WNK1 drives glioblastoma progression

About This Grant

ABSTRACT Glioblastoma, the most common primary malignant brain cancer, remains uniformly fatal despite current standard of care consisting of maximal safe surgical resection followed by chemotherapy and radiation. Glioblastoma is characterized by a high degree of heterogeneity, including the presence of therapeutically resistant cancer stem cells that drive tumor recurrence after therapy. Cancer stem cells are greatly influenced by cues received from the surrounding tumor microenvironment that activate signaling pathways promoting cell growth, self-renewal, and therapeutic resistance. Here, in preliminary data, we observed that glioblastoma cancer stem cells from patient-derived xenografts express the gap junction protein connexin 43 (Cx43), which drives their survival. Mechanistically, Cx43 is required to maintain expression of the proto-oncogene MYC, a critical factor for cancer stem cells that is increased in recurrent GBM. Expression of the kinase WNK lysinedeficient protein kinase 1 (WNK1) occurs downstream of Cx43 and is also required for normal levels of MYC. Interestingly, while WNK1 expression is necessary to preserve both MYC mRNA and MYC protein levels, WNK1 kinase activity appears to only be necessary for MYC mRNA expression and does not affect MYC protein levels. Based on this observation, we hypothesize that WNK1 drives GBM growth and MYC expression through both kinase-dependent and kinase-independent mechanisms. We will test this hypothesis through the following specific aims: 1) that WNK1 is required for MYC mRNA expression in a kinase-dependent manner, 2) that WNK1 regulates MYC protein in a kinase-independent manner, and 3) that a kinase-independent function of WNK1 is essential for GBM growth and therapeutic resistance. The immediate goal of this project is to provide detailed mechanistic insight into the function of kinase-dependent and kinase-independent functions of WNK1 in GBM and interrogate a potentially targetable and novel signaling node. Our longer-term goal is to translate these findings into improved treatments for patients with glioblastoma. We will utilize in vitro and organoid systems where possible for mechanistic studies and integrate these with in vivo preclinical models that better represent the tumor microenvironment. These preclinical models resemble the human condition in that glioblastoma cells do not exist in isolation and are greatly impacted by other cell types within the tumor microenvironment. As these critical interactions cannot be effectively modeled in vitro, it is essential that we use mouse models for preclinical studies to enable meaningful comparisons to human GBM formation and response to therapies.