Gemcitabine diphosphate choline is a major metabolite linked to the Kennedy pathway in pancreatic cancer models in vivo

Tumor metabolic alterations after neoadjuvant chemoradiotherapy predict postoperative recurrence in patients with pancreatic cancer

OBJECTIVE

We investigated the metabolic changes in pancreatic ductal adenocarcinoma to identify the mechanisms of treatment response of neoadjuvant chemoradiation therapy.

METHODS

Frozen tumor and non-neoplastic pancreas tissues were prospectively obtained from 88 patients with pancreatic ductal adenocarcinoma who underwent curative-intent surgery. Sixty-two patients received neoadjuvant chemoradiation therapy and 26 patients did not receive neoadjuvant therapy (control group). Comprehensive analysis of metabolites in tumor and non-neoplastic pancreatic tissue was performed by capillary electrophoresis-mass spectrometry.

RESULTS

Capillary electrophoresis-mass spectrometry detected 90 metabolites for analysis among more than 500 ionic metabolites quantified. There were significant differences in 27 tumor metabolites between the neoadjuvant chemoradiation therapy and control groups. There were significant differences in eight metabolites [1-MethylnNicotinamide, Carnitine, Glucose, Glutathione (red), N-acetylglucosamine 6-phosphate, N-acetylglucosamine 1-phosphate, UMP, Phosphocholine] between good responder and poor responder for neoadjuvant chemoradiation therapy. Among these metabolites, phosphocholine, Carnitine and Glutathione were associated with recurrence-free survival only in the neoadjuvant chemoradiation therapy group. Microarray confirmed marked gene suppression of choline transporters [CTL1-4 (SLC44A1-44A4)] in pancreatic ductal adenocarcinoma tissue of neoadjuvant chemoradiation therapy group.

CONCLUSION

The present study identifies several important metabolic consequences and potential neoadjuvant chemoradiation therapy targets in pancreatic ductal adenocarcinoma. Choline metabolism is one of the key pathways involved in recurrence of the patients with pancreatic ductal adenocarcinoma who received neoadjuvant chemoradiation therapy.

Suppression of Endothelial Cell FAK Expression Reduces Pancreatic Ductal Adenocarcinoma Metastasis after Gemcitabine Treatment

Despite substantial advances in the treatment of solid cancers, resistance to therapy remains a major obstacle to prolonged progression-free survival. Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers, with a high level of liver metastasis. Primary PDAC is highly hypoxic, and metastases are resistant to first-line treatment, including gemcitabine. Recent studies have indicated that endothelial cell (EC) focal adhesion kinase (FAK) regulates DNA-damaging therapy-induced angiocrine factors and chemosensitivity in primary tumor models. Here, we show that inducible loss of EC-FAK in both orthotopic and spontaneous mouse models of PDAC is not sufficient to affect primary tumor growth but reduces liver and lung metastasis load and improves survival rates in gemcitabine-treated, but not untreated, mice. EC-FAK loss did not affect primary tumor angiogenesis, tumor blood vessel leakage, or early events in metastasis, including the numbers of circulating tumor cells, tumor cell homing, or metastatic seeding. Phosphoproteomics analysis showed a downregulation of the MAPK, RAF, and PAK signaling pathways in gemcitabine-treated FAK-depleted ECs compared with gemcitabine-treated wild-type ECs. Moreover, low levels of EC-FAK correlated with increased survival and reduced relapse in gemcitabine-treated patients with PDAC, supporting the clinical relevance of these findings. Altogether, we have identified a new role of EC-FAK in regulating PDAC metastasis upon gemcitabine treatment that impacts outcome.

SIGNIFICANCE

These findings establish the potential utility of combinatorial endothelial cell FAK targeting together with gemcitabine in future clinical applications to control metastasis in patients with pancreatic ductal adenocarcinoma.

