Mechanisms of apoptosis-induction by rottlerin: therapeutic implications for B-CLL.

Constitutively activated signaling pathways contribute to the apoptosis-defect of B-CLL cells. Protein kinase C-delta is a permanently activated kinase and a putative downstream target of phosphatidylinositol-3 kinase in B-CLL. Blockade of protein kinase C-delta (PKC-delta) by the highly specific inhibitor rottlerin induces apoptosis in chronic lymphocytic leukaemia (CLL) cells. By co-culturing bone marrow stromal and CLL cells, we determined that the proapoptotic effect of rottlerin is not abolished in the presence of survival factors, indicating that a targeted therapy against PKC-delta might be a powerful approach for the treatment of CLL patients. The downstream events following rottlerin treatment engage mitochondrial and non-mitochondrial pathways and ultimately activate caspases that execute the apoptotic cell death. Herein we report that the inhibition of PKC-delta decreases the expression of the important antiapoptotic proteins Mcl-1 and XIAP accompanied by a loss of the mitochondrial membrane potential Deltapsi. In addition, we discovered that ZAP-70-expressing cells are significantly more susceptible to rottlerin-induced cell death than ZAP-70 negative cells. We finally observed that rottlerin can augment cell toxicity induced by standard chemotherapeutic drugs. Conclusively, PKC-delta is a promising new target in the combat against CLL.

Constitutive activation of the MAPkinase p38 is critical for MMP-9 production and survival of B-CLL cells on bone marrow stromal cells.

In the present work we investigated the role and biological significance of mitogen activated protein kinases (MAPK) in B-cell chronic lymphocytic leukaemia (B-CLL). The MAPK p38 was constitutively activated in B-CLL, but not in normal peripheral B cells. In addition, we demonstrated that the upstream kinases of p38, MKK3/6 were also constitutively activated in B-CLL cells. Furthermore, we determined by EMSA that the p38 MAP kinase pathway was not linked to the constitutive high expression of NF-kappaB, a critical survival factor of B-CLL cells. Recently, it has been shown that serum levels of angiogenic factors like VEGF, bFGF and MMP-9 are elevated in the serum of CLL patients and correlate with an unfavorable prognosis. We showed that the constitutive expression of MMP-9 was dependent on p38-activity and inhibition of p38 strongly downregulated MMP-9 expression. Coculture of B-CLL cells and stromal cells can protect spontaneous apoptosis of leukemic B cells. To determine the role of permanently activated p38 and MMP-9 expression, we cocultured B-CLL cells with bone marrow stromal cells. Survival of B-CLL cells on stroma was severely impaired when p38 was inhibited. Furthermore, blockade of MMP-9 activity also antagonized the antiapoptotic effect of stromal cells.

Cyclin-dependent kinase inhibitor Roscovitine induces apoptosis in chronic lymphocytic leukemia cells.

A new class of cell cycle inhibitors is currently entering clinical trials. These drugs exert their activity by inhibition of cyclin-dependent kinases (cdk) and induce cell cycle arrest and apoptosis in cancer cells. Roscovitine, a cdk2-inhibitor that is in preclinical evaluation, induced apoptosis in B-CLL cells at doses that were not cytotoxic for normal human B cells. At 20 microM, Roscovitine induced apoptosis in 21 of 28 B-CLL samples and was equally effective in zap-70-positive or -negative samples. Caspase-3 was cleaved in B-CLL cells exposed to Roscovitine and the pancaspase inhibitor z.VAD.fmk-blocked Roscovitine-induced apoptosis. Expression of the proapoptotic protein Bak was increased and Bax cleavage and conformational change was observed in Roscovitine-treated B-CLL cells. Antiapoptotic proteins Mcl-1 and XIAP were downregulated, but the expression of Bcl-2 remained unchanged. In contrast to previous reports in cancer cell lines, Roscovitine treatment was not accompanied by nuclear accumulation of p53. Cyc202 (R-Roscovitine) is in early clinical trials in cancer patients. Given its powerful effects on zap-70-positive and -negative B-CLL cells, but not on normal lymphocytes, Roscovitine might be an attractive drug to be tested in this incurable disease.

Organizational change and development.

Recent analyses of organizational change suggest a growing concern with the tempo of change, understood as the characteristic rate, rhythm, or pattern of work or activity. Episodic change is contrasted with continuous change on the basis of implied metaphors of organizing, analytic frameworks, ideal organizations, intervention theories, and roles for change agents. Episodic change follows the sequence unfreeze-transition-refreeze, whereas continuous change follows the sequence freeze-rebalance-unfreeze. Conceptualizations of inertia are seen to underlie the choice to view change as episodic or continuous.