, for the first time, these data demonstrate that LW6 enhances the anti-tumor effects of gemcitabine and inhibits autophagic flux. This suggests that the combination therapy of LW6 plus gemcitabine may be a novel therapeutic strategy for pancreatic cancer patients.

Mitochondrial pyruvate carrier 1 expression controls cancer epithelial-mesenchymal transition and radioresistance

Mitochondrial pyruvate carrier (MPC) is known to cause different expressions in normal and cancer cells. We observed a change in phenotype with the suppression of MPC expression. We knocked down MPC1 and/or MPC2 using siRNA or shRNA. We observed its cell morphology and accompanying molecular marker. Furthermore, the radioresistance of the MPC knockdown cell line was examined using a colony formation assay. MPC1‐suppressed cells changed their morphology to a spindle shape. Epithelial‐mesenchymal transition (EMT) was suspected, and examination of the EMT marker by PCR showed a decrease in E‐cadherin and an increase in fibronectin. Focusing on glutamine metabolism as the mechanism of this phenomenon, we knocked down the glutamine‐metabolizing enzyme glutaminase (GLS). EMT was also observed in GLS‐suppressed cells. Furthermore, when MPC1‐suppressed cells were cultured in a glutamine‐deficient medium, changes in EMT markers were suppressed. In addition, MPC1‐suppressed cells also increased with a significant difference in radioresistance. Decreased MPC1 expression favorably affects EMT and radioresistance of cancer.

PFKFB3/HIF-1α feedback loop modulates sorafenib resistance in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is a prevalent malignancy with increasing incidence and extremely poor prognosis worldwide. The multi-kinase inhibitor sorafenib is widely used as a first-line systematic treatment agent of advanced hepatocellular carcinoma. However, the benefit of sorafenib in clinical treatment is often impeded by drug resistance. Therefore, it is of critical importance to investigate the molecular mechanisms underlying sorafenib resistance in HCC. The present study shows that expression of the key glycolytic enzyme PFKFB3 is significantly up-regulated in both HCC cell lines and tissues. Thereafter, the expression of PFKFB3 was elevated in hepatocellular carcinoma cell after sorafenib treatment, which was confirmed in Gene Expression Omnibus (GEO) datasets. As predicted, the overexpression of PFKFB3 significantly enhanced HCC cells resistance to sorafenib by decreasing expression of the apoptosis-related molecules as well as apoptotic cells. Additionally, blockage of hypoxia-inducible factor-1α (HIF-1α) restricted the enhancement of PFKFB3. More interestingly, we initially found that exogenous expression of PFKFB3 significantly up-regulated the protein levels of HIF-1α in both SK-Hep-1 and SMMC-7721 cells. Further mechanistic study uncovered that HIF-1α deficiency impaired sorafenib resistance induced by PFKFB3 overexpression in HCC cells. To conclude, here we reveal a previously unrecognised positive feedback loop exists between PFKFB3 and HIF-1α and a novel HIF-1α-dependent role of PFKFB3 in regulating sorafenib resistance in HCC cells, suggesting new potential therapeutic targets for HCC treatment.

Combination of ERK and autophagy inhibition as a treatment approach for pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is characterized by KRAS- and autophagy-dependent tumorigenic growth, but the role of KRAS in supporting autophagy has not been established. We show that, to our surprise, suppression of KRAS increased autophagic flux, as did pharmacological inhibition of its effector ERK MAPK. Furthermore, we demonstrate that either KRAS suppression or ERK inhibition decreased both glycolytic and mitochondrial functions. We speculated that ERK inhibition might thus enhance PDAC dependence on autophagy, in part by impairing other KRAS- or ERK-driven metabolic processes. Accordingly, we found that the autophagy inhibitor chloroquine and genetic or pharmacologic inhibition of specific autophagy regulators synergistically enhanced the ability of ERK inhibitors to mediate antitumor activity in KRAS-driven PDAC. We conclude that combinations of pharmacologic inhibitors that concurrently block both ERK MAPK and autophagic processes that are upregulated in response to ERK inhibition may be effective treatments for PDAC.