Method To Visualize the Intratumor Distribution and Impact of Gemcitabine in Pancreatic Ductal Adenocarcinoma by Multimodal Imaging

Gemcitabine (dFdC) is a common treatment for pancreatic cancer; however, it is thought that treatment may fail because tumor stroma prevents drug distribution to tumor cells. Gemcitabine is a pro-drug with active metabolites generated intracellularly; therefore, visualizing the distribution of parent drug as well as its metabolites is important. A multimodal imaging approach was developed using spatially coregistered mass spectrometry imaging (MSI), imaging mass cytometry (IMC), multiplex immunofluorescence microscopy (mIF), and hematoxylin and eosin (H&E) staining to assess the local distribution and metabolism of gemcitabine in tumors from a genetically engineered mouse model of pancreatic cancer (KPC) allowing for comparisons between effects in the tumor tissue and its microenvironment. Mass spectrometry imaging (MSI) enabled the visualization of the distribution of gemcitabine (100 mg/kg), its phosphorylated metabolites dFdCMP, dFdCDP and dFdCTP, and the inactive metabolite dFdU. Distribution was compared to small-molecule ATR inhibitor AZD6738 (25 mg/kg), which was codosed. Gemcitabine metabolites showed heterogeneous distribution within the tumor, which was different from the parent compound. The highest abundance of dFdCMP, dFdCDP, and dFdCTP correlated with distribution of endogenous AMP, ADP, and ATP in viable tumor cell regions, showing that gemcitabine active metabolites are reaching the tumor cell compartment, while AZD6738 was located to nonviable tumor regions. The method revealed that the generation of active, phosphorylated dFdC metabolites as well as treatment-induced DNA damage primarily correlated with sites of high proliferation in KPC PDAC tumor tissue, rather than sites of high parent drug abundance.

Microenvironmental Factors Modulating Tumor Lipid Metabolism: Paving the Way to Better Antitumoral Therapy

Metabolic reprogramming is one of the emerging hallmarks of cancer and is driven by both the oncogenic mutations and challenging microenvironment. To satisfy the demands of energy and biomass for rapid proliferation, the metabolism of various nutrients in tumor cells undergoes important changes, among which the aberrant lipid metabolism has gained increasing attention in facilitating tumor development and metastasis in the past few years. Obstacles emerged in the aspect of application of targeting lipid metabolism for tumor therapy, due to lacking of comprehensive understanding on its regulating mechanism. Tumor cells closely interact with stromal niche, which highly contributes to metabolic rewiring of critical nutrients in cancer cells. This fact makes the impact of microenvironment on tumor lipid metabolism a topic of renewed interest. Abundant evidence has shown that many factors existing in the tumor microenvironment can rewire multiple signaling pathways and proteins involved in lipid metabolic pathways of cancer cells. Hence in this review, we summarized the recent progress on the understanding of microenvironmental factors regulating tumor lipid metabolism, and discuss the potential of modulating lipid metabolism as an anticancer approach.

Identification of CCT3 as a prognostic factor and correlates with cell survival and invasion of head and neck squamous cell carcinoma

BACKGROUND

Recurrent locally advanced or metastatic head and neck squamous cell carcinoma (HNSCC) is associated with dismal prognosis because of its highly invasive behavior and resistance to conventional intensive chemotherapy. The identification of effective markers for early diagnosis and prognosis is important for reducing mortality and ensuring that therapy for HNSCC is effective. Chaperonin-containing TCP-1 3 (CCT3) folds cancer-related proteins to control carcinogenesis. The prognostic value and growth association of CCT3 and HNSCC remain unknown.

METHODS

The GEO, Oncomine and UALCAN databases were used to examine CCT3 expression in HNSCC. A few clinical HNSCC samples with normal tissues were used to detect CCT3 expression by using immunohistochemistry method. The TCGA-HNSC dataset was used to evaluate the association between expression of CCT3 and prognosis. The molecular mechanism was investigated with gene set enrichment analysis (GSEA). CCK-8 and wound healing assays were used to detect cell growth and invasion of HNSCC, respectively.

