Establishing a mouse model of lung metastases using ultrasound-guided right heart ventricle injection

We report a technique to generate a murine model of lung metastases by selectively injecting tumor cells into the right heart ventricle under ultrasound guidance. First, we describe cell preparation and reference animal preparation as previously described. We then detail the technique using a previously described 3D-printed instrument stabilization device. Finally, we describe tumor growth surveillance using bioluminescent imaging. For complete details on the use and execution of this protocol, please refer to Labora et al.1.

Generation of liver metastases in a mouse model using ultrasound-guided intravenous injection

Here, we present a protocol to generate a murine model of liver metastasis by directly injecting tumor cells into the portal vein under ultrasound guidance. We describe steps for animal and cell preparation and two techniques for injecting tumor cells. One technique is freehand, while the other technique is device-assisted using a 3D-printed prototype device. Finally, we describe tumor surveillance with bioluminescent imaging.

Abstract P4-08-09: Deoxycytidine kinase (dCK) inhibition is synthetic lethal with BRCA2-deficiency

BRCA2 is a well-established cancer driver in several human malignancies. While the remarkable success of PARP inhibitors proved the clinical potential of targeting BRCA deficiencies, the emergence of resistance mechanisms underscores the importance of seeking novel Synthetic Lethal (SL) targets for future drug development efforts. In this work, we performed a BRCA2-centric SL screen with a collection of plant-derived compounds from South America. We identified the steroidal alkaloid Solanocapsine as a selective SL inducer, and we were able to substantially increase its potency by deriving multiple analogs. The use of two complementary chemoproteomic approaches led to the identification of the nucleotide salvage pathway enzyme deoxycytidine kinase (dCK) as Solanocapsine’s target responsible for its BRCA2-liked SL induction. Additional confirmatory evidence was obtained by using a highly specific dCK inhibitor (DI-87), which induces SL in multiple BRCA2-deficient and KO contexts. Interestingly, dCK-induced SL is mechanistically different from the one induced by PARP inhibitors. dCK inhibition generates substantially lower levels of DNA damage, and cytotoxic phenotypes are associated exclusively with mitosis, thus suggesting that the fine-tuning of nucleotide supply in mitosis is critical for the survival of BRCA2-deficient cells. Moreover, by using a xenograft model of contralateral tumors, we show that dCK impairment suffices to trigger SL in-vivo. Taken together, our findings unveil dCK as a promising new target for BRCA2-deficient cancers, which provides future therapeutic alternatives to PARP inhibitors.

Citation Format: María L. Guantay, Cintia A. Garro, Sebastian Siri, María Pansa, Sonja Ghidelli-Disse, Natalia Paviolo, Ana Racca, Viviana Nicotra, Caius Radu, José L. Bocco, Rosana Felice, Israel Gloger, Marcel Muelbaier, Gerard Drewes, Kevin Madauss, Manuela García, Vanesa Gottifredi, Gastón Soria. Deoxycytidine kinase (dCK) inhibition is synthetic lethal with BRCA2-deficiency [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-08-09.

Deoxycytidine kinase (dCK) inhibition is synthetic lethal with BRCA2 deficiency

BRCA2 is a well-established cancer driver in several human malignancies. While the remarkable success of PARP inhibitors proved the clinical potential of targeting BRCA deficiencies, the emergence of resistance mechanisms underscores the importance of seeking novel Synthetic Lethal (SL) targets for future drug development efforts. In this work, we performed a BRCA2-centric SL screen with a collection of plant-derived compounds from South America. We identified the steroidal alkaloid Solanocapsine as a selective SL inducer, and we were able to substantially increase its potency by deriving multiple analogs. The use of two complementary chemoproteomic approaches led to the identification of the nucleotide salvage pathway enzyme deoxycytidine kinase (dCK) as Solanocapsine's target responsible for its BRCA2-linked SL induction. Additional confirmatory evidence was obtained by using the highly specific dCK inhibitor (DI-87), which induces SL in multiple BRCA2-deficient and KO contexts. Interestingly, dCK-induced SL is mechanistically different from the one induced by PARP inhibitors. dCK inhibition generates substantially lower levels of DNA damage, and cytotoxic phenotypes are associated exclusively with mitosis, thus suggesting that the fine-tuning of nucleotide supply in mitosis is critical for the survival of BRCA2-deficient cells. Moreover, by using a xenograft model of contralateral tumors, we show that dCK impairment suffices to trigger SL in-vivo. Taken together, our findings unveil dCK as a promising new target for BRCA2-deficient cancers, thus setting the ground for future therapeutic alternatives to PARP inhibitors.

Abstract 6649: Inhibiting adenosine signaling and KRAS enhances the effect of α-PD-1 therapy in a KRASG12C/TP53R172H/+ pancreatic cancer model

Introduction: High levels of adenosine (ADO) in the tumor microenvironment have been shown to suppress immune responses and curtail T cell activation in the presence of anti-PD-1/PD-L1 blocking antibodies. CD73 catalyzes the extracellular generation of ADO from adenosine monophosphate (AMP). KRAS mutations, of which 60% were derived from pancreatic ductal adenocarcinoma (PDAC) samples, were associated with significantly upregulated CD73 expression, which resulted in a worsening prognosis. These immunosuppressive effects can be counteracted by CD73 inhibitors or by a dual ADO receptor (A2aR/A2bR) antagonist.

Method: Linear models were used to evaluate the ability of 299 pan-cancer consensus oncogenic drivers to predict CD73 expression independent of tumor type in the TCGA dataset. Changes in gene expression induced by KRAS inhibition were determined by RNAseq. Metabolic and proteomic alterations induced by KRAS inhibition were determined by LC-MS. C57BL/6J mice bearing established KP4662-G12C (KRASG12C/TP53R172H/+) tumors (at least 150 mm3) were treated as indicated: A1421 (CD73i; 30 mg/kg/day, s.c.), anti-PD1 (Clone RMP 1-14; 10 mg/kg; twice per week, i.p), and MRTX-1257 (KRASi, 100 mg/kg/day, p.o.). Treatment efficacy was monitored in a blinded manner using micro-computed tomography (mCT). A1412 and MRTX-1257 were provided by Arcus Biosciences.

