Introduction:
The transition between epithelial and mesenchymal states (EMT) comprises cellular
and molecular processes essential for local tumor growth and dissemination. We investigate
the function of glycosphingolipids (GSL) in EMT in ovarian cancer and their role in
disease outcome.
Materials and methods:
CRISPR-Cas9-technology was employed to generate A4GALT-knockout sublines from several parental ovarian cancer cell lines. GSL expression
profile was determined by flow cytometry. Gene and protein expression were determined
by RT-qPCR and Western blotting, respectively. Publicly available transcriptomic data
sets were used to compute overall survival and relapse-free survival.
Results:
Ovarian cancer cells with epithelial features have elevated expression of genes encoding
glycosyltransferases (e.g. A4GALT) responsible for globoside biosynthesis and this elevated expression was associated
with better outcome (OS, RFS) in ovarian cancer patients. Deletion of A4GALT and subsequent depletion of globosides induced EMT-typical changes: switch from cobble-stone
to fibroblast-like morphology; loss of E-cadherin expression as consequence of epigenetic
silencing of CDH1; elevated capacities to migrate and disseminate (zebrafish-model), anchorage-independent
(anoikis-resistance) proliferation; chemoresistance; adaptation of cancer stem cell-like
features. Intriguingly, accurate E-cadherin-mediated cell-cell adhesion required both
functional A4GALT and globosides.
Conclusion:
We propose a model in which A4GALT function and expression of globosides are required
and accurate expression/localization of E-cadherin are essential for the epithelial
cell state and in which, conversely, A4GALT deletion-imposed loss of globosides and
concomitant epigenetic silencing of E-cadherin expression induces EMT associated with
chemoresistance and acquisition of cancer stem cell-like features. This model reveals
potential therapeutic targets to prevent cancer dissemination.
