Object: Supratentorial primitive neuroectodermal tumor (PNET) and medulloblastoma are highly malignant embryonal brain tumors. They share morphological similarities, but differ in their differentiation patterns and global gene expression. The authors compared the expression of specific genes involved in neuroglial differentiation in supratentorial PNETs and medulloblastomas to define the distinct characters of these tumors.
Methods: The mRNA expression of 8 genes (SOX2, NOTCH1, ID1, ASCL-1, NEUROD1, NEUROG1, NEUROG2, and NRG1) was evaluated in 25 embryonal tumors (12 supratentorial PNETs and 13 medulloblastomas) by quantitative real-time polymerase chain reaction. The expression levels of the transcripts of these genes were compared between the tumor groups. Activation of the JAK/STAT3 pathway was assessed by immunoblotting. Relative expression levels of STAT3 and phosphorylated STAT3 proteins were compared.
Results: Supratentorial PNETs expressed significantly higher levels of SOX2, NOTCH1, ID1, and ASCL-1 transcripts, whereas the transcription of proneural basic helix-loop-helix factors, NEUROD1, NEUROG1 (significantly), and NEUROG2 (not significantly) was upregulated in medulloblastomas. The proportion of phosphorylated STAT3alpha relative to STAT3alpha was significantly greater in supratentorial PNETs than in medulloblastomas, indicating activation of the JAK/STAT3 pathway in supratentorial PNETs.
Conclusions: These results indicate that supratentorial PNET predominantly has glial features and medulloblastoma largely follows a neuronal differentiation pattern. These divergent differentiation patterns may be related to the location and origin of each tumor.