Infliximab prevents increased systolic blood pressure and upregulates the AKT/eNOS pathway in the aorta of spontaneously hypertensive rats

High systolic blood pressure caused by endothelial dysfunction is a comorbidity of metabolic syndrome that is mediated by local inflammatory signals. Insulin-induced vasorelaxation due to endothelial nitric oxide synthase (eNOS) activation is highly dependent on the activation of the upstream insulin-stimulated serine/threonine kinase (AKT) and is severely impaired in obese, hypertensive rodents and humans. Neutralisation of circulating tumor necrosis factor-α (TNFα) with infliximab improves glucose homeostasis, but the consequences of this pharmacological strategy on systolic blood pressure and eNOS activation are unknown. To address this issue, we assessed the temporal changes in the systolic pressure of spontaneously hypertensive rats (SHR) treated with infliximab. We also assessed the activation of critical proteins that mediate insulin activity and TNFα-mediated insulin resistance in the aorta and cardiac left ventricle. Our data demonstrate that infliximab prevents the upregulation of both systolic pressure and left ventricle hypertrophy in SHR. These effects paralleled an increase in AKT/eNOS phosphorylation and a reduction in the phosphorylation of inhibitor of nuclear factor-κB (Iκβ) and c-Jun N-terminal kinase (JNK) in the aorta. Overall, our study revealed the cardiovascular benefits of infliximab in SHR. In addition, the present findings further suggested that the reduction of systolic pressure and left ventricle hypertrophy by infliximab are secondary effects to the reduction of endothelial inflammation and the recovery of AKT/eNOS pathway activation.

The regulation of NHE₁ and NHE₃ activity by angiotensin II is mediated by the activation of the angiotensin II type I receptor/phospholipase C/calcium/calmodulin pathway in distal nephron cells

Angiotensin II (Ang II), acting via the AT1 receptor, induces an increase in intracellular calcium [Ca(2+)]i that then interacts with calmodulin (CaM). The Ca(2+)/CaM complex directly or indirectly activates sodium hydrogen exchanger 1 (NHE1) and phosphorylates calmodulin kinase II (CaMKII), which then regulates sodium hydrogen exchanger 3 (NHE3) activity. In this study, we investigated the cellular signaling pathways responsible for Ang II-mediated regulation of NHE1 and NHE3 in Madin-Darby canine kidney (MDCK) cells. The NHE1- and NHE3-dependent pHi recovery rates were evaluated by fluorescence microscopy using the fluorescent probe BCECF/AM, messenger RNA was evaluated with the reverse transcription polymerase chain reaction (RT-PCR), and protein expression was evaluated by immunoblot. We demonstrated that treatment with Ang II (1pM or 1 nM) for 30 min induced, via the AT1 but not the AT2 receptor, an equal increase in NHE1 and NHE3 activity that was reduced by the specific inhibitors HOE 694 and S3226, respectively. Ang II (1 nM) did not change the total expression of NHE1, NHE3 or calmodulin, but it induced CaMKII, cRaf-1, Erk1/2 and p90(RSK) phosphorylation. The stimulatory effects of Ang II (1 nM) on NHE1 or NHE3 activity or protein abundance was reduced by ophiobolin-A (CaM inhibitor), KN93 (CaMKII inhibitor) or PD98059 (Mek inhibitor). These results indicate that after 30 min, Ang II treatment may activate G protein-dependent pathways, including the AT1/PLC/Ca(2+)/CaM pathway, which induces CaMKII phosphorylation to stimulate NHE3 and induces cRaf-1/Mek/Erk1/2/p90(RSK) activity to stimulate NHE1

Cytosolic flagellin-induced lysosomal pathway regulates inflammasome-dependent and -independent macrophage responses

