Necrocide 1 mediates necrotic cell death and immunogenic response in human cancer cells.

Many anticancer agents induce apoptosis, mitotic catastrophe or cellular senescence. Here, we report the functional characterization of an experimental inducer of tumor necrosis factor (TNF)-independent necrosis, necrocide-1 (NC1). NC1 (but not its stereoisomer) killed a panel of human cancer cells (but not normal cells) at nanomolar concentrations and with a non-apoptotic, necrotic morphotype, both in vitro and in vivo. NC1-induced killing was not inhibited by caspase blockers, anti-apoptotic BCL2 overexpression or TNFα neutralization, suggesting that NC1 elicits a bona fide necrotic pathway. However, pharmacological or genetic inhibition of necroptosis, pyroptosis and ferroptosis failed to block NC1-mediated cell death. Instead, NC1 elicited reactive oxygen species (ROS) production by mitochondria, and elimination of mitochondrial DNA, quenching of mitochondrial ROS, as well as blockade of mitochondrial permeability transition with cyclosporine A, interfered with NC1-induced cell death. NC1 induced hallmarks of immunogenic cell death incurring calreticulin (CALR) exposure, ATP secretion and high mobility group box 1 (HMGB1) release. Taken together, these data identify a previously uncharacterized signaling cascade leading to an immunogenic variant of mitochondrion-regulated necrosis, supporting the notion that eliciting regulated necrosis may constitute a valid approach for anticancer therapy.

Mitochondrial control of cellular life, stress, and death.

Since the discovery that mitochondrial membrane permeabilization represents a critical step in the regulation of intrinsic apoptosis, mitochondria have been viewed as pluripotent organelles, controlling cell death as well as several aspects of cell survival. Mitochondria constitute the most prominent source of ATP and are implicated in multiple anabolic and catabolic circuitries. In addition, mitochondria coordinate cell-wide stress responses, such as autophagy, and control nonapoptotic cell death routines, such as regulated necrosis. Thus, mitochondria seem to regulate a continuum of cellular functions, spanning from physiological metabolism to stress responses and death. The involvement of mitochondria in both vital and lethal processes is crucial for both embryonic and postembryonic development, as well as for the maintenance of adult tissue homeostasis. In line with this notion, primary mitochondrial defects or alterations in the signaling pathways that converge on or emanate from mitochondria underpin a large number of human diseases, including premature aging, neurodegenerative disorders, cardiovascular disorders, and cancer. Here, we provide an overview of the molecular mechanisms that enable mitochondria to sustain cell survival, coordinate stress responses, and mediate cell death, linking these pathways--whenever relevant--to cardiovascular health and disease.

Non-apoptotic functions of apoptosis-regulatory proteins.

During the past two decades, apoptotic cell death has been the subject of an intense wave of investigation, leading to the discovery of multiple gene products that govern both its induction and execution. In parallel, it has progressively become evident that most, if not all, proteins that had initially been discovered for their essential role in apoptosis also mediate a wide range of non-apoptotic functions. On the one hand, apoptotic regulators and executioners are involved in non-lethal physiological processes as diverse as cell cycle progression, differentiation, metabolism, autophagy and inflammation. On the other hand, pro-apoptotic proteins can control other modalities of programmed cell death, in particular regulated necrosis. In this review, we summarize the unconventional roles of the apoptotic core machinery from a functional perspective and discuss their pathophysiological implications.

Novel small molecule drugs inhibit tumor cell metabolism and show potent anti-tumorigenic potential.

BACKGROUND: Rapidly dividing tumor cells have an increased demand for nutrients to support their characteristic unabated growth; this demand is met by an increased availability of nutrients such as amino acids through vasculogenesis and by the enhanced cellular entry of nutrients through the upregulation of specific transporters. Deprivation of intracellular amino acids or block of amino acid uptake has been shown to be cytotoxic to many established human cancer cell lines in vitro and in human cancer xenograft models. RESULTS: In this paper, we provide evidence that the two small molecule oxyphenisatine analogs TOP001 and TOP216 exert their anti-cancer effect by affecting tumor cell metabolism and inducing intracellular amino acid deprivation, leading to a block of cell proliferation. GCN2-mediated phosphorylation of eIF2α as well as mTOR pathway inhibition supports the above notion. In addition, these novel anti-cancer compounds inhibit DNA and protein synthesis and induce apoptosis in a broad spectrum of cancer cell lines. In vivo, the compounds induce tumor stasis and regression in mouse xenograft models of human breast, prostate, ovarian and pancreatic cancer, both when administered intravenously and orally. CONCLUSION: In conclusion, these small molecules, built on a 1,3-dihydroindole-2-one scaffold, elicit strong anti-proliferative and cytotoxic activity, and importantly, a strong anti-tumorigenicity is observed in in vivo xenograft models of human breast, ovary, prostate and pancreatic cancers encouraging the translation of this class of compounds into the clinic.

Synthesis and antitumor effect in vitro and in vivo of substituted 1,3-dihydroindole-2-ones.

Optimization of the anticancer activity for a class of compounds built on a 1,3-dihydroindole-2-one scaffold was performed. In comparison with recently published derivatives of oxyphenisatin the new analogues exhibited an equally potent antiproliferative activity in vitro and improved tolerability and activity in vivo. The best compounds from this series showed low nanomolar antiproliferative activity toward a series of cancer cell lines (compound (S)-38: IC(50) of 0.48 and 2 nM in MCF-7 (breast) and PC3 (prostate), respectively) and potent antitumor effects in well tolerated doses in xenograft models. The racemic compound (RS)-38 showed complete tumor regression at a dose of 20 mg/kg administered iv on days 1 and 7 in a PC3 rat xenograft.