Combating pancreatic cancer with PI3K pathway inhibitors in the era of personalised medicine

Pancreatic ductal adenocarcinoma (PDAC) is among the most deadly solid tumours. This is due to a generally late-stage diagnosis of a primarily treatment-refractory disease. Several large-scale sequencing and mass spectrometry approaches have identified key drivers of this disease and in doing so highlighted the vast heterogeneity of lower frequency mutations that make clinical trials of targeted agents in unselected patients increasingly futile. There is a clear need for improved biomarkers to guide effective targeted therapies, with biomarker-driven clinical trials for personalised medicine becoming increasingly common in several cancers. Interestingly, many of the aberrant signalling pathways in PDAC rely on downstream signal transduction through the mitogen-activated protein kinase and phosphoinositide 3-kinase (PI3K) pathways, which has led to the development of several approaches to target these key regulators, primarily as combination therapies. The following review discusses the trend of PDAC therapy towards molecular subtyping for biomarker-driven personalised therapies, highlighting the key pathways under investigation and their relationship to the PI3K pathway.

MUC1-C Integrates Chromatin Remodeling and PARP1 Activity in the DNA Damage Response of Triple-Negative Breast Cancer Cells

The oncogenic MUC1-C protein is overexpressed in triple-negative breast cancer (TNBC) cells and contributes to their epigenetic reprogramming and chemoresistance. Here we show that targeting MUC1-C genetically or pharmacologically with the GO-203 inhibitor, which blocks MUC1-C nuclear localization, induced DNA double-strand breaks and potentiated cisplatin (CDDP)-induced DNA damage and death. MUC1-C regulated nuclear localization of the polycomb group proteins BMI1 and EZH2, which formed complexes with PARP1 during the DNA damage response. Targeting MUC1-C downregulated BMI1-induced H2A ubiquitylation, EZH2-driven H3K27 trimethylation, and activation of PARP1. As a result, treatment with GO-203 synergistically sensitized both mutant and wild-type BRCA1 TNBC cells to the PARP inhibitor olaparib. These findings uncover a role for MUC1-C in the regulation of PARP1 and identify a therapeutic strategy for enhancing the effectiveness of PARP inhibitors against TNBC. SIGNIFICANCE: These findings demonstrate that targeting MUC1-C disrupts epigenetics of the PARP1 complex, inhibits PARP1 activity, and is synergistic with olaparib in TNBC cells.

Mitochondrial superoxide disrupts the metabolic and epigenetic landscape of CD4+ and CD8+ T-lymphocytes

While the role of mitochondrial metabolism in controlling T-lymphocyte activation and function is becoming more clear, the specifics of how mitochondrial redox signaling contributes to T-lymphocyte regulation remains elusive. Here, we examined the global effects of elevated mitochondrial superoxide (O₂^-) on T-lymphocyte activation using a novel model of inducible manganese superoxide dismutase (MnSOD) knock-out. Loss of MnSOD led to specific increases in mitochondrial O₂^- with no evident changes in hydrogen peroxide (H₂O₂), peroxynitrite (ONOO^-), or copper/zinc superoxide dismutase (CuZnSOD) levels. Unexpectedly, both mitochondrial and glycolytic metabolism showed significant reductions in baseline, maximal capacities, and ATP production with increased mitochondrial O₂^- levels. MnSOD knock-out T-lymphocytes demonstrated aberrant activation including widespread dysregulation in cytokine production and increased cellular apoptosis. Interestingly, an elevated proliferative signature defined by significant upregulation of cell cycle regulatory genes was also evident in MnSOD knock-out T-lymphocytes, but these cells did not show accelerated proliferative rates. Global disruption in T-lymphocyte DNA methylation and hydroxymethylation was also observed with increased mitochondrial O₂^-, which was correlated to alterations in intracellular metabolite pools linked to the methionine cycle. Together, these results demonstrate a mitochondrial redox and metabolic couple that when disrupted may alter cellular processes necessary for proper T-lymphocyte activation.

Identification of key pathways and hub genes in basal-like breast cancer using bioinformatics analysis

Background

Basal-like breast cancer (BLBC) is the most aggressive subtype of breast cancer (BC) and links to poor outcomes. As the molecular mechanism of BLBC has not yet been completely discovered, identification of key pathways and hub genes of this disease is an important way for providing new insights into exploring the mechanisms of BLBC initiation and progression.

Objective

The aim of this study was to identify potential gene signatures of the development and progression of the BLBC via bioinformatics analysis.