RESULTS

CCT3 expression was significantly up-regulated in HNSCC in both mRNA and protein levels. In addition, up-regulated CCT3 expression was associated with various clinicopathological parameters. High expression of CCT3 was significantly correlated with inferior survival of HNSCC patients. Knockdown of CCT3 significantly inhibited cell growth and invasion of HNSCC cell lines. GSEA analysis indicated that CCT3 was closely correlated with tumor-related signaling pathways and HNSCC cell survival.

CONCLUSION

Our findings suggest that CCT3 is a biomarker of poor prognosis and related to the process of HNSCC.

Measuring the rate of in-vitro drug release from polymeric nanoparticles by 19F solution state NMR spectroscopy

We report what we believe is the first use of ¹⁹F NMR spectroscopy to directly measure in-vitro release (IVR) from polymeric nanoparticles (PNPs). Using ¹⁹F NMR we selectively measured IVR of AZD2811 from PNPs. Due to rapid nuclear relaxation in solid-like environments only AZD2811 in solution is detected, and physical separation from the PNPs isn't required. The NMR approach and ultra-centrifugation/UHPLC were shown to be equivalent. The selectivity of ¹⁹F NMR means it is readily applied to complex IVR media such as recombinant human serum albumin (rHSA).

Complete loss of ATM function augments replication catastrophe induced by ATR inhibition and gemcitabine in pancreatic cancer models

BACKGROUND

Personalised medicine strategies may improve outcomes in pancreatic ductal adenocarcinoma (PDAC), but validation of predictive biomarkers is required. Having developed a clinical trial to assess the ATR inhibitor, AZD6738, in combination with gemcitabine (ATRi/gem), we investigated ATM loss as a predictive biomarker of response to ATRi/gem in PDAC.

METHODS

Through kinase inhibition, siRNA depletion and CRISPR knockout of ATM, we assessed how ATM targeting affected the sensitivity of PDAC cells to ATRi/gem. Using flow cytometry, immunofluorescence and immunoblotting, we investigated how ATRi/gem synergise in ATM-proficient and ATM-deficient cells, before assessing the impact of ATM loss on ATRi/gem sensitivity in vivo.

RESULTS

Complete loss of ATM function (through pharmacological inhibition or CRISPR knockout), but not siRNA depletion, sensitised to ATRi/gem. In ATM-deficient cells, ATRi/gem-induced replication catastrophe was augmented, while phospho-Chk2-T68 and phospho-KAP1-S824 persisted via DNA-PK activity. ATRi/gem caused growth delay in ATM-WT xenografts in NSG mice and induced regression in ATM-KO xenografts.

CONCLUSIONS

ATM loss augments replication catastrophe-mediated cell death induced by ATRi/gem and may predict clinical responsiveness to this combination. ATM status should be carefully assessed in tumours from patients with PDAC, since distinction between ATM-low and ATM-null could be critical in maximising the success of clinical trials using ATM expression as a predictive biomarker.

Pancreatic adenocarcinoma preferentially takes up and is suppressed by synthetic nanoparticles carrying apolipoprotein A-II and a lipid gemcitabine prodrug in mice

We hypothesised that synthetic HDL nanoparticles carrying a gemcitabine prodrug and apolipoprotein A-II (sHDLGemA2) would target scavenger receptor-B1 (SR-B1) to preferentially and safely deliver gemcitabine into pancreatic ductal adenocarcinoma (PDAC). We designed, manufactured and characterised sHDLGemA2 nanoparticles sized ~130 nm, incorporating 20 mol% of a gemcitabine prodrug within the lipid bilayer, which strengthens on adding ApoA-II. We measured their ability to inhibit growth in cell lines and cell-derived and patient-derived murine PDAC xenografts. Fluorescent-labelled sHDLGemA2 delivered gemcitabine inside xenografts. Xenograft levels of active gemcitabine after sHDLGemA2 were similar to levels after high-dose free gemcitabine. Growth inhibition in mice receiving 4.5 mg gemcitabine/kg/d, carried in sHDLGemA2, was equivalent to inhibition after high-dose (75 mg/kg/d) free gemcitabine, and greater than inhibition after low-dose (4.5 mg/kg/d) free gemcitabine. sHDLGemA2 slowed growth in semi-resistant cells and a resistant human xenograft. sHDLGemA2 targeted xenografts more effectively than sHDLGemA1. SR-B1 was over-expressed in PDAC cells and xenografts. Targeting by ApoA-II was suppressed by anti-SR-B1. Because sHDLGemA2 provided only ~6% of the free gemcitabine dose for an equivalent response, patient side effects can be greatly reduced, and the sHDLGemA2 concept should be developed through clinical trials.

