Paradoxical Roles of Elongation Factor-2 Kinase in Stem Cell Survival.

Protein synthesis inhibition is an immediate response during stress to switch the composition of protein pool in order to adapt to the new environment. It was reported that this response could be either protective or deleterious. However, how cells choose to live or die upon protein synthesis inhibition is largely unknown.

Autophagy and transporter-based multi-drug resistance.

All the therapeutic strategies for treating cancers aim at killing the cancer cells via apoptosis (programmed cell death type I). Defective apoptosis endow tumor cells with survival. The cell can respond to such defects with autophagy.

Design and synthesis of N-substituted indazole-3-carboxamides as poly(ADP-ribose)polymerase-1 (PARP-1) inhibitors(†).

A group of novel N-1-substituted indazole-3-carboxamide derivatives were synthesized and evaluated as inhibitors of poly(ADP-ribose)polymerase-1 (PARP-1). A structure-based design strategy was applied to a weakly active unsubstituted 1H-indazole-3-carboxamide 2, by introducing a three carbon linker between 1H-indazole-3-carboxamide and different heterocycles, and led to compounds 4 [1-(3-(piperidine-1-yl)propyl)-1H-indazole-3-carboxamide, IC(50) =36μm] and 5 [1-(3-(2,3-dioxoindolin-1-yl)propyl)-1H-indazole-3-carboxamide, IC(50) = 6.8μm].

Hyperoxia sensing: from molecular mechanisms to significance in disease.

Oxygen therapy using mechanical ventilation with hyperoxia is necessary to treat patients with respiratory failure and distress. However, prolonged exposure to hyperoxia leads to the generation of excessive reactive oxygen species (ROS), causing cellular damage and multiple organ dysfunctions. As the lungs are directly exposed, hyperoxia can cause both acute and chronic inflammatory lung injury and compromise innate immunity.

Immortalized mouse epithelial cell models to study the role of apoptosis in cancer.

Human cancer cell lines are widely used to model cancer but also have serious limitations. As an alternate approach, we have developed immortalized mouse epithelial cell model systems that are applicable to different tissue types and involve generation of immortalized cell lines that are genetically defined. By applying these model systems to mutant mice, we have extended the powerful approach of mouse genetics to in vitro analysis.

Role of the polarity determinant crumbs in suppressing mammalian epithelial tumor progression.

Most tumors are epithelial-derived, and although disruption of polarity and aberrant cellular junction formation is a poor prognosticator in human cancer, the role of polarity determinants in oncogenesis is poorly understood. Using in vivo selection, we identified a mammalian orthologue of the Drosophila polarity regulator crumbs as a gene whose loss of expression promotes tumor progression. Immortal baby mouse kidney epithelial cells selected in vivo to acquire tumorigenicity displayed dramatic repression of crumbs3 (crb3) expression associated with disruption of tight junction formation, apicobasal polarity, and contact-inhibited growth.

Induction of apoptosis by diterpenes from the soft coral Xenia elongata.

Four new diterpenes ( 1- 4) were isolated from the soft coral Xenia elongata using a novel cell-based screen for apoptosis-inducing, potential anticancer compounds. The molecular structures of the diterpenes were determined using a combination of NMR and mass spectrometry. The bioactivities were confirmed using a specific apoptosis induction assay based on genetically engineered mammalian lines with differential, defined capacities for apoptosis.

ERK1/2-dependent phosphorylation of BimEL promotes its rapid dissociation from Mcl-1 and Bcl-xL.

The proapoptotic protein Bim is expressed de novo following withdrawal of serum survival factors. Here, we show that Bim-/- fibroblasts and epithelial cells exhibit reduced cell death following serum withdrawal in comparison with their wild-type counterparts. In viable cells, Bax associates with Bcl-2, Bcl-x(L) and Mcl-1.

Autophagy suppresses tumor progression by limiting chromosomal instability.

Autophagy is a bulk degradation process that promotes survival under metabolic stress, but it can also be a means of cell death if executed to completion. Monoallelic loss of the essential autophagy gene beclin1 causes susceptibility to metabolic stress, but also promotes tumorigenesis. This raises the paradox that the loss of a survival pathway enhances tumor growth, where the exact mechanism is not known.

NBK/BIK antagonizes MCL-1 and BCL-XL and activates BAK-mediated apoptosis in response to protein synthesis inhibition.

Ribonucleases, antibiotics, bacterial toxins, and viruses inhibit protein synthesis, which results in apoptosis in mammalian cells. How the BCL-2 family of proteins regulates apoptosis in response to the shutoff of protein synthesis is not known. Here we demonstrate that an Escherichia coli toxin, MazF, inhibited protein synthesis by cleavage of cellular mRNA and induced apoptosis in mammalian cells.

Nutlin-3 protects kidney cells during cisplatin therapy by suppressing Bax/Bak activation.

Nutlins, the newly developed small molecule antagonists of MDM2, activate p53 and induce apoptosis in cancer cells, offering a novel strategy of chemotherapy. Recent studies have further suggested synergistic effects of nutlins with other chemotherapeutic drugs. However, it is unclear whether nutlins increase or decrease the side effects of these drugs in normal non-malignant cells or tissues.

