Philippe Marchetti

In recent years, our knowledge regarding the metabolism of melanoma has greatly advanced and consequently new therapeutic strategies are being developed. This review is focused on metabolic path ways contributing to melanoma proliferation, the influence of BRAF inhibitors on those metabolic pathwaysand finally a presentation of potential therapeutic strategies aimed at blocking metabolic signaling pathways and thereforemelanoma development.

Since these twenty last years, there is an increasing interest for large-scale analysis of biological function. In the field of transcriptome, the emergence of microarray-based technologies and the design of DNA biochips allow high-throughput studies of RNA expression in cell and tissue at a given moment. In the field of proteome, methods of reference are still the 2D electrophoresis followed by analysis with mass spectrometry. Technological progress makes it possible to apply microarray methods to proteomics study : they are protein biochips or protein arrays. Expression analysis of proteins in a cell or a tissue in simultaneous and highly parallel way give further information for large-scale studies of signaling pathway. Numerous applications of protein microarray-based assays are described in basic biological research and in medical research to identify diagnostic biomarkers of inflammatory and cancerous pathologies and to find out news drugs and new therapeutic targets. This rev...

Killer cell inhibitory receptors (KIRs) inhibit NK and T cell cytotoxicity when recognizing MHC class I molecules on target cells. They possess two tandem intracytoplasmic immunoreceptor tyrosine-based inhibition motifs (ITIMs) that, when phosphorylated, each bind to the two Src homology 2 domain-bearing protein tyrosine phosphatases SHP-1 and SHP-2 in vitro. Using chimeric receptors having an intact intracytoplasmic KIR domain bearing both ITIMs (N + C-KIR), a deleted domain containing the N-terminal ITIM only (N-KIR), or a deleted domain containing the C-terminal ITIM only (C-KIR), we examined the respective contributions of the two ITIMs in the inhibition of cell activation in two experimental models (a rat mast cell and a mouse B cell line) that have been widely used to analyze KIR functions. We found that the two KIR ITIMs play distinct roles. When coaggregated with immunoreceptor tyrosine-based activation motif-bearing receptors such as high-affinity IgE receptors or B cell re...

In several models of lymphocyte apoptosis, two alterations of mitochondrial function precede advanced DNA fragmentation: (1) a reduction of mitochondrial transmembrane potential (delta psi m) and (2) an increase in mitochondrial generation of superoxide anion. Here we show that two fluorochromes allow for the identification of analogous mitochondrial perturbations in circulating T lymphocytes from human immunodeficiency virus (HIV)-1+ donors. The first among these fluorochromes, the cationic lipophilic dye DiOC6(3), measures delta psi m; the second marker, hydroethidine (HE), is nonfluorescent, unless it is oxidized by superoxide anions to the product ethidium (Eth). CD4+ or CD8+ cells from clinically asymptomatic HIV-1 carriers contain a significantly elevated percentage of cells endowed with enhanced HE --> Eth conversion and/or reduced DiOC6(3) uptake as compared with normal controls. Phenotypic characterization of (HE --> Eth)high cells from HIV+ donors shows that these ce...

Variations in calcium concentration within the endoplasmic reticulum ([Ca(2+)](ER)) may play a role in cell growth. This study evaluates the regulation of calcium pools by growth modulators of prostate cancer (PC) cells, the insulin growth factor (IGF), and the tumor necrosis growth factor-alpha (TNFalpha) as well as evaluating the possible role of [Ca(2+)](ER) variations as signals for growth modulation. We show that IGF (5 ng/ml), which increases cell growth, induces an increase in [Ca(2+)](ER) whereas TNFalpha (1 ng/ml) which reduces cell proliferation and induces apoptosis, reduces [Ca(2+)](ER). IGF-induced [Ca(2+)](ER) increase is correlated to an overexpression of the sarcoendoplasmic calcium-ATPase 2B (SERCA2b), whereas TNFalpha-induced [Ca(2+)](ER) decrease is associated to a reduction in SERCA2b expression. Pretreatment with epidermal growth factors (EGF) or IGF does not prevent TNFalpha from affecting the induction of apoptosis, [Ca(2+)](ER) reduction and SERCA2b downregulation. Reduction in [Ca(2+)](ER) induced by thapsigargin (TG) (from 1 pM to 1 microM, 48 h) reduces LNCaP growth in a dose dependent manner and induces apoptosis when cells are treated with 1 microM TG. We also show that a transient TG application (1 pM, 1 nM, 1 microM 15 min) is insufficient to induce a long lasting decrease in [Ca(2+)](ER), since [Ca(2+)](ER) remains identical to the control for 48 h following TG application. These treatments (1 pM and 1 nM, 15 min) do not modify cell growth. However, TG (1 microM, 15 min) induces apoptosis. We thus identify [Ca(2+)](ER) and SERCA2b as a central targets for causing LNCaP PC cell life or death induced by growth modulators. Furthermore our results indicate that calcium pool contents can regulate cell growth.

