The beta-catenin--TCF-1 pathway ensures CD4(+)CD8(+) thymocyte survival.

The association of trans-acting T cell factors (TCFs) or lymphoid enhancer factor 1 (LEF-1) with their coactivator beta-catenin mediates transient transcriptional responses to extracellular Wnt signals. We show here that T cell maturation depends on the presence of the beta-catenin--binding domain in TCF-1. This domain is necessary to mediate the survival of immature CD4(+)CD8(+) double-positive (DP) thymocytes. Accelerated spontaneous thymocyte death in the absence of TCF-1 correlates with aberrantly low expression of the anti-apoptotic protein Bcl-x(L). Increasing anti-apoptotic effectors in thymocytes by the use of a Bcl-2 transgene rescued TCF-1-deficient DP thymocytes from apoptosis. Thus, TCF-1, upon association with beta-catenin, transiently ensures the survival of immature T cells, which enables them to generate and edit T cell receptor (TCR) alpha chains and attempt TCR-mediated positive selection.

Cutaneous cancer stem cell maintenance is dependent on beta-catenin signalling.

Continuous turnover of epithelia is ensured by the extensive self-renewal capacity of tissue-specific stem cells. Similarly, epithelial tumour maintenance relies on cancer stem cells (CSCs), which co-opt stem cell properties. For most tumours, the cellular origin of these CSCs and regulatory pathways essential for sustaining stemness have not been identified. In murine skin, follicular morphogenesis is driven by bulge stem cells that specifically express CD34. Here we identify a population of cells in early epidermal tumours characterized by phenotypic and functional similarities to normal bulge skin stem cells. This population contains CSCs, which are the only cells with tumour initiation properties. Transplants derived from these CSCs preserve the hierarchical organization of the primary tumour. We describe beta-catenin signalling as being essential in sustaining the CSC phenotype. Ablation of the beta-catenin gene results in the loss of CSCs and complete tumour regression. In addition, we provide evidence for the involvement of increased beta-catenin signalling in malignant human squamous cell carcinomas. Because Wnt/beta-catenin signalling is not essential for normal epidermal homeostasis, such a mechanistic difference may thus be targeted to eliminate CSCs and consequently eradicate squamous cell carcinomas.

Sawhorse-type diruthenium tetracarbonyl complexes containing porphyrin-derived ligands as highly selective photosensitizers for female reproductive cancer cells.

Diruthenium tetracarbonyl complexes of the type [Ru2(CO)4(l2-g2-O2CR)2L2] containing a Ru-Ru backbone with four equatorial carbonyl ligands, two carboxylato bridges, and two axial two-electron ligands in a sawhorse-like geometry have been synthesized with porphyrin-derived substituents in the axial ligands [1: R is CH3, L is 5-(4-pyridyl)-10,15,20-triphenyl-21,23H-porphyrin], in the bridging carboxylato ligands [2: RCO2H is 5-(4-carboxyphenyl)-10,15,20-triphenyl-21,23H-porphyrin, L is PPh3; 3: RCO2H is 5-(4-carboxyphenyl)-10,15,20-triphenyl-21,23H-porphyrin, L is 1,3,5-triaza-7-phosphatricyclo [3.3.1.1]decane], or in both positions [4: RCO2H is 5-(4-carboxyphenyl)-10,15,20-triphenyl-21,23H-porphyrin, L is 5-(4-pyridyl)-10,15,20-triphenyl-21,23H-porphyrin]. Compounds 1-3 were assessed on different types of human cancer cells and normal cells. Their uptake by cells was quantified by fluorescence and checked by fluorescence microscopy. These compounds were taken up by human HeLa cervix and A2780 and Ovcar ovarian carcinoma cells but not by normal cells and other cancer cell lines (A549 pulmonary, Me300 melanoma, PC3 and LnCap prostate, KB head and neck, MDAMB231 and MCF7 breast, or HT29 colon cancer cells). The compounds demonstrated no cytotoxicity in the absence of laser irradiation but exhibited good phototoxicities in HeLa and A2780 cells when exposed to laser light at 652 nm, displaying an LD50 between 1.5 and 6.5 J/cm2 in these two cell lines and more than 15 J/cm2 for the others. Thus, these types of porphyric compound present specificity for cancer cell lines of the female reproductive system and not for normal cells; thus being promising new organometallic photosensitizers.

Novel soluble HLA-A2/MELAN-A complexes selectively stain a differentiation defective subpopulation of CD8+ T cells in patients with melanoma.

