Glioblastomas rank among the most lethal of human cancers despite aggressive multimodal therapy. Most cancers kill their hosts through metastases but glioblastomas are nearly universally deadly in the absence of spread beyond the neuraxis due to spread into normal brain and resistance to conventional therapies. The lifespan and quality-of-life for glioblastoma patients has improved with better surgical resection, refined radiation administration and the addition of the oral methylator, temozolomide, during radiation, but median survival remains less than two years. The explanation for the failure of current therapy to extend patient survival has many causes, but one contributing force may be the presence of complex intratumoral heterogeneity derived from heterogeneous expression of oncogenic drivers as well as cellular hierarchies that phenocopy the normal brain hierarchy, albeit with aberrant control. Glioblastomas, like all cancers, can be considered a complex ecosystem that effectively responds to anti-tumor defenses of the body and additional cytotoxic therapy through the collective action of the neoplastic compartment in concert with infiltrating immune cells, vasculature, and reactive astrocytes that can act both as tumor suppressor and enhancer. Normal tissue specific stem cells pose danger due to their ability to undergo sustained proliferation. In response, stem cells reside in specific niches from which their derive maintenance cues but are also constrained in proliferation and undergo differentiation upon exiting the niche. Cancer stem cells share some cell autonomous regulatory pathways with the stem cells in the organs from which they were derived but also recreate elements of a niche. The stem cell niche is a structural construct but also is associated with regional variation in oxygen, pH, and nutrient availability. Thus, it is almost certain that the metabolic reprogramming that occurs within the context of oncogenesis represents an element of the cancer stem cell niche that requires control of metabolic stress responses. Aberrant metabolic control is required for tumor initiation and maintenance. Genetic derangements hardwire self-renewal into tumors but the cellular hierarchy is maintained through the interplay between core stem cell intrinsic transcriptional regulation, metabolism, and niche cues. We recently demonstrated that brain tumor stem cells coopt a high affinity glucose transporter (GLUT3) expressed in neurons to withstand metabolic stress. As mitochondrial morphology is linked to lineage specification, we investigated another mechanism critical to brain metabolism, mitochondrial dynamics. In preliminary studies, we found that brain tumor stem cells displayed molecular regulation distinct from non-stem tumor cells and neural progenitor cells. As targeting mitochondrial dynamics has been linked to neural protection in degenerative disease, these results suggest that targeting mitochondrial dynamics may represent a selective point of fragility for brain tumor stem cells. In the proposed studies we will investigate the role of mitochondrial dynamics and metabolic control in the maintenance of brain tumor stem cells, regulation of the epigenetic stem cell state, and as a therapeutic modality. Collectively, successful completion of the proposed studies will provide an enhanced model of glioma hierarchy and inform the development of novel clinical trials.
Glioblastomas are the most common and lethal brain cancer, containing stem-like cells called brain tumor stem cells that are highly resistant to conventional therapies. Brain tumor stem cells regulate their metabolism distinct from normal brain stem cells and differentiated cancer cells, providing potentially new ways to target these cancer cells. The proposed studies will focus on the regulation of the power plants of cells, the mitochondria, in resistant tumor cells to develop new therapies.
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