Methods and results

The differential expressed genes (DEGs) including 40 up-regulated and 21 down-regulated DEGs were identified between GSE25066 and GSE21422 microarrays, and these DEGs were significantly enriched in the terms related to oncogenic or suppressive roles in BLBC progression. In addition, KEGG pathway and GSEA (Gene Set Enrichment Analysis) enrichment analyses were performed for DEGs between the basal type and non-basal-type breast cancer from GSE25066 microarray. These DEGs were enriched in pathways such as cell cycle, cytokine-cytokine receptor interaction, chemokine signaling pathway, central carbon metabolism signaling and TNF signaling pathway. Moreover, the protein-protein interaction (PPI) network was constructed with those 61 DEGs using the Cytoscape software, and the biological significance of putative modules was established using MCODE. The module 1 was found to be closely related with a term of mitosis regulation and enriched in cell cycle pathway, and thus confirmed the pathological characteristic of BLBC with a high mitotic index. Furthermore, prediction values of the top 10 hub genes such as CCNB2, BUB1, NDC80, CENPE, KIF2C, TOP2A, MELK, TPX2, CKS2 and KIF20A were validated using Oncomine and Kaplan-Meier plotter.

Conclusion

Our results suggest the intriguing possibility that the hub genes and modules in the PPI network contributed to in-depth knowledge about the molecular mechanism of BLBC, paving a way for more accurate discovery of potential treatment targets for BLBC patients.

Reactivation of Dihydroorotate Dehydrogenase-Driven Pyrimidine Biosynthesis Restores Tumor Growth of Respiration-Deficient Cancer Cells

Cancer cells without mitochondrial DNA (mtDNA) do not form tumors unless they reconstitute oxidative phosphorylation (OXPHOS) by mitochondria acquired from host stroma. To understand why functional respiration is crucial for tumorigenesis, we used time-resolved analysis of tumor formation by mtDNA-depleted cells and genetic manipulations of OXPHOS. We show that pyrimidine biosynthesis dependent on respiration-linked dihydroorotate dehydrogenase (DHODH) is required to overcome cell-cycle arrest, while mitochondrial ATP generation is dispensable for tumorigenesis. Latent DHODH in mtDNA-deficient cells is fully activated with restoration of complex III/IV activity and coenzyme Q redox-cycling after mitochondrial transfer, or by introduction of an alternative oxidase. Further, deletion of DHODH interferes with tumor formation in cells with fully functional OXPHOS, while disruption of mitochondrial ATP synthase has little effect. Our results show that DHODH-driven pyrimidine biosynthesis is an essential pathway linking respiration to tumorigenesis, pointing to inhibitors of DHODH as potential anti-cancer agents.

Cytosolic 5'-nucleotidase 1A is overexpressed in pancreatic cancer and mediates gemcitabine resistance by reducing intracellular gemcitabine metabolites

BACKGROUND

Cytosolic 5'-nucleotidase 1A (NT5C1A) dephosphorylates non-cyclic nucleoside monophosphates to produce nucleosides and inorganic phosphates. Here, we investigate NT5C1A expression in pancreatic ductal adenocarcinoma (PDAC) and its impact on gemcitabine metabolism and therapeutic efficacy.

METHODS

NT5C1A expression was determined by semiquantitative immunohistochemistry using tissue microarrays. Gemcitabine metabolites and response were assessed in several human and murine PDAC cell lines using crystal violet assays, Western blot, viability assays, and liquid chromatography tandem mass-spectrometry (LC-MS/MS).

FINDINGS

NT5C1A was strongly expressed in tumor cells of a large subgroup of resected PDAC patients in two independent patient cohorts (44-56% score 2 and 8-26% score 3, n = 414). In contrast, NT5C1A was expressed at very low levels in the tumor stroma, and neither stromal nor tumoral expression was a prognostic marker for postoperative survival. In vitro, NT5C1A overexpression increased gemcitabine resistance by reducing apoptosis levels and significantly decreased intracellular amounts of cytotoxic dFdCTP in +NT5C1A tumor cells. Co-culture experiments with conditioned media from +NT5C1A PSCs improved gemcitabine efficacy in tumor cells. In vivo, therapeutic efficacy of gemcitabine was significantly decreased and serum levels of the inactive gemcitabine metabolite dFdU significantly increased in mice bearing NT5C1A overexpressing tumors.

INTERPRETATION

NT5C1A is robustly expressed in tumor cells of resected PDAC patients. Moreover, NT5C1A mediates gemcitabine resistance by decreasing the amount of intracellular dFdCTP, leading to reduced tumor cell apoptosis and larger pancreatic tumors in mice. Further studies should clarify the role of NT5C1A as novel predictor for gemcitabine treatment response in patients with PDAC.