Multimeric MHC I-peptide complexes containing phycoerythrin-streptavidin are widely used to detect and investigate antigen-specific CD8+ (and CD4+) T cells. Because such reagents are heterogeneous, we compared their binding characteristics with those of monodisperse dimeric, tetrameric and octameric complexes containing linkers of variable length and flexibility on Melan-A-specific CD8+ T cell clones and peripheral blood mononuclear cells (PBMC) from HLA-A*0201(+) melanoma patients. Striking binding differences were observed for different defined A2/Melan-A(26-35) complexes on T cells depending on their differentiation stage. In particular, short dimeric but not octameric A2/Melan-A(26-35) complexes selectively and avidly stained incompletely differentiated effector-memory T cells clones and populations expressing CD27 and CD28 and low levels of cytolytic mediators (granzymes and perforin). This subpopulation was found in PBMC from all six melanoma patients analyzed and proliferated on peptide stimulation with only modest phenotypic changes. By contrast influenza matrix(58-66) -specific CD8+ PBMC from nine HLA-A*0201(+) healthy donors were efficiently stained by A2/Flu matrix(58-61) multimers, but not dimer and upon peptide stimulation proliferated and differentiated from memory into effector T cells. Thus PBMC from melanoma patients contain a differentiation defective sub-population of Melan-A-specific CD8+ T cells that can be selectively and efficiently stained by short dimeric A2/Melan- A(26-35) complexes, which makes them directly accessible for longitudinal monitoring and further investigation.

Role of Wnt/β-catenin in intestinal homeostasis

RESUME: La voie de signalisation Wnt est, dérégulée dans approximativement 90% des tumeurs colorectales humaines. La protéine ß-caténine, transducteur central de la voie de signalisation Wnt, peut directement moduler la transcription des gènes en interagissant avec des facteurs de transcription de la famille TCF/LEF. Afin d'étudier le rôle de la voie de signalisation Wnt dans l'homéostasie de l'épithélium intestinal normal, nous avons généré un modèle marin d'ablation inductible du gène de la ß-caténine. Cette ablation dans les souris adultes a provoqué une perte rapide de cellules progénitrices et des structures des cryptes de la muqueuse intestinale, cdincidant avec un blocage de la prolifération et une augmentation de la différentiation entérocytique. Notamment, les ceIIules souches intestinales sont induites à se différentier de façon terminale suite au blocage de la voie de signalisation Wnt, provoquant une perte complète de l'homéostasie intestinale. Le profil transcriptionnel des cryptes isolées par la microdissection au laser a confirmé ces observations et nous a permis d'identifier des gènes potentiellement responsables du maintien des cellules souches intestinales. Nos résultats démontrent donc la nécessité de la voie de signalisation Wnt/ß-catenin pour le maintien de l'épithélium intestinal. Ceci remet en question les efforts ciblant la voie de signalisation aberrante de Wnt en tant que nouvelle stratégie pour le traitement du cancer colorectal. SUMMARY: The Wnt signaling pathway is deregulated in over 90% of human colorectal cancers. ß-Catenin, the central signal transducer of the Wnt pathway, can directly modulate gene expression by interacting with transcription factors of the TCF/LEF-family. In order to investigate the role of Wnt signaling in the homeostasis of normal intestinal epithelium, we use atissue-specific, inducible ß-catenin gene ablation mouse model. Loss of ß-catenin in adult mice resulted in a rapid loss of progenitor cells and crypt structures, coinciding with blocked proliferation and with increased enterocytic differentiation. Importantly, intestinal stem cells were induced to terminally differentiate upon this block of Wnt signaling, resulting in a complete loss of intestinal homeostasis. Transcriptional profiling of mutant crypt RNA isolated by laser capture microdissection confirmed those observations and allowed us to identify genes potentially responsible for the maintenance of intestinal stem cells. Thus, our data show an essential requirement of Wnt/ß-catenin signaling in the maintenance of intestinal epithelium. This challenges attempts to target aberrant Wnt signaling as a new therapeutic strategy to treat colorectal cancer.

Polymorphisms of CD16A and CD32 Fcgamma receptors and circulating immune complexes in Meniere's disease: a case-control study.

