Motility and stem cell properties induced by the epithelial-mesenchymal transition require destabilization of lipid rafts

Abstract

The Epithelial-Mesenchymal Transition (EMT) is a developmental program that provides cancer cells with the characteristics necessary for metastasis, including increased motility and stem cell properties. The cellular and molecular mechanisms underlying this process are not yet fully understood, hampering efforts to develop therapeutics. In recent years, it has become apparent that EMT is accompanied by wholesale changes in diverse signaling pathways that are initiated by proteins at the plasma membrane (PM). The PM contains thousands of lipid and protein species that are dynamically and spatially organized into lateral membrane domains, an example of which are lipid rafts. Since one of the major functions of rafts is modulation of signaling originating at the PM, we hypothesized that the signaling changes occurring during an EMT are associated with alterations in PM organization. To test this hypothesis, we used Giant Plasma Membrane Vesicles (GPMVs) to study the organization of intact plasma membranes isolated from live cells. We observed that induction of EMT significantly destabilized lipid raft domains. Further, this reduction in stability was crucial for the maintenance of the stem cell phenotype and EMT-induced remodeling of PM-orchestrated pathways. Exogenously increasing raft stability by feeding cells with ω-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) repressed these phenotypes without altering EMT markers, and inhibited the metastatic capacity of breast cancer cells. Hence, modulating raft properties regulates cell phenotype, suggesting a novel approach for targeting the impact of EMT in cancer.

The mystery of membrane organization: composition, regulation and roles of lipid rafts

“…the fish oil component ω-3 docosahexaenoic acid, are robustly incorporated into cellular membranes, where they induce extensive remodelling of lipid compositions and biophysical properties, including increasing the stability of raft-like domains 67 . A study relating these effects to cell behaviour showed that ω-3 docosahexaenoic acid incorporation and concomitant increase in the stability of raft-like domains can repress stem cell properties and motility of breast cancer cells, by interfering with plasma membrane remodelling necessary for the process of epithelial–mesenchymal transition 139 .…”

The Continuing Mystery of Lipid Rafts

“…A model epithelial cell line that develops a discrete apical PM in culture on porous filter substrates (Madine-Darby Canine Kidney; MDCK) revealed clear remodeling of the lipidome during cellular polarization, which could be largely reversed by inducing an in vitro model of an epithelial-to-mesenchymal transition (EMT) 53 . These distinct lipid profiles are manifested in biophysical changes, as EMT induced by several independent means dramatically reduced the stability of domain formation in siolation GPMVs 73 . Notably, these effects could be partially reversed by altering cellular lipidomes via dietary lipids 73 .…”

“…These distinct lipid profiles are manifested in biophysical changes, as EMT induced by several independent means dramatically reduced the stability of domain formation in siolation GPMVs 73 . Notably, these effects could be partially reversed by altering cellular lipidomes via dietary lipids 73 . EMT is thought to be involved in several cancer phenotypes, including migration and escape from apoptosis, so the observations that EMT is associated with distinctive lipidomic and biophysical characteristics that are tunable by dietary pertubations may have important translational implications for cancer diagnosis and treatment.…”

“…Moreover, these lipidomic characteristics are not stable and constant, but rather affected by both endogenous processes (e.g. cell cycle 81 ) and exogenous cues, including dietary fats 54, 73 . A dramatic recent example is remodeling of the lipid composition of neuronal synapses during post-natal development in the rat 82 .…”

Distinguishing Mechanisms Underlying EMT Tristability

“…Overexpression of SNAIL significantly upregulates the expression of FOXC2 while overexpression of FOXC2 does not affect SNAIL levels (49,52) (Figure S8). This suggests that SNAIL functions as an upstream regulator of FOXC2.…”