Hypoxia-Induced Metabolomic Alterations in Pancreatic Cancer Cells

Hypoxic conditions in the pancreatic tumor microenvironment lead to the stabilization of hypoxia-inducible factor-1 alpha (HIF-1α), which acts as the master regulator of cancer cell metabolism. HIF-1α-mediated metabolic reprogramming results in large-scale metabolite perturbations. Characterization of the metabolic intermediates and the corresponding metabolic pathways altered by HIF-1α would facilitate the identification of therapeutic targets for hypoxic microenvironments prevalent in pancreatic ductal adenocarcinoma and other solid tumors. Targeted metabolomic approaches are versatile in quantifying multiple metabolite levels in a single platform and, thus, enable the characterization of multiple metabolite alterations regulated by HIF-1α. In this chapter, we describe a detailed metabolomic approach for characterizing the hypoxia-induced metabolomic alterations using pancreatic cancer cell lines cultured in normoxic and hypoxic conditions. We elaborate the methodology of cell culture, hypoxic exposure, metabolite extraction, and relative quantification of polar metabolites from normoxia- and hypoxia-exposed cell extracts, using a liquid chromatography-coupled tandem mass spectrometry approach. Herein, using our metabolomic data, we also present the methods for metabolomic data representation.

Hypoxia-Mediated In Vivo Tumor Glucose Uptake Measurement and Analysis

Most solid tumors are hypoxic in nature due to the limited supply of oxygen to internal tissues. Hypoxia plays an important role in metabolic adaptations of tumors that contribute significantly to cancer pathogenesis. Among the several metabolic alterations induced by hypoxia, hypoxia-mediated increased glucose uptake serves as the hallmark of metabolic reprogramming. Hypoxia-mediated stabilization of hypoxia-inducible factor-1 alpha (HIF-1α) transcription factor leads to altered expression of several glycolytic genes and glucose transporters, which results in increased glucose uptake by tumor cells. Here we describe an easy and simple way of measuring the hypoxia-mediated tumor glucose uptake in vivo. The method is based on fluorescent imaging probe, RediJect 2-DG, which is a nonradioactive fluorescent-tagged glucose molecule. We have discussed orthotopic tumor implantation of HIF-1α knockdown and control pancreatic cancer cells and glucose uptake measurement in vivo by using IVIS imaging system along with reagent preparations.

Molecular and Physiological Evaluation of Pancreatic Cancer-Induced Cachexia

Cachexia, a complex metabolic syndrome, is characterized by involuntary weight loss along with muscle wasting and fat depletion leading to poor quality of life of patients. About 80% of pancreatic cancer patients exhibit cachectic phenotype at the time of diagnosis. Here, we present the several molecular and physiological parameters, which we utilize to study the pancreatic cancer-induced cachexia in in vitro models and preclinical mice models of pancreatic cancer. We have described myotube and adipocyte-based in vitro models of muscle and fat wasting, including methods of cell culture, differentiation, and treatment with cancer cell-conditioned medium. Furthermore, we have explained the methods of evaluation of key cachectic markers for muscles. Next, we have detailed the orthotopic implantation mouse models of pancreatic cancer and evaluation of different physiological parameters, including body weight, food intake, body composition analysis, glucose tolerance test, insulin resistance test, grip strength measurement, and rotarod performance test. We have also explained morphological parameters and molecular markers to evaluate the muscle wasting in pancreatic cancer-induced cachexia.

NMR Metabolomics Protocols for Drug Discovery

Drug discovery is an extremely difficult and challenging endeavor with a very high failure rate. The task of identifying a drug that is safe, selective, and effective is a daunting proposition because disease biology is complex and highly variable across patients. Metabolomics enables the discovery of disease biomarkers, which provides insights into the molecular and metabolic basis of disease and may be used to assess treatment prognosis and outcome. In this regard, metabolomics has evolved to become an important component of the drug discovery process to resolve efficacy and toxicity issues and as a tool for precision medicine. A detailed description of an experimental protocol is presented that outlines the application of NMR metabolomics to the drug discovery pipeline. This includes (1) target identification by understanding the metabolic dysregulation in diseases, (2) predicting the mechanism of action of newly discovered or existing drug therapies, (3) and using metabolomics to screen a chemical lead to assess biological activity. Unlike other OMICS approaches, the metabolome is "fragile" and may be negatively impacted by improper sample collection, storage, and extraction procedures. Similarly, biologically irrelevant conclusions may result from incorrect data collection, preprocessing or processing procedures, or the erroneous use of univariate and multivariate statistical methods. These critical concerns are also addressed in the protocol.

