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Inhibitors targeting the mitogen‐activated protein kinase (MAPK) pathway and immune checkpoint molecules have dramatically improved the survival of patients with BRAFV600‐mutant melanoma. For BRAF/RAS wild‐type (WT) melanoma patients, however, immune checkpoint inhibitors remain the only effective therapeutic option with 40% of patients responding to PD‐1 inhibition. In the present study, a large panel of 10 BRAFV600‐mutant and 13 BRAF/RAS WT melanoma cell lines was analyzed to examine MAPK dependency and explore the potential utility of MAPK inhibitors in this melanoma subtype. We now show that the majority of BRAF/RAS WT melanoma cell lines (8/13) display some degree of sensitivity to trametinib treatment and resistance to trametinib in this melanoma subtype is associated with, but not mediated by NF1 suppression. Although knockdown of NF1 stimulates RAS and CRAF activity, the activation of CRAF by NF1 knockdown is limited by ERK‐dependent feedback in BRAF‐mutant cells, but not in BRAF/RAS WT melanoma cells. Thus, NF1 is not a dominant regulator of MAPK signaling in BRAF/RAS WT melanoma, and co‐targeting multiple MAP kinase nodes provides a therapeutic opportunity for this melanoma subtype. [ABSTRACT FROM AUTHOR]

The extracellular matrix (ECM) affects cancer cell characteristics. Inability of normal epithelial cells to attach to the ECM induces apoptosis (anoikis). Cancer cells are often anoikis resistant, a prerequisite for their metastatic spread. Previously we demonstrated that the placenta manipulates its surrounding ECM in a way that prevents breast cancer cells (BCCL) attachment and induces their motility and aggregation. This fits with the fact that although breast cancer during pregnancy is often advanced, metastasis to the placenta is rarely observed. Placental intervillous space provides suitable conditions for cancer cell arrival. Yet, the outcome of the short communication between the placental ECM to the BCCL and its effect on BCCL malignant potential are unknown, and are the focus of our study. In the current study we analyzed the effect of placental ECM on BCCL survival pathways and drug resistance. Microarray analysis suggested activation of the NF‐κB and stress response pathways. Indeed, the placenta‐conditioned ECM induced autophagy in ERα + BCCL, inactivated the NF‐κB inhibitor (IκB) and increased integrin α5 in the BCCL. The autophagy mediated MCF‐7 and T47D migration and the placental ECM‐BCCL interactions reduced the BCCL sensitivity to Taxol. We also demonstrated by using siRNA that integrin α5 was responsible for the MCF‐7 autophagy and suggest this molecule as a suitable target for therapy. What's new? Pregnancy‐associated breast cancer is usually identified in a more advanced stage of the disease. Yet, metastasis to the placenta is rare. Placenta‐conditioned extracellular matrix (ECM) prevents breast cancer cell (BCCL) adhesion and facilitates their motility and aggregation, but the effect of placental ECM on BCCL survival pathways and drug resistance remain unknown. Here, the authors report that placental ECM‐BCCL interactions induce elevated levels of integrin‐a5, IkB phosphorylation, and autophagy in BCCL and reduce their sensitivity to the drug Taxol. Integrin‐a5 modulates the autophagy that mediates the cell aggregation and survival, and thus emerges as a potentially suitable target for therapy. [ABSTRACT FROM AUTHOR]

Colorectal cancer (CRC) is the third most common cancer diagnosed worldwide. The limitations of cisplatin-based chemotherapy have prompted intense interest among scientists to search for alternative metal-based anticancer medicines. Gold(III) complexes have been among the most widely investigated since they showed higher cytotoxicity than cisplatin and promising in vitro and in vivo anticancer activities in CRC but their clinical usefulness has been limited by their poor stability under physiological conditions. A novel gold(III) porphyrin complexes [gold(III) porphyrin-adamantane chloride (SN1) and gold(III) porphyrin mono-acetate chloride (SN2)] with improved aqueous stability were synthesized. SN1 and SN2 reduced the survival of human CRC HT-29 and HCT-116 cell lines, caused cell cycle arrest in G 2 /M phase, and we observed downregulation of the expression of cyclin B1 and cyclin-dependent kinase 1 (Cdk1) along with up-regulation of the active form of p53, p21 and Bcl-2–associated X (Bax). Furthermore, SN1 and SN2 induced apoptosis by the intrinsic pathway, since they lead to the cleavage of caspase 9, caspase 3 and poly(ADP-ribose) polymerase (PARP), and up-regulating Bax. Phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), nuclear factor-κB (NF-κB) and extracellular signal-regulated kinases (ERK) are important for cell survival and proliferation. SN1 and SN2 lead to decrease in the activity of Akt where the phosphorylated form decreased with time as well as they caused an important decrease in the phosphorylation of ERK and activity of NF-κB. Finally, SN1 and SN2 complexes affected p38/mitogen-activated protein kinase (MAPK) pathway then we recorded an increase in the cyclooxygenase-2 expression and its enzymatic product prostaglandin E 2 . [ABSTRACT FROM AUTHOR]

