TWIST1 mediated epithelial mesenchymal transition (EMT) in Glioblastoma (GBM)
The EMT state in GBM is associated with invasion and promotion of stem-cell phenotypes. Given the importance of these properties for GBM formation, treatment resistance and progression, the identification of regulators of EMT in GBM are of great clinical relevance. We first identified TWIST1 expression in gliomas and reported its correlations with increased tumor grade, invasion and glioma stem cell (GSC) properties. We also characterized the functional importance of periostin (POSTN), a TWIST1 regulated protein, with similar pro-EMT effects in glioma. Our current efforts are directed at developing a deeper understanding of how TWIST1 regulates specific aspects of this phenotype through post-translational modifications, dimerization motifs and protein-binding partners. These studies are anticipated to inform therapeutic strategies that target TWIST1 through direct disruption of protein interactions. Given, the difficulty in drugging transcription factors we are concurrently performing RNAseq and ChiPseq studies to define genes directly or indirectly regulated by TWIST1 that could serve as more druggable surrogate targets to inhibit TWIST1 mediated EMT.
Twist1 (TW), a bHLH transcription factor, is a critical regulator of epithelial–mesenchymal transition, invasion, metastasis, cell stemness and increased malignancy in multiple cancers. In glioblastoma (GBM) increased TW expression correlates with poor prognosis and experimentally promotes invasion, stem cell properties and its inhibition markedly reduce tumorigenicity of human GBM cells. TW function and stability are regulated through site-specific phosphorylation events and formation of homo-dimers or heterodimers with other bHLH TFs such as E12. In particular, malignant phenotypes of carcinomas are enhanced by TW:E12 (T:E) heterodimer expression and phosphorylation of serine 68 (S68) in TW which promotes TW stability [1,2]. However, the functional importance of TW post-translational modifications and pharmacologic approaches to target TW have not been studied in GBM. To date, only one drug- harmine, has been reported to have specific inhibitory effects on TW in NSLC cells. Harmine is a β-carboline alkaloid isolated from the seeds of Peganum harmala
, possesses both antitumor and anti-nociceptive effects and inhibits human DNA topoisomerase. Our aim is to determine the potential clinical utility of harmine as a TW specific therapy in GBM through analysis of its effects on TW S68 phosphorylation, dimerization motifs and malignant phenotypes in GBM cells.
“Oncoslice”; Microfluidic Drug Delivery for Pre-Clinical Screening of Patient Derived Tumor Cultures
Precision cancer medicine seeks to enhance treatment response and reduce toxicity by treating patients with drugs that target their unique profile of cancer driver mutations. However, clinical decision making can be confounded by the availability of multiple drugs for a specific mutation(s)/pathway(s) or the lack of available drugs with specific activity against identified driver mutations. In addition, the potential activities of non-selective chemotherapies, irradiation and immunotherapies, alone or in combination with targeted drugs, are difficult to predict. Given this, pre-clinical screens that can inform patient tumor specific drug responses, both targeted and standard genotoxic drugs alone or in combination, are of great potential clinical importance. Further, biologic substrates that most closely phenocopy the 3D and stromal elements of the native tumor micro-environment are expected to be more predictive of therapeutic responses than isolated cells in culture. In collaboration with investigators at the University of Washington (Albert Folch, UW BioE and Ray Monnat, UW Pathology/Genome Sciences) we developed a microfluidic platform for drug delivery to patient derived organotypic tumor slice cultures (“Oncoslice”). The platform permits comparison of dose-response curves to multiple drugs alone or in serial combination in a 3D environment expected to retain stromal features of the parental cancer. Our current work is focused on comparing cell biology and drug responses between freshly isolated GBM slice cultures, matching reconstituted 3D tissue-engineered models (GBM-on-chip) and isolated tumor cells in culture. The efficacy of selected drugs will be tested in vivo to establish the differences in predictive power between the various pre-clinical biological substrates. Future work will also focus on adapting the platforms to accommodate testing of immunotherapies.
Aging and Glioblastoma Malignancy
Increased age is arguably the most robust predictor of survival for all glioma patients. However, the mechanisms which drive this clinical phenotype remain largely unknown. To facilitate the study of aging in glioma we created a unique syngeneic mouse model and showed that the impact of aging on malignancy derived from cell intrinsic changes in glioma cells of origin, neural progenitor cells (NPCs) rather than host brain. Aging related cell intrinsic changes associated with increased malignancy included increased genomic instability and hypoxia tolerance and HIF1 regulated gene expression, the latter being validated in human GBM. Current work is focused on exploring the role of differential hypoxic responses and epigenetic changes in regulating age-dependent malignancy.
Intratumoral Molecular Heterogeneity
Glioma Stem Cell (GSC) Electrophysiology as a Potential Therapeutic Target in GBM
The electrophysiology of GBM and the surrounding brain at the cellular and tissue levels have not been well characterized. A better understanding of the electrophysiologic properties of glioma cells and the electrical crosstalk with other tumor and stromal cells may provide novel therapeutic strategies to target glioma malignancy or alleviate tumor associated neurotoxicity. In collaboration with Nino Ramirez’s lab at Seattle Children’s Hospital Center for Integrative Brain Research (CIBR) we are working on understanding the mechanisms that regulate the electrophysiological characteristics of glioma stem cells (GSCs) in isolation or in the context of the tumor and brain environment, and whether these properties can be manipulated as a therapeutic strategy.
Clinical Research Projects
- TSPO-PET imaging of Brain Metastasis
- Brain Metastasis Registry
- Neural Biorepository