NAIP5/NLRC4 (neuronal apoptosis inhibitory protein 5/nucleotide oligomerization domain-like receptor family, caspase activation recruitment domain domain-containing 4) inflammasome activation by cytosolic flagellin results in caspase-1-mediated processing and secretion of IL-1β/IL-18 and pyroptosis, an inflammatory cell death pathway. Here, we found that although NLRC4, ASC, and caspase-1 are required for IL-1β secretion in response to cytosolic flagellin, cell death, nevertheless, occurs in the absence of these molecules. Cytosolic flagellin-induced inflammasome-independent cell death is accompanied by IL-1α secretion and is temporally correlated with the restriction of Salmonella Typhimurium infection. Despite displaying some apoptotic features, this peculiar form of cell death do not require caspase activation but is regulated by a lysosomal pathway, in which cathepsin B and cathepsin D play redundant roles. Moreover, cathepsin B contributes to NAIP5/NLRC4 inflammasome-induced pyroptosis and IL-1α and IL-1β production in response to cytosolic flagellin. Together, our data describe a pathway induced by cytosolic flagellin that induces a peculiar form of cell death and regulates inflammasome-mediated effector mechanisms of macrophages

Emerging role of angiotensin type 2 receptor (AT2R)/Akt/NO pathway in vascular smooth muscle cell in the hyperthyroidism

Hyperthyroidism is characterized by increased vascular relaxation and decreased vascular contraction and is associated with augmented levels of triiodothyronine (T3) that contribute to the diminished systemic vascular resistance found in this condition. T3 leads to augmented NO production via PI3K/Akt signaling pathway, which in turn causes vascular smooth muscle cell (VSMC) relaxation; however, the underlying mechanisms involved remain largely unknown. Evidence from human and animal studies demonstrates that the renin-angiotensin system (RAS) plays a crucial role in vascular function and also mediates some of cardiovascular effects found during hyperthyroidism. Thus, in this study, we hypothesized that type 2 angiotensin II receptor (AT2R), a key component of RAS vasodilatory actions, mediates T3 induced-decreased vascular contraction. Marked induction of AT2R expression was observed in aortas from T3-induced hyperthyroid rats (Hyper). These vessels showed decreased protein levels of the contractile apparatus: α-actin, calponin and phosphorylated myosin light chain (p-MLC). Vascular reactivity studies showed that denuded aortic rings from Hyper rats exhibited decreased maximal contractile response to angiotensin II (AngII), which was attenuated in aortic rings pre-incubated with an AT2R blocker. Further study showed that cultured VSMC stimulated with T3 (0.1 µmol/L) for 24 hours had increased AT2R gene and protein expression. Augmented NO levels and decreased p-MLC levels were found in VSMC stimulated with T3, both of which were reversed by a PI3K/Akt inhibitor and AT2R blocker. These findings indicate for the first time that the AT2R/Akt/NO pathway contributes to decreased contractile responses in rat aorta, promoted by T3, and this mechanism is independent from the endothelium.

Studio del pathway della Displasia Ectodermica Anidrotica (EDA)