Data: Direct KRAS inhibition reduced but did not abolish CD73 and A2aR/A2bR expression in multiple PDAC models. Metabolic analyses indicated that KRAS inhibition increased ADO and AMP levels. KRAS inhibition in PDAC models induced gene expression changes consistent with increased tumor immunogenicity. In a murine model of pancreatic cancer-bearing the KRASG12C mutation, co-administration of a CD73 inhibitor with anti-PD-1 in established tumors resulted in significant tumor growth retardation, comparable to KRASG12C inhibition alone. Durable tumor regression was observed when mice were treated with the triple combination therapy. These data support the rationale for the clinical development of modulators of immunosuppressive adenosine signaling in pancreatic cancer.

Conclusion: Here, we show that direct inhibition of mutant KRAS in pancreatic cancer models yields complex immunomodulatory effects. While antigen presentation pathways are transcriptionally upregulated and the expression of immunosuppressive chemokine is reduced, KRAS inhibition also reprograms nucleotide metabolism leading to elevated levels of ADO. These findings suggest that co-targeting mutant KRAS and adenosine signaling may enhance immunotherapy against pancreatic cancer and potentially other KRAS driven malignancies.

Citation Format: THUC LE, Evan Abt, Woosuk Kim, Akshata Udyavar, Arthur Cho, Joe Capri, Jing Cui, Razmik Ghukasyan, Luyi Li, Daniel DiRenzo, Brandon Rosen, Timothy Donahue, Matt Walters, Caius Radu. Inhibiting adenosine signaling and KRAS enhances the effect of α-PD-1 therapy in a KRASG12C/TP53R172H/+ pancreatic cancer model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6649.

Abstract 5345: Heterogeneous tumor PSMA expression represents a resistance mechanism to PSMA-targeted radioligand therapy

Radioligand therapy (RLT) with prostate-specific membrane antigen (PSMA)-targeting ligands is effective in ~50% of patients with advanced prostate cancer (PC). Causes for RLT failure are not well understood. The prevalent PSMA heterogeneity in PC might contribute to RLT failure. Here we investigate the relationship between RLT efficacy and PSMA levels per cell, and PSMA heterogeneity. PC cells expressing different levels of PSMA (RM1-PSMA low, medium, high, or RM1-YFP that do not express PSMA), or a mix of PSMA− and PSMA+ cells (RM1-YFP/ RM1-PSMA-high; PC3/ PC3-PIP) at various ratios were subcutaneously injected into NSG mice. Mice were treated with 177Lu- or 225Ac-PSMA617 (RLT) and tumor growth was monitored. In a subset of mice, radioligand uptake (γ-counting), DNA damage and PSMA expression (anti-53BP1 and -PSMA immunohistochemistry, respectively) were quantified in tumors resected 2 days after RLT. Increasing PSMA levels and fractions of PSMA+ cells improved RLT efficacy in both, the RM1 and PC3 model. PSMA expression correlated with radioligand uptake into the tumor and the degree of DNA damage and. Treatment with 225Ac-PSMA617 (vs. 177Lu-PSMA617) improved RLT outcomes and tended to enhance the differences in therapeutic efficacy between experimental groups. Taken together, we demonstrate in mouse models of PC that optimal anti-tumor efficacy of RLT hinges on homogenously high target expression. Although PSMA-RLT is effective even in tumors with low PSMA levels or with a small number of PSMA+ cells, low or heterogeneous PSMA expression might result in undertreatment and selection of treatment resistant clones. Systematic assessment of intra- and inter-lesion PSMA heterogeneity is currently not feasible clinically; however, this issue might be addressed by individual patient dosimetry to optimize safely delivered maximal tumor doses. Clinical studies designed to determine intra- and inter-lesion PSMA heterogeneity and to optimize PSMA-RLT for each patient are highly warranted.

Citation Format: Katharina Lueckerath, Kyle Current, Catherine Meyer, Clara Magyar, Christine E. Mona, Joel Almajano, Roger Slavik, Andreea D. Stuparu, Chloe Cheng, David Dawson, Caius Radu, Johannes Czernin. Heterogeneous tumor PSMA expression represents a resistance mechanism to PSMA-targeted radioligand therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5345.

Abstract C01: Porcupine inhibition redirects mitochondrial metabolism in Wnt-dependent pancreatic cancer

Wnt/β-catenin signaling plays important roles in pancreatic ductal adenocarcinoma (PDA) tumor initiation and progression via broad-ranging effects on proliferation, differentiation, survival, and stemness. Although Wnt has been shown to promote glycolysis in colon cancer, its role in regulating metabolism in PDA has not been well explored. For this study, RNF43-mutant cell lines were selected as exemplars of ligand-dependent autocrine Wnt signaling in PDA. These cell lines harbor an inactivating mutation in RNF43 that confers Wnt growth-dependency and response to LGK974, a PORCN inhibitor that blocks Wnt ligand secretion and signaling. Global transcriptomic, proteomic, and metabolomic analysis revealed several metabolites and putative mediators of metabolism that are directly or indirectly linked to autocrine Wnt signaling. Pharmacologic inhibition of Wnt by LGK974 led to the accumulation of pyruvate and lactate, as well as reduced tricarboxylic acid cycle metabolites and decreased mitochondrial membrane potential as measured by tetramethylrhodamine and JC-1 assays. These metabolic changes were accompanied by cell cycle arrest and downregulation of transcriptional programs involved in cell cycle progression, DNA replication, and nucleotide metabolism. Importantly, LGK974 results were phenocopied by siRNA-mediated knockdown of WNT7B and rescued with WNT3A conditioned media. Thus, inhibition of mitochondrial oxidative phosphorylation by LGK974 in RNF43-mutant PDA appears linked to its inhibition of canonical Wnt signaling, an adaptation and potential metabolic vulnerability that could be leveraged to therapeutic advantage via combinatorial strategies. Altogether, these results suggest tissue context and mechanisms of Wnt pathway activation may profoundly influence its role in regulating cancer metabolism.

Citation Format: Kristina Y. Aguilera, Rana Riahi, Edris A. Saadat, Anna R. Lay, Thuc Le, Timothy R. Donahue, Caius Radu, David W. Dawson. Porcupine inhibition redirects mitochondrial metabolism in Wnt-dependent pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr C01.

Development and preclinical pharmacology of a novel dCK inhibitor, DI-87

BACKGROUND

Deoxycytidine kinase (dCK) is an essential enzyme for production of nucleotides via the salvage pathway; DI-87 is a novel dCK inhibitor in preclinical development for use in anticancer therapy. The current study utilizes PET imaging to evaluate PK-PD relationships and to determine optimal dosing of the drug.

