MELK and EZH2 in glioma stem cells (NIH/R01)

ABSTRACT
Article-005

Glioblastoma multiforme (GBM) is a devastating brain cancer with a mean survival of only 14.6 months. Current standard-of-care therapies provide only palliation, indicating an urgent need to develop more effective therapeutic options. GBMs display a hierarchy of differentiation states within the tumor, similar to normal brain development processes. Molecular signals that initiate and maintain gliomas commonly overlap with those involved in stem cell development, and indeed accumulating evidence suggests that GBM stem-like cells (GSCs) contribute to tumor propagation, recurrence and the eventual loss of life associated with these lesions. However, molecular mechanisms that regulate GSC survival and therapy resistance remain poorly understood, and this has hampered efforts to develop effective therapies that prevent GBM growth and recurrence.

Our recent studies and preliminary data have discovered a novel molecular signaling cascade that may control the survival, proliferation, and therapy resistance of GSCs. This pathway involves the mitotic kinase MELK, methyl transferase EZH2, and oncogenic transcription factor STAT3. Importantly, dysregulation of this pathway accelerates GSC growth and promotes GBM malignancy, and are tightly associated with poor patient outcome. This project will interrogate the role of this MELK-EZH2-STAT3 pathway in GSC self-renewal, survival, GBM progression, and radiation resistance. Our data strongly indicate that inhibition of the MELK-EZH2-STAT3 signaling axis by targeting the upstream effector MELK may have profound clinical implications since it can simultaneously block multiple oncogenic signaling pathways all of which are the well-known therapeutic targets. Toward this goal, we have developed a small-molecule MELK inhibitor that could decrease GSC survival and tumor growth in vivo. We anticipate that this study will yield a new paradigm for GSC biology and a novel therapeutic approach to target key regulators of GSC, which may lead to the translation into improved therapies.

Public Health Relevance Statement
Glioblastoma multiforme (GBM) is a devastating cancer with a mean survival of only 14.6 months and few therapeutic options. Standard treatment regimen for GBM is maximal surgical resection followed by radiotherapy and chemotherapy, which has only a palliative effect on patients survival. Thus, more effective treatment is urgently needed. This proposal will determine the molecular mechanisms of the newly identified MELK/EZH2/STAT3 pathway in GBM cells and examine whether targeting this pathway would be a safe and efficient therapeutic strategy for GBM.