A mouse model system to genetically dissect the molecular mechanisms regulating tumorigenesis.

The vast majority of human tumors are of epithelial origin and result from the accumulation of mutations that alter the function of pathways that control critical cellular processes, including proliferation, checkpoint regulation, and apoptosis. Authentically replicating these events in animal models is critical to understanding the biology of cancer and for testing the feasibility of novel therapies. We developed a mouse model that recapitulates the steps of epithelial tumor progression of multiple tissue types (kidney, breast, ovarian surface, and prostate epithelia), which takes advantage of the power of mouse genetics, and that allows for biochemical analysis, genetic selection, and screening.

Autophagy promotes tumor cell survival and restricts necrosis, inflammation, and tumorigenesis.

Defective apoptosis renders immortalized epithelial cells highly tumorigenic, but how this is impacted by other common tumor mutations is not known. In apoptosis-defective cells, inhibition of autophagy by AKT activation or by allelic disruption of beclin1 confers sensitivity to metabolic stress by inhibiting an autophagy-dependent survival pathway. While autophagy acts to buffer metabolic stress, the combined impairment of apoptosis and autophagy promotes necrotic cell death in vitro and in vivo.

Grm5 expression is not required for the oncogenic role of Grm1 in melanocytes.

Melanoma is the aberrant proliferation of melanocytes, the cells in the skin responsible for pigment (melanin) production. In its early stages, melanoma can be surgically removed with great success, however, advanced stages of melanoma have a high mortality rate due to the lack of responsiveness to currently available therapies. We have previously characterized a mouse melanoma model, TG-3, which has implicated the ectopic expression of metabotropic glutamate receptor 1 (Grm1, formerly mGluR1), in melanomagenesis and metastasis [Pollock et al.

Hypoxia and defective apoptosis drive genomic instability and tumorigenesis.

Genomic instability is a hallmark of cancer development and progression, and characterizing the stresses that create and the mechanisms by which cells respond to genomic perturbations is essential. Here we demonstrate that antiapoptotic BCL-2 family proteins promoted tumor formation of transformed baby mouse kidney (BMK) epithelial cells by antagonizing BAX- and BAK-dependent apoptosis. Cell death in vivo correlated with hypoxia and induction of PUMA (p53 up-regulated modulator of apoptosis).

ASAP, a novel protein complex involved in RNA processing and apoptosis.

Different isoforms of a protein complex termed the apoptosis- and splicing-associated protein (ASAP) were isolated from HeLa cell extract. ASAP complexes are composed of the polypeptides SAP18 and RNPS1 and different isoforms of the Acinus protein. While Acinus had previously been implicated in apoptosis and was recently identified as a component of the spliceosome, RNPS1 has been described as a general activator of RNA processing.

Association of Bax and Bak homo-oligomers in mitochondria. Bax requirement for Bak reorganization and cytochrome c release.

ATP depletion induced by hypoxia or mitochondrial inhibitors results in Bax translocation from cytosol to mitochondria and release of cytochrome c from mitochondria into cytosol in cultured rat proximal tubule cells. Translocated Bax undergoes further conformational changes to oligomerize into high molecular weight complexes (Mikhailov, V., Mikhailova, M.

BAX and BAK mediate p53-independent suppression of tumorigenesis.

BAX and BAK are essential regulators of proapoptotic signaling, and the disruption of apoptosis is linked to the development of cancer. To investigate the role of BAX and BAK in tumorigenesis, primary baby mouse kidney epithelial cells (BMKs) from wild-type, BAX-, BAK-, or BAK- and BAK-deficient mice were transformed by adenovirus E1A and dominant-negative p53 (p53DD). In wild-type BMKs, the expression of E1A and inactivation of p53 was sufficient for transformation but not tumorigenesis.

Bak and Bax function to limit adenovirus replication through apoptosis induction.

Adenovirus infection and expression of E1A induces both proliferation and apoptosis, the latter of which is blocked by the adenovirus Bcl-2 homologue E1B 19K. The mechanism of apoptosis induction and the role that it plays in productive infection are not known. Unlike apoptosis mediated by death receptors, infection with proapoptotic E1B 19K mutant viruses did not induce cleavage of Bid but nonetheless induced changes in Bak and Bax conformation, Bak-Bax interaction, caspase 9 and 3 activation, and apoptosis.

Bax and Bak independently promote cytochrome C release from mitochondria.

Pro-apoptotic Bax and Bak have been implicated in the regulation of p53-dependent apoptosis. We assessed the ability of primary baby mouse kidney (BMK) epithelial cells from bax(-/-), bak(-/-), and bax(-/-) bak(-/-) mice to be transformed by E1A alone or in conjunction with dominant-negative p53 (p53DD). Although E1A alone transformed BMK cells from p53-deficient mice, E1A alone did not transform BMK cells from bax(-/-), bak(-/-), or bax(-/-) bak(-/-) mice.