Open Access Dissertation
Date of Award
Kenneth V. Honn
Cancer cell metastasis is the single most threatening occurrence of tumor progression and predicts patient prognosis as well as survival. Invasion can be regulated by the Met receptor tyrosine kinase (c-Met), integrin beta4, and the lipid enzyme, 12-Lipoxygenase (12-LOX). Therefore we sought to determine if beta4, c-MET and 12-LOX comprise a signaling axis. c-Met is implicated in cancer cell dissemination through regulation of invasion in EMT where cell-cell junctions are disturbed to allow motility. Furthermore, beta4 promotes cellular adhesion to the extracellular matrix through hemidesmosomes. However, the homeostatic signaling functions of beta4's cytoplasmic tail can be hijacked by growth factor receptors during tumor growth to promote tumor cell survival and metastasis. Beta4 interacts with 12-LOX, an enzyme that metabolizes arachidonic acid to yield 12(S)-HETE, a bioactive lipid that also promotes invasion, tumor growth, and resistance to apoptosis. Our findings reveal that c-Met and beta4 interact in a cell type and condition specific manner. HGF treatment led to beta4 phosphorylation, disruption of the c-Met interaction, and concomitant 12-LOX recruitment. However, despite 12-LOX recruitment, LC-MS analyses showed that HGF stimulation did not lead to increased 12(S)-HETE production. 12-LOX knockdown with shRNA abolished HGF-induced beta4 phosphorylation and downstream signaling, leading to decreased HGF-induced invasion and cell scattering. Inhibition of beta4 interaction with 12-LOX using specifically designed peptides recapitulated the 12-LOX knockdown phenotype. Additionally, inhibition of 12-LOX led to decreased HGF-induced invasion. This is the first demonstration that 12-LOX may have a novel function in modulating c-MET and beta4 signaling through a scaffolding function and outlines a clear rationale to target all three proteins in cancer therapeutics.
Tovar, Elizabeth, "A Novel Function For 12-Lipoxygenase In C-Met And Integrin β4 Axis Crosstalk" (2014). Wayne State University Dissertations. 1029.