E-cadherin in oral SCC: an analysis of the confusing literature and new insights related to its immunohistochemical expression

E-cadherin plays a crucial structural role in cell-cell contacts in epithelial tissues, and a functional role in signaling pathways that regulate cell proliferation, differentiation, and survival. Reduced immunoexpression of E-cadherin adhesions is largely considered as being equivalent to defective functionality and malignancy, and has been used as a prognostic parameter. A critical analysis of studies on E-cadherin immunoexpression in oral carcinomas revealed a wide range of both technical and interpretational aspects. This paper highlights biological characteristics of E-cadherin with respect to its expression in normal and neoplastic epithelial cells and to its interrelations with the tumor microenvironment that can have an impact on immunohistochemical results and their application in the clinical setting.     

Beta-phenylpyruvate and glucose uptake in isolated mouse soleus muscle and cultured C2C12 muscle cells

Previous investigation demonstrated the potential of beta-phenylpyruvate at high concentration to cause hypoglycemia in mice totally deprived of insulin. For further elucidation of the glucose-lowering mechanism, glucose uptake, and quantity of glucose transporters (GLUT1 and GLUT4) in mouse soleus muscle and C2C12 muscle cell lines were investigated following incubation with beta-phenylpyruvate in various concentrations. A marked enhancement of glucose uptake was demonstrated that peaked at 0.5 and 1.0 mM beta-phenylpyruvate in soleus muscle (P<0.01) and C2C12 cells (P<0.001), respectively. Kinetic analysis in C2C12 cells showed a twofold increase in Vmax compared with controls (P<0.001). In addition, both GLUT1 and GLUT4 levels were increased following exposure to beta-phenylpyruvate. Our findings point to a peripheral hypoglycemic effect of beta-phenylpyruvate.     

The association of Sam68 with Vav1 contributes to tumorigenesis

Vav1 functions in the hematopoietic system as a specific GDP/GTP nucleotide exchange factor regulated by tyrosine phosphorylation. An intact C-terminal SH3 domain of Vav1 (Vav1SH3C) was shown to be necessary for Vav1-induced transformation, yet the associating protein(s) necessary for this activity have not yet been identified. Using a proteomics approach, we identified Sam68 as a Vav1SH3C-associating protein. Sam68 (Src-associated in mitosis of 68 kD) belongs to the heteronuclear ribonucleoprotein particle K (hnRNP-K) homology (KH) domain family of RNA-binding proteins. The Vav1/Sam68 interaction was observed in vitro and in vivo. Mutants of Vav1SH3C previously shown to lose their transforming potential did not associate with Sam68. Co-expression of Vav1 and Sam68 in Jurkat T cells led to increased localization of Vav1 in the nucleus and changes in cell morphology. We then tested the contribution of Sam68 to known functions of Vav1, such as focus-forming in NIH3T3 fibroblasts and NFAT stimulation in T cells. Co-expression of oncogenic Vav1 with Sam68 in NIH3T3 fibroblasts resulted in a dose-dependent increase in foci, yet no further enhancement of NFAT activity was observed in Jurkat T cells, as compared to cells overexpressing only Vav1 or Sam68. Our results strongly suggest that Sam68 contributes to transformation by oncogenic Vav1.     

Coordinated gene networks regulating Arabidopsis plant metabolism in response to various stresses and nutritional cues

The expression pattern of any pair of genes may be negatively correlated, positively correlated, or not correlated at all in response to different stresses and even different progression stages of the stress. This makes it difficult to identify such relationships by classical statistical tools such as the Pearson correlation coefficient. Hence, dedicated bioinformatics approaches that are able to identify groups of cues in which there is a positive or negative expression correlation between pairs or groups of genes are called for. We herein introduce and discuss a bioinformatics approach, termed Gene Coordination, that is devoted to the identification of specific or multiple cues in which there is a positive or negative coordination between pairs of genes and can further incorporate additional coordinated genes to form large coordinated gene networks. We demonstrate the utility of this approach by providing a case study in which we were able to discover distinct expression behavior of the energy-associated gene network in response to distinct biotic and abiotic stresses. This bioinformatics approach is suitable to a broad range of studies that compare treatments versus controls, such as effects of various cues, or expression changes between a mutant and the control wild-type genotype.     

Distinct stem cell populations regenerate the follicle and interfollicular epidermis

The regeneration of the skin and its appendages is thought to occur by the regulated activation of a dedicated stem cell population. A population of cells in the bulge region of the hair follicle has been identified as the putative stem cell of both the follicle and the interfollicular epidermis. While this assertion is supported by a variety of surrogate assays, there has been no direct confirmation of the normal contribution of these cells to the regeneration of structures other than the cycling portion of the hair follicle. Here, we report lineage analysis revealing that the follicular epithelium is derived from cells in the epidermal placode that express Sonic hedgehog. This analysis also demonstrates that the stem cells resident in the follicular bulge that regenerate the follicle are neither the stem cells of the epidermis nor the source of the stem cells of the epidermis in the absence of trauma.     

RNA interference in Agrobacterium rhizogenes-transformed roots of Arabidopsis and Medicago truncatula

RNA interference (RNAi) is a powerful reverse genetic tool to study gene function. The data presented here show that Agrobacterium rhizogenes-mediated RNAi is a fast and effective tool to study genes involved in root biology. The Arabidopsis gene KOJAK, involved in root hair development, was efficiently knocked down. A. rhizogenes-mediated root transformation is a fast method to generate adventitious, genetically transformed roots. In order to select for co-transformed roots a binary vector was developed that enables selection based on DsRED1 expression, with the additional benefit that chimaeric roots can be discriminated. The identification of chimaeric roots provided the opportunity to examine the extent of systemic spread of the silencing signal in the composite plants of both Arabidopsis and Medicago truncatula. It is shown that RNA silencing does not spread systemically to non-co-transformed (lateral) roots and only inefficiently to the non-transgenic shoot. Furthermore, evidence is presented which shows that RNAi is cell autonomous in the root epidermis.     

Gibberellic Acid (GA3) Inhibits ROS Increase in Chloroplasts During Dark-Induced Senescence of Pelargonium Cuttings

The temporal and spatial changes in reactive oxygen species (ROS) during dark treatment of Pelargonium cuttings and the effect of gibberellic acid (GA₃) on ROS levels were studied. ROS-related fluorescence was detected in mitochondria and cytoplasm of epidermal cells and in chloroplasts. By monitoring dichlorofluorescein (DCF) fluorescence, an initial decrease in ROS was observed under darkness in the epidermal cell cytoplasm and the chloroplasts, which was followed by an increase on the third day. Following 3 days under darkness, the size and the structure of the chloroplasts also changed, and they became more sensitive to illumination as judged by a higher accumulation of ROS. Pretreatment of leaves with GA₃ did not prevent the structural changes in the chloroplasts, but it inhibited the increase in ROS levels in all cell compartments, including the chloroplasts. It is suggested that the inhibition of ROS increase by GA₃ prevented complete disintegration of chloroplasts during dark-induced senescence and thereby enabled the maintenance of chlorophyll levels in the tissue.