Androgen deprivation therapy (ADT) is the mainstay treatment for advanced prostate cancer (PC). Most patients eventually progress to a condition known as castration-resistant prostate cancer (CRPC), characterized by lack of response to ADT. Although new androgen receptor signaling (ARS) inhibitors and chemotherapeutic agents have been introduced to overcome resistance to ADT, many patients progress because of primary or acquired resistance to these agents. This comprehensive review aims at exploring the mechanisms of resistance and progression of PC, with specific focus on alterations which lead to the activation of androgen receptor (AR)-independent pathways of survival. Our work integrates available clinical and preclinical data on agents which target these pathways, assessing their potential clinical implication in specific settings of patients. Given the rising interest of the scientific community in cancer immunotherapy strategies, further attention is dedicated to the role of immune evasion in PC. [ABSTRACT FROM AUTHOR]

Genomic instability (GIN) is a hallmark of most cancer cells. However, compared to most human cancer cell types, the retinoblastoma tumor cells show a relatively stable genome. The fundamental basis of this genomic stability has yet to be elucidated, and the role of certain proteins involved in cell cycle regulation may be the key to the development of these specific genotypes. We examined whether thyroid hormone receptor beta 1 and 2 (TRβ1 and TRβ2), known to regulate tumorigenesis, and PTTG1, a mitotic checkpoint protein, play a role in maintaining genomic stability in retinoblastoma. In order to elucidate the role of these proteins in development of aneuploidy/polyploidy, an indicator of GIN, we first studied comparative GIN in retinoblastomas and multiple RB mutant cancer cell lines using single nucleotide polymorphism (SNP) analysis. We then utilized pLKO lentiviral vectors to selectively modify expression of the targeted cell cycle proteins and interpret their effect on downstream cell cycle proteins and their relative effects on the development of polyploidy in multiple tumor cell lines. The SNP analysis showed that retinoblastomas displayed relatively fewer genomic copy number changes as compared to other RB1-deficient cancer cell lines. Both TRβ1 and TRβ2 knockdown led to accumulation of E2F1 and PTTG1 and increased GIN as demonstrated by an increase in polyploidy. Downregulation of PTTG1 led to a relative decrease in GIN while upregulation of PTTG1 led to a relative increase in GIN. Knockdown of E2F1 led to a downstream decrease in PTTG1 expression. Rb-knockdown also upregulated E2F1 and PTTG1 leading to increased GIN. We showed that Rb is necessary for PTTG1 inhibition and genomic stability. A relatively stable genome in retinoblastoma tumor cells is maintained by TRβ1 and TRβ2-mediated PTTG1 inhibition, counteracting Rb-deficiency-related GIN. TRβ1, TRβ2 and Rb-KD all led to the downstream PTTG1 accumulation, apparently through an activation of E2F1 resulting in extensive genomic instability as seen in other Rb-deficient tumors. [ABSTRACT FROM AUTHOR]

Purpose: In this study, we first aimed to evaluate the effects in vitro and in vivo, of the Hsp90 inhibitor NVP-AUY922, in endometrial cancer (EC). We also aimed to track nuclear factor kappa B (NF-κB) signalling, a key pathway involved in endometrial carcinogenesis and to check whether NVP-AUY922 treatment modulates it both in vitro and in vivo.Procedures: I n vitro effects of NVP-AUY922 on EC cell growth and the signalling pathways were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), clonogenic assays, Western Blot and luciferase assay. NVP-AUY922 effect on Ishikawa (IK) xenograft growth was evaluated in vivo, and NF-κB activity was monitored using bioluminescence imaging.Results: NVP-AUY922 inhibited the growth of three endometrial cell lines tested in vitro. In vivo, NVP-AUY922 reduced tumour growth of 47 % (p = 0.042) compared to control condition. Moreover, the bioluminescence signal of the tumours harbouring IK NF-κB-LUC cells was significantly reduced in NVP-AUY922-treated animals compared to untreated ones.Conclusions: NVP-AUY922 reduced EC tumour growth and NF-κB signalling both in vitro and in vivo. As therapeutic resistance of EC remains a challenge for oncologists nowadays, we think that NVP-AUY922 represents a valid alternative to conventional chemotherapy, and we believe that this approach for assessing and tracking the activation of NF-κB pathway may be of therapeutic benefit. [ABSTRACT FROM AUTHOR]