Depletion of Macrophages Improves Therapeutic Response to Gemcitabine in Murine Pancreas Cancer

BACKGROUND

The tumor microenvironment (TME) is composed of fibro-inflammatory cells and extracellular matrix (ECM) components. However, the exact contribution of the various TME compartments towards therapeutic response is unknown. Here, we aim to dissect the specific contribution of tumor-associated macrophages (TAMs) towards drug delivery and response in pancreatic ductal adenocarcinoma (PDAC).

METHODS

The effect of gemcitabine was assessed in human and murine macrophages, human pancreatic stellate cells (hPSCs), and tumor cells (L3.6pl, BxPC3 and KPC) in vitro. The drug metabolism of gemcitabine was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Preclinical studies were conducted using KrasG12D;p48-Cre and KrasG12D;p53172H;Pdx-Cre mice to investigate gemcitabine delivery at different stages of tumor progression and upon pharmacological TAM depletion.

RESULTS

Gemcitabine accumulation was significantly increased in murine PDAC tissue compared to pancreatic intraepithelial neoplasia (PanIN) lesions and healthy control pancreas tissue. In vitro, macrophages accumulated and rapidly metabolized gemcitabine resulting in a significant drug scavenging effect for gemcitabine. Finally, pharmacological TAM depletion enhanced therapeutic response to gemcitabine in tumor-bearing KPC mice.

CONCLUSION

Macrophages rapidly metabolize gemcitabine in vitro, and pharmacological depletion improves the therapeutic response to gemcitabine in vivo. Our study supports the notion that TAMs might be a promising therapeutic target in PDAC.

Identification of Resistance Pathways Specific to Malignancy Using Organoid Models of Pancreatic Cancer

PURPOSE

KRAS is mutated in the majority of pancreatic ductal adenocarcinoma. MAPK and PI3K-AKT are primary KRAS effector pathways, but combined MAPK and PI3K inhibition has not been demonstrated to be clinically effective to date. We explore the resistance mechanisms uniquely employed by malignant cells.

EXPERIMENTAL DESIGN

We evaluated the expression and activation of receptor tyrosine kinases in response to combined MEK and AKT inhibition in KPC mice and pancreatic ductal organoids. In addition, we sought to determine the therapeutic efficacy of targeting resistance pathways induced by MEK and AKT inhibition in order to identify malignant-specific vulnerabilities.

RESULTS

Combined MEK and AKT inhibition modestly extended the survival of KPC mice and increased Egfr and ErbB2 phosphorylation levels. Tumor organoids, but not their normal counterparts, exhibited elevated phosphorylation of ERBB2 and ERBB3 after MEK and AKT blockade. A pan-ERBB inhibitor synergized with MEK and AKT blockade in human PDA organoids, whereas this was not observed for the EGFR inhibitor erlotinib. Combined MEK and ERBB inhibitor treatment of human organoid orthotopic xenografts was sufficient to cause tumor regression in short-term intervention studies.

CONCLUSIONS

Analyses of normal and tumor pancreatic organoids revealed the importance of ERBB activation during MEK and AKT blockade primarily in the malignant cultures. The lack of ERBB hyperactivation in normal organoids suggests a larger therapeutic index. In our models, pan-ERBB inhibition was synergistic with dual inhibition of MEK and AKT, and the combination of a pan-ERBB inhibitor with MEK antagonists showed the highest activity both in vitro and in vivo.

