This request for supplemental funding represents a direct extension of our NCI-funded research on new treatments for glioblastoma (GBM). The central hypothesis of our GBM research is that these cells require inhibition of the c-Cbl ubiquitin ligase (by pix) to generate tumors, escape chemotherapy and escape oxidative stressors. This work has gone so well that we will soon be initiating clinical trials of our new therapies. One of the consequences of our GBM research is that we have developed a sophisticated understanding of the mechanisms by which the inhibitory complex between c-Cbl and Pix is regulated. Our data indicate that this complex is formed as a result of increased activation of p21-activated kinases (PAKs), which appears to be due to increased signaling along the sphingosine-1-phosphate (S1P) pathway. As one component of testing whether our understanding of regulation of c-Cbl inhibition is correct, we have been treating oligodendrocyte progenitor cells (OPCs) with S1P and with the S1P analog FTY720. These experiments allow us to test whether the inhibitory complex formation is induced by S1P signaling, to better understand the consequences of c-Cbl inhibition in glial progenitor cells as a complement to understanding the effects of c-Cbl activation in GBM cells, and to understand the ability of this complex to allow cells to escape the deleterious effects of oxidative stress (an important component of Alzheimer?s disease (AD). As part of our attempts to understand consequences of c-Cbl inhibition, we are analyzing responses to pro- oxidative stimuli in OPCs with S1P-induced inhibitory complexes or treated with anti-oxidants. The stimulus of greatest interest, in respect to this supplement, is amyloid-(1-42) oligomers, which oxidizes cells and is the most toxic form of A. OPCs are studied due to the extensive myelin damage in AD. Based on our current understanding, we hypothesized that A(1-42) oligomers will activate the redox/Fyn/c-Cbl (RFC) pathway and cause hyper-activation of c-Cbl in OPCs. This is indeed the case, and activation of the RFC pathway appears to be critical for A toxicity in OPCs. Genetic knockout of Fyn kinase or c-Cbl in OPCs protects against A toxicity and RFC pathway activation, as do anti-oxidants. A(1-42) oligomers also activate the RFC pathway in neurons. We also have confirmed, in studies on other pro-oxidative signals, that generation of the c-Cbl/pix inhibitory complex in OPCs protects cells from the effects of pro-oxidative signals on promoting cell-cycle exit. We now seek the opportunity to utilize A(1-42) oligomers as an important pro-oxidative insult for analyzing the consequences of c-Cbl inhibition in glial progenitor cells and neurons, including IPSC-derived OPCs and neurons that are inherently more vulnerable to A due to AD-relevant mutations in presenilin-1 or expression of apoliprotein E4. At the same time, the experiments we propose will offer a new mechanism of A toxicity that integrates multiple pathways of potential therapeutic interest for AD and offers the possibility of better understanding how to create rational therapeutic cocktails able to slow or stop disease progression.
This supplemental funding request builds directly on our NCI-sponsored research on glioblastomas, in which we have discovered new mechanisms by which these tumor cells escape induction of cell stress and cell death. The discoveries made in this research have provided new insights into how normal cells can be protected against multiple clinically relevant insults, and particularly stresses associated with Alzheimer?s disease. In addition, our discoveries enable us to beneficially modulate multiple proteins of potential therapeutic interest in Alzheimer?s disease and provide new insights into how to create rational combinations of protective agents composed of drugs that are already in clinical use for other purposes.