Melanoma is one of the most aggressive forms of cancer with a continuously growing incidence worldwide and is usually resistant to chemotherapy agents, which is due in part to a strong resistance to apoptosis. Previously, we had showed that B16-F0 murine melanoma cells undergoing apoptosis are able to delay their own death induced by ursolic acid (UA), a natural pentacyclic triterpenoid compound. We had demonstrated that tyrosinase and TRP-1 up-regulation in apoptotic cells and the subsequent production of melanin were implicated in an apoptosis resistance mechanism. Several resistance mechanisms to apoptosis have been characterized in melanoma such as hyperactivation of DNA repair mechanisms, drug efflux systems, and reinforcement of survival signals (PI3K/Akt, NF-κB and Raf/MAPK pathways). Otherwise, other mechanisms of apoptosis resistance involving different proteins, such as cyclooxygenase-2 (COX-2), have been described in many cancer types. By using a strategy of specific inhibition of each ways, we suggested that there was an interaction between melanogenesis and COX-2/PGE 2 pathway. This was characterized by analyzing the COX-2 expression and activity, the expression of tyrosinase and melanin production. Furthermore, we showed that anti-proliferative and proapoptotic effects of UA were mediated through modulation of multiple signaling pathways including Akt and ERK-1/2 proteins. Our study not only uncovers underlying molecular mechanisms of UA action in human melanoma cancer cells but also suggest its great potential as an adjuvant in treatment and cancer prevention. [ABSTRACT FROM AUTHOR]

Ultimately, the common final pathway of any glomerular disease is podocyte effacement, podocyte loss, and, eventually, glomerular scarring. There has been a long-standing debate on the underlying mechanisms for podocyte depletion, ranging from necrosis and apoptosis to detachment of viable cells from the glomerular basement membrane. However, this debate still continues because additional pathways of programmed cell death have been reported in recent years. Interestingly, viable podocytes can be isolated out of the urine of proteinuric patients easily, emphasizing the importance of podocyte detachment in glomerular diseases. In contrast, detection of apoptosis and other pathways of programmed cell death in podocytes is technically challenging. In fact, we still are lacking direct evidence showing, for example, the presence of apoptotic bodies in podocytes, leaving the question unanswered as to whether podocytes undergo mechanisms of programmed cell death. However, understanding the mechanisms leading to podocyte depletion is of particular interest because future therapeutic strategies might interfere with these to prevent glomerular scarring. In this review, we summarize our current knowledge on podocyte cell death, the different molecular pathways and experimental approaches to study these, and, finally, focus on the mechanisms that prevent the onset of programmed cell death. [ABSTRACT FROM AUTHOR]

Oxaliplatin is a third-generation platinum compound approved for clinical use relatively recently as compared to other drugs of the same class. Its main cellular target is DNA, where similarly to cisplatin and carboplatin it forms cross-links. However, due to a unique indication for colorectal cancer, synergistic interaction with fluoropyrimidines and peculiar toxicity profile, oxaliplatin is different from those compounds. Multiple lines of evidence indicate differences in transport and metabolism, consequences of DNA platination, as well as DNA repair and transduction of DNA damage. Here, we explore the preclinical features that may explain the unique properties of oxaliplatin in the clinics. Among them, the capability to accumulate in tumor cells via organic cation transporters, to kill KRAS mutant cells and to activate immunogenic cell death appears helpful to explain in part its clinical behavior. The continuous investigation of the molecular pharmacology of oxaliplatin is expected to provide clues to the definitions of predictors of drug activity and toxicity to translate to the clinical setting. [ABSTRACT FROM AUTHOR]

Castration and androgen receptor (AR) pathway inhibitors induce profound and sustained responses in advanced prostate cancer. However, the inevitable recurrence is associated with reactivation of the AR and progression to a more aggressive phenotype termed castration-resistant prostate cancer (CRPC). AR reactivation can occur directly through genomic modification of the AR gene, or indirectly via co-factor and co-chaperone deregulation. This mechanistic heterogeneity is further complicated by the stress-driven induction of a myriad of overlapping cellular survival pathways. In this review, we describe the heterogeneous and evolvable molecular landscape of CRPC and explore recent successes and failures of therapeutic strategies designed to target AR reactivation and adaptive survival pathways. We also discuss exciting areas of burgeoning anti-tumour research, and their potential to improve the survival and management of patients with CRPC. [ABSTRACT FROM AUTHOR]