METHODS

NSG mice bearing CEM tumors had plasma and tumor PK assessed using mass spectrometry following oral administration of DI-87. dCK inhibition was assessed after a single dose of oral DI-87 followed by a [¹⁸F]CFA PET probe and PET imaging. Tumor growth inhibition was assessed by orally administering DI-87 with concurrent intraperitoneal thymidine.

RESULTS

DI-87 had an in vitro EC₅₀ of 10.2 nM with low protein binding. Peak DI-87 concentrations were observed between 1-3 h and 3-9 h in plasma and tumor, respectively, with tumor concentrations less than one third of plasma. Full dCK inhibition, as evaluated by PET imaging, was observed as early as 3 h following 25 mg/kg dosing and was maintained for 12 h, with full recovery of enzyme activity after 36 h. When DI-87 was administered as repeated doses in combination with thymidine, full dCK inhibition was maintained at 12 h (25 mg/kg twice daily dose) and led to maximal tumor growth inhibition.

CONCLUSIONS

DI-87 is a promising new compound for use in combination therapy against tumors expressing dCK. Utilizing a [¹⁸F]CFA PET probe targeting the pathway of interest allowed for efficient and accurate identification of the optimal dose for growth inhibition.

Association between PNPLA3[G]/I148M variant, steatosis and fibrosis stage in hepatitis C virus - genetic matters

There is an established correlation between the PNPLA3 rs738409 C > G single nucleotide polymorphism (SNP) and hepatic steatosis and fibrosis in hepatitis C virus (HCV) infected patients. However not all data is convergent regarding the exact impact of this SNP on the pattern of disease progression in different clinical settings. In this study, we aimed to further bridge the knowledge gap on this topic by investigating the role of the G allele in promoting steatosis, fibrosis and disease progression in relation to other metabolic and anthropometric host factors. Two hundred and fifty consecutive patients, previously diagnosed with chronic hepatitis C (CHC) underwent liver biopsy. Histology was assessed using the Metavir scoring system. Transient elastography was used for follow-up. Ninety-eight patients were genotyped for PNPLA3 rs738409 and followed up for fibrosis progression. PNPLA3 rs738409[G] allele was significantly correlated with severe steatosis (P = 0.04), severe fibrosis at the time of enrollment (P = 0.0005) and fibrosis progression with an OR of 10.31 (95% CI 1.06 - 99.59, P = 0.04), after a mean follow-up time of 62.85 (95%CI: 52.21 - 76.15) months. Severe steatosis at the time of enrollment had an OR of 11.02 (95% CI 1.48 - 82.09, P = 0.01) for the association with fibrosis progression. The HOMA-IR index was also positively correlated with severe fibrosis (P = 0.03) and fibrosis progression on univariate analysis (P = 0.02). PNPLA3 rs738409[G] allele is a reliable predictor for steatosis and fibrosis in CHC. The presence of G allele, along with severe steatosis and insulin resistance are significant predictors for fibrosis progression.

Abstract 1832: Ligand-dependent Wnt signaling directs metabolic adaptations to promote pancreatic tumorigenesis

Wnt/β-catenin signaling plays important roles in pancreatic adenocarcinoma (PDA) tumor initiation and progression via broad-ranging effects on proliferation, differentiation, survival, and stemness. Although Wnt has been shown to promote glycolysis in colon cancer, its role in regulating metabolism in PDA has not been explored in any detail. For this study, the AsPC-1 cell line was selected as an exemplar of ligand-dependent autocrine Wnt signaling in PDA. AsPC-1 harbors an inactivating mutation in RNF43 that confers Wnt growth-dependency and response to LGK974, a PORCN inhibitor that blocks Wnt ligand secretion and signaling. Global transcriptomic, proteomic, and metabolomic analysis revealed several metabolites and putative mediators of metabolism that are directly or indirectly linked to autocrine Wnt signaling in AsPC-1. In contrast to colon cancer, pharmacologic inhibition of Wnt by LGK974 in AsPC-1 led to the accumulation of pyruvate and lactate, as well as reduced tricarboxylic acid cycle metabolites and decreased mitochondrial membrane potential as measured by tetramethylrhodamine assay. These metabolic changes were accompanied by cell cycle arrest and downregulation of transcriptional programs involved in cell cycle progression, DNA replication, and nucleotide metabolism. Pyruvate analogs dichloroacetate and oxamate, that respectively target pyruvate dehydrogenase kinase and lactate dehydrogenase, restored mitochondrial membrane potential in the context of LGK974. Importantly, LGK974 results were phenocopied by siRNA-mediated knockdown of WNT7B. Thus, inhibition of mitochondrial oxidative phosphorylation by LGK974 in RNF43-mutant PDA appears mechanistically linked to its inhibition of canonical Wnt signaling, an adaptation and potential metabolic vulnerability that could be leveraged to therapeutic advantage via combinatorial strategies. Altogether, these results suggest tissue context and differing mechanisms of Wnt pathway activation or signal strength may profoundly influence its role in regulating cancer metabolism.

Citation Format: Kristina Y. Aguilera, Rana Riahi, Edris A. Saadat, Anna R. Lay, Thuc Le, Anthony Cabebe, Timothy R. Donahue, Caius Radu, David W. Dawson. Ligand-dependent Wnt signaling directs metabolic adaptations to promote pancreatic tumorigenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1832.

Abstract 3881: Relating tumor drug concentrations to target effect with semi physiologic PK-PD modeling in drug development: An application using a novel dCK inhibitor

Introduction: Deoxycytidine kinase (dCK) is essential for DNA synthesis through salvage pathways and DI-87 is a novel dCK inhibitor in preclinical development. This study used PET imaging to measure dCK inhibition and pharmacokinetic-pharmacodynamic (PK-PD) modeling to relate tumor drug levels to tissue with dCK activity and tumor shrinkage.

Methods: Oral DI-87 was administered to NSG mice with plasma and tumor PK assessed over 24 hrs by mass spectrometry. NSG mice with CEM tumors were administered varying doses of DI-87 followed by the [18F]CFA PET probe and PET imaging. NSG mice with CEM tumors were administered thymidine and DI-87 concurrently and tumor growth monitored. PK-PD modeling was conducted with NONMEM (v. 7.3).