Anhidrotic Ectodermal Dysplasia (EDA), is the most frequent form among Ectodermal Dysplasias, hereditary genetic disorders causing ectodermal appendages defective development. Indeed, EDA is characterized by defective formation of hair follicles, sweat glands and teeth both in human patients and animals. EDA, the gene mutated in Anhidrotic Ectodermal Dysplasia, encodes Ectodysplasin, a TNF family member that activates NF-kB mediated transcription. This disease can occur with mutations in other EDA-NF-kB pathway members, as EDA receptor, EDAR and its adapter, EDARADD. Moreover, mutations in TRAF6, NEMO, IKB and NF-kBs genes are responsible for Immunodeficiency associated EDA (EDA-ID). Several molecules, as SHH, WNT/DKK, BMP and LTβ, have already been reported to be EDA pathway regulators or effectors although the knowledge of the full spectrum of EDA targets remains incomplete. During the first part of the research project a gene expression analysis was performed in primary keratinocytes from Wild-type and Tabby (EDA model mouse) mice to identify novel EDA target genes. Earlier expression profiling at various developmental time points in Tabby and Wild-type mouse skin reported genes differentially expressed in the two samples and, to increase the resolution to find genes whose expression may be restricted to epidermal cells, the study was extended to primary keratinocyte cultures established from E19 Wild-type and Tabby skin. Using microarrays bearing 44,000 gene probes, we found 385 “preliminary candidate” genes whose expression was significantly affected by Eda defect. By comparing expression profiles to those from Eda-A1 (where Eda-A1 is highly expressed) transgenic skin, we restricted the list to 38 “candidate EDA targets”, 14 of which were already known to be expressed in hair follicles or epidermis. This work confirmed expression changes for 3 selected genes, Tbx1, Bmp7, and Jag1, both in primary keratinocytes and in Wild-type and Tabby whole skin, by Q-PCR and Western blotting analyses. Thus, this study detected novel candidate pathways downstream of EDA. In the second part of the research project, plasmid constructs were produced and analyzed to create a transgenic mouse model for Immunodeficiency associated EDA disease (XL-EDA-ID). In particular, plasmids containing mouse Wild-type and mutated Nemo cDNA under K-17 epidermis-specific promoter control and a Flag tag, were prepared, on the way to confine transgene expression to mice epidermis and to determine EDA phenotype without immunodeficiency for a comparison to Tabby model phenotype. EDA-ID mutations reported in patients and selected for this study are: C417R (C409R in mouse), causing Zinc Finger protein domain destabilization and A288G (A282G in mouse) affecting oligomerization of the protein. Moreover, the ex-novo mutation, ZnF, C-terminal Zinc Finger domain deletion, was tested. Thus, the constructs were analyzed by transient transfection, Western blotting and luciferase assays techniques, detecting Nemo Wild-type and mutant protein products and residue NF-kB activity in presence of mutants, after TNF stimulation. In particular, MEF_Nemo-/- cell line was used to monitor NF-kB activity without endogenous Nemo gene. Results show reduced NF-kB activity in presence of mutated Nemo forms compared to Wild-type: 81% for A282G (A288G in human); 24% for C409R (C417R in human); 15% for ZnF. C409R mutation (C417R in human), reported in 6 EDA-ID human patients, was selected to prepare transgenic model mouse. Mice (white, FVP) born following K17-promoter-Flag-Nemo_C409R plasmid region pronuclear injection, were analyzed for the transgene presence in the genotype and a preliminar examination of their phenotype was performed. In particular, one mouse showed considerable coat defects if compared to Wild-type mice. This preliminar analysis suggests a possible influence of Nemo mutant over-expression in epidermis without immunodeficiency. Still, more microscopic studies to analyze hair subtypes, Guard, Awl and Zigzag (usually alterated inTabby mouse model), Immunohistochemistry experiments to detect epidermis restricted Nemo expression and sweat glands analysis, will follow. This and other transgene positive mice will be crossed with black mice C57BL6 to obtain at least two indipendent agouti lines to analyze. Theses mice will be used in EDA target genes detection through microarrays. Following, plasmid constructs containing other Nemo mutant forms (A282G and ZnF) might be studied by the same experimental approaches to prepare more transgenic model mice to compare to Nemo_C409R and Tabby mouse models.

Computational investigation of the Plasmodium falciparum fatty acid biosynthetic pathway toward the discovery of novel antimalarials

The structural peculiarities of a protein are related to its biological function. In the fatty acid elongation cycle, one small carrier protein shuttles and delivers the acyl intermediates from one enzyme to the other. The carrier has to recognize several enzymatic counterparts, specifically interact with each of them, and finally transiently deliver the carried substrate to the active site. Carry out such a complex game requires the players to be flexible and efficiently adapt their structure to the interacting protein or substrate. In a drug discovery effort, the structure-function relationships of a target system should be taken into account to optimistically interfere with its biological function. In this doctoral work, the essential role of structural plasticity in key steps of fatty acid biosynthesis in Plasmodium falciparum is investigated by means of molecular simulations. The key steps considered include the delivery of acyl substrates and the structural rearrangements of catalytic pockets upon ligand binding. The ground-level bases for carrier/enzyme recognition and interaction are also put forward. The structural features of the target have driven the selection of proper drug discovery tools, which captured the dynamics of biological processes and could allow the rational design of novel inhibitors. The model may be perspectively used for the identification of novel pathway-based antimalarial compounds.