Cerebellar granule neurons (CGNs) constitute the most abundant neuronal population in the mammalian brain. Their postnatal generation and the feasibility to induce their apoptotic death in vitro make them an excellent model to study the effect of several neurotransmitters and neurotrophins. Here, we first review which factors are involved in the generation and proliferation of CGNs in the external granule layer (EGL) and in the regulation of their differentiation and migration to internal granule layer (IGL). Special attention was given to the role of several neurotrophins and the NMDA subtype of glutamate receptor. Then, using the paradigm of potassium deprivation in cultured CGNs, we address several extracellular factors that promote the survival of CGNs, with particular emphasis on the cellular mechanisms. The role of specific protein kinases leading to the regulation of transcription factors and recent data involving the small G protein family is also discussed. Finally, the participation of some members of Bcl-2 family and the inhibition of mitochondria-related apoptotic pathway is also considered. Altogether, these studies evidence that CGNs are a key model to understand the development and the survival of neuronal populations. [ABSTRACT FROM AUTHOR]

CLL remains an incurable disease, making it crucial to continue searching for new therapies efficient in all CLL cases. We have studied the effect of combining arsenic trioxide (ATO) with fludarabine, a frontline drug in CLL. We have found a synergistic interaction between 1 μM ATO and 5 μM fludarabine that significantly enhanced the cytotoxic effect of the individual drugs. Importantly, ATO sensitized fludarabine-resistant cells to the action of this drug. The mechanism behind this effect included the downregulation of phospho-Akt, phospho-ERK, and the Mcl-1/Bim and Bcl-2/Bax ratios. The combination of ATO and fludarabine partially overcame the survival effect induced by co-culturing CLL cells with stromal cells. Therefore, low concentrations of ATO combined with fludarabine may be an efficient therapeutic strategy in CLL patients. [ABSTRACT FROM AUTHOR]

Ischemia/reperfusion (I/R) injury still represents an important cause of morbidity following hepatic surgery and limits the use of marginal livers in hepatic transplantation. Transient blood flow interruption followed by reperfusion protects tissues against damage induced by subsequent I/R. This process known as ischemic preconditioning (IP) depends upon intrinsic cytoprotective systems whose activation can inhibit the progression of irreversible tissue damage. Compared to other organs, liver IP has additional features as it reduces inflammation and promotes hepatic regeneration. Our present understanding of the molecular mechanisms involved in liver IP is still largely incomplete. Experimental studies have shown that the protective effects of liver IP are triggered by the release of adenosine and nitric oxide and the subsequent activation of signal networks involving protein kinases such as phosphatidylinositol 3-kinase, protein kinase C δ/ε and p38 MAP kinase, and transcription factors such as signal transducer and activator of transcription 3, nuclear factor-κB and hypoxia-inducible factor 1. This article offers an overview of the molecular events underlying the preconditioning effects in the liver and points to the possibility of developing pharmacological approaches aimed at activating the intrinsic protective systems in patients undergoing liver surgery. [ABSTRACT FROM AUTHOR]

There is accumulating evidence that breast cancer may arise from mutated mammary stem/progenitor cells which have been termed breast cancer-initiating cells (BCIC). BCIC identified in clinical specimens based on membrane phenotype (CD44+/CD24-/low and/or CD133+ expression) or enzymatic activity of aldehyde dehydrogenase 1 (ALDH1+), have been demonstrated to have stem/progenitor cell properties, and are tumorigenic when injected in immunocompromized mice at very low concentrations. BCIC have also been isolated and in vitro propagated as non-adherent spheres of undifferentiated cells, and stem cell patterns have been recognized even in cancer cell lines. Recent findings indicate that aberrant regulation of self renewal is central to cancer stem cell biology. Alterations in genes involved in self-renewal pathways, such as Wnt, Notch, sonic hedgehog, PTEN and BMI, proved to play a role in breast cancer progression. Hence, targeting key elements mediating the self renewal of BCIC represents an attractive option, with a solid rationale, clearly identifiable molecular targets, and adequate knowledge of the involved pathways. Possible concerns are related to the poor knowledge of tolerance and efficacy of inhibiting self-renewal mechanisms, because the latter are key pathways for a variety of biological functions and it is unknown whether their interference would kill BCIC or simply temporarily stop them. Thus, efforts to develop BCIC-targeted therapies should not only be focused on interfering on self-renewal, but could seek to identify additional molecular targets, like those involved in regulating EMT-related pathways, in reversing the MDR phenotype, in inducing differentiation and controlling cell survival pathways. [ABSTRACT FROM AUTHOR]

