Extracellular localization of catalase is associated with the transformed state of malignant cells

Abstract

Oncogenic transformation is dependent on activated membrane-associated NADPH oxidase (NOX). However, the resultant extracellular superoxide anions are also driving the NO/peroxynitrite and the HOCl pathway, which eliminates NOX-expressing transformed cells through selective apoptosis induction. Tumor progression is dependent on dominant interference with intercellular apoptosis-inducing ROS signaling through membraneassociated catalase, which decomposes H 2 O 2 and peroxynitrite and oxidizes NO. Particularly, the decomposition of extracellular peroxynitrite strictly requires membraneassociated catalase. We utilized small interfering RNA (siRNA)-mediated knockdown of catalase and neutralizing antibodies directed against the enzyme in combination with challenging H 2 O 2 or peroxynitrite to determine activity and localization of catalase in cells from three distinct steps of multistage oncogenesis. Nontransformed cells did not generate extracellular superoxide anions and only showed intracellular catalase activity. Transformed cells showed superoxide anion-dependent intercellular apoptosis-inducing ROS signaling in the presence of suboptimal catalase activity in their membrane. Tumor cells exhibited tight control of intercellular apoptosis-inducing ROS signaling through a high local concentration of membrane-associated catalase. These data demonstrate that translocation of catalase to the outside of the cell membrane is already associated with the transformation step. A strong local increase in the concentration of membrane-associated catalase is achieved during tumor progression and is controlled by tumor cell-derived H 2 O 2 and by transglutaminase.

The Antitumor Effect of Singlet Oxygen

“…Oxidation of NO by compound I of catalase (reaction step #14 in Figure 1) is catalyzed by two subsequent one-electron transfers (reaction steps #6-8 in Figure 2) (6,19,20). Catalase is released by tumor cells and is then attached to the tumor cells through transglutaminase (21). In this way, transglutaminase becomes an integral part of the protective system of tumor cells.…”

“…A recent analysis (70) connected the data on ROS/RNS constituents in CAP with the established knowledge of sitespecific ROS/RNS interactions and with experimental data on ROS/RNS interactions with tumor cells and nonmalignant cells (5,7,8,21,31,71). Importantly, model experiments (31) have shown that 1 O 2 can act selectively against membrane-bound catalase of tumor cells, thus restoring their sensitivity to intercellular induction of apoptosis.…”

Central Signaling Elements of Intercellular Reactive Oxygen/Nitrogen Species-dependent Induction of Apoptosis in Malignant Cells

“…This concept is in agreement with the pioneering work of Deichman et al , who have shown that tumor progression requires establishment of resistance to H 2 O 2 (12, 13). Resistance is achieved through the expression of membraneassociated catalase (8,14,15). Catalase interferes with the HOCl signaling pathway through decomposition of H 2 O 2 and with NO/PON signaling through oxidation of NO and decomposition of PON (5,8,16,17).…”

“…Catalase interferes with the HOCl signaling pathway through decomposition of H 2 O 2 and with NO/PON signaling through oxidation of NO and decomposition of PON (5,8,16,17). Recent quantitative characterization of membrane-associated catalase has shown that localization of catalase on the outside of cells is already associated with the transformed state of the cells, however, at a concentration that is not sufficient to prevent intercellular ROS-dependent signaling (15). Catalase seems to be released by tumor cells and is covalently attached to the cells through the action of transglutaminase-2 (15).…”

“…The efficiency of knockdown of NOX1, DUOX1 and catalase was based on functional quantitative assays and was more than 90% (3,15). The efficiency of knockdown of iNOS, neuronal NO synthase (nNOS), acidic sphingomyelinase (SMAse), NADPH oxidase organizer-1 (NOXO1), NADPH oxidase activator-1 (NOXA1), cytochrome c and mitochondrial SOD was proven through complete block of apoptosis after knockdown.…”