Simultaneous isotope dilution quantification and metabolic tracing of deoxyribonucleotides by liquid chromatography high resolution mass spectrometry

Quantification of cellular deoxyribonucleoside mono- (dNMP), di- (dNDP), triphosphates (dNTPs) and related nucleoside metabolites are difficult due to their physiochemical properties and widely varying abundance. Involvement of dNTP metabolism in cellular processes including senescence and pathophysiological processes including cancer and viral infection make dNTP metabolism an important bioanalytical target. We modified a previously developed ion pairing reversed phase chromatography-mass spectrometry method for the simultaneous quantification and ¹³C isotope tracing of dNTP metabolites. dNMPs, dNDPs, and dNTPs were chromatographically resolved to avoid mis-annotation of in-source fragmentation. We used commercially available ¹³C¹⁵N-stable isotope labeled analogs as internal standards and show that this isotope dilution approach improves analytical figures of merit. At sufficiently high mass resolution achievable on an Orbitrap mass analyzer, stable isotope resolved metabolomics allows simultaneous isotope dilution quantification and ¹³C isotope tracing from major substrates including ¹³C-glucose. As a proof of principle, we quantified dNMP, dNDP and dNTP pools from multiple cell lines. We also identified isotopologue enrichment from glucose corresponding to ribose from the pentose-phosphate pathway in dNTP metabolites.

Insights into gemcitabine resistance and the potential for therapeutic monitoring

INTRODUCTION

Gemcitabine is an important component of pancreatic cancer clinical management. Unfortunately, acquired gemcitabine resistance is widespread and there are limitations to predicting and monitoring therapeutic outcomes.

OBJECTIVE

To investigate the potential of metabolomics to differentiate pancreatic cancer cells that develops resistance or respond to gemcitabine treatment.

RESULTS

We applied 1D ¹H and 2D ¹H-¹³C HSQC NMR methods to profile the metabolic signature of pancreatic cancer cells. ¹³C₆-glucose labeling identified 30 key metabolites uniquely altered between wild-type and gemcitabine-resistant cells upon gemcitabine treatment. Gemcitabine resistance was observed to reprogram glucose metabolism and to enhance the pyrimidine synthesis pathway. Myo-inositol, taurine, glycerophosphocholine and creatinine phosphate exhibited a "binary switch" in response to gemcitabine treatment and acquired resistance.

CONCLUSION

Metabolic differences between naïve and resistant pancreatic cancer cells and, accordingly, their unique responses to gemcitabine treatment were revealed, which may be useful in the clinical setting for monitoring a patient's therapeutic response.

Oncogenic KRAS supports pancreatic cancer through regulation of nucleotide synthesis

Oncogenic KRAS is the key driver of pancreatic ductal adenocarcinoma (PDAC). We previously described a role for KRAS in PDAC tumor maintenance through rewiring of cellular metabolism to support proliferation. Understanding the details of this metabolic reprogramming in human PDAC may provide novel therapeutic opportunities. Here we show that the dependence on oncogenic KRAS correlates with specific metabolic profiles that involve maintenance of nucleotide pools as key mediators of KRAS-dependence. KRAS promotes these effects by activating a MAPK-dependent signaling pathway leading to MYC upregulation and transcription of the non-oxidative pentose phosphate pathway (PPP) gene RPIA, which results in nucleotide biosynthesis. The use of MEK inhibitors recapitulates the KRAS-dependence pattern and the expected metabolic changes. Antagonizing the PPP or pyrimidine biosynthesis inhibits the growth of KRAS-resistant cells. Together, these data reveal differential metabolic rewiring between KRAS-resistant and sensitive cells, and demonstrate that targeting nucleotide metabolism can overcome resistance to KRAS/MEK inhibition.

The role of metabolic adaptation to nutrient stress in pancreatic cancer

Pancreatic cancer is the fourth most common cause of cancer-related mortality, with a dismal prognosis that has changed little over the past few decades. Despite extensive efforts in understanding the oncogenetics of this pathology, pancreatic cancer remained largely elusive. One of the main characteristics of pancreatic cancer is the reduced level of oxygen and nutrient perfusion, caused by the new matrix formation, through the activation of stromal cells (desmoplasia). This stromal reaction leads to metabolic adaptations in surviving tumor cells in order to cope with these challenging conditions. The oncogenic signaling driven by KRAS mutation is necessary to fuel pancreatic tumors by activating key metabolic processes, including enhanced glycolysis and glutamine consumption. Here we review our current understanding of the pancreatic cancer metabolism as well as discuss recent work pointing to the importance of various metabolic strategies as well as autophagy and macropinocytosis as critical nutrient supply pathways. The elucidation of these metabolic networks may highlight new opportunities to further develop novel therapeutic strategies.

