Alexandra Filipovich

The vascular endothelial growth factor receptor tyrosine kinase inhibitors vatalanib and pazopanib potently induce apoptosis in chronic lymphocytic leukemia cells in vitro and in vivo.

Purpose: There is evidence that vascular endothelial growth factor (VEGF) is a critical microenvironmental factor that exerts angiogenesis-independent effects on the survival of chronic lymphocytic leukemia (CLL) cells. Vatalanib and pazopanib are potent orally available VEGF receptor tyrosine kinase inhibitors. We investigated the efficacy and selectivity of both compounds in CLL cells, simulated potential combination with conventional cytostatics, and tested the effect of both substances on CLL-like tumor xenografts. Experimental Design: Primary CLL and normal peripheral blood cells were tested for viability after incubation with varying concentrations of both inhibitors. Further, phosphorylation status of VEGF receptor on treatment, caspase activation, and poly(ADP-ribose) polymerase cleavage were assessed. Combinations of each inhibitor with fludarabine, vincristine, and doxorubicin were analyzed for possible synergistic effects in vitro. For in vivo testing, mice grafted with the CLL-like cell line JVM-3 were treated orally with each inhibitor. Results: Vatalanib and pazopanib decreased phosphorylation of the VEGF receptor, along with induction of apoptosis in CLL cells in clinically achievable concentrations. Healthy B cells were only mildly affected. Immunoblots showed downregulation of the antiapoptotic proteins XIAP and MCL1, whereas poly(ADP-ribose) polymerase cleavage was increased. Combinations with conventional cytostatic agents resulted in synergistic effects. Treatment of xenografted mice with 100 mg/kg of body weight for 21 days resulted in tumor inhibition rates of 76% (vatalanib) and 77% (pazopanib). In two mice, a total tumor eradication could be observed. No gross systemic toxicity occurred. Conclusion: We conclude that VEGF inhibition is a promising new therapeutic approach in CLL. Vatalanib and pazopanib seem to be effective and safe candidates to be further evaluated for this purpose. Clin Cancer Res; 16(13); 3390–8. ©2010 AACR.

High lymphoid enhancer- binding factor-1 expression is associated with disease progression and poor prognosis in chronic lymphocytic leukemia

We determined lymphoid enhancer-binding factor-1 (LEF1) mRNA expression in 112 chronic lymphocytic leukemia (CLL) samples and assessed correlations with the prognostic markers ZAP70 and CD38, Binet stages, the percentage of lymphocytes in the peripheral blood, and fibromodulin (FMOD) transcripts. The mean LEF1 relative expression ratios (RER) were 53.72 and 37.10 in ZAP70-positive and ZAP70-negative patients, respectively (P=0.004). However, we did not observe a significant difference in LEF1 expression between CD38-positive and CD38-negative patients. Moreover, patients requiring treatment showed a mean LEF1 RER of 85.61 whereas patients in recently diagnosed Binet A stage had a mean of only 22.01 (P<0.001). We also found significant correlations of LEF1 with the percentage of lymphocytes and FMOD expression. Our results suggest that high LEF1 expression is associated with poor prognosis and disease progression. Thus, LEF1 might be involved in the process of disease progression and possibly can serve as a molecular parameter for risk assessment and/or monitoring of CLL.

Physiological inhibitors of Wnt signaling

Wnt signaling is crucial for cell proliferation and differentiation. It represents a complex network with mechanisms of self‐regulation through positive and negative feedback. Recent increasing interest in this signaling pathway has led to the discovery of many new proteins that down‐regulate Wnt activity. Here, we provide a short description of the most important and best‐studied inhibitors, group them according to the target molecule within the Wnt cascade, and discuss their clinical potential. Although most of the inhibitors discussed here may also interact with proteins from other signaling pathways, we focus only on their ability to modulate Wnt signaling.

Evidence for non-functional Dickkopf-1 (DKK-1) signaling in chronic lymphocytic leukemia (CLL).

Purpose:  Wnt signaling was demonstrated to be activated in chronic lymphocytic leukemia (CLL). It is thought to be responsible for the extended survival of CLL cells in vivo. Dickkopf1 (DKK1) is known to antagonize Wnt signaling by direct high‐affinity binding to the extracellular domain of WNT coreceptor lipoprotein receptor‐related protein 6 (LRP6). The purpose of this study was to investigate the effect of DKK1 in B‐CLL cells in vitro.