SPARC dependent collagen deposition and gemcitabine delivery in a genetically engineered mouse model of pancreas cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is characterised by extensive matrix deposition that has been implicated in impaired drug delivery and therapeutic resistance. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein that regulates collagen deposition and is highly upregulated in the activated stroma subtype with poor prognosis in PDAC patients.

METHODS

KrasG12D;p48-Cre;SPARC-/- (KC-SPARC-/-) and KrasG12D;p48-Cre;SPARCWT (KC-SPARCWT) were generated and analysed at different stages of carcinogenesis by histological grading, immunohistochemistry for epithelial and stromal markers, survival and preclinical analysis. Pharmacokinetic and pharmacodynamic studies were conducted by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunohistochemistry following gemcitabine treatment (100 mg/kg) in vivo.

FINDINGS

Global genetic ablation of SPARC in a KrasG12D driven mouse model resulted in significantly reduced overall and mature collagen deposition around early and advanced pancreatic intraepithelial neoplasia (PanIN) lesions and in invasive PDAC (p < .001). However, detailed pathological scoring and molecular analysis showed no effects on PanIN to PDAC progression, vessel density (CD31), tumour incidence, grading or metastatic frequency. Despite comparable tumour kinetics, ablation of SPARC resulted in a significantly shortened survival in KC-SPARC-/- mice (280 days versus 485 days, p < .03, log-rank-test). Using LC-MS/MS, we show that SPARC dependent collagen deposition does not affect intratumoural gemcitabine accumulation or immediate therapeutic response in tumour bearing KC-SPARCWT and KC-SPARC-/-mice.

INTERPRETATION

Global SPARC ablation reduces the collagen-rich microenvironment in murine PDAC. Moreover, global SPARC depletion did not affect tumour growth kinetics, grading or metastatic frequency. Notably, the dense-collagen matrix did not restrict access of gemcitabine to the tumour. These findings may have direct translational implications in clinical trial design.

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.

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.

Depicting Changes in Tumor Biology in Response to Cetuximab Monotherapy or Combination Therapy by Apoptosis and Proliferation Imaging Using 18F-ICMT-11 and 18F-FLT PET

Imaging biomarkers must demonstrate their value in monitoring treatment. Two PET tracers, the caspase-3/7-specific isatin-5-sulfonamide 18F-ICMT-11 (18F-(S)-1-((1-(2-fluoroethyl)-1H-[1,2,3]-triazol-4-yl)methyl)-5-(2(2,4-difluoro-phenoxymethyl)-pyrrolidine-1-sulfonyl)isatin) and 18F-FLT (3'-deoxy-3'-18F-fluorothymidine), were used to detect early treatment-induced changes in tumor biology and determine whether any of these changes indicate a response to cetuximab, administered as monotherapy or combination therapy with gemcitabine. Methods: In mice bearing cetuximab-sensitive H1975 tumors (non-small lung cancer), the effects of single or repeated doses of the antiepidermal growth factor receptor antibody cetuximab (10 mg/kg on day 1 only or on days 1 and 2) or a single dose of gemcitabine (125 mg/kg on day 2) were investigated by 18F-ICMT-11 or 18F-FLT on day 3. Imaging was also performed after 2 doses of cetuximab (days 1 and 2) in mice bearing cetuximab-insensitive HCT116 tumors (colorectal cancer). For imaging-histology comparison, tumors were evaluated for proliferation (Ki-67 and thymidine kinase 1 [TK1]), cell death (cleaved caspase-3 and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling [TUNEL]), and target engagement (epidermal growth factor receptor expression) by immunohistochemistry, immunofluorescence, and immunoblotting, respectively. Tumor and plasma were analyzed for thymidine and gemcitabine metabolites by liquid chromatography-mass spectrometry. Results: Retention of both tracers was sensitive to cetuximab in H1975 tumors. 18F-ICMT-11 uptake and ex vivo cleaved caspase-3 staining notably increased in tumors treated with repeated doses of cetuximab (75%) and combination treatment (46%). Although a single dose of cetuximab was insufficient to induce apoptosis, it did affect proliferation. Significant reductions in tumor 18F-FLT uptake (44%-50%; P < 0.001) induced by cetuximab monotherapy and combination therapy were paralleled by a clear decrease in proliferation (Ki-67 decrease, 72%-95%; P < 0.0001), followed by a marked tumor growth delay. TK1 expression and tumor thymidine concentrations were profoundly reduced. Neither imaging tracer depicted the gemcitabine-induced tumor changes. However, cleaved caspase-3 and Ki-67 staining did not significantly differ after gemcitabine treatment whereas TK1 expression and thymidine concentrations increased. No cetuximab-induced modulation of the imaging tracers or other response markers was detected in the insensitive model of HCT116. Conclusion:18F-ICMT-11 and 18F-FLT are valuable tools to assess cetuximab sensitivity depicting distinct and time-variant aspects of treatment response.

