Induction of lysosomal membrane permeabilization by compounds that activate p53-independent apoptosis

Abstract

The p53 protein activates cellular death programs through multiple pathways. Because the high frequency of p53 mutations in human tumors is believed to contribute to resistance to commonly used chemotherapeutic agents, it is important to identify drugs that induce p53-independent cell death and to define the mechanisms of action of such drugs. Here we screened a drug library (the National Cancer Institute mechanistic set; 879 compounds with diverse mechanisms of actions) and identified 175 compounds that induced caspase cleavage of cytokeratin-18 in cultured HCT116 colon cancer cells at <5 M. Interestingly, whereas most compounds elicited a stronger apoptotic response in cells with functional p53, significant apoptosis was observed also in p53-null cells. A subset of 15 compounds showing weak or no dependence on p53 for induction of apoptosis was examined in detail. Of these compounds, 11 were capable of activating caspase-3 in enucleated cells. Seven such compounds with nonnuclear targets were found to induce lysosomal membrane permeabilization (LMP). Translocation of the lysosomal proteases cathepsin B and cathepsin D into the cytosol was observed after treatment with these drugs, and apoptosis was inhibited by pepstatin A, an inhibitor of cathepsin D. Apoptosis depended on Bax, suggesting that LMP induced a mitochondrial apoptotic pathway. We conclude that a large number of potential anticancer drugs induce p53-independent apoptosis and that LMP is a mediator of many such responses.anticancer drugs ͉ cathepsin D ͉ M30 antibody

Anticancer properties of the novel nitric oxide-donating compound (S,R)-3-phenyl-4,5-dihydro-5-isoxazole acetic acid-nitric oxide in vitro and in vivo

“…It is known that NO may shift the electron transport chain in more reduced state, promoting the O 2 -formation and subsequent generation of other ROS and reactive nitrogen species responsible for further destruction of cells (4,28). It was shown previously that ROS and reactive nitrogen species mediated apoptotic and autophagic cell death (5,20,39). Treatment of cells with parental compound VGX-1027 did not release ROS, whereas significant amounts of these molecules were determined in the presence of GIT-27NO even after 5 min of incubation.…”

CDDO-Me, a synthetic triterpenoid, inhibits expression of IL-6 and Stat3 phosphorylation in multi-drug resistant ovarian cancer cells

“…Quantification of apoptosis was also evaluated using the M30-Apoptosense ELISA assay kit, as per manufacturer's instructions (Peviva AB, Bromma, Sweden; ref. [11]). OVCAR8 and OVCAR8 TR cells were seeded at 8000 cells/per well in a 96-well plate for 24 hours before the addition of paclitaxel, cisplatin, and CDDO-Me.…”

Lysosomal membrane permeabilization in cell death

“…The discovery of alternative non-apoptotic cell death pathways might stimulate the development of novel therapeutic strategies . In this regard, new therapeutic approaches to treat cancer through lysosomal destablization are emerging and several experimental anticancer agents developed by the NIH seem to kill cells through p53-independent LMP (Erdal et al, 2005). Indeed, the lysosomotropic detergent siramesine has an antitumorigenic effect in vivo in mouse models of fibrosarcoma and breast cancer when administered concomitantly with tumor induction (Ostenfeld et al, 2005).…”