| The mammary gland is a unique and specialized epidermal organ; mammary organogenesis begins in the embryo but is not fully complete until puberty. As such, formation of the mammary gland depends on temporally and spatially regulated developmental steps that require coordination of multiple biological and cell signaling processes; many of which have parallels with cancer development. Research describing the events that occur between birth and puberty is lacking and little is known about human breast development of youth. Since mammary gland development requires a coordinated balance between cell growth, proliferation, and apoptosis, it is critical to understand which signaling pathways are utilized to relay developmental signals, and how these pathways and their targets interact and cooperate with age. Additionally, interactions between integrin molecules and their laminin ligands, especially Laminin-5 (Ln-5; also known as Laminin-332), regulate multiple facets of both embryonic development and tumor growth, invasion, and metastasis. alpha6beta4 integrin serves as a marker to detect distant metastases in the early stages of specific malignancies and beta4 integrin overexpression has been found in basal-like breast cancers, correlating with aggressiveness to institute a prognostic beta4 signature that increases with tumor grade. The mechanism alpha6beta4 integrin utilizes to modulate oncogenic signaling through association with Ln-5 molecules in the ECM is the basis for the recombinant protein (rG3, the third of five G domains of Ln-5) produced for the work reported in this dissertation. Here, it is shown there are specific transcriptional differences and a unique interaction of a gene set over time that contributes to postnatal mammary gland development, and this model clearly shares similarities and signaling pathways with oncogenic development. Especially important are pathways of the adaptive and innate immunities, ECM remodeling and integrin interactions, and extrinsic and intrinsic TP53-mediated apoptosis, greater understanding of which could lead to early detection of potential tumorigenic growth and identification of potential treatment avenues. Presented is a comprehensive model of early mammary development along with several panels of biomarkers that possess a role in normal mammary development, are involved in aggressive cancers, and are affected by apoptosis induced by rG3 treatment. rG3 has proven to be a valuable tool to study apoptotic pathways and the crosstalk among those pathways. |