Results: DI-87 plasma concentrations peaked at 3 hr; tumor peak concentrations occurred later. Tumor concentrations were less than one third of plasma concentrations. Full dCK inhibition by PET imaging occurred between 10 and 25 mg/kg and decreasing doses led to faster recovery of activity. Full recovery of enzyme activity occurred by 36 hrs with full inhibition being maintained at the 12 hr time point at the 25 mg/kg dose. Maximal growth inhibition occurred with full dCK inhibition over the dosing range (25 mg/kg BID) when DI-87 was given in combination therapy with thymidine; thus increased doses led to more persistent dCK inhibition with predictable increased growth inhibition.

Conclusions: Combining PET probes with PK-PD modeling led to an optimized dosing schedule for combination therapy with DI-87.

Citation Format: Soumya Poddar, Mina Nikanjam, Edmund Capparelli, Thuc Le, Liu Wei, Caius Radu. Relating tumor drug concentrations to target effect with semi physiologic PK-PD modeling in drug development: An application using a novel dCK inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3881.

Abstract 4228: Integrated drug high-throughput screening and quantitative phosphoproteomics rationalizes combination therapy for mutant KRAS pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a highly recalcitrant malignancy for which better therapies are urgently needed. KRAS is the most frequently altered gene in PDAC and it orchestrates a number of effector pathways that ultimately drives PDAC growth and proliferation. The recent development of allele-specific inhibitors of oncogenic KRAS G12C, such as ARS-1620, provides an unprecedented opportunity to explore direct targeting of oncogenic KRAS signaling in PDAC. Nearly 3% PDAC patient harbor KRAS G12C, corresponding to ~1,600 new cases of PDAC/year in the US alone for which currently there are no robust targeted therapies. Even if the inhibitor effectively block KRAS function, compensatory mechanism will probably be triggered to overcome the KRAS-mutant PDAC.To better position the direct mutant KRAS inhibitor, we have developed a platform that includes: a high-throughput screen anchored with ARS-1620 to identify companion inhibitor to further dial down the oncogenic KRAS signaling, quantitative mass spectrometric method to map out the adaptive signaling mechanisms of this combination therapy, and bioinformatics pipeline to reveal and rank targetable kinases that drive the adaptive resistance mechanism. To do so, we will apply our platform on a panel of KRAS G12C primary PDAC models. We will profile the proteomic/phosphoproteomic changes of cells treated with combination therapy to identify adaptive signaling pathways that could be potentially targeted.High-throughput chemical-genomics screening identified receptor tyrosine kinases (RTKs) to be synergistic to the KRAS inhibitor, ARS-1620. In particular, multiple epidermal growth factor receptor (EGFR) inhibitors restrict growth of patient-derived PDAC, XWR200, when combined with ARS-1620. When profiling the proteomic/phosphoproteomics changes induced by the combination therapy, we quantified nearly 9600 protein groups and 44,000 phosphopeptides with 36,000 class 1 phosphopeptides having quantitation in all groups (FDR < 1%). We interrogated the Drug Signature Database (DSigDB) using the ~2,400 significantly-altered proteins (FDR < 0.1%) and found the protein gene set to be highly correlated to genes downregulated by topoisomerase inhibition. To identify adaptive signaling pathways, we performed kinase-substrate enrichment analysis (KSEA) on the phosphoproteomic dataset containing ~8,000 significantly altered phosphopeptides (FDR < 1%). KSEA identified hyperactivation of several G2/M checkpoint kinases such as Aurora kinases A and B. This integrative platform has revealed synergistic drug combinations with ARS-1620 and the phosphoproteomics has prescribed possibly the third drug of the combination therapy.

Note: This abstract was not presented at the meeting.

Citation Format: Joseph Capri, Thuc Le, Caius Radu, Timothy Donahue. Integrated drug high-throughput screening and quantitative phosphoproteomics rationalizes combination therapy for mutant KRAS pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4228.

Increased lactate dehydrogenase activity is dispensable in squamous carcinoma cells of origin

Although numerous therapeutic strategies have attempted to target aerobic glycolysis to inhibit tumor progression, these approaches have not resulted in effective clinical outcomes. Murine squamous cell carcinoma (SCC) can be initiated by hair follicle stem cells (HFSCs). HFSCs utilize aerobic glycolysis, and the activity of lactate dehydrogenase (Ldh) is essential for HFSC activation. We sought to determine whether Ldh activity in SCC is critical for tumorigenesis or simply a marker of the cell type of origin. Genetic abrogation or induction of Ldh activity in HFSC-mediated tumorigenesis shows no effect on tumorigenesis as measured by number, time to formation, proliferation, volume, epithelial to mesenchymal transition, gene expression, or immune response. Ldha-null tumors show dramatically reduced levels of glycolytic metabolites by metabolomics, and significantly reduced glucose uptake by FDG-PET live animal imaging. These results suggest that squamous cancer cells of origin do not require increased glycolytic activity to generate cancers.

Most tumours are characterized by increased aerobic glycolytic activity. Here the authors show that elevated  aerobic glycolysis is not essential for cancer initiation by testing the effect of lactate dehydrogenase depletion on the ability of hair follicle stem cells (HFSCs) to form squamous cell carcinoma (SCC) in mouse genetic models.

[Environmental exposure chambers (EEC): A novel tool for pathophysiological and pharmaceutical research]

Airborne allergic diseases (allergic asthma, rhinitis and conjunctivitis) have reached epidemic proportions and are a great burden for both society and individuals. Therefore we need to better understand the physiopathological mechanisms and to increase clinical research in these diseases. However, traditional outpatient studies are difficult and have number of limitations, in particular the variability of allergen exposure. Yet allergen provocation tests, especially bronchial challenges in asthma, are excellent tools to measure the efficiency of anti-allergic therapies. Environmental exposure chambers (EEC) allow the performance of controlled allergen provocation tests on a large scale with remarkable sensitivity, specificity and reproducibility. Moreover, they allow a precise collection of allergic symptoms, making them interesting tools for patho-physiological and clinical studies. During the last thirty years, they have assisted the study of anti-allergic therapies and provided data on their pharmacodynamic characteristics, particularly in allergic rhinitis. However, there are still no EEC tests centered on asthma. The EEC of Strasbourg (ALYATEC^®) was developed to fulfill two objectives: to allow standardized allergenic and non-allergenic exposures with better control of the parameters than in other EEC and to offer a place to study asthma and anti-asthmatic therapies safely.