Reconstruction and analysis of the NF-kB pathway interactome: a systems biology approach

Background. One of the phenomena observed in human aging is the progressive increase of a systemic inflammatory state, a condition referred to as “inflammaging”, negatively correlated with longevity. A prominent mediator of inflammation is the transcription factor NF-kB, that acts as key transcriptional regulator of many genes coding for pro-inflammatory cytokines. Many different signaling pathways activated by very diverse stimuli converge on NF-kB, resulting in a regulatory network characterized by high complexity. NF-kB signaling has been proposed to be responsible of inflammaging. Scope of this analysis is to provide a wider, systemic picture of such intricate signaling and interaction network: the NF-kB pathway interactome. Methods. The study has been carried out following a workflow for gathering information from literature as well as from several pathway and protein interactions databases, and for integrating and analyzing existing data and the relative reconstructed representations by using the available computational tools. Strong manual intervention has been necessarily used to integrate data from multiple sources into mathematically analyzable networks. The reconstruction of the NF-kB interactome pursued with this approach provides a starting point for a general view of the architecture and for a deeper analysis and understanding of this complex regulatory system. Results. A “core” and a “wider” NF-kB pathway interactome, consisting of 140 and 3146 proteins respectively, were reconstructed and analyzed through a mathematical, graph-theoretical approach. Among other interesting features, the topological characterization of the interactomes shows that a relevant number of interacting proteins are in turn products of genes that are controlled and regulated in their expression exactly by NF-kB transcription factors. These “feedback loops”, not always well-known, deserve deeper investigation since they may have a role in tuning the response and the output consequent to NF-kB pathway initiation, in regulating the intensity of the response, or its homeostasis and balance in order to make the functioning of such critical system more robust and reliable. This integrated view allows to shed light on the functional structure and on some of the crucial nodes of thet NF-kB transcription factors interactome. Conclusion. Framing structure and dynamics of the NF-kB interactome into a wider, systemic picture would be a significant step toward a better understanding of how NF-kB globally regulates diverse gene programs and phenotypes. This study represents a step towards a more complete and integrated view of the NF-kB signaling system.

Immagi-nazione e post-nazione in tre scrittrici scozzesi contemporanee: Jackie Kay, A. L. Kennedy, Ali Smith

Il presente studio affronta la complessa relazione esistente tra i concetti di donna, identità e nazione nell’ambito del rinnovato progetto politico scozzese avviato dalla devolution. La letteratura femminile e la cultura scozzese contemporanea vengono dunque esaminate in un’ottica postcoloniale, coordinando una prospettiva storico-sociale a un’analisi discorsiva della nazione, comportando inoltre continui riferimenti alle più recenti teorie femministe e di genere. La produzione letteraria di Jackie Kay, A. L. Kennedy e Ali Smith infatti sembra rendere possibile un’apertura della nozione di Scottishness, consentendo un approfondimento dei temi della differenza sessuale e culturale, immaginando propriamente la Scozia in senso post-nazionale.

Sonic Hedgehog pathway impairment in Neural Precursor Cells of the Ts65Dn mouse, an animal model of Down syndrome

Mental retardation in Down syndrome (DS) has been imputed to the decreased brain volume, which is evident starting from the early phases of development. Recent studies in a widely used mouse model of DS, the Ts65Dn mouse, have shown that neurogenesis is severely impaired during the early phases of brain development, suggesting that this defect may be a major determinant of brain hypotrophy and mental retardation in individuals with DS. Recently, it has been found that in the cerebellum of Ts65Dn mice there is a defective responsiveness to Sonic Hedgehog (Shh), a potent mitogen that controls cell division during brain development, suggesting that failure of Shh signaling may underlie the reduced proliferation potency in DS. Based on these premises, we sought to identify the molecular mechanisms underlying derangement of the Shh pathway in neural precursor cells (NPCs) from Ts65Dn mice. We found that the expression levels of the Shh receptor Patched1 (Ptch1) were increased compared to controls both at the RNA and protein level. Partial silencing of Ptch1 expression in trisomic NPCs restored cell proliferation, indicating that proliferation impairment was due to Ptch1 overexpression. We further found that the overexpression of Ptch1 in trisomic NPCs is related to increased levels of AICD, a transcription-promoting fragment of amyloid precursor protein (APP). Increased AICD binding to the Ptch1 promoter favored its acetylated status, thus enhancing Ptch1 expression. Taken together, these data provide novel evidence that Ptch1 over expression underlies derangement of the Shh pathway in trisomic NPCs, with consequent proliferation impairment. The demonstration that Ptch1 over expression in trisomic NPCs is due to an APP fragment provides a link between this trisomic gene and the defective neuronal production that characterizes the DS brain.

