The GD3 ganglioside promotes cell growth, plasticity and chemotherapy resistance of human glioblastoma cancer stem cells.

BACKGROUND: Glioblastoma is the most aggressive primary brain tumour with no curative treatment and inevitable relapse. Therapeutic resistance is, at least, related to the presence of cancer stem-like cells in these tumours. Here, we aimed to demonstrate that the GD3 ganglioside was a relevant marker and actionable target for glioblastoma cancer stem-like cells. METHODS: To this end, we used commercial glioblastoma cell lines, human glioblastoma samples, organotypic culture and xenografted mouse models to study GD3 antigen expression and consequences of its downregulation through a shRNA strategy targeting the ST8SIA1 mRNA which encodes the key enzyme for GD3 synthesis. We performed mono-dimensional Thin Layer Chromatography to analyse ganglioside composition of the glioblastoma samples and RNA-seq analyses to reveal oncogenic pathways and more specifically transcripts affected by ST8SIA1 silencing. Besides, we evaluated GD3 role in stemness of glioblastoma cancer cell, phenotype, microenvironment interaction, and invasion abilities. RESULTS: We showed that GD3 is the main ganglioside in glioblastoma and that patient-derived cancer stem-like cell lines strongly expressed GD3. This GD3 + population decreased significantly after cell differentiation. GD3(+) cells sorted from patient samples had stem-like cell properties: they were plastic, clonogenic, and tumorigenic after orthotopic engraftment. Silencing of ST8SIA1/GD3 was associated with a decrease in sphere size, self-renewal and migratory capacities and increased mouse survival. Moreover, increased temozolomide sensitivity was recorded. Finally, data from RNA-seq showed that silencing ST8SIA1/GD3 decreased oncogenic pathways and more specifically the expression of ADAMTS1 and IL33 transcripts. CONCLUSIONS: Taken together, our results suggest that GD3 ganglioside is essential for glioblastoma cancer stem-like cell properties, opening promising targeted therapeutic development.