Abstract: A primary response to inflammation is an increased survival of the target cell. Several pathways have been identified that promote maintenance of the cell. The principal mechanism for the extended survival is through induction of anti-apoptotic Bcl-2 family proteins. Bcl-2 was the founding member of this family with five additional members, Bcl-XL, Bcl-W, Bcl-B, Bfl-1, and Mcl-1, discovered mostly in hematological malignancies. Another mechanism that could add to cell survival is the Pim kinase pathway. This family of enzymes is associated with Myc-driven transcription, cell cycle regulation, degradation of pro-apoptotic proteins, and protein translation. Chronic lymphocytic leukemia serves as an optimal model to understand the mechanism by which these two protein families provide survival advantage to cells. In addition, since this malignancy is known to be maintained by microenvironment milieu, this further adds advantage to investigate mechanisms by which these pro-survival proteins are induced in the presence of stromal support. Multiple mechanisms exists that result in increase in transcript and protein level of anti-apoptotic Bcl-2 family members. Following these inductions, post-translational modifications occur resulting in increased stability of pro-survival proteins, while Pim-mediated phosphorylation inhibits pro-apoptotic protein activity. Furthermore, there is a cross-talk between these two (Bcl-2 family proteins and Pim family proteins) pathways that co-operate with each other for CLL cell survival and maintenance. Vigorous efforts are being made to create small molecules that affect these proteins directly or indirectly. Several of these pharmacological inhibitors are in early clinical trials for patients with hematological malignancies. [ABSTRACT FROM AUTHOR]

Abstract: The advent of drugs targeting tumor-associated prosurvival alterations of cancer cells has changed the interest of antitumor drug development from cytotoxic drugs to target-specific agents. Although single-agent therapy with molecularly targeted agents has shown limited success in tumor growth control, a promising strategy is represented by the development of rational combinations of target-specific agents and conventional antitumor drugs. Activation of survival/antiapoptotic pathways is a common feature of cancer cells that converge in the development of cellular resistance to cytotoxic agents. The survival pathways implicated in cellular response to drug treatment are primarily PI3K/Akt and Ras/MAPK, which also mediate the signalling activated by growth factors and play a role in the regulation of critical processes including cell proliferation, metabolism, apoptosis and angiogenesis. Inhibitors of PI3K, Akt and mTOR have been shown to sensitize selected tumor cells to cytotoxic drugs through multiple downstream effects. Moreover, the MAPK pathway, also implicated in the regulation of gene expression in response to stress stimuli, can interfere with the chemotherapy-induced proapoptotic signals. Targeting Hsp90, which acts as a molecular chaperone for survival factors including Akt, may have the potential advantage to simultaneously block multiple oncogenic pathways. Overall, the available evidence supports the interest of rationally designed approaches to enhance the efficacy of conventional antitumor treatments through the inhibition of survival pathways and the notion that the concomitant targeting of multiple pathways may be a successful strategy to deal with tumor heterogeneity and to overcome drug resistance of tumor cells. [ABSTRACT FROM AUTHOR]

Abstract: Elimination of infected cells via programmed cell death plays a fundamental role in the defense of multicellular organisms against bacteria, viruses, and parasites. Several pathogens have therefore evolved sophisticated strategies to modulate the host cell death programme for their survival. This review aims to summarize recent findings on how bacterial pathogens interfere with the host cell death apparatus. [Copyright &y& Elsevier]

Hepatic ischemia/reperfusion injury (IRI) is aggravated by steatosis and is a main risk factor in fatty liver transplantation. Adenosine receptors (ARs) are emerging as therapeutic targets in liver diseases. By using cellular and in vivo systems of hepatic steatosis and IRI, here we evaluated the effects of pharmacological A2AR and A1R activation. The A2AR agonist CGS21680 protected the primary steatotic murine hepatocyte from IR damage and the activation of ASK1 and JNK. Such an effect was attributed to a phosphatidylinositol-3-kinase (PI3K)/Akt-dependent inhibition of ASK1. By contrast, the A1R agonist CCPA enhanced IR damage, intracellular steatosis and oxidative species (OS) production, thereby further increasing the lipid/OS-dependent ASK1-JNK stimulation. The CGS2680 and CCPA effects were nullified by a genetic ASK1 downregulation in steatotic hepatoma C1C7 cells. In steatotic mice livers, CGS21680 protected against hepatic IRI and ASK1/JNK activation whereas CCPA aggravated hepatic steatosis and IRI, and enhanced ASK1 and JNK stimulation. These results evidence a novel mechanism of CGS21680-mediated hepatoprotection, i.e., the PI3K/AKT-dependent inhibition of ASK1, and they show that CGS21680 and CCPA reduces and enhances the IRI of fatty liver, respectively, by preventing or increasing the activation of the cytotoxic ASK1/JNK axis. They also indicate the selective employment of A2AR agonists as an effective therapeutic strategy to prevent IRI in human fatty liver surgery. [ABSTRACT FROM AUTHOR]

