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Abstract  Cysteine cathepsins are proteolytic enzymes that reside in endolysosomal vesicles. Some are expressed constitutively while others are transcriptionally regulated. However, the expression and subcellular localization of cathepsins changes during cancer progression and cathepsins have been shown to be causally involved in various aspects of tumorigenesis including metastasis. The use of mouse models of breast cancer genetically ablated for cathepsin B has shown that both the growth of the primary tumor and the extend of lung metastasis is reduced by the loss of cathepsin B. The role of cathepsins in involution of the mammary gland has received little attention although it is clear that cathepsins are involved in tissue remodeling in the second phase of involution. We discuss here the roles of cathepsins and their endogenous inhibitors in breast tumorigenesis and post-lactational involution. [ABSTRACT FROM AUTHOR]

Abstract  The transcription factor Stat3 is essential for timely initiation of post-lactational regression and orchestrates the processes of cell death and tissue remodelling that occur during the first 6 days of involution in the mouse. Paradoxically, STAT3 is also frequently found to be constitutively active in breast cancer and tumors can become addicted to STAT3. This raises two interesting questions: 1) do the high levels of active Stat3 present in the mammary epithelium during involution promote tumor spread and 2) how do tumor cells escape the pro-apoptotic effects of Stat3? In order to address these questions, it is essential to understand the role of Stat3 in involution and the mechanisms by which Stat3 regulates both cell death and tissue remodelling. A number of studies have been undertaken using genetically modified mice and microarray analyses and two significant findings arose from these investigations. Firstly, post-lactational regression is associated with an acute phase and inflammatory response in addition to cell death and secondly, Stat3 alone is insufficient to induce involution in the absence of the NF-κB regulatory kinase IKKβ. Both Stat3 and NF-κB have been shown to regulate the expression of genes involved in inflammatory signalling and the acute phase response. These findings suggest a role for the innate immune response in mammary epithelial cell fate during involution and highlight potential roles for this response in tissue remodelling-associated breast cancer metastasis. [ABSTRACT FROM AUTHOR]

Understanding how environmental factors affect the longevity of roots is essential if root mortality linked nutrient cycling processes within ecosystems are to be understood, and the impact of natural and anthropogenic climate change properly evaluated. In this study the longevity of roots at two geographically and climatically distinct sites were compared to identify the scale of change that can occur due to environmental differences. Minirhizotron tubes were inserted into swards sown with the same variety of Lolium perenne and Trifolium repens at sites in the UK and Italy. Roots were viewed using a video camera and digitized images of roots generated at intervals. From these images the life history of individual roots was determined and compared. There were few differences in patterns of longevity between different species at the same site. Major differences, however, were observed between roots of the same species at different sites. For example, 73% of Trifolium repens roots failed to survive for 21 d in Italy compared to only 29% at the UK site. Similarly, over 84% of Lolium perenne roots failed to survive for more than 21 d in Italy compared to 38% in the UK. These data suggest that environmental factors can have a major impact on root longevity. Copyright 2000 Annals of Botany Company [ABSTRACT FROM AUTHOR]