Analyses of the isoform expression profile using quantitative real-time PCR and immunoblotting showed that the mRNA levels (Supplementary Fig. 1a) and corresponding protein expression levels (Fig. 1b) of PFK in all examined GBM cell lines were substantially higher than were the levels in NHA, whereas more variable mRNA and protein expression levels of PFKL and PFKM were observed in GBM cell lines. Here, PFKL is linked to glioblastoma.