Histone deacetylase inhibitors provoke a tumor supportive phenotype in pancreatic cancer associated fibroblasts

Although histone deacetylase inhibitors (HDACi) are a promising class of anti-cancer drugs, thus far, they have been unsuccessful in early phase clinical trials for pancreatic ductal adenocarcinoma (PDAC). One potential reason for their poor efficacy is the tumor stroma, where cancer-associated fibroblasts (CAFs) are a prominent cell type and a source of resistance to cancer therapies. Here, we demonstrate that stromal fibroblasts contribute to the poor efficacy of HDACi's in PDAC. HDACi-treated fibroblasts show increased biological aggressiveness and are characterized by increased secretion of pro-inflammatory tumor-supportive cytokines and chemokines. We find that HDAC2 binds to the enhancer and promoter regions of pro-inflammatory genes specifically in CAFs and in silico analysis identified AP-1 to be the most frequently associated transcription factor bound in these regions. Pharmacologic inhibition of pathways upstream of AP-1 suppresses the HDACi-induced inflammatory gene expression and tumor-supportive responses in fibroblasts. Our findings demonstrate that the combination of HDACi's with chemical inhibitors of the AP-1 signaling pathway attenuate the inflammatory phenotype of fibroblasts and may improve the efficacy of HDACi in PDAC and, potentially, in other solid tumors rich in stroma.

Abstract 4064: Relating tumor drug concentrations to target effect with semi-physiologic PK-PD modeling in drug development: an application using a novel dCK inhibitor

Introduction: While plasma concentrations are commonly studied in preclinical and clinical studies, drug concentrations in tumor and effects on molecular targets may be more appropriate for determining drug dosing and predicting response to therapy. The current study assessed tumor and plasma drug levels of DI87, a novel deoxycytidine kinase (dCK) inhibitor, and determined the relationship to dCK activity using a PET biomarker and imaging.

Methods: NSG mice with CEM tumors were treated with DI87 (25 or 50 mg/kg) by oral gavage for a single dose. Tumor and plasma concentrations were assessed over 24 hrs (50 mg/kg dose, 5 times points, N=4 separate mice per time point). Plasma and tumor DI87 concentrations were quantified by LC-MS/MS. dCK activity was determined by PET imaging of a biomarker for dCK activity over 27 hrs ([18F]-clofarabine probe was injected 3 hrs prior to imaging) after a single dose of DI87 (50 mg/kg or 25 mg/kg, 5 time points, 4 mice per time point). Nonlinear mixed effects modeling (NONMEM v. 7.2) was used to build a semi-physiologic pharmacokinetic (PK) model to describe tumor and plasma concentrations (tumor volume fixed to observed median tumor size). The PK model was linked to an inhibitory indirect response pharmacodynamic (PD) model of dCK activity in the tumor using a pooled naïve approach to describe the relationship between drug levels in the tumor and dCK inhibition.

Results: Peak tumor DI87 concentrations were lower (1.15 ± 0.64 μg/mL vs. 13.5 ± 4.5 μg/mL) and occurred later (9 vs. 3 hr) than peak plasma concentrations. Despite limited tumor sampling, the semi-physiologic model described tumor concentrations well (R2=0.71). The PK model had a plasma clearance of 0.52 L/hr/kg with a half-life of 3.7 hr. DI87 exposure in the tumor (AUC) was 17% of that observed in plasma. Maximal and near complete dCK inhibition occurred at 9 hr for both the 50 mg/kg and 25 mg/kg doses with recovery of dCK activity beginning at 27 hr post-dose. The predicted tumor concentration at 12 hr of 0.36 μg/mL was sufficient to maintain maximal dCK inhibition. The initiation of recovery of dCK activity corresponded to the decline in tumor DI87 concentrations, but maintained significant inhibition at 27 hr (25% of baseline). The relationship between dCK activity and DI87 tumor concentrations was well characterized by a sigmoid Emax PD model with a large Hill coefficient. This resulted in a dramatic increase of effect over a small range of concentrations. The EC50 was within the range of tumor concentrations observed in the study (0.21 μg/mL).

Conclusions: The use of semi-physiologic PK models that include tumor drug concentrations from limited preclinical data can increase knowledge of the PK-PD for novel therapeutics. This approach enhances understanding of time-dependent effects on molecular drugs targets and can improve selection of rational clinical dosing regimens for phase I clinical trials.

Citation Format: Mina Nikanjam, Soumya Poddar, Edmund Capparelli, Thuc Le, Liu Wei, Caius Radu. Relating tumor drug concentrations to target effect with semi-physiologic PK-PD modeling in drug development: an application using a novel dCK inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4064. doi:10.1158/1538-7445.AM2017-4064

Skeletal muscle action of estrogen receptor α is critical for the maintenance of mitochondrial function and metabolic homeostasis in females

Impaired estrogen receptor α (ERα) action promotes obesity and metabolic dysfunction in humans and mice; however, the mechanisms underlying these phenotypes remain unknown. Considering that skeletal muscle is a primary tissue responsible for glucose disposal and oxidative metabolism, we established that reduced ERα expression in muscle is associated with glucose intolerance and adiposity in women and female mice. To test this relationship, we generated muscle-specific ERα knockout (MERKO) mice. Impaired glucose homeostasis and increased adiposity were paralleled by diminished muscle oxidative metabolism and bioactive lipid accumulation in MERKO mice. Aberrant mitochondrial morphology, overproduction of reactive oxygen species, and impairment in basal and stress-induced mitochondrial fission dynamics, driven by imbalanced protein kinase A-regulator of calcineurin 1-calcineurin signaling through dynamin-related protein 1, tracked with reduced oxidative metabolism in MERKO muscle. Although muscle mitochondrial DNA (mtDNA) abundance was similar between the genotypes, ERα deficiency diminished mtDNA turnover by a balanced reduction in mtDNA replication and degradation. Our findings indicate the retention of dysfunctional mitochondria in MERKO muscle and implicate ERα in the preservation of mitochondrial health and insulin sensitivity as a defense against metabolic disease in women.

