Glycoglycerolipid analogues inhibit PKC translocation to the plasma membrane and downstream signaling pathways in PMA-treated fibroblasts and human glioblastoma cells, U87MG

Glycoglycerolipid analogues, derived from 2-O-β-d-galactosylglycerol, have been synthesized on the base of the structure of natural glycoglycerolipids showing anti-tumor and anti-inflammatory efficacy. These compounds have been previously demonstrated to inhibit phorbol 12-myristate-13-acetate (PMA) induced tumor promotion in mouse skin, but their mechanism of action has never been elucidated. In this work, we studied the effects of glycoglycerolipid analogues on PKC activation induced by PMA and its downstream target molecules, in human fibroblasts. Our results proved that: a) the tested compounds were able to block PKC translocation to the plasma membrane, promoted by PMA, in a dose-dependent manner (IC50: 0.48 μM for the most active compound 2); b) the efficacy of these compounds was strongly connected to their acyl chain linked to galactose; in particular, the addition of hexanoyl and branched chains enhanced PKC inhibition, the presence of a cyclohexane ring and an excessive length of the acyl chain, or its lack, exerted a negative effect; c) the inhibition of PKC translocation blocked enzyme activation and downstream signaling pathways, MAPK and FAK, involved in proliferation and adhesion/migration control. In addition, the branched glycoglycerolipid (compound 2) was able to inhibit PKC translocation and activation in naturally highly PKC activating glioblastoma cells, U87MG. As consequence, U87MG cell proliferation and, especially, migration potential resulted to be markedly reduced (−30% and −84%, respectively). Thus, these results reveal the role of a PKC-dependent mechanism in glycoglycerolipid analogues mediated protective effects and highlight their possible employment in the field of prevention/treatment of cancer.

Glycoglycerolipid analogues block PMA-promoted PKC translocation to the plasma membrane.Figure optionsDownload as PowerPoint slideHighlights
► Glycoglycerolipid analogues derived from 2-O-β-d-galactosylglycerol are studied.
► They block PKC translocation to the fibroblast plasma membrane promoted by PMA.
► Downstream signaling pathways MAPK and FAK are blocked.
► The branched compound inhibits PKC translocation in U87MG glioblastoma cells.
► U87MG cell migration is markedly reduced by the branched compound