The Influence of Metabolism on Drug Response in Cancer

Resistance to therapeutic agents, either intrinsic or acquired, is currently a major problem in the treatment of cancers and occurs in virtually every type of anti-cancer therapy. Therefore, understanding how resistance can be prevented, targeted and predicted becomes increasingly important to improve cancer therapy. In the last decade, it has become apparent that alterations in cellular metabolism are a hallmark of cancer cells and that a rewired metabolism is essential for rapid tumor growth and proliferation. Recently, metabolic alterations have been shown to play a role in the sensitivity of cancer cells to widely-used first-line chemotherapeutics. This suggests that metabolic pathways are important mediators of resistance toward anticancer agents. In this review, we highlight the metabolic alterations associated with resistance toward different anticancer agents and discuss how metabolism may be exploited to overcome drug resistance to classical chemotherapy.

Revisiting the role of dihydroorotate dehydrogenase as a therapeutic target for cancer

Identified as a hallmark of cancer, metabolic reprogramming allows cancer cells to rapidly proliferate, resist chemotherapies, invade, metastasize, and survive a nutrient-deprived microenvironment. Rapidly growing cells depend on sufficient concentrations of nucleotides to sustain proliferation. One enzyme essential for the de novo biosynthesis of pyrimidine-based nucleotides is dihydroorotate dehydrogenase (DHODH), a known therapeutic target for multiple diseases. Brequinar, leflunomide, and teriflunomide, all of which are potent DHODH inhibitors, have been clinically evaluated but failed to receive FDA approval for the treatment of cancer. Inhibition of DHODH depletes intracellular pyrimidine nucleotide pools and results in cell cycle arrest in S-phase, sensitization to current chemotherapies, and differentiation in neural crest cells and acute myeloid leukemia (AML). Furthermore, DHODH is a synthetic lethal susceptibility in several oncogenic backgrounds. Therefore, DHODH-targeted therapy has potential value as part of a combination therapy for the treatment of cancer. In this review, we focus on the de novo pyrimidine biosynthesis pathway as a target for cancer therapy, and in particular, DHODH. In the first part, we provide a comprehensive overview of this pathway and its regulation in cancer. We further describe the relevance of DHODH as a target for cancer therapy using bioinformatic analyses. We then explore the preclinical and clinical results of pharmacological strategies to target the de novo pyrimidine biosynthesis pathway, with an emphasis on DHODH. Finally, we discuss potential strategies to harness DHODH as a target for the treatment of cancer.

Subversion of Systemic Glucose Metabolism as a Mechanism to Support the Growth of Leukemia Cells

From an organismal perspective, cancer cell populations can be considered analogous to parasites that compete with the host for essential systemic resources such as glucose. Here, we employed leukemia models and human leukemia samples to document a form of adaptive homeostasis, where malignant cells alter systemic physiology through impairment of both host insulin sensitivity and insulin secretion to provide tumors with increased glucose. Mechanistically, tumor cells induce high-level production of IGFBP1 from adipose tissue to mediate insulin sensitivity. Further, leukemia-induced gut dysbiosis, serotonin loss, and incretin inactivation combine to suppress insulin secretion. Importantly, attenuated disease progression and prolonged survival are achieved through disruption of the leukemia-induced adaptive homeostasis. Our studies provide a paradigm for systemic management of leukemic disease.

RNA-Binding Protein HuR Regulates Both Mutant and Wild-Type IDH1 in IDH1-Mutated Cancer

