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Abstract
Recently, we involved the carbohydrate-binding protein Galectin-3 (Gal-3) as a druggable target for KRAS-mutant-addicted lung and pancreatic cancers. Here, using glioblastoma patient-derived stem cells (GSCs), we identify and characterize a subset of Gal-3high glioblastoma (GBM) tumors mainly within the mesenchymal subtype that are addicted to Gal-3-mediated macropinocytosis. Using both genetic and pharmacologic inhibition of Gal-3, we showed a significant decrease of GSC macropinocytosis activity, cell survival and invasion, in vitro and in vivo. Mechanistically, we demonstrate that Gal-3 binds to RAB10, a member of the RAS superfamily of small GTPases, and β1 integrin, which are both required for macropinocytosis activity and cell survival. Finally, by defining a Gal-3/macropinocytosis molecular signature, we could predict sensitivity to this dependency pathway and provide proof-of-principle for innovative therapeutic strategies to exploit this Achilles’ heel for a significant and unique subset of GBM patients.
Highlights
We involved the carbohydrate-binding protein Galectin-3 (Gal-3) as a druggable target for KRAS-mutant-addicted lung and pancreatic cancers
We define a Gal-3/ macropinocytosis molecular signature that can be used to predict sensitivity to this dependency pathway. By identifying this dependency pathway defined by a molecular signature rather than an oncogenetic status, we provide proof-of-principle for new therapeutic strategies to exploit this vulnerability for a significant subset of GBM patients and potentially for other WT KRAS cancers showing macropinocytosis addiction
Because our previous study showed that Gal-3 gives rise to mutant KRAS addiction by directly binding to the cell surface receptor integrin αvβ[3], we hypothesized that Gal-3 could mediate macropinocytosis allowing mesenchymal glioblastoma patient-derived stem cells (GSCs) to survive in the stressful brain tumor microenvironment
Summary
We involved the carbohydrate-binding protein Galectin-3 (Gal-3) as a druggable target for KRAS-mutant-addicted lung and pancreatic cancers. Using glioblastoma patient-derived stem cells (GSCs), we identify and characterize a subset of Gal-3high glioblastoma (GBM) tumors mainly within the mesenchymal subtype that are addicted to Gal-3mediated macropinocytosis. GBMs are composed of multiple cell types, including cancer stem cells, namely GBM stem cells (GSCs)[9] These cells display many properties such as self-renewing and tumor-initiating properties, differentiation capacities and they are able to survive the harsh hypoxic and nutrient deprived brain tumor microenvironment. We showed that integrin αvβ3-positive pancreatic and lung cancer cells are uniquely addicted to mutant KRAS and we defined Gal-3 as a critical mediator of this activity, functioning through the regulation of macropinocytosis[14]. There was an increase of ROS levels in KRAS-mutant cells in 3D culture, as well as in tumor xenografts and in PDX tumors[14]
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