Proteome-wide Profiling of Clinical PARP Inhibitors Reveals Compound-Specific Secondary Targets

Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) are a promising class of targeted cancer drugs, but their individual target profiles beyond the PARP family, which could result in differential clinical use or toxicity, are unknown. Using an unbiased, mass spectrometry-based chemical proteomics approach, we generated a comparative proteome-wide target map of the four clinical PARPi, olaparib, veliparib, niraparib, and rucaparib. PARPi as a class displayed high target selectivity. However, in addition to the canonical targets PARP1, PARP2, and several of their binding partners, we also identified hexose-6-phosphate dehydrogenase (H6PD) and deoxycytidine kinase (DCK) as previously unrecognized targets of rucaparib and niraparib, respectively. Subsequent functional validation suggested that inhibition of DCK by niraparib could have detrimental effects when combined with nucleoside analog pro-drugs. H6PD silencing can cause apoptosis and further sensitize cells to PARPi, suggesting that H6PD may be, in addition to its established role in metabolic disorders, a new anticancer target.

[Reconstruction of Defects after Oncologic Resection and Radiation - Indications for Microsurgical Reconstruction]

The surgical treatment of soft tissue sarcomas in the extremities frequently requires radiation therapy to achieve local tumour control. However, both adjuvant and neoadjuvant radiation are associated with significant morbidity caused by impaired wound healing, ulcers or osteonecrosis with subsequent fractures. This is due to altered local cell mediator levels, fibrosis occurring simultaneously with decreased cell division rates and diminished vascularity. This article describes a number of local conservative treatment options, all of which have limited success rates. In addition, it describes plastic surgical treatment options for radiation-induced local morbidity. Surgical reconstruction includes the full range of plastic reconstructive techniques. However, less complex options such as random pattern flaps or split thickness skin grafts are often associated with complications. Therefore, a large number of cases require free tissue transfer.

Structural characterization of new deoxycytidine kinase inhibitors rationalizes the affinity-determining moieties of the molecules

Deoxycytidine kinase (dCK) is a key enzyme in the nucleoside salvage pathway that is also required for the activation of several anticancer and antiviral nucleoside analog prodrugs. Additionally, dCK has been implicated in immune disorders and has been found to be overexpressed in several cancers. To allow the probing and modulation of dCK activity, a new class of small-molecule inhibitors of the enzyme were developed. Here, the structural characterization of four of these inhibitors in complex with human dCK is presented. The structures reveal that the compounds occupy the nucleoside-binding site and bind to the open form of dCK. Surprisingly, a slight variation in the nature of the substituent at the 5-position of the thiazole ring governs whether the active site of the enzyme is occupied by one or two inhibitor molecules. Moreover, this substituent plays a critical role in determining the affinity, improving it from >700 to 1.5 nM in the best binder. These structures lay the groundwork for future modifications that would result in even tighter binding and the correct placement of moieties that confer favorable pharmacodynamics and pharmacokinetic properties.

PET imaging to non-invasively study immune activation leading to antitumor responses with a 4-1BB agonistic antibody

Background

Molecular imaging with positron emission tomography (PET) may allow the non-invasive study of the pharmacodynamic effects of agonistic monoclonal antibodies (mAb) to 4-1BB (CD137). 4-1BB is a member of the tumor necrosis factor family expressed on activated T cells and other immune cells, and activating 4-1BB antibodies are being tested for the treatment of patients with advanced cancers.

Methods

We studied the antitumor activity of 4-1BB mAb therapy using [¹⁸ F]-labeled fluoro-2-deoxy-2-D-glucose ([¹⁸ F]FDG) microPET scanning in a mouse model of colon cancer. Results of microPET imaging were correlated with morphological changes in tumors, draining lymph nodes as well as cell subset uptake of the metabolic PET tracer in vitro.

Results

The administration of 4-1BB mAb to Balb/c mice induced reproducible CT26 tumor regressions and improved survival; complete tumor shrinkage was achieved in the majority of mice. There was markedly increased [¹⁸ F]FDG signal at the tumor site and draining lymph nodes. In a metabolic probe in vitro uptake assay, there was an 8-fold increase in uptake of [³H]DDG in leukocytes extracted from tumors and draining lymph nodes of mice treated with 4-1BB mAb compared to untreated mice, supporting the in vivo PET data.

Conclusion

Increased uptake of [¹⁸ F]FDG by PET scans visualizes 4-1BB agonistic antibody-induced antitumor immune responses and can be used as a pharmacodynamic readout to guide the development of this class of antibodies in the clinic.

Fast metabolic response to drug intervention through analysis on a miniaturized, highly integrated molecular imaging system

We report on a radiopharmaceutical imaging platform designed to capture the kinetics of cellular responses to drugs.

METHODS

A portable in vitro molecular imaging system comprising a microchip and a β-particle imaging camera permitted routine cell-based radioassays of small numbers of either suspended or adherent cells. We investigated the kinetics of responses of model lymphoma and glioblastoma cancer cell lines to (18)F-FDG uptake after drug exposure. Those responses were correlated with kinetic changes in the cell cycle or with changes in receptor tyrosine kinase signaling.

RESULTS

The platform enabled direct radioassays of multiple cell types and yielded results comparable to those from conventional approaches; however, the platform used smaller sample sizes, permitted a higher level of quantitation, and did not require cell lysis.

CONCLUSION

The kinetic analysis enabled by the platform provided a rapid (≈ 1 h) drug screening assay.

Application of a rapid, simple, and accurate adenovirus-based method to compare PET reporter gene/PET reporter probe systems

PURPOSE

This study aims to use a simple, quantitative method to compare the HSV1sr39TK/(18) F-FHBG PET reporter gene/PET reporter probe (PRG/PRP) system with PRGs derived from human nucleoside kinases.

PROCEDURES

The same adenovirus vector is used to express alternative PRGs. Equal numbers of vectors are injected intravenously into mice. After PRP imaging, quantitative hepatic PET signals are normalized for transduction by measuring hepatic viral genomes.

RESULTS

The same adenovirus vector was used to express equivalent amounts of HSV1sr39TK, mutant human thymidine kinase 2 (TK2-DM), and mutant human deoxycytidine kinase (dCK-A100VTM) in mouse liver. HSV1sr39TK expression was measured with (18) F-FHBG, TK2-DM and dCK-A100VTM with (18) F-L-FMAU. TK2-DM/(18) F-L-FMAU and HSV1sr39TK/(18) F-FHBG had equivalent sensitivities; dCK-A100VTM/(18) F-L-FMAU was twice as sensitive as HSV1sr39TK/(18) F-FHBG.

