ERBB4 and breast cancer: Our GBM samples, while demonstrating lower overall levels of ERBB4 mRNA in comparison to normal matched brain samples, show elevated JM-a and CYT-2 expression, suggesting that JM-a–CYT-2 has a role in GBM tumorigenesis, similar to its oncogenic role in breast cancer [24] but distinct from medulloblastoma (in which JM-a–CYT-1 is the oncogenic variant) [16,20].