We as well as others have recently shown that Hsp90 is overexpressed in multiple myeloma (MM) and critically contributes to tumour cell survival. Pharmacologic blockade of Hsp90 has consistently been found to induce MM cell death. However, most data have been obtained with MM cell lines whereas knowledge about the molecular effects of pharmacologic Hsp90 blockade in primary tumour cells is limited. Furthermore, these investigations have so far focused on geldanamycin derivatives. We analysed the biochemical effects of a novel diarylisoxazole-based Hsp90 inhibitor (NVP-AUY922) on signalling pathways and cell death in a large set of primary MM tumour samples and in MM cell lines. Treated cells displayed the molecular signature and pharmacodynamic properties for abrogation of Hsp90 function, such as downregulation of multiple survival pathways and strong upregulation of Hsp70. NVP-AUY922 treatment efficiently induced MM cell apoptosis and revealed both sensitive and resistant subgroups. Sensitivity was not correlated with TP53 mutation or Hsp70 induction levels and stromal cells from the bone marrow microenvironment were unable to abrogate NVP-AUY922-induced apoptosis of MM cells. Thus, NVP-AUY922 may be a promising drug for treatment of MM and clinical studies are warranted.Leukemia (2008) 22, 1604–1612; doi:10.1038/leu.2008.111; published online 15 May 2008 [ABSTRACT FROM AUTHOR]

Depending on multiple factors DNA damage leads either to cell cycle arrest or apoptosis. One of the main players deciding the fate of a cell is the tumor suppressor p53 that modulates these responses in a transcription-dependent and -independent manner. Over the past few years, however, strong evidence accumulated that p53 engages also powerful pro-survival pathways by transcriptionally activating a multitude of genes whose products efficiently counteract apoptosis. Our review summarizes the current knowledge concerning approximately forty p53-regulated proteins that exert their anti-apoptotic potential by interfering with diverse cellular processes. These activities are surely essential for normal development and maintenance of a healthy organism, but may easily turn into the dark side of the tumor suppressor p53 contributing to tumorigenesis.Cell Death and Differentiation (2008) 15, 959–976; doi:10.1038/cdd.2008.33; published online 21 March 2008 [ABSTRACT FROM AUTHOR]

Abstract: Previous investigations have revealed that dental monomers could affect intracellular pathways leading to cell survival or cell death. Mitogen-activated protein kinase (MAPK) and protein kinase B (AKT) might mediate cell responses as well as cell survival and apoptosis. The purpose of this study was to evaluate the effects of 2-hydroxyethyl methacrylate (HEMA) on the ERK1/2 and AKT pathways in human primary pulp fibroblasts (HPCs). HPCs were treated with various concentrations of HEMA, after which viability and reactive oxygen species levels were determined by flow cytometry with Annexin V-PI staining and 2,7-dichlorofluorescine diacetate, respectively. Whole-cell extracts were immunoblotted with anti-P-Akt or anti–P-ERK1/2. Cell viability decreased in a dose-dependent manner after HEMA exposure, showing a significant decrease with 10 mmol/L HEMA (p < .05). HEMA treatment resulted in a 4-fold increase in reactive oxygen species formation (p < .05). A short HEMA exposure (30–90 minutes) increased ERK1/2 phosphorylation, whereas a decrease in the AKT phosphorylation was observed. Selective inhibitors of the ERK (PD98059) and AKT (LY294002) pathways amplified HPC cell damage after HEMA exposure. Our findings demonstrated that HEMA exposure modulates the ERK and AKT pathways in different manners, and that in turn, they function in parallel to mediate pro-survival signaling in pulp cells subjected to HEMA cytotoxicity. [Copyright &y& Elsevier]

Abstract: Ex-vivo studies have suggested that imatinib-resistance in chronic myeloid leukemia (CML) patients occurs despite adequate suppression of BCR-ABL activity. Whether BCR-ABL phosphorylation levels differ between imatinib-sensitive and -resistant patients is not known. We compared the phosphorylation of BCR-ABL in 54 previously untreated CML patients and 62 imatinib-resistant CML patients with progressive disease. Resistant patients had significantly lower levels of BCR-ABL, CrkL and AKT phosphorylation than previously untreated patients, but STAT5 phosphorylation showed no difference. These observations suggest that imatinib- resistance is not necessarily dependent on higher activity in BCR-ABL-dependent pathways, but is likely due to the activation of other pathways. [Copyright &y& Elsevier]

