Early dose of Adenosine, postRadiofrequency abLation of accessory pathwaY in determining acute procedural success (EARLY study).

INTRODUCTION: Post ablation of the accessory pathway (AP), the patient is observed in the catheterization laboratory for a variable period for resumption of pathway conduction. Aim of the study was to determine whether the administration of intravenous adenosine at 10 min after ablation of AP would have the same diagnostic accuracy as waiting for 30 min in predicting the resumption of AP conduction. METHODS: This was a prospective interventional study conducted in two centers. Post ablation of the AP, intravenous adenosine was administered at 10 min to look for dormant pathway conduction. The response was recorded as positive (presence of pathway conduction), negative (absence), or indeterminate (not able to demonstrate AV and VA block and inability to ascertain AP conduction). RESULTS: The study included 110 procedures performed in 109 patients. Adenosine administration at 10 min showed positive result in 3 cases (2.7%), negative result in 99 cases (90%) and indeterminate result in 8 cases (7.3%). Reconnection of accessory pathway at 30 min postablation was seen in 8 cases (7.3%). Of these 8 cases, 10 min adenosine administration showed positive test in 3 patients and negative test in 5 patients. Adenosine test at 10 min has a sensitivity, specificity, positive predictive value, and negative predictive value of 37.5%, 100%, 100%, and 94.9% in identifying the recurrence of accessory pathway conduction at 30 min, respectively. CONCLUSION: Absence of pathway conduction on administration of adenosine 10 min postablation does not help predict the absence of resumption of conduction thereafter.

Altered Gemcitabine and Nab-paclitaxel Scheduling Improves Therapeutic Efficacy Compared with Standard Concurrent Treatment in Preclinical Models of Pancreatic Cancer.

PURPOSE: Concurrent gemcitabine and nab-paclitaxel treatment is one of the preferred chemotherapy regimens for metastatic and locally advanced pancreatic ductal adenocarcinoma (PDAC). Previous studies demonstrate that caveolin-1 (Cav-1) expression is critical for nab-paclitaxel uptake into tumors and correlates with response. Gemcitabine increases nab-paclitaxel uptake by increasing Cav-1 expression. Thus, we hypothesized that pretreatment with gemcitabine would further enhance the sensitivity of PDAC to nab-paclitaxel by increasing Cav-1 expression and nab-paclitaxel uptake. EXPERIMENTAL DESIGN: We investigated the sensitivity of different gemcitabine and nab-paclitaxel treatment regimens in a panel of PDAC cell lines and orthotopic xenograft models. The sensitivity of different treatment regimens was compared with the standard concurrent treatment. RESULTS: Pretreatment with gemcitabine before nab-paclitaxel increased Cav-1 and albumin uptake and significantly decreased proliferation and clonogenicity compared with concurrent treatment, which correlated with increased levels of apoptosis. Cav-1 silencing reduced the uptake of albumin, and therapeutic advantage was observed when cells were pretreated with gemcitabine prior to nab-paclitaxel. In addition, we observed that pretreatment with gemcitabine resulted in partial synchronization of cells in the G2-M-phase at the time of nab-paclitaxel treatment, providing another mechanism for the benefit of altered scheduling. In heterotopic and orthotopic xenograft models, the altered schedule of gemcitabine prior to nab-paclitaxel significantly delayed tumor growth compared with concurrent delivery without added toxicity. CONCLUSIONS: Pretreatment with gemcitabine significantly increased nab-paclitaxel uptake and correlated with an increased treatment efficacy and survival benefit in preclinical models, compared with standard concurrent treatment. These results justify preclinical and clinical testing of this altered scheduling combination.

Cells isolated from residual intracranial tumors after treatment express iPSC genes and possess neural lineage differentiation plasticity.

BACKGROUND: The goal of this study is to identify and characterize treatment resistant tumor initiating cells (TRTICs) using orthotopic xenografts. METHODS: TRTICs were enriched from GBM cell lines using mouse xenografts treated with fractionated doses of radiation and temozolomide. TRTICs were characterized by neurosphere clonogenicity and self-renewal, serial xenotransplantation, differentiation potential, and mRNA & miRNA transcriptomic profiling. We use an unbiased approach to identify antigens encoding TRTIC and glioma stem cells (GSC) populations. Co-culture experiments of TRTIC and differentiated cells were conducted to evaluate the reliance of TRTIC differentiation on the secretome of differentiated cells. FINDINGS: TRTICs acquire stem-like gene expression signatures and increased side population staining resulting from the activation of multi-drug resistance genes. Genetic and functional characterization of TRTICs shows a striking resemblance with GSCs. TRTICs can differentiate towards specific progeny in the neural stem cell lineage. TRTIC-derived tumors display all the histological hallmarks of glioblastoma (GBM) and exhibit a miRNA-transcript and mRNA-transcriptomic profile associated with aggressiveness. We report that CD24+/CD44+ antigens are expressed in TRTICs and patient-derived GSCs. Double positive CD24+/CD44+ exhibit treatment resistance and enhanced tumorigenicity. Interestingly, co-culture experiments with TRTICs and differentiated cells indicated that the regulation of TRTIC differentiation could rely on the secretome in the tumor niche. INTERPRETATION: Radiation and temozolomide treatment enriches a population of cells that have increased iPSC gene expression. As few as 500 cells produced aggressive intracranial tumors resembling patient GBM. CD24+/CD44+ antigens are increased in TRTICs and patient-derived GSCs. The enrichment for TRTICs may result in part from the secretome of differentiated cells. FUND: NIH/NCI 1RC2CA148190, 1R01CA108633, 1R01CA188228, and The Ohio State University Comprehensive Cancer Center.

