Consistent with the Western blot and immunohistochemical analyses, the PKM1-expresing normal brain samples exhibited high levels of PK activity while the PK activity of the astrocytomas, which expressed lower levels of the constitutively active PKM1, was uniformly lower than that noted in normal brain regardless of PKM2 expression (Fig. 2D). Here, PKM is linked to astrocytoma (excluding glioblastoma).