CONCLUSIONS

The human PRG/PRP sensitivities are comparable and/or better than HSV1sr39TK/(18) F-FHBG. However, for clinical use, identification of the best PRP substrate for each enzyme, characterization of probe distribution, and consequences of overexpressing nucleoside kinases must be evaluated.

Evaluation of the Genisys4, a bench-top preclinical PET scanner

The Genisys4 is a small bench-top preclinical PET scanner designed to enable imaging in biology, biochemistry, and pharmacology laboratories and imaging centers. Here, we compare its performance with that of a well-established preclinical PET scanner.

METHODS

Subcutaneous and lung tumor xenografts were used to compare lesion detectability and treatment responses to chemotherapy (gemcitabine) using (18)F-FDG PET. The size of subcutaneous xenografts (L1210 and L1210-10K leukemia cells) and lung metastases (B-16 melanoma cells) was measured on small-animal CT images. Tumor (18)F-FDG uptake was expressed as percentage injected dose per gram. Using list-mode data, serial images of the left ventricular blood pool were used to generate time-activity curves.

RESULTS

Subcutaneous xenografts (range, 4-12 mm; mean ± SD, 6.1 ± 1.7 mm) and lung metastases (range, 1-5 mm; mean, 2.1 ± 1.2 mm) were detected equally well with both scanners. Tumor (18)F-FDG uptake measured with both scanners was highly correlated for subcutaneous xenografts (r(2) = 0.93) and lung metastases (r(2) = 0.83). The new Genisys4 scanner and the established scanner provided comparable treatment response information (r(2) = 0.93). Dynamic imaging sequences permitted the generation of left ventricular blood-pool time-activity curves with both scanners.

CONCLUSION

Using subcutaneous and lung xenografts, a novel and an established preclinical PET scanner provided equivalent information with regard to lesion detection, tumor (18)F-FDG uptake, tumor response to treatment, and generation of time-activity curves. Thus, the Genisys4 provides a small, efficient bench-top preclinical PET alternative for quantitatively studying murine tumor models in biology, biochemistry, and pharmacology laboratories and preclinical imaging centers.

Increased anticoagulant response to low-molecular-weight heparin in plasma from patients with advanced cirrhosis

INTRODUCTION

Cirrhotic patients may present thrombotic complications that warrant anticoagulant therapy. However, the efficacy of low-molecular-weight heparin (LMWH) in this clinical setting is still unclear.

AIMS/METHODS

To evaluate the in vitro effect of LMWH on thrombin generation (TG) in cirrhotic patients at different stages of liver disease. Thirty cirrhotics (10 Child Pugh A, 10 Child Pugh B and 10 Child Pugh C), 10 subjects with inherited type 1 antithrombin (AT) defect and 10 healthy controls were studied. TG was determined at baseline and with anti-Xa levels after the addition of enoxaparin at 0.35 and 0.7 U anti-Xa mL. The endogenous thrombin potential (ETP) ratio at 0.35 and 0.7 U anti-Xa mL was obtained by dividing ETP with LMWH by ETP at baseline.

RESULTS

Mean AT levels in all cirrhotic subgroups and in patients with AT deficiency were significantly lower than in controls. The 0.35 ETP ratio was significantly lower in cirrhotic patients than in controls (0.26 ± 0.1 vs. 0.48 ± 0.1, P < 0.001) and the reduction paralleled the severity of liver disease, in spite of the concomitant decrease in AT and anti-Xa activity. AT-deficient subjects showed a significantly increased 0.35 ETP ratio compared with both cirrhotic patients and controls (0.69 ± 1 vs. 0.26 ± 0.1, P < 0.001, and vs. 0.48 ± 0.1, P = 0.04 respectively). LMWH at 0.7 U anti-Xa mL completely inhibited TG in 9/30 cirrhosis patients with more advanced liver disease (Child Pugh B and C), whereas complete TG abolition was seen in only 1/10 controls.

CONCLUSIONS

Cirrhotic patients show an increased response to LMWH, which correlates with the severity of liver disease, in spite of reduced AT and anti-Xa activity levels. Thrombin generation may be a useful tool to monitor the response to LMWH in cirrhotic patients.

A novel pathophysiological-based panel of biomarkers for the diagnosis of nonalcoholic steatohepatitis

Non-invasive biochemical markers are useful to distinguish between nonalcoholic steatohepatitis (NASH) and simple steatosis. The aim of this study was to test the diagnostic value of a panel of biomarkers derived from the pathophysiological events involved in the development of NASH. A total of 79 patients: 20 not-NASH and 59 NASH were included in the study. Definitive NASH was defined according to Kleiner's classification. In all subjects, parameters of the metabolic syndrome, insulin resistance (HOMA-IR), adiponectin, interleukin-6 (IL-6) and total cytokeratin-18 (M65 antigen) were determined. Univariate and multivariate analysis were used to identify independent predictors of NASH. In multivariate analysis three markers were independently predictors of NASH: adiponectin, IL-6 and M65 levels. In decreasing order, the independent predictors of NASH (NAS≥5) were M65 with an AUROC of 0.791, IL-6 with an AUROC of 0.727 and adiponectin with an AUROC of 0.709. The combination of two biomarkers yelded an AUROC of 0.828 for M65 and IL-6, 0.841 for adiponectin and M65 and 0.852 for adiponectin and IL-6. The best value was obtained by triple combination: adiponectin, M65 and IL-6 with and AUROC of 0.903, Sp=85.7% (PPV=94.2%) and Se=84.5% (NPV=66.7%). In conclusion, a novel pathophysiological - based panel of biomarkers combining total CK-18, IL-6 and adiponectin may be useful to predict NASH.

3'-deoxy-3'-[18F]fluorothymidine positron emission tomography for response assessment in soft tissue sarcoma: a pilot study to correlate imaging findings with tissue thymidine kinase 1 and Ki-67 activity and histopathologic response

BACKGROUND

This study sought to determine whether [(18)F]fluorothymidine (FLT) positron emission tomography (PET)/computed tomography (CT) imaging allows assessment of tumor viability and proliferation in patients with soft tissue sarcomas who are treated with neoadjuvant therapy.