The ATR Inhibitor AZD6738 Synergizes with Gemcitabine In Vitro and In Vivo to Induce Pancreatic Ductal Adenocarcinoma Regression

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest cancers, and overall survival rates have barely improved over the past five decades. The antimetabolite gemcitabine remains part of the standard of care but shows very limited antitumor efficacy. Ataxia telangiectasia and Rad3-related protein (ATR), the apical kinase of the intra-S-phase DNA damage response, plays a central role in safeguarding cells from replication stress and can therefore limit the efficacy of antimetabolite drug therapies. We investigated the ability of the ATR inhibitor, AZD6738, to prevent the gemcitabine-induced intra-S-phase checkpoint activation and evaluated the antitumor potential of this combination in vitro and in vivo In PDAC cell lines, AZD6738 inhibited gemcitabine-induced Chk1 activation, prevented cell-cycle arrest, and restrained RRM2 accumulation, leading to the strong induction of replication stress markers only with the combination. Moreover, synergistic growth inhibition was identified in a panel of 5 mouse and 7 human PDAC cell lines using both Bliss Independence and Loewe models. In clonogenic assays, the combination abrogated survival at concentrations for which single agents had minor effects. In vivo, AZD6738 in combination with gemcitabine was well tolerated and induced tumor regression in a subcutaneous allograft model of a KrasG12D; Trp53R172H; Pdx-Cre (KPC) mouse cancer cell line, significantly extending survival. Remarkably, the combination also induced regression of a subgroup of KPC autochthonous tumors, which generally do not respond well to conventional chemotherapy. Altogether, our data suggest that AZD6738 in combination with gemcitabine merits evaluation in a clinical trial in patients with PDAC. Mol Cancer Ther; 17(8); 1670-82. ©2018 AACR.

Pancreatic cancer: from bench to bedside

Pancreatic cancer is recognized as the king of carcinoma, and the gap between basic research and clinical practice is difficult to improve the treatment effect. Translational medicine builds an important bridge between pancreatic cancer basic research and clinical practice from the pathogenesis, early diagnosis of pancreatic carcinoma, drug screening, treatment strategies and metastasis prediction. This article will carry on the concrete elaboration to the above several aspects.

