High CD49d protein and mRNA expression predicts poor outcome in chronic lymphocytic leukemia.

CD49d plays a critical role in leucocyte trafficking, activation and survival, and facilitates interactions between leucocytes and stromal cells. Recent data give evidence for the prognostic relevance of CD49d protein expression in B-CLL. In our study we analyzed both the expression of CD49d protein and mRNA in a cohort of 101 CLL patients. The percentage of leukemic B-cells expressing CD49d determined by flow cytometry ranged from 0 to 100%. 37 patients with high CD49d protein expression >or=45% (according to ROC analysis) had a significantly shorter treatment-free survival (TFS) and overall survival (OS) than 64 patients with low CD49d expression (median TFS: 116 versus 43 months, p=0.015; median OS: not reached in both groups, p=0.018). CD49d protein expression was strongly associated with CD38 status (p=0.0001) and ZAP-70 status (p=0.03) but not with IGVH mutation. In multivariate analysis high CD49d expression was a significantly independent prognostic factor (HR 3.0; p=0.005). According to the strong correlation of CD49d protein expression with CD49d mRNA expression (r=0.39; p<0.0001) we could confirm the results on mRNA level with worse prognosis for patients with high mRNA level. Collectively, our data confirm the prognostic significance supporting the idea to use CD49d as target molecules for therapeutic approaches in B-CLL.

FCRL2 mRNA expression is inversely associated with clinical progression in chronic lymphocytic leukemia.

Fc receptor-like 2 (FCRL2) is highly expressed on B-cell chronic lymphocytic leukemia (B-CLL) cells and could possibly influence disease pathogenesis. Therefore, we investigated FCRL2 mRNA expression in a large cohort with 152 CLL patients in order to assess its role in risk prediction in B-CLL. FCRL2 mRNA expression was found to be expressed at considerably higher levels in peripheral blood mononuclear cells (PBMC) of B-CLL patients compared to controls (range 1.35- to 210-fold upregulation; P < 0.0001) and cells of other hematological diseases. Patients with high FCRL2 expression (according to ROC-analysis) had a significantly longer treatment-free survival (TFS) and overall survival (OS) than patients with low FCRL2 expression (median TFS: 119 vs. 34 months, P < 0.0001; median OS: 321 months vs. not reached, P = 0.009). Univariate comparisons found that FCRL2 expression was weakly associated with IGHV mutation status (P = 0.05), CD38 status (P < 0.0001) and ZAP-70 status (P < 0.0001). Furthermore, we show that the combination of FCRL2 with ZAP70-, CD38- or IGHV-status could further significantly refine the prognostic information provided by either of the factors alone in TFS and OS. In multivariate analysis low FCRL2 expression was a significant independent prognostic factor (HR 2.4; P = 0.005). Here we demonstrate that the level of FCRL2 expression is correlated with prognosis in B-CLL.

Polyoma and SV40 proteins differentially regulate PP2A to activate distinct cellular signaling pathways involved in growth control.

Binding of Src family kinases to membrane-associated polyoma virus middle T-antigen (PyMT) can result in the phosphorylation of PyMT tyrosine 250, which serves as a docking site for the binding of Shc and subsequent activation of the Raf-MEK-ERK (MAP) kinase cascade. In a screen for PyMT variants that could not activate the ARF tumor suppressor, we isolated a cytoplasmic nontransforming mutant (MTA) that encoded a C-terminal truncated form of the PyMT protein. Surprisingly, MTA was able to strongly activate the MAP kinase pathway in the absence of Src family kinase and Shc binding. Interestingly, the polyoma small T-antigen (PyST), which shares with MTA both partial amino acid sequence homology and cellular location, also activates the MAP kinase cascade. Activation of the MAP kinase cascade by both MTA and PyST has been demonstrated to be PP2A-dependent. Neither MTA nor PyST activate the phosphorylation of AKT. The SV40 small T-antigen, which is similar to PyST in containing a J domain and in binding to the PP2A AC dimer, does not activate the MAP kinase cascade, but does stimulate phosphorylation of AKT in a PP2A-dependent manner. These findings highlight a novel role of PP2A in stimulating the MAP kinase cascade and indicate that the similar polyoma and SV40 small T-antigens influence PP2A to activate discrete cellular signaling pathways involved in growth control.

A small heat-shock protein, p26, from the crustacean Artemia protects mammalian cells (Cos-1) against oxidative damage.

A small heat-shock protein (p26) purified from stress-resistant embryos of the crustacean, Artemia franciscana, was introduced into cultured cells of green monkey kidney (Cos-1) using the BioPORTER delivery system. Cells containing p26 exhibited impressive resistance to hydrogen peroxide compared to controls. Introduction of the disaccharide trehalose did not provide protection against oxidative damage, but enhanced substantially the protective performance of p26 when both were present. These studies extend previous research on the protective role played by p26 in cells exposed to various forms of stress, presumably through its ability to function as a molecular chaperone.

Role for PP2A in ARF signaling to p53.

Activation of the ARF-p53 tumor suppressor pathway is one of the cell's major defense mechanisms against cancer induced by oncogenes. The ARF-p53 pathway is dysfunctional in a high proportion of human cancers. The regulation of the ARF-p53 signaling pathway has not yet been well characterized. In this study polyoma virus (Py) is used as a tool to better define the ARF-p53 signaling pathway. Py middle T-antigen (PyMT) induces ARF, which consequently up-regulates p53. We show that Py small T-antigen (PyST) blocks ARF-mediated activation of p53. This inhibition requires the small T-antigen PP2A-interacting domain. Our results reveal a previously unrecognized role of PP2A in the modulation of the ARF-p53 tumor suppressor pathway.