Immunohistochemical expression of cell-cycle regulators in pediatric embryonal brain tumors.

Embryonal tumors constitute the most common malignant brain tumor group in children. Experimental results indicate that genes involved in cell cycle and signal transduction are deregulated in medulloblastoma (MB) and atypical teratoid/rhabdoid tumors (AT/RT). The cell cycle is regulated by protein complexes composed of a regulatory subunit called Cyclin and a catalytic domain named Cyclin-dependent kinase (CDK). Cyclins and CDKs are in turn regulated by cyclin-dependent kinase inhibitors (CDKI) which inhibit cell-cycle progression. Cyclins D and Cyclin E are important for the passage of cells through G1 to S phase. P-27, a member of the universal CDKI family, is important in regulating the G1/S transition. Thus, the purpose of this study was to investigate the expression of p-27, Cyclin D3, and Cyclin E, and their possible prognostic significance in pediatric embryonal brain tumors. We retrospectively evaluated 51 children with embryonal tumors that were treated surgically in our institute. All patients had regular follow up examinations. The streptavidin-biotin HRP method was performed on paraffin sections for detection of p-27, Cyclin D3, and Cyclin E. There were 42 cases of MB and nine cases of AT/RT. Cyclin D3 expression was detected in 11/42 MB and 3/9 AT/RT patients. Cyclin E expression was detected in 28/42 MB and 8/9 AT/RT patients. High expression of Ki-67 (>50 %) and p-27 (>50 %) was observed in 23.8-73.8 % of MB patients. Combined high Ki-67 and p-27 expression was observed in 21.4 % cases of MB. In these cases there was expression of Cyclin E in 88.8 % and Cyclin D3 in 22.2 % of MB. No significant correlation was found between Ki-67 and p-27, Cyclin D3, and E. No correlation was found between Cyclin D3, Cyclin E, p-27, and overall survival. Increased p-27 and Cyclin E expression was detected in a substantial number of MB patients and in nearly all AT/RT patients. Further studies on a larger number of patients are needed to clarify a possible correlation of p-27 and Cyclin E with tumor behavior.

CDK11p58 Promotes Microglia Activation via Inducing Cyclin D3 Nuclear Localization.

Microglia activation has been implicated in the pathogenesis of many neurological diseases. These reactive microglia are capable of producing a variety of proinflammatory mediators and potentially neurotoxic compounds. The increase of cell number and expression of CD11b are the main features of activated microglia. In this study, we examined the suppressive effects of CDK11p58 on microglia activation induced by lipopolysaccharide (LPS) in vitro. We found that in the activated microglia, the expression of CDK11p58 increased and the overexpression of CDK11p58 could reduce the increased proliferation and CD11b expression in LPS-activated microglia. Such suppressive effects might be resulted from the interaction with cyclin D3 which promoted CDK11p58 nuclear localization. Our results suggested that CDK11p58 acted to regulate microglia activation through CDK11p58 and cyclin D3 interaction.

Inorganic arsenic impairs proliferation and cytokine expression in human primary T lymphocytes.

Inorganic arsenic is a toxic environmental contaminant to which humans are mainly exposed through drinking water. This metalloid impairs functions of several key immune cells. Particularly, it reduces IL-2 secretion and proliferation of blood peripheral mononuclear cells stimulated by lectins that, however, do not mimic physiological T cell activation. The present study used isolated human T cells activated, in a more physiological manner, through stimulation with CD3/CD28 antibodies, to carefully analyze the impact of arsenic on T cell proliferation and cytokine expression. We demonstrate that non cytotoxic concentrations of sodium arsenite (As(III), 0.25-2µM) significantly reduce T cell proliferation by increasing the percentage of non dividing cells blocked in G1 phase and by preventing cyclin D3 and CDC25A expression. They also markedly, although not totally, reduces IL-2 expression at both mRNA and protein levels; however, metalloid-dependent inhibition of T cells could not be reversed by addition of recombinant IL-2. In addition, As(III) markedly reduces secretion of interferon-γ without impairing that of IL-4 and IL-13; it also decreases interferon-γ mRNA levels but increases those of IL-13. Finally, simultaneously to its immune effects, As(III) rapidly and potently increases expression of the redox-sensitive genes HMOX1, NQO1 and GCLM in activated T cells without altering the levels of reactive oxygen species. In conclusion, our results demonstrate that As(III) inhibits T cell proliferation, independently of IL-2, and alters the Th balance of cytokines secreted by co-stimulated T cells which thus constitute direct targets of this major environmental contaminant.