Feed

Glioblastoma (GBM), the most common and aggressive primary brain tumor, exhibits profound metabolic reprograming that sustains its progression and therapy resistance. Our previously published work demonstrated that C3G expression is downregulated in GBM, which enhances migration and invasion. Here, we show that C3G silencing or knockout in GBM cells reprograms glucose metabolism favoring glycolysis and lactate production through upregulation of PKM2 and LDHA. Furthermore, Seahorse metabolic profiling further revealed increased respiratory capacity and glycolysis upon C3G downregulation or depletion. Mechanistically, C3G silencing increases the levels of the splicing factor PTBP1, which forces PKM splicing towards PKM2 expression as demonstrated by transient PTBP1 silencing, although other splicing factors such as SRSF3 could also contribute to PKM2 expression. Additionally, C3G downregulation or depletion enhances sphere formation, stemness and tumor initiating capacity in GBM cells, which is rescued by C3G re-expression in C3G knockout GBM cells. This enhanced stemness induced by C3G silencing in GBM cells is prevented by transient PTBP1 or PKM2 silencing or pharmacological inhibition of PKM2 with compound 3K, which also decreases cell viability within the spheres (3D-cell cultures) and the expression of stemness markers. However, in 2D-cell cultures compound 3K increases cell viability in C3G-silenced GBM cells, while decreasing that of C3G knockout cells. This supports a specific role for C3G/PKM2 axis in GBM cancer stem cells through mechanisms likely dependent on both PKM2-mediated metabolic reprogramming and nuclear effects on gene transcription. Altogether, our findings identify C3G as a novel regulator of GBM metabolism and stemness acting through PKM2, unveiling new potential diagnostic and therapeutic implications for C3G in a subset of GBM patients.