LRP1 modulates APP trafficking and APP metabolism within compartments of the secretory pathway. Increased AICD generation is ineffective in nuclear translocation and transcriptional activation

LRP1 modulates APP trafficking and metabolism within compartments of the secretory pathway The amyloid precursor protein (APP) is the parent protein to the amyloid beta peptide (Abeta) and is a central player in Alzheimer’s disease (AD) pathology. Abeta liberation depends on APP cleavage by beta- and gamma-secretases. To date, only a unilateral view of APP processing exists, excluding other proteins, which might be transported together and/or processed dependent on each other by the secretases described above. The low density lipoprotein receptor related protein 1 (LRP1) was shown to function as such a mediator of APP processing at multiple steps. Newly synthesized LRP1 can interact with APP, implying an interaction between these two proteins early in the secretory pathway. Therefore, we wanted to investigate whether LRP1 can mediate APP trafficking along the secretory pathway, and, if so, whether it affects APP processing. Indeed, we demonstrate that APP trafficking is strongly influenced by LRP1 transport through the endoplasmic reticulum (ER) and Golgi compartments. LRP1-constructs with ER- and Golgi-retention motifs (LRP-CT KKAA, LRP-CT KKFF) had the capacity to retard APP trafficking at the respective steps in the secretory pathway. Here, we provide evidence that APP metabolism occurs in close conjunction with LRP1 trafficking, highlighting a new role of lipoprotein receptors in neurodegenerative diseases. Increased AICD generation is ineffective in nuclear translocation and transcriptional activity A sequence of amyloid precursor protein (APP) cleavages gives rise to the APP intracellular domain (AICD) together with amyloid beta peptide (Abeta) and/or p3 fragment. One of the environmental factors identified favouring the accumulation of AICD appears to be a rise in intracellular pH. This accumulation is a result of an abrogated cleavage event and does not extend to other secretase substrates. AICD can activate the transcription of artificially expressed constructs and many downstream gene targets have been discussed. Here we further identified the metabolism and subcellular localization of the constructs used in this well documented gene reporter assay. We also co-examined the mechanistic lead up to the AICD accumulation and explored possible significances for its increased expression. We found that most of the AICD generated under pH neutralized conditions is likely that cleaved from C83. Furthermore, the AICD surplus is not transcriptionally active but rather remains membrane tethered and free in the cytosol where it interacts with Fe65. However, Fe65 is still essential in AICD mediated transcriptional transactivation although its exact role in this set of events is unclear.

adaptive capabilities of the pi3k/akt/mtor pathway in acute myeloid leukemia revealed by the use of selective inhibitors

Because of its aberrant activation, the PI3K/AKT/mTOR signaling pathway represents a pharmacological target in blast cells from patients with acute myelogenous leukemia (AML). Using Reverse Phase Protein Microarrays (RPMA), we have analyzed 20 phosphorylated epitopes of the PI3K/Akt/mTor signal pathway of peripheral blood and bone marrow specimens of 84 patients with newly diagnosed AML. Fresh blast cells were grown for 2 h, 4 h or 20 h untreated or treated with a panel of phase I or phase II Akt allosteric inhibitors, either alone or in combination with the mTOR kinase inhibitor Torin1 or the broad RTK inhibitor Sunitinib. By unsupervised hierarchical clustering a strong phosphorylation/activity of most of the sampled members of the PI3K/Akt/mTOR pathway was observed in 70% of samples from AML patients. Remarkably, however, we observed that inhibition of Akt phosphorylation, as well as of its substrates, was transient, and recovered or even increased far above basal level after 20 h in 60% samples. We demonstrated that inhibition of Akt induces FOXO-dependent insulin receptor expression and IRS-1 activation, attenuating the effect of drug treatment by reactivation of PI3K/Akt. Consistent with this model we found that combined inhibition of Akt and RTKs is much more effective than either alone, revealing the adaptive capabilities of signaling networks in blast cells and highliting the limations of these drugs if used as monotherapy.