METHODS

Twenty patients with biopsy-proven, resectable, high-grade soft tissue sarcoma underwent [(18)F]FLT PET/CT imaging before and after neoadjuvant therapy. Histologic subtypes included sarcomas not otherwise specified (n = 5), malignant peripheral nerve sheath tumors (n = 3), gastrointestinal stromal tumors (n = 3), leiomyosarcomas (n = 3), angiosarcomas (n = 2), and others (n = 4). Changes in [(18)F]FLT peak standardized uptake value (SUVpeak) were correlated with percent necrosis in excised tissue, whereas posttreatment [(18)F]FLT tumor uptake was correlated with thymidine kinase 1 (TK1) expression and Ki-67 staining indices in excised tumor tissue.

RESULTS

Tumor FLT SUVpeak averaged 7.1 ± 3.7 g/mL (range, 1.9-16.1 g/mL) at baseline and decreased significantly to 2.7 ± 1.6 g/mL (range, 0.8-6.0 g/mL) at follow-up (P < .001); however, marked reductions in SUV were not specific for histopathological response. The posttreatment SUVpeak did not correlate with TK1 (P = .27) or Ki-67 expression (P = .21).

CONCLUSIONS

Marked reductions in [(18)F]FLT tumor uptake in response to neoadjuvant treatment were observed in most patients with sarcoma. However, these reductions were not specific for histopathologic response to neoadjuvant therapy. Furthermore, posttreatment [(18)F]FLT tumor uptake was unrelated to tumor proliferation by Ki-67 and TK1 staining. These results question the value of [(18)F]FLT PET imaging for treatment response assessments in patients with soft tissue sarcoma.

PARASURG hybrid parallel robot for minimally invasive surgery

This paper presents the parallel hybrid robot, PARASURG 9M, for robotically assisted surgery, a robot which was entirely designed and produced in Romania. It is a versatile robot, being composed of a positioning and orientation module, PARASURG 5M with five degrees of freedom, having the possibility of attaching at its end either a laparoscope or an active surgical instrument for cutting/grasping, PARASIM, with four degrees of freedom. Based on its mathematical modelling, the first low-cost experimental model of the surgical robot has been built. The robot is part of the surgical robotic system, PARAMIS, with three arms, one used as a laparoscope holder, and other two for manipulating active instruments. When it is used as a manipulator of the camera, the user has the possibility to give commands in a large area for the positioning of the laparoscope using different interfaces: joystick, microphone, keyboard & mouse and haptic device. If the active surgical instrument, PARASIM, is attached, the robot commands are given through a haptic device. The main features that make the PARASURG 9M surgical robot suited for minimally invasive surgery are: precision, the elimination of the natural tremor of the surgeon, direct control over a smooth, precise, stable view of the internal surgical field for the surgeon. It also eliminates the need of a second surgeon to be present for the entire procedure (in the case of using the robot as a camera holder). In addition, there is improvement of surgeon dexterity in the case of using the PARASIM active instrument and better ergonomics in using the robot (in the case of the classic laparoscopy, the surgeon must adopt a difficult position for a long period of time, while the robot never gets tired). Having a relatively easy to understand, intuitive commanding system, the surgeons can rapidly adapt to the use of the PARASURG 9M robot in surgical procedures.

Homozygous F5 deep-intronic splicing mutation resulting in severe factor V deficiency and undetectable thrombin generation in platelet-rich plasma

BACKGROUND

Coagulation factor (F) V deficiency is associated with a bleeding tendency of variable severity, but phenotype determinants are largely unknown. Recently, we have shown that three patients with undetectable plasma FV and mild bleeding symptoms had sufficient residual platelet FV to support thrombin generation in platelet-rich plasma (PRP). Therefore, we hypothesized that FV-deficient patients with severe bleeding manifestations may lack platelet FV.

OBJECTIVES

To characterize a FV-deficient patient with a severe bleeding diathesis.

PATIENTS/METHODS

We performed FV mutation screening and functional studies in a 31-year-old male (FV:C < 1%) with umbilical bleeding at birth, recurrent hemarthrosis and muscle hematomas, and a recent intracranial hemorrhage.

RESULTS

The proband was homozygous for a deep-intronic mutation (F5 IVS8 +268A→G) causing the inclusion of a pseudo-exon with an in-frame stop codon in the mature F5 mRNA. Although platelet FV antigen was detectable by immunoprecipitation followed by Western blotting, no FV activity could be demonstrated in the proband's plasma or platelets with a prothrombinase-based assay. Moreover, no thrombin generation was observed in PRP triggered with 1-50 pm tissue factor (even in the presence of platelet agonists), whereas an acquired FV inhibitor was excluded. Clot formation in the proband's whole blood, as assessed by thromboelastometry, was markedly delayed but not abolished.

CONCLUSIONS

This is the first report of a pathogenic deep-intronic mutation in the F5 gene. Our findings indicate that the minimal FV requirement for viability is extremely low and suggest that thrombin generation in PRP may predict bleeding tendency in patients with undetectable plasma FV.

Abstract SY03-02: Tumor metabolic phenotyping and treatment stratification by positron emission tomography

The ability to noninvasively measure key metabolic pathways in living subjects may assist the development of new, more efficacious therapies against cancer. Here we show that two new positron emission tomography (PET) probes, 1-(2′-deoxy-2′-18F-fluoro-β-D-arabinofuranosyl)cytosine (18F-FAC) and 1-(2′-deoxy-2′-18F-fluoro-β-L-arabinofuranosyl)-5-methylcytosine (L-18F-FMAC), detect distinct phenotypic signatures of tumor nucleoside metabolism. 18F-FAC and L-18F-FMAC accumulation in tumors measured in vivo by PET is indicative of the activities of deoxycytidine kinase (dCK) and cytidine deaminase (CDA), two key enzymes in nucleic acid metabolism. Metabolic subtypes detected by 18F-FAC and L-18F-FMAC were shown to correspond to the differential utilization by cancer cells of the nucleoside salvage pathway to generate and maintain deoxyribonucleotide pools required to sustain tumor growth. We also show that the metabolic subtypes defined by 18F-FAC and L-18F-FMAC PET measurements correlate with markedly distinct sensitivities to therapeutic interventions. These findings support the utility of PET-based phenotyping of tumor nucleoside metabolism for treatment stratification in cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr SY03-02. doi:10.1158/1538-7445.AM2011-SY03-02