Matrix metalloproteinase 7 mediates mammary epithelial cell tumorigenesis through the ErbB4 receptor

Novel bis-(arylsulfonamide) hydroxamate-based selective MMP inhibitors

A series of bis-(arylsulfonamide) hydroxamate inhibitors were synthesized. These compounds exhibit good potency against MMP-7 and MMP-9 depending on the nature, steric bulk, and substitution pattern of the substituents in the benzene ring. In general, the preliminary structure-activity relationships (SAR) suggest that among the DAPA hydroxamates (i) electron-rich benzene rings of the sulfonamides may produce better inhibitors than electron-poor analogs. However, potential H-bond acceptors can reverse the trend depending on the isozyme; (ii) isozyme selectivity between MMP-7 and -9 can be conferred through steric bulk and substitution pattern of the substituents in the benzene ring, and (iii) the MMP-10 inhibition pattern of the compounds paralleled that for MMP-9.

HER4 intracellular domain (4ICD) activity in the developing mammary gland and breast cancer

The HER4 receptor tyrosine kinase was the final member of the EGFR-family to be discovered. In contrast to the other three members of this receptor family which function primarily as mitogenic effectors in the breast, HER4 appears to have multiple divergent functions in the normal and malignant breast. Interestingly, the majority of HER4 activities in the breast including pregnancy induced differentiation and lactation initiation, transcriptional activation, tumor cell proliferation, growth suppression, and induction of apoptosis appear to be mediated by an independently signaling soluble HER4 intracellular domain (4ICD). The 4ICD can accumulate within the nucleus or mitochondria and subcellular localization of 4ICD in part determines the physiological response of breast cells to 4ICD action. Here I will discuss the evidence supporting the role of 4ICD as the critical effector of HER4 signaling in the breast. In addition a developmental and temporal model of 4ICD action in the normal breast and during the progression of breast cancer will be presented to explain the paradox of divergent HER4 and 4ICD activities.

Role of ErbB4 in breast cancer

Members of the ErbB subfamily of receptor tyrosine kinases are important regulators of normal mammary gland physiology, and aberrations in their signaling have been associated with breast tumorigenesis. Therapeutics targeting epidermal growth factor receptor (EGFR = ErbB1) or ErbB2 in breast cancer have been approved for clinical use. In contrast, relatively little is known about the biological significance of ErbB4 signaling in breast cancer. This review focuses on recent advances in our understanding about the role of ErbB4 in breast carcinogenesis, as well as in the potential clinical relevance of ErbB4 in breast cancer prognostics and therapy.