SMO inhibitor specifically targets the Hedgehog Pathway and reverts the drug-resistance of Leukemic Stem Cells

Abnormal Hedgehog signaling is associated with human malignancies. Smo, a key player of that signaling, is the most suitable target to inhibit this pathway. To this aim several molecules, antagonists of Smo, have been synthesized, and some of them have started the phase I in clinical trials. Our hospital participated to one of these studies which investigated the oral administration of a new selective inhibitor of Smo (SMOi). To evaluate ex vivo SMOi efficacy and to identify new potential clinical biomarkers of responsiveness, we separated bone marrow CD34+ cells from 5 acute myeloid leukemia (AML), 1 myelofibrosis (MF), 2 blastic phases chronic myeloid leukemia (CML) patients treated with SMOi by immunomagnetic separation, and we analysed their gene expression profile using Affimetrix HG-U133 Plus 2.0 platform. This analysis, showed differential expression after 28 days start of therapy (p-value ≤ 0.05) of 1,197 genes in CML patients and 589 genes in AML patients. This differential expression is related to Hedgehog pathway with a p-value = 0.003 in CML patients and with a p-value = 0.0002 in AML patients, suggesting that SMOi targets specifically this pathway. Among the genes differentially expressed we observed strong up-regulation of Gas1 and Kif27 genes, which may work as biomarkers of responsiveness of SMOi treatment in CML CD34+ cells whereas Hedgehog target genes (such as Smo, Gli1, Gli2, Gli3), Bcl2 and Abca2 were down-regulated, in both AML and CML CD34+ cells. It has been reported that Bcl-2 expression could be correlated with cancer therapy resistance and that Hedgehog signaling modulate ATP-binding (ABC) cassette transporters, whose expression has been correlated with chemoresistance. Moreover we confirmed that in vitro SMOi treatment targets Hedgehog pathway, down-regulate ABC transporters, Abcg2 and Abcb1 genes, and in combination with tyrosine kinase inhibitors (TKIs) could revert the chemoresistance mechanism in K562 TKIs-resistant cell line.

Genus Bifidobacterium: taxonomy studies and gene expression analysis on folate pathway

Folates (vitamin B9) are essential water soluble vitamins, whose deficiency in humans may contribute to the onset of several diseases, such as anaemia, cancer, cardiovascular diseases, neurological problems as well as defects in embryonic development. Human and other mammals are unable to synthesize ex novo folate obtaining it from exogenous sources, via intestinal absorption. Recently the gut microbiota has been identified as an important source of folates and the selection and use of folate producing microorganisms represents an innovative strategy to increase human folate levels. The aim of this thesis was to gain a fundamental understanding of folate metabolism in Bifidobacterium adolescentis. The work was subdivided in three main phases, also aimed to solve different problems encountered working with Bifidobacterium strains. First, a new identification method (based on PCR-RFLP of hsp60 gene) was specifically developed to identify Bifidobacterium strains. Secondly, Bifidobacterium adolescentis biodiversity was explored in order to recognize representing strains of this species to be screened for their folate production ability. Results showed that this species is characterized by a wide variability and support the idea that a possible new taxonomic re-organization would be required. Finally B. adolescentis folate metabolism was studied using a double approach. A quantitative analysis of folate content was complemented by the examination of expression levels of genes involved in folate related pathways. For the normalization process, required to increase the robustness of the qRT-PCR analysis, an appropriate set of reference genes was tested using two different algorithms. Results demonstrate that B.adolescentis strains may represent an endogenous source of natural folate and they could be used to fortify fermented dairy products. This bio-fortification strategy presents many advantages for the consumer, providing native folate forms more bio-available, and not implicated in the discussed controversy concerning the safety of high intake of synthetic folic acid.

