Citations

Background The Purkinje network appears to play a pivotal role in the triggering as well as maintenance of ventricular fibrillation. Irreversible electroporation ( IRE ) using direct current has shown promise as a nonthermal ablation modality in the heart, but its ability to target and ablate the Purkinje tissue is undefined. Our aim was to investigate the potential for selective ablation of Purkinje/fascicular fibers using IRE . Methods and Results In an ex vivo Langendorff model of canine heart (n=8), direct current was delivered in a unipolar manner at various dosages from 750 to 2500 V, in 10 pulses with a 90‐μs duration at a frequency of 1 Hz. The window of ventricular fibrillation vulnerability was assessed before and after delivery of electroporation energy using a shock on T‐wave method. IRE consistently eradicated all Purkinje potentials at voltages between 750 and 2500 V (minimum field strength of 250–833 V/cm). The ventricular electrogram amplitude was only minimally reduced by ablation: 0.6±2.3 mV ( P =0.03). In 4 hearts after IRE delivery, ventricular fibrillation could not be reinduced. At baseline, the lower limit of vulnerability to ventricular fibrillation was 1.8±0.4 J, and the upper limit of vulnerability was 19.5±3.0 J. The window of vulnerability was 17.8±2.9 J. Delivery of electroporation energy significantly reduced the window of vulnerability to 5.7±2.9 J ( P =0.0003), with a postablation lower limit of vulnerability=7.3±2.63 J, and the upper limit of vulnerability=18.8±5.2 J. Conclusions Our study highlights that Purkinje tissue can be ablated with IRE without any evidence of underlying myocardial damage.

Abstract Resistance is one the main reason for overall decrease in survival of cancer patient treated with cisplatin in different types of cancer. Cisplatin kills cancer cells by various mechanisms, but mainly through formation of inter- and intra stand crosslinks of DNA. Different types of translesion polymerase including Polymerase kappa (POLK) are involved in repair of DNA lesions. We observed high expression levels of POLK in cisplatin resistant bladder and ovarian cancer cells compared to parental cells. Due to its low proof-reading activity POLK can incorporate 8-oxo-dGTP into DNA. The MTH1 protein (Nudix hydrolase- NUDT1) sanitizes oxidized dNTP pools to prevent incorporation of damaged bases during DNA replication. Recently we have generated MTH1 inhibitors that damage the DNA and induce cancer specific cell death through incorporation of more oxidized dNTPs. We found cisplatin resistant bladder cancer cells (NTUB1/P) were more sensitive to MTH1 inhibitors in comparison to parental NTUB1 cells. As POLK is involved in incorporation of 8-oxo-dGTP into DNA, we hypothesized that high expression levels of POLK in cisplatin resistant cells make them more sensitive to MTH1 inhibitors as more 8-oxo-dGTP would be incorporated into DNA, resulting in more DNA damage and cell death in comparison to parental cells. Indeed, we observes higher induction of cleaved-PARP, γH2AX, cleaved-Caspase 3 and more annexin v positive cells in cisplatin resistant NTUB1/P cells in comparison to parental NTUB1 cells upon treatment with MTH1 inhibitors. MTH1 inhibitor also significantly delays the NTUB1/P xenograft tumor growth in comparison to vehicle treatment in immunosuppressive mice. Knocking down POLK in cisplatin resistant NTUB1/P cells by siRNA resulted in decreased incorporation of 8-oxo-dGTP and sensitivity to MTH1 inhibitors compared to non target control cells. Overexpression of POLK in NTUB1 and NTUB1/P cells results in further sensitization to MTH1 inhibitors. In conclusion elevated levels of POLK in cisplatin resistance cells determines increased sensitivity towards MTH1 inhibitors. Thus MTH1 inhibitors can be a potential promising therapy for the treatment of cisplatin resistant tumors in patients. Citation Format: Kumar Sanjiv, Helge Gad, Sean Rudd, Rachel Hurley, Patric Herr, José Manuel Calderón Montaño, Oliver Mortusewicz, Tobias Koolmeister, Sylvain Jaques, Estefanía Burgos Morón, Andreas Hoglund, Te-Chang Lee, Martin Scobie, Scott Kaufmann, John Weroha, Ulrika Warpman Berglund, Andrea Wahner Hendrickson, Thomas Helleday. Polymerase kappa determines the sensitivity of MTH1 inhibitors to cisplatin-resistant cell. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1260.

Objective Obstructive sleep apnoea (OSA) and obesity are both associated with endothelial dysfunction, which precedes the development of atherosclerosis. As obesity is highly prevalent in OSA, we wanted to test the hypothesis that OSA is associated with endothelial dysfunction independently of obesity. Design Cross-sectional, population-based study. Setting Norwegian university hospital. Patients Seventy-one subjects (median age 44 years, 35% female) were recruited from a population-based study in Norway. Participants were categorised as obese (body mass index (BMI) ≥30 kg/m2), non-obese (BMI<30 kg/m2) with OSA (apnoea–hypopnoea index (AHI)≥10), or non-obese without OSA (AHI<5). Interventions None. Main outcome measures Endothelial function measured by brachial artery ultrasound and expressed as percentage of flow-mediated dilation (FMD%). Results When non-obese subjects without OSA were used as the reference (FMD% (mean±SD) 10.1±6.3), endothelial function was found to be impaired in subjects with OSA (FMD% 6.4±3.2) (p=0.003). FMD% did not differ between obese (6.0±3.4) and non-obese (6.7±3.1) OSA subjects (p=0.3). By univariate linear regression analysis, AHI, BMI, gender and baseline brachial artery diameter were significantly associated with FMD%. When these variables were entered into a multivariate model, only AHI was significantly associated with FMD%. Conclusions OSA is associated with endothelial dysfunction independently of obesity and conventional risk factors.