NAMPT inhibition sensitizes pancreatic adenocarcinoma cells to tumor-selective, PAR-independent metabolic catastrophe and cell death induced by ß-lapachone.

Nicotinamide phosphoribosyltransferase (NAMPT) inhibitors (e.g., FK866) target the most active pathway of NAD(+) synthesis in tumor cells, but lack tumor-selectivity for use as a single agent. Reducing NAD(+) pools by inhibiting NAMPT primed pancreatic ductal adenocarcinoma (PDA) cells for poly(ADP ribose) polymerase (PARP1)-dependent cell death induced by the targeted cancer therapeutic, ß-lapachone (ß-lap, ARQ761), independent of poly(ADP ribose) (PAR) accumulation. ß-Lap is bioactivated by NADPH:quinone oxidoreductase 1 (NQO1) in a futile redox cycle that consumes oxygen and generates high levels of reactive oxygen species (ROS) that cause extensive DNA damage and rapid PARP1-mediated NAD(+) consumption. Synergy with FK866+ß-lap was tumor-selective, only occurring in NQO1-overexpressing cancer cells, which is noted in a majority (∼85%) of PDA cases. This treatment strategy simultaneously decreases NAD(+) synthesis while increasing NAD(+) consumption, reducing required doses and treatment times for both drugs and increasing potency. These complementary mechanisms caused profound NAD(P)(+) depletion and inhibited glycolysis, driving down adenosine triphosphate levels and preventing recovery normally observed with either agent alone. Cancer cells died through an ROS-induced, µ-calpain-mediated programmed cell death process that kills independent of caspase activation and is not driven by PAR accumulation, which we call NAD(+)-Keresis. Non-overlapping specificities of FK866 for PDA tumors that rely heavily on NAMPT-catalyzed NAD(+) synthesis and ß-lap for cancer cells with elevated NQO1 levels affords high tumor-selectivity. The concept of reducing NAD(+) pools in cancer cells to sensitize them to ROS-mediated cell death by ß-lap is a novel strategy with potential application for pancreatic and other types of NQO1+ solid tumors.

A comparative study of the immunity region of lambdoid phages including Shiga-toxin-converting phages: molecular basis for cross immunity.

Comparison of eight lambdoid phages, including three Shiga-toxin converting phages, has been carried out with respect to the immunity region, especially the recognition helices of their repressor and CRO proteins on the one hand, and operator sequences on the other. Some as yet unassigned components of the regulatory circuits have been inferred by computer search. The cross immunity phenomenon shown by phages VT2-Sa and lambda is explained on the basis of similarity in their sequences. In addition, the similarity of 933W and HK022 in the sequences of their recognition helices of repressor and CRO, on the one hand, and operators, on the other, has led us to predict that they will have identical or similar immunity specificity. This homology has enabled us also to locate the OL (and consequently PL) of phage 933W that has been thought to be non-existent.