Abstract: Huntington''s disease (HD) has a mitochondrial dysfunction causing the vulnerability to the excitotoxicity and activations of multiple cell death pathways. Recent evidences suggest that the hematopoietic cytokine, granulocyte-colony stimulating factor (G-CSF), exerts pleiotropic neuroprotection in acute neural injury with activating various survival pathways. Thus, we investigated whether G-CSF can modulate neurodegeneration in an HD animal model induced by 3-nitropropionic acid (3NP), which inhibits mitochondrial succinate dehydrogenase complex II. Either G-CSF (50 μg/kg/day) or saline (as vehicle) was administered intraperitoneally for 5 days with 3NP (63 mg/kg/day) continuous osmotic pump infusion into male Lewis rats. We measured motor scales (0–8) daily and sacrificed rats at 5 days. We observed that G-CSF receptors were expressed in 3NP-induced degenerating striatum. Rats treated with G-CSF showed less degree of neurologic deficits. In the G-CSF-treated rats, the striatal lesion volume measured by Nissl staining, TUNEL+ apoptotic cells, Fluorojade C+ degenerating neurons, and c-Jun+ cells were all decreased. In western blotting, G-CSF activated survival pathways including p-ERK, p-eNOS, p-STAT3, and p-Akt. In summary, G-CSF was found to have neuroprotective effects and save striatal cells through activations of survival pathways in the 3NP-induced striatal degeneration model for HD. [Copyright &y& Elsevier]

Chronic lymphocytic leukemia (CLL) is characterized by survival advantage and accumulation of CD5+ mature B lymphocytes. Expression of zeta-chain-associated protein-70 (ZAP-70), normally present in T lymphocytes or immature B cells, is associated with disease aggressiveness, as IgVH mutational status, and some proteins implicated in survival signal pathways are found to be constitutively activated in CLL cells. ZAP-70 signaling is regulated through molecular adaptors, such as the proto-oncogene product c-Casitas B lineage lymphoma (c-Cbl). The aim of this study was to determine the implication of this proto-oncogene product in CLL in survival signals. It appeared that expression of c-Cbl was increased in CLL and not correlated to that of B cell linker protein or ZAP-70. Furthermore, c-Cbl was significantly hypophosphorylated in progressive disease, so that hypophosphorylated form of c-Cbl (c-Cbl.P) along with ZAP-70, set a cutoff ratio distributing patients with stable situation below 1, and those with progressive disease equal or above 1. Given that phospholipase gamma 2 (PLCγ2) function is also influenced by c-Cbl hypophosphorylation, the ratio of PLCγ2 to c-Cbl.P was measured in CLL B cells and consistently found to be ≥ 1 in Binet stage B CLL patients, as opposed to stage A CLL patients. These findings invite analysis of the role of c-Cbl in CLL. [ABSTRACT FROM AUTHOR]

Background/Aims: Glycine hepatoprotection is well known. However, the mechanisms involved are still poorly characterized. Methods: Glycine protection was investigated in isolated rat hepatocytes pretreated with 2 mmol/L glycine 15min before incubation under hypoxic conditions. Results: Glycine significantly reduced Na+ overload and hepatocyte death caused by hypoxia. Glycine protection required the activation of a signal pathway involving Src, Pyk2 and p38 MAP kinases. Glycine treatment also induced a 11% increase of hepatocyte volume and transient ATP release. The prevention of cell swelling by hepatocyte incubation in a hypertonic medium as well as the degradation of extracellular ATP with apyrase or the block P2 purinergic receptors with suramin reverted glycine-induced cytoprotection and inhibited Src, Pyk2 and p38 MAPK activation. Glycine down-modulated Na+/H+ exchanger (NHE) activity, without affecting the development of intracellular acidosis during hypoxia. Such an effect was reverted by inhibiting p38 MAPK that also abolished glycine protection against Na+ overload caused by hypoxia. Conclusions: Glycine-induced ATP release in response to a moderate hepatocyte swelling led to the autocrine stimulation of P2 receptors and to the activation of Src, Pyk2 and p38 MAPK that increased hepatocyte resistance to hypoxia by preventing Na+ influx through NHE. [Copyright &y& Elsevier]

