Dual regulation of proliferation and apoptosis: c-myc in bitransgenic murine mammary tumor models

Recent progress in the study of c-Myc has convincingly demonstrated that it possesses a dual role in regulating both proliferation and apoptosis; howe ver, the manner in which c-Myc influences these cellular response pathways remains incompletely characterized. Deregulation of c-Myc expression, via m any mechanisms, is a common feature of multiple cancers and is an especiall y prominent feature of many breast cancers. Of significant interest to thos e who study mammary gland development and neoplasia is the unresolved natur e and contribution of apoptosis to breast tumorigenesis. Recently, the use of transgenic mice and gene-knockout mice has allowed investigators to eval uate the pathological mechanisms by which different genes influence tumor d evelopment and progression. In this review, we address two distinct c-myc-c ontaining bitransgenic murine mammary tumor models and discuss the contribu tion and possible future directions for resolution of cancer-relevant molec ular pathways influenced by c-Myc.