BACKGROUND: Autoimmune diseases with elevated circulating autoantibodies drive tissue damage and the onset of disease. The Fcγ receptors bind IgG subtypes modulating the clearance of circulating immune complexes (CIC). The inner ear damage in Ménière's disease (MD) could be mediated by an immune response driven by CIC. We examined single-nucleotide polymorphism (SNPs) in the CD16A and CD32 genes in patients with MD which may determine a Fcγ receptor with lower binding to CIC. METHODS: The functional CD16A (FcγRIIIa*559A > C, rs396991) and CD32A (FcγRIIa*519A > G, rs1801274) SNPs were analyzed using PCR-based TaqMan Genotyping Assay in two cohorts of 156 mediterranean and 112 Galicia patients in a case-control study. Data were analyzed by χ2 with Fisher's exact test and Cochran-Armitage trend test (CATT). CIC were measured by ELISA for C1q-binding CIC. RESULTS: Elevated CIC were found in 7% of patients with MD during the intercrisis period. No differences were found in the allelic frequency for rs396991 or rs1801274 in controls subjects when they were compared with patients with MD from the same geographic area. However, the frequency of AA and AC genotypes of CD16A (rs396991) differed among mediterranean and Galicia controls (Fisher's test, corrected p = 6.9 × 10-4 for AA; corrected p = 0.02 for AC). Although genotype AC of the CD16A receptor was significantly more frequent in mediterranean controls than in patients, [Fisher's test corrected p = 0.02; OR = 0.63 (0.44-0.91)], a genetic additive effect for the allele C was not observed (CATT, p = 0.23). Moreover, no differences were found in genotype frequencies for rs396991 between patients with MD and controls from Galicia (CATT, p = 0.14). The allelic frequency of CD32 (rs1801274) was not different between patients and controls either in mediterranean (p = 0.51) or Galicia population (p = 0.11). CONCLUSIONS: Elevated CIC are not found in most of patients with MD. Functional polymorphisms of CD16A and CD32 genes are not associated with onset of MD.

Functional characterization of E- and P-cadherin in invasive breast cancer cells

BACKGROUND Alterations in the cadherin-catenin adhesion complexes are involved in tumor initiation, progression and metastasis. However, the functional implication of distinct cadherin types in breast cancer biology is still poorly understood. METHODS To compare the functional role of E-cadherin and P-cadherin in invasive breast cancer, we stably transfected these molecules into the MDA-MB-231 cell line, and investigated their effects on motility, invasion and gene expression regulation. RESULTS Expression of either E- and P-cadherin significantly increased cell aggregation and induced a switch from fibroblastic to epithelial morphology. Although expression of these cadherins did not completely reverse the mesenchymal phenotype of MDA-MB-231 cells, both E- and P-cadherin decreased fibroblast-like migration and invasion through extracellular matrix in a similar way. Moreover, microarray gene expression analysis of MDA-MB-231 cells after expression of E- and P-cadherins revealed that these molecules can activate signaling pathways leading to significant changes in gene expression. Although the expression patterns induced by E- and P-cadherin showed more similarities than differences, 40 genes were differentially modified by the expression of either cadherin type. CONCLUSION E- and P-cadherin have similar functional consequences on the phenotype and invasive behavior of MDA-MB-231 cells. Moreover, we demonstrate for the first time that these cadherins can induce both common and specific gene expression programs on invasive breast cancer cells. Importantly, these identified genes are potential targets for future studies on the functional consequences of altered cadherin expression in human breast cancer.

Susceptibility of Anopheles campestris-like and Anopheles barbirostris species complexes to Plasmodium falciparum and Plasmodium vivax in Thailand

Nine colonies of five sibling species members of Anopheles barbirostris complexes were experimentally infected with Plasmodium falciparum and Plasmodium vivax. They were then dissected eight and 14 days after feeding for oocyst and sporozoite rates, respectively, and compared with Anopheles cracens. The results revealed that Anopheles campestris-like Forms E (Chiang Mai) and F (Udon Thani) as well as An. barbirostris species A3 and A4 were non-potential vectors for P. falciparum because 0% oocyst rates were obtained, in comparison to the 86.67-100% oocyst rates recovered from An. cracens. Likewise, An. campestris-like Forms E (Sa Kaeo) and F (Ayuttaya), as well as An. barbirostris species A4, were non-potential vectors for P. vivax because 0% sporozoite rates were obtained, in comparison to the 85.71-92.31% sporozoite rates recovered from An. cracens. An. barbirostris species A1, A2 and A3 were low potential vectors for P. vivax because 9.09%, 6.67% and 11.76% sporozoite rates were obtained, respectively, in comparison to the 85.71-92.31% sporozoite rates recovered from An. cracens. An. campestris-like Forms B and E (Chiang Mai) were high-potential vectors for P. vivax because 66.67% and 64.29% sporozoite rates were obtained, respectively, in comparison to 90% sporozoite rates recovered from An. cracens.

Efficient in vivo induction of CTL by cell-associated covalent H-2Kd-peptide complexes.