The constitutive activation of the DNA damage response pathway is a novel therapeutic target in aggressive B-cell lymphoma

The recent finding that MYC-driven cancers are sensitive to inhibition of the DNA damage response (DDR) pathway, prompted us to investigate the role of DDR pathway as therapeutic target in diffuse large B-cell lymphoma (DLBCL), which frequently overexpresses the MYC oncogene. In a preliminary immunohistochemical study conducted on 99 consecutive DLBCL patients, we found that about half of DLBCLs showed constitutive expression of the phosphorylated forms of checkpoint kinases (CHK) and CDC25c, markers of DDR activation, and of phosphorylated histone H2AX (γH2AX), marker of DNA damage and genomic instability. Constitutive γH2AX expression correlated with c-MYC levels and DDR activation, and defined a subset of tumors characterised by poor outcome. Next, we used the CHK inhibitor PF-0477736 as a tool to investigate whether the inhibition of the DDR pathway might represent a novel therapeutic approach in DLBCL. Submicromolar concentrations of PF-0477736 hindered proliferation in DLBCL cell lines with activated DDR pathway. These results were fully recapitulated with a different CHK inhibitor (AZD-7762). Inhibition of checkpoint kinases induced rapid DNA damage accumulation and apoptosis in DLBCL cell lines and primary cells. These data suggest that pharmacologic inhibition of DDR through targeting of CHK kinases may represent a novel therapeutic strategy in DLBCL. The second part of this work is the clinical, molecular and functional description of a paradigmatic case of primary refractory Burkitt lymphoma characterized by spatial intratumor heterogeneity for the TP53 mutational status, high expression levels of genomic instability and DDR activation markers, primary resistance to chemotherapy and exquisite sensitivity to DDR inhibitors.

Study of PI3K/Akt signaling pathway as potential molecular target for T-cell acute lymphoblastic leukemia (T-ALL) treatment: pan-inhibition of PI3K catalitic isoforms as better therapeutic approach

Class I phosphatidylinositol 3-kinases (PI3Ks) are heterodimeric lipid kinases consisting of a regulatory subunit and one of four catalytic subunits (p110α, p110β, p110γ or p110δ). p110γ/p110δ PI3Ks are highly enriched in leukocytes. In general, PI3Ks regulate a variety of cellular processes including cell proliferation, survival and metabolism, by generating the second messenger phosphatidylinositol-3,4,5-trisphosphate (PtdIns(3,4,5)P3). Their activity is tightly regulated by the phosphatase and tensin homolog (PTEN) lipid phosphatase. PI3Ks are widely implicated in human cancers, and in particular are upregulated in T-cell acute lymphoblastic leukemia (T-ALL), mainly due to loss of PTEN function. These observations lend compelling weight to the application of PI3K inhibitors in the therapy of T-ALL. At present different compounds which target single or multiple PI3K isoforms have entered clinical trials. In the present research, it has been analyzed the therapeutic potential of the pan-PI3K inhibitor BKM120, an orally bioavailable 2,6-dimorpholino pyrimidine derivative, which has entered clinical trials for solid tumors, on both T-ALL cell lines and patient samples. BKM120 treatment resulted in cell cycle arrest and apoptosis, being cytotoxic to a panel of T-ALL cell lines and patient T-lymphoblasts. Remarkably, BKM120 synergized with chemotherapeutic agents currently used for treating T-ALL patients. BKM120 efficacy was confirmed in in vivo studies to a subcutaneous xenotransplant model of human T-ALL. Because it is still unclear which agents among isoform-specific or pan inhibitors can achieve the greater efficacy, further analyses have been conducted to investigate the effects of PI3K inhibition, in order to elucidate the mechanisms responsible for the proliferative impairment of T-ALL. Overall, these results indicated that BKM120 may be an efficient treatment for T-ALLs that have aberrant up-regulation of the PI3K signaling pathway and strongly support clinical application of pan-class I PI3K rather than single-isoform inhibitors in T-ALL treatment.