Isocitrate dehydrogenase 1 (IDH1) is the most commonly mutated metabolic enzyme in human malignancy. A heterozygous genetic alteration, arginine 132, promotes the conversion of α-ketoglutarate to D-2-hydroxyglutarate (2-HG). Although pharmacologic inhibitors of mutant IDH1 are promising, resistance mechanisms to targeted therapy are not understood. Additionally, the role of wild-type IDH1 (WT.IDH1) in cancer requires further study. Recently, it was observed that the regulatory RNA-binding protein, HuR (ELAVL1), protects nutrient-deprived cancer cells without IDH1 mutations, by stabilizing WT.IDH1 transcripts. In the present study, a similar regulatory effect on both mutant (Mut.IDH1) and WT.IDH1 transcripts in heterozygous IDH1-mutant tumors is observed. In ribonucleoprotein immunoprecipitation assays of IDH1-mutant cell lines, wild-type and mutant IDH1 mRNAs each bound to HuR. Both isoforms were profoundly downregulated at the mRNA and protein levels after genetic suppression of HuR (siRNAs or CRISPR deletion) in HT1080 (R132C IDH1 mutation) and BT054 cells (R132H). Proliferation and invasion were adversely affected after HuR suppression and metabolomic studies revealed a reduction in Pentose Phosphate Pathway metabolites, nucleotide precursors, and 2-HG levels. HuR-deficient cells were especially sensitive to stress, including low glucose conditions or a mutant IDH1 inhibitor (AGI-5198). IDH1-mutant cancer cells were rescued by WT.IDH1 overexpression to a greater extent than Mut.IDH1 overexpression under these conditions. This study reveals the importance of HuR's regulation of both mutant and wild-type IDH1 in tumors harboring a heterozygous IDH1 mutation with implications for therapy. IMPLICATIONS: This study highlights the HuR-IDH1 (mutant and wild-type IDH1) regulatory axis as a critical, actionable therapeutic target in IDH1-mutated cancer, and incomplete blockade of the entire HuR-IDH1 survival axis would likely diminish the efficacy of drugs that selectively target only the mutant isoenzyme.

Role of transmembrane glycoprotein mucin 1 (MUC1) in various types of colorectal cancer and therapies: Current research status and updates

Colorectal carcinoma (CRC) is the third most common malignant tumor in the world. In recent years, the morbidity and mortality of CRC have increased in the world due to increasingly ageing population, modern dietary habits, environmental change, genetic disorders and chronic intestinal inflammation. Despite recent advances in earlier detection and improvements in chemotherapy, the 5-year survival rate of patients with metastatic CRC remains low. Therefore, novel effective treatment strategies for primary or metastatic CRC have emerged to enhance cure rate as well as elongation of patient's survival. Immunotherapy has been proposed for a potentially effective therapeutic approach to the treatment of CRC. Tumor vaccination in preclinical and clinical studies has supported the antitumor activity induced by immunization with CRC cell vaccines. Epithelial cell molecule Mucin 1 (MUC1), a transmembrane glycoprotein aberrantly overexpressed in various cancers including CRC, has been used as a candidate target antigen in the peptide, dendritic cell, and whole tumor vaccines. Several clinical trials in progress reveal the immunogenicity and suitability of MUC1 that acted as immunotherapeutic vaccines for CRC/colorectal cancer stem cells (CCSC). The present review summarizes the potential roles of MUC1 on CRC/CCSC vaccines according to the latest data. Moreover, this review also discusses the novel strategies for targeting CCSC via inducing an immune response against MUC1 to achieve the best prevention and treatment effects in animal models and clinical trails.

Hypoxia-Induced PLOD2 is a Key Regulator in Epithelial-Mesenchymal Transition and Chemoresistance in Biliary Tract Cancer

BACKGROUND

The prognosis of biliary tract cancer (BTC) is unfavorable due to its chemoresistance. Hypoxia triggers epithelial-to-mesenchymal transition (EMT), which is closely related to drug resistance. In this study, we focused on the functional roles of procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (PLOD2), a hypoxia-induced gene, in BTC, and assessed the clinical significance of PLOD2.

METHODS

The expression of PLOD2 under hypoxia was assessed in BTC cell lines. Gemcitabine-resistant (GR) BTC cell lines were transfected with small interfering RNA (siRNA) against PLOD2, and EMT markers and chemoresistance were evaluated. PLOD2 expression was also characterized using immunohistochemistry in BTC clinical specimens following resection. Patient survival was analyzed and the role of PLOD2 expression was examined.

RESULTS

The expression of PLOD2 was induced by hypoxia in vitro and was upregulated in BTC-GR cell lines, which had low expression of epithelial markers and high expression of mesenchymal markers. Downregulation of PLOD2 by siRNA resulted in improved chemoresistance, recovery of epithelial markers, and reduction of mesenchymal markers. In the resected BTC samples, PLOD2 expression was significantly correlated with lymph node metastasis (p = 0.037) and stage (p = 0.001). Recurrence-free survival (p = 0.011) and overall survival (p < 0.001) rates were significantly lower in patients with high expression of PLOD2. PLOD2 expression was an independent prognostic factor for overall survival (p = 0.019).