Abstract: Prostate cancers are genetically and phenotypically heterogenous. The heterogeneous nature of prostate cancer may be a consequence of mutations in different cell types (basal stem, transit amplifying or luminal cells) resulting in different malignant maturation pathways. One consistent characterization of these cancers, however, is their eventual progression to a hormonal refractory state. The development of effective novel therapeutic strategies requires an understanding of the mechanisms for the development of such a refractory state. Targeting proliferative and survival pathways provides a rationale for drug design and development for hormone refractory prostate cancer. Prostate cancer cells, however, develop an enhanced redundancy in downstream survival signaling. Hence, new combinational therapies must be developed with the understanding that compensatory mechanisms evolve under selective pressure. [Copyright &y& Elsevier]

Interferon a (IFN-a) has been widely used in the treatment of human solid and haematologic malignancies. Although the antitumour activity of IFN-a is well recognised at present, no major advances have been achieved in the last few years. Recent findings have provided new information on the molecular mechanisms of the antitumour activity of the cytokine. In fact, IFN-a appears to block cell proliferation, at least in part, through the induction of apoptotic effects. This cytokine can also regulate the progression of tumour cells through the different phases of the cell cycle inducing an increase of the expression of the cyclin-dependent kinase inhibitors p21 and p27. However, it must be considered that IFN-a is a physiologic molecule with ubiquitously expressed receptors that is likely to activate survival mechanisms in the cell. We have recently identified an epidermal growth factor (EGF) Ras-dependent protective response to the apoptosis induced by IFN-a in epidermoid cancer cells. The identification of tissue- and/or tumour-specific survival pathways and their selective targeting might provide a new approach to improve the efficacy of IFN-a-based treatment of human cancer. Moreover, new pegylated species of IFN-a are now available with a more favourable pharmacokinetic profile. We will review these achievements, and we will specifically address the topic of IFN-a-based molecularly targeted combinatory antitumour approaches. [ABSTRACT FROM AUTHOR]

Executioner caspases induce the biochemical and cellular changes characteristic of apoptosis. Activation of caspases is therefore regarded as “the kiss of death” resulting in the cell’s demise. Recent reports indicate however that in some situations, caspase activation may induce other responses than apoptosis. These findings raise the question of how cells manage to counteract the killing activities of executioner caspases. Experiments performed in our laboratory have unraveled a mechanism that allows cells to survive in the presence of activated executioner caspases. This mechanism is based on the partial cleavage of RasGAP into an N-terminal fragment that activates the Ras–PI3K–Akt survival pathway. This protective pathway may be activated to allow cells to use executioner caspases for other purposes than inducing apoptosis. [Copyright &y& Elsevier]

The regulation of neuronal growth and survival during development requires interplay between extrinsic and intrinsic factors. Among the latter, transcription factors play a key role. In the nematode, the transcription factor CES-2 predisposes neurosecretory motoneurons to death, whereas E4BP4 (NFIL3), one of its vertebrate homologs, regulates survival of pro-B lymphocytes. We show that E4BP4 is expressed by embryonic rat and chicken motoneurons in vivo, with levels being highest in neurons that survive the period of naturally occurring cell death. Overexpression of E4BP4 by electroporation of purified motoneurons in culture protected them almost completely against cell death triggered by removal of neurotrophic factors or activation of death receptors. Moreover, E4BP4 strongly enhanced neuronal cell size and axonal growth. Axons of motoneurons transfected with E4BP4 were 3.5-fold longer than control neurons grown on laminin; this effect required the activity of P13 kinase. In vivo, overexpression of E4BP4 in chicken embryos reduced the number of dying motoneurons by 45%. Our results define E4BP4 as a novel intrinsic regulator of motoneuron growth and survival. Pathways regulated by E4BP4 are of potential interest both for understanding neuromuscular development and for promoting neuronal survival and regeneration in pathological situations. [ABSTRACT FROM AUTHOR]

Metazoan living cells exposed to microgravity undergo dramatic changes in morphological and biological properties, which ultimately lead to apoptosis and phenotype reprogramming. However, apoptosis can occur at very different rates depending on the experimental model, and in some cases, cells seem to be paradoxically protected from programmed cell death during weightlessness. These controversial results can be explained by considering the notion that the behavior of adherent cells dramatically diverges in respect to that of detached cells, organized into organoids-like, floating structures. We investigated both normal (MCF10A) and cancerous (MCF-7) breast cells and found that appreciable apoptosis occurs only after 72 h in MCF-7 cells growing in organoid-like structures, in which major modifications of cytoskeleton components were observed. Indeed, preserving cell attachment to the substrate allows cells to upregulate distinct Akt- and ERK-dependent pathways in MCF-7 and MCF-10A cells, respectively. These findings show that survival strategies may differ between cell types but cannot provide sufficient protection against weightlessness-induced apoptosis alone if adhesion to the substrate is perturbed. [ABSTRACT FROM AUTHOR]