A novel procedure is presented describing the induction of antigen-specific cytolytic T lymphocytes (CTL) in vivo, that uses as immunogen syngeneic Concanavalin A stimulated spleen cells expressing H-2Kd (Kd) molecules photocrosslinked with a photoreactive peptide derivative. The Kd restricted Plasmodium berghei circumsporozoite (PbCS) peptide 253-260 (YIPSAEKI) was conjugated with photoreactive iodo-4-azidosalicylic acid (IASA) at the NH2-terminus and with 4-azidobenzoic acid (ABA) at the TCR contact residue Lys259 to make IASA-YIPSAEK(ABA)I. Selective photoactivation of the IASA group allowed specific photoaffinity labeling of cell-associated Kd molecules. Optimal peptide derivative binding to Kd molecules of concanavalin A stimulated spleen cells was obtained upon 4-6 h incubation at 26 degrees C in the presence of human beta 2 microglobulin. Photocrosslinking prevented the rapid dissociation of cell-associated Kd-peptide derivative complexes at 37 degrees C. The photoaffinity labeled cells were injected i.p. into syngeneic recipients. After 10 days, the peritoneal exudate lymphocytes were harvested and in vitro stimulated with peptide derivative pulsed P815 mastocytoma cells. The resulting bulk cultures displayed high cytolytic activity that was specific for IASA-YIPSAEK(ABA)I and YIPSAEK(ABA)I. In contrast, peritoneal exudate lymphocytes from mice inoculated with concanavalin A blasts that were pulsed, but not photocrosslinked, with IASA-YIPSAEK(ABA)I expressed only marginal levels of IASA-YIPSAEK(ABA)I-specific cytolytic activity. This immunization strategy, using neither adjuvants nor potentially hazardous transfected/transformed cells, is safe and should be universally applicable.

In vivo expansion of T reg cells with IL-2-mAb complexes: induction of resistance to EAE and long-term acceptance of islet allografts without immunosuppression.

Via a transcription factor, Foxp3, immunoregulatory CD4(+)CD25(+) T cells (T reg cells) play an important role in suppressing the function of other T cells. Adoptively transferring high numbers of T reg cells can reduce the intensity of the immune response, thereby providing an attractive prospect for inducing tolerance. Extending our previous findings, we describe an in vivo approach for inducing rapid expansion of T reg cells by injecting mice with interleukin (IL)-2 mixed with a particular IL-2 monoclonal antibody (mAb). Injection of these IL-2-IL-2 mAb complexes for a short period of 3 d induces a marked (>10-fold) increase in T reg cell numbers in many organs, including the liver and gut as well as the spleen and lymph nodes, and a modest increase in the thymus. The expanded T reg cells survive for 1-2 wk and are highly activated and display superior suppressive function. Pretreating with the IL-2-IL-2 mAb complexes renders the mice resistant to induction of experimental autoimmune encephalomyelitis; combined with rapamycin, the complexes can also be used to treat ongoing disease. In addition, pretreating mice with the complexes induces tolerance to fully major histocompatibility complex-incompatible pancreatic islets in the absence of immunosuppression. Tolerance is robust and the majority of grafts are accepted indefinitely. The approach described for T reg cell expansion has clinical potential for treating autoimmune disease and promoting organ transplantation.

CD8beta endows CD8 with efficient coreceptor function by coupling T cell receptor/CD3 to raft-associated CD8/p56(lck) complexes.

The extraordinary sensitivity of CD8+ T cells to recognize antigen impinges to a large extent on the coreceptor CD8. While several studies have shown that the CD8beta chain endows CD8 with efficient coreceptor function, the molecular basis for this is enigmatic. Here we report that cell-associated CD8alphabeta, but not CD8alphaalpha or soluble CD8alphabeta, substantially increases the avidity of T cell receptor (TCR)-ligand binding. To elucidate how the cytoplasmic and transmembrane portions of CD8beta endow CD8 with efficient coreceptor function, we examined T1.4 T cell hybridomas transfected with various CD8beta constructs. T1.4 hybridomas recognize a photoreactive Plasmodium berghei circumsporozoite (PbCS) peptide derivative (PbCS (4-azidobezoic acid [ABA])) in the context of H-2K(d), and permit assessment of TCR-ligand binding by TCR photoaffinity labeling. We find that the cytoplasmic portion of CD8beta, mainly due to its palmitoylation, mediates partitioning of CD8 in lipid rafts, where it efficiently associates with p56(lck). In addition, the cytoplasmic portion of CD8beta mediates constitutive association of CD8 with TCR/CD3. The resulting TCR-CD8 adducts exhibit high affinity for major histocompatibility complex (MHC)-peptide. Importantly, because CD8alphabeta partitions in rafts, its interaction with TCR/CD3 promotes raft association of TCR/CD3. Engagement of these TCR/CD3-CD8/lck adducts by multimeric MHC-peptide induces activation of p56(lck) in rafts, which in turn phosphorylates CD3 and initiates T cell activation.