CONCLUSIONS

The expression of PLOD2 influenced chemoresistance through EMT, and high expression of PLOD2 was a significant unfavorable prognostic factor in BTC patients. PLOD2 might be a potential therapeutic target for overcoming chemoresistance.

miR-301a plays a pivotal role in hypoxia-induced gemcitabine resistance in pancreatic cancer

Hypoxia is a hallmark of pancreatic cancer (PC) and is associated with gemcitabine resistance. However, the mechanisms underlying hypoxia-induced gemcitabine resistance in PC remain greatly unknown. Our previous work showed that miR-301a, a hypoxia-sensitive miRNA, is involved in PC metastasis under hypoxia via regulation of its target gene P63. Here, we showed that miR-301a was upregulated in a NF-κB independent manner and promoted gemcitabine resistance under hypoxic conditions in vitro. In addition, TAp63, a member of the P63 family, reversed hypoxia-induced gemcitabine resistance by promoting degradation of HIF-1α. Furthermore, we proved that TAp63 was a functional downstream target of miR-301a and mediated the biological properties of miR-301a in PC. Taken together, these findings indicate that miR-301a exerts as a critical regulator involved in hypoxia-induced gemcitabine resistance in PC and may have potentials to be a therapeutic target for PC patients.

Metabolic Reprogramming by Dual AKT/ERK Inhibition through Imipridones Elicits Unique Vulnerabilities in Glioblastoma

Purpose: The goal of this study is to enhance the efficacy of imipridones, a novel class of AKT/ERK inhibitors that displayed limited therapeutic efficacy against glioblastoma (GBM).Experimental Design: Gene set enrichment, LC/MS, and extracellular flux analyses were used to determine the mechanism of action of novel imipridone compounds, ONC206 and ONC212. Orthotopic patient-derived xenografts were utilized to evaluate therapeutic potency.Results: Imipridones reduce the proliferation of patient-derived xenograft and stem-like glioblastoma cell cultures in vitro and in multiple xenograft models in vivo ONC212 displayed the highest potency. High levels of c-myc predict susceptibility to growth inhibition and apoptosis induction by imipridones and increased host survival in orthotopic patient-derived xenografts. As early as 1 hour, imipridones elicit on-target inhibition, followed by dephosphorylation of GSK3β at serine 9. GSK3β promotes phosphorylation of c-myc at threonine 58 and enhances its proteasomal degradation. Moreover, inhibition of c-myc by BRD4 antagonists sensitizes for imipridone-induced apoptosis in stem-like GBM cells in vitro and in vivo Imipridones affect energy metabolism by suppressing both glycolysis and oxidative phosphorylation, which is accompanied by a compensatory activation of the serine-one carbon-glycine (SOG) pathway, involving the transcription factor ATF4. Interference with the SOG pathway through novel inhibitors of PHGDH results in synergistic cell death induction in vitro and in vivo Conclusions: These results suggest that c-myc expression predicts therapeutic responses to imipridones and that imipridones lead to suppression of tumor cell energy metabolism, eliciting unique metabolic vulnerabilities that can be exploited for clinical relevant drug combination therapies. Clin Cancer Res; 24(21); 5392-406. ©2018 AACR.

Potential role of HIF-1-responsive microRNA210/HIF3 axis on gemcitabine resistance in cholangiocarcinoma cells

MicroRNA-210 (miR-210) is a robust target for hypoxia-inducible factor, and its overexpression has been detected in a variety of solid tumors. However, the role of miR-210 in the development, progression and response to therapy in cholangiocarcinoma (CCA) remains undefined. We report here that high miR-210 expression was significantly correlated with the shorter survival of CCA patients. Overexpression of miR-210 inhibited CCA cell proliferation at the G2/M phase and reduced the gemcitabine sensitivity in CCA cells under CoCl₂-induced pseudohypoxia. Concomitantly, inhibition of endogenous miR-210 activity using miRNA sponges increased cell proliferation under CoCl₂-induced pseudohypoxia, resulting in an increase in gemcitabine sensitivity in CCA cells. We showed that HIF-3α, a negative controller of HIF-1α, was a target of miR-210 constituting a feed-forward hypoxic regulatory loop. Our data suggest an important role of miR-210 in sustaining HIF-1α activity via the suppression of HIF-3α, regulating cell growth and chemotherapeutic drug resistance in CCA.