MYC and central nervous system cancer: While one study suggested that glioma cells express GS to produce glutamine from glutamate and ammonia, which in turn facilitates purine synthesis from glutamine during glutamine starvation, another team reported that GS is induced and thus nucleotide synthesis is stimulated by oncogenic Myc that is known to up-regulate glutaminolysis, suggesting paradoxical functions of Myc in glutamine metabolism.