In a number of experimental systems, the early stage of the apoptotic process, i.e. the stage which precedes nuclear disintegration, is characterized by the breakdown of the inner mitochondrial transmembrane potential (delta psi m). Here we address the question as to whether mitochondrial permeability transition (PT) pores may account for the delta psi m dissipation in lymphocyte apoptosis. Drugs known for their PT-inhibitory potential (bongkrekic acid, cyclosporin A, and the non-immunosuppressive cyclosporin A analogue N-methyl-Val-4-cyclosporin A) are capable of preventing the apoptotic delta psi m disruption. Moreover, pharmacological modulation of PT-mediated delta psi m dissipation can prevent apoptosis. Thus, while suppressing the delta psi m disruption, bongkrekic acid also inhibits the apoptotic chromatinolysis. In conclusion, these data are compatible with the hypothesis that apoptotic delta psi m disruption is mediated by the formation of PT pores and that PT-mediated delta psi m disruption is a critical event of the apoptotic cascade.

We have recently shown that lymphocyte apoptosis induced by dexamethasone or superantigens is accompanied by reduction of mitochondrial transmembrane potential (delta psi m) which precedes nuclear DNA fragmentation. Here, we demonstrate that fluorochromes such as 3,3' dihexyloxacarbocyanine iodide [DiOC6(3)] which measure delta psi m, or fluorochromes such as hydroethidine (HE) which measure mitochondrial superoxide anion production allow the identification of thymocytes or peripheral T lymphocytes which are eliminated by apoptosis in vivo. In mice bearing transgenic alpha/beta T cell receptor (TCR) specific for a class I-restricted male-specific peptide, the superoxide-mediated oxidation of HE into ethidium (Eth) is enhanced among thymocytes which are being deleted due to negative selection (CD4+ CD8+ cells expressing the transgenic TCR in male mice) or lack of positive selection (CD4+ CD8- thymocytes from female mice). delta psi m reduction and/or enhanced HE oxidation are also found when apoptosis is induced by a series of pathogenic agents. Thus, lethal irradiation provokes mitochondrial and nuclear signs of apoptosis, and both these alterations are absent in mice bearing a p53 null mutation, underlying the correlation between mitochondrial perturbation and nuclear apoptosis. Similarly, superantigen-triggered deletion of peripheral T cells in vivo is accompanied by enhanced HE-->Eth conversion and reduced DiOC6(3) uptake. More importantly, as compared to normal controls, CD4+ or CD8+ cells from clinically asymptomatic human immunodeficiency virus-1 (HIV-1) carriers also contain a significantly elevated percentage of cells endowed with reduced DiOC6(3) uptake. In superantigen- and HIV-induced apoptosis, the percentage of T lymphocytes with a subnormal DiOC6(3) uptake is more important than that of cells marked by enhanced HE-->Eth conversion. In conclusion, mitochondrial alterations precede and/or accompany nuclear signs of apoptosis induced by physiological and a variety of different pathogenic agents in vivo.

We tested whether inhibition of mitochondrial membrane potential dissipation by CsA (ciclosporin A) would prevent doxorubicin-induced myocardial and mitochondrial dysfunction. Acute and subchronic models of doxorubicin exposition were performed in mice with either a single intraperitoneal bolus (10 mg/kg of body weight, intraperitoneal) or one injection of 4 mg·kg(-1) of body weight·week(-1) during 5 weeks. Follow-up was at 1.5 weeks and 16 weeks in acute and subchronic models respectively. Mice received either CsA (1 mg/kg of body weight, intraperitoneal on alternate days) or saline until follow-up. Heart function was evaluated by echocardiography. Mitochondrial measurements included oxygen consumption, membrane potential and externally added calcium-induced mitochondrial permeability transition. Mitochondrial mass was evaluated by transmission electronic microscopy and mtDNA (mitochondrial DNA) content. Mitochondrial dynamics were detected as the expression of GTPases involved in mitochondrial fusion and fission. In both the acute and chronic models, doxorubicin decreased left ventricular fractional shortening and survival. Heart function and survival were improved by CsA, but not by tacrolimus (FK506), a ciclosporin derivative with no inhibitory effect on the mitochondrial transition pore. In the acute model, doxorubicin exposure was associated with increased mtDNA content, mitochondrial fragmentation and changes in mitochondrial fusion- and fission-related transcripts [increases in Mfn2 (mitofusin 2), Opa1 (optic atrophy 1 homologue) and Fis1 (fission 1 homologue), and no changes in Drp1 (dynamin 1-like)]. CsA did not alter mitochondrial biogenesis, but prevented mitochondrial fragmentation and partially restored the mitochondrial energy-producing capacity. These findings suggest that in vivo CsA treatment may limit MPTP (mitochondrial permeability transition pore) opening, mitochondrial potential loss and contractile depression in acute and chronic models of cardiac toxicity induced by doxorubicin.