Exploring the Potent Inhibition of CTP Synthase by Gemcitabine-5'-Triphosphate

CTP synthase (CTPS) catalyzes the conversion of UTP to CTP and is a target for the development of antiviral, anticancer, antiprotozoal, and immunosuppressive agents. Exposure of cell lines to the antineoplastic cytidine analogue gemcitabine causes depletion of intracellular CTP levels, but the direct inhibition of CTPS by its metabolite gemcitabine-5'-triphosphate (dF-dCTP) has not been demonstrated. We show that dF-dCTP is a potent competitive inhibitor of Escherichia coli CTPS with respect to UTP [K_i =(3.0±0.1) μm], and that its binding affinity exceeds that of CTP ≈75-fold. Site-directed mutagenesis studies indicated that Glu149 is an important binding determinant for both CTP and dF-dCTP. Comparison of the binding affinities of the 5'-triphosphates of 2'-fluoro-2'-deoxycytidine and 2'-fluoro-2'-deoxyarabinocytidine revealed that the 2'-F-arabino group contributes markedly to the strong binding of dF-dCTP. Geminal 2'-F substitution on UTP (dF-dUTP) did not result in an increase in binding affinity with CTPS. Remarkably, CTPS catalyzed the conversion of dF-dUTP into dF-dCTP, thus suggesting that dF-dCTP might be regenerated in vivo from its catabolite dF-dUTP.

Anti-stromal treatment together with chemotherapy targets multiple signalling pathways in pancreatic adenocarcinoma

Stromal targeting for pancreatic ductal adenocarcinoma (PDAC) is rapidly becoming an attractive option, due to the lack of efficacy of standard chemotherapy and increased knowledge about PDAC stroma. We postulated that the addition of stromal therapy may enhance the anti-tumour efficacy of chemotherapy. Gemcitabine and all-trans retinoic acid (ATRA) were combined in a clinically applicable regimen, to target cancer cells and pancreatic stellate cells (PSCs) respectively, in 3D organotypic culture models and genetically engineered mice (LSL-Kras(G12D) (/+) ;LSL-Trp53(R172H) (/+) ;Pdx-1-Cre: KPC mice) representing the spectrum of PDAC. In two distinct sets of organotypic models as well as KPC mice, we demonstrate a reduction in cancer cell proliferation and invasion together with enhanced cancer cell apoptosis when ATRA is combined with gemcitabine, compared to vehicle or either agent alone. Simultaneously, PSC activity (as measured by deposition of extracellular matrix proteins such as collagen and fibronectin) and PSC invasive ability were both diminished in response to combination therapy. These effects were mediated through a range of signalling cascades (Wnt, hedgehog, retinoid, and FGF) in cancer as well as stellate cells, affecting epithelial cellular functions such as epithelial-mesenchymal transition, cellular polarity, and lumen formation. At the tissue level, this resulted in enhanced tumour necrosis, increased vascularity, and diminished hypoxia. Consequently, there was an overall reduction in tumour size. The enhanced effect of stromal co-targeting (ATRA) alongside chemotherapy (gemcitabine) appears to be mediated by dampening multiple signalling cascades in the tumour-stroma cross-talk, rather than ablating stroma or targeting a single pathway. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Understanding the Complexity of Porous Graphitic Carbon (PGC) Chromatography: Modulation of Mobile-Stationary Phase Interactions Overcomes Loss of Retention and Reduces Variability

Porous graphitic carbon (PGC) is an important tool in a chromatographer's armory that retains polar compounds with mass spectrometry (MS)-compatible solvents. However, its applicability is severely limited by an unpredictable loss of retention, which can be attributed to contamination. The solutions offered fail to restore the original retention and our observations of retention time shifts of gemcitabine/metabolites on PGC are not consistent with contamination. The mobile phase affects the ionization state of analytes and the polarizable PGC surface that influences the strength of dispersive forces governing retention on the stationary phase. We hypothesized that failure to maintain the same PGC surface before and after running a gradient is a cause of the observed retention loss/variability on PGC. Herein, we optimize the choice of mobile phase solvent in a gradient program with three parts: a preparatory phase, which allows binding of analytes to column; an elution phase, which gives the required separation/peak shape; and a maintenance phase, to preserve the required retention capacity. Via liquid chromatography/tandem mass spectrometry (LC-MS/MS) analysis of gemcitabine and its metabolites extracted from tumor tissue, we demonstrate reproducible chromatography on three PGC columns of different ages. This approach simplifies use of the PGC to the same level as that of a C-18 column, removes the need for column regeneration, and minimizes run times, thus allowing PGC columns to be used to their full potential.