Lack of Constitutively Active DNA Repair Sensitizes Glioblastomas to Akt Inhibition and Induces Synthetic Lethality with Radiation Treatment in a p53-Dependent Manner.

Treatment refractory glioblastoma (GBM) remains a major clinical problem globally, and targeted therapies in GBM have not been promising to date. The Cancer Genome Atlas integrative analysis of GBM reported the striking finding of genetic alterations in the p53 and PI3K pathways in more than 80% of GBMs. Given the role of these pathways in making cell-fate decisions and responding to genotoxic stress, we investigated the reliance of these two pathways in mediating radiation resistance. We selected a panel of GBM cell lines and glioma stem cells (GSC) with wild-type TP53 (p53-wt) and mutant TP53, mutations known to interfere with p53 functionality (p53-mt). Cell lines were treated with a brain permeable inhibitor of P-Akt (ser473), phosphatidylinositol ether lipid analogue (PIA), with and without radiation treatment. Sensitivity to treatment was measured using Annexin-V/PI flow cytometry and Western blot analysis for the markers of apoptotic signaling, alkaline COMET assay. All results were verified in p53 isogenic cell lines. p53-mt cell lines were selectively radiosensitized by PIA. This radiosensitization effect corresponded with an increase in DNA damage and a decrease in DNA-PKcs levels. TP53 silencing in p53-wt cells showed a similar response as the p53-mt cells. In addition, the radiosensitization effects of Akt inhibition were not observed in normal human astrocytes, suggesting that this treatment strategy could have limited off-target effects. We demonstrate that the inhibition of the PI3K/Akt pathway by PIA radiosensitizes p53-mt cells by antagonizing DNA repair. In principle, this strategy could provide a large therapeutic window for the treatment of TP53-mutant tumors. Mol Cancer Ther; 17(2); 336-46. ©2017 AACRSee all articles in this MCT Focus section, "Developmental Therapeutics in Radiation Oncology."

NNMT Silencing Activates Tumor Suppressor PP2A, Inactivates Oncogenic STKs, and Inhibits Tumor Forming Ability.

Purpose: To identify potential molecular hubs that regulate oncogenic kinases and target them to improve treatment outcomes for glioblastoma patients.Experimental Design: Data mining of The Cancer Genome Atlas datasets identified nicotinamide-N-methyl transferase (NNMT) as a prognostic marker for glioblastoma, an enzyme linked to the reorganization of the methylome. We tested our hypothesis that NNMT plays a crucial role by modulating protein methylation, leading to inactivation of tumor suppressors and activation of oncogenes. Further experiments were performed to understand the underlying biochemical mechanisms using glioblastoma patient samples, established, primary, and isogenic cells.Results: We demonstrate that NNMT outcompetes leucine carboxyl methyl transferase 1 (LCMT1) for methyl transfer from principal methyl donor SAM in biological systems. Inhibiting NNMT increased the availability of methyl groups for LCMT1 to methylate PP2A, resulting in the inhibition of oncogenic serine/threonine kinases (STK). Further, NNMT inhibition retained the radiosensitizer nicotinamide and enhanced radiation sensitivity. We have provided the biochemical rationale of how NNMT plays a vital role in inhibiting tumor suppressor PP2A while concomitantly activating STKs.Conclusions: We report the intricate novel mechanism in which NNMT inhibits tumor suppressor PP2A by reorganizing the methylome both at epigenome and proteome levels and concomitantly activating prosurvival STKs. In glioblastoma tumors with NNMT expression, activation of PP2A can be accomplished by FDA approved perphenazine (PPZ), which is currently used to treat mood disorders such as schizophrenia, bipolar disorder, etc. This study forms a foundation for further glioblastoma clinical trials using PPZ with standard of care treatment. Clin Cancer Res; 23(9); 2325-34. ©2016 AACR.

Methionine and Kynurenine Activate Oncogenic Kinases in Glioblastoma, and Methionine Deprivation Compromises Proliferation.

PURPOSE: We employed a metabolomics-based approach with the goal to better understand the molecular signatures of glioblastoma cells and tissues, with an aim toward identifying potential targetable biomarkers for developing more effective and novel therapies. EXPERIMENTAL DESIGN: We used liquid chromatography coupled with mass spectrometry (LC-MS/Q-TOF and LC-MS/QQQ) for the discovery and validation of metabolites from primary and established glioblastoma cells, glioblastoma tissues, and normal human astrocytes. RESULTS: We identified tryptophan, methionine, kynurenine, and 5-methylthioadenosine as differentially regulated metabolites (DRM) in glioblastoma cells compared with normal human astrocytes (NHAs). Unlike NHAs, glioblastoma cells depend on dietary methionine for proliferation, colony formation, survival, and to maintain a deregulated methylome (SAM:SAH ratio). In methylthioadenosine phosphorylase (MTAP)-deficient glioblastoma cells, expression of MTAP transgene did not alter methionine dependency, but compromised tumor growth in vivo We discovered that a lack of the kynurenine-metabolizing enzymes kynurenine monooxygenase and/or kynureninase promotes the accumulation of kynurenine, which triggers immune evasion in glioblastoma cells. In silico analysis of the identified DRMs mapped the activation of key oncogenic kinases that promotes tumorigenesis in glioblastoma. We validated this result by demonstrating that the exogenous addition of DRMs to glioblastoma cells in vitro results in oncogene activation as well as the simultaneous downregulation of Ser/Thr phosphatase PP2A. CONCLUSIONS: We have connected a four-metabolite signature, implicated in the methionine and kynurenine pathways, to the promotion and maintenance of glioblastoma. Together, our data suggest that these metabolites and their respective metabolic pathways serve as potential therapeutic targets for glioblastoma. Clin Cancer Res; 22(14); 3513-23. ©2016 AACR.