| The purpose of this dissertation is to discern the biological differences between overexpressed full length protein kinase C epsilon (wtPKCepsilon) and a deletion mutant lacking the LKKQET actin binding motif (DeltaPKCepsilon), which lead to fatal metastatic cancer or begin tumor growth, respectively. The impairment of metastatic invasiveness is the future cure for cancer, being that greater than 50% of cancer patients die because of metastatic spread to other bodily organs. The contents within aim at deciphering both the metastatic potential for wtPKCepsilon and the lack thereof for DeltaPKCepsilon, due primarily to the regulation by filamentous actin. Using a NIH-3T3 fibroblast PKCepsilon overproducing cell model, it has been observed that the alpha5beta1 integrin regulation and beta1 integrin conformation avidity states play a crucial role in the primary rate-limiting step of the invasive process that leads to systemic intravasation. The mechanism responsible for metastatic potential in wtPKCepsilon cells concerns a kinase dependent up-regulation of alpha5beta1 and a kinase independent activation of the beta1 integrin subunit via PKCepsilon induced actin polymerization. In all regards, each of these mechanisms is impaired with the deletion of the actin-binding motif as observed in DeltaPKCepsilon cells, resulting in begin tumor growth only. Additionally, mechanisms involving integrin dependent cell adhesion to substrates correspond to that of motile phenotypes between wtPKCepsilon and DeltaPKCepsilon, and explain why initial motile behaviors oppose that of previous findings for invasive and non-invasive cell behavior. The results herein suggest that PKCepsilon metastatic activity centers around the regulation of the actin-binding partner and is reliant on cytoskeletal substrate phosphorylation and the effects of uncontrolled, stabilized cellular actin polymerization. |
