Background: Calpains are intracellular calcium-dependent proteases implicated in cancer. Results: Calpain 2 knockdown in breast cancer cells correlated with reduced in vitro proliferation, migration, and in vivo tumorigenicity as well as reduced Akt activation, increased nuclear FoxO localization, and increased p27 Kip1 expression. Conclusion: Calpain 2 promotes proliferation of cancer cells through Akt- Kip1 signaling. Significance: Calpain 2 represents a potential therapeutic target in breast cancer.

We describe a group of small-molecule inhibitors of Jun kinase (JNK)-dependent apoptosis. AEG3482, the parental compound, was identified in a screening effort designed to detect compounds that reduce apoptosis of neonatal sympathetic neurons after NGF withdrawal. We show that AEG3482 blocks apoptosis induced by the p75 neurotrophin receptor (p75NTR) or its cytosolic interactor, NRAGE, and demonstrate that AEG3482 blocks proapoptotic JNK activity. We show that AEG3482 induces production of heat shock protein 70 (HSP70), an endogenous inhibitor of JNK, and establish that HSP70 accumulation is required for the AEG3482-induced JNK blockade. We show that AEG3482 binds HSP90 and induces HSF1-dependent HSP70 mRNA expression and find that AEG3482 facilitates HSP70 production while retaining HSP90 chaperone activity. These studies establish that AEG3482 inhibits JNK activation and apoptosis by a mechanism involving induced expression of HSP proteins.

We report herein that expression of ␣2␤1 integrin increased human erythroleukemia K562 transfectant (KX2C2) cell movement after extravasation into liver parenchyma. In contrast, a previous study demonstrated that ␣2␤1 expression conferred a stationary phenotype to human rhabdomyosarcoma RD transfectant (RDX2C2) cells after extravasation into the liver. We therefore assessed the adhesive and migratory function of ␣2␤1 on KX2C2 and RDX2C2 cells using a ␣2␤1-specific stimulatory monoclonal antibody (mAb), JBS2, and a blocking mAb, BHA2.1. In comparison with RDX2C2 cells, KX2C2 were only weakly adherent to collagen and laminin. JBS2 stimulated ␣2␤1-mediated interaction of KX2C2 cells with both collagen and laminin resulting in increases in cell movement on both matrix proteins. In the presence of Mn 2ϩ , JBS2-stimulated adhesion on collagen beyond an optimal level for cell movement. In comparison, an increase in RDX2C2 cell movement on collagen required a reduction in its adhesive strength provided by the blocking mAb BHA2.1. Consistent with these in vitro findings, in vivo videomicroscopy revealed that ␣2␤1-mediated postextravasation cell movement of KX2C2 cells in the liver tissue could also be stimulated by JBS2. Thus, results demonstrate that ␣2␤1 expression can modulate postextravasation cell movement by conferring either a stationary or motile phenotype to different cell types. These findings may be related to the differing metastatic activities of different tumor cell types. INTRODUCTIONIt is well established that ␤1 integrins represent the major receptors for providing the functional linkage between extracellular matrix (ECM) proteins and cytoskeletal components (for review, Hynes, 1992). The expression of ␣2␤1 integrin as receptors for collagen and laminin has been associated with the morphogenesis of mammary epithelial cells (Berdichevsky et al., 1992; Keely et al., 1995a,b) and differentiation of the human erythroleukemia cell line K562 (Burger et al., 1992). In comparison, ␣2␤1 expression was down-regulated on keratinocytes undergoing terminal differentiation (Adams and Watt, 1990). In addition, ␣2␤1 has also been associated with the metastatic activities of tumor cells. Interestingly, there is both a direct correlation (Dedhar and Saulnier, 1990;Chan et al., 1991;Klein et al., 1991;Mortarini et al., 1991;Danen et al., 1993;Chen et al., 1994;Santala et al., 1994) and an inverse correlation (Pignatelli et al., 1990(Pignatelli et al., , 1991Zutter, et al., 1990Zutter, et al., , 1995 of ␣2␤1 expression with tumor metastasis. The exact mechanisms whereby ␣2␤1 enhances or, in some cases, reduces the metastatic activities of tumor cells are still unclear. One possibility is that ␣2␤1 may confer distinct cell functions among the tumor cells. The present study focuses on ␣2␤1 interaction with ECM proteins and its in vivo effect on cell movement.Studies in recent years have demonstrated three distinct modes of ligand binding for ␣2␤1: no ligandbinding activity, binding collagen but not laminin, and binding both ...

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