510P - CD47 regulates cellular and metabolic plasticity in glioblastoma

Background

Glioblastoma (GBM) is the most common and aggressive form of primary brain tumor with poor survival rates. While conventional therapies including surgery, chemotherapy, and radiotherapy extend patient survival, recurrence within 6-9 months is common with no effective therapy. Thus, novel treatment strategies that have greater specificity and efficacy are warranted. Analyzing the Ivy Glioblastoma Atlas Project's transcriptomics data based on anatomic structures (http://www.brain-map.org/), we identified that CD47, a ubiquitously expressed receptor known to block phagocytosis by interacting with SIRPα on myeloid cells, is abundantly expressed on the leading invasive edge of GBM patient tumors. Increased expression of CD47 is also associated with poorer survival in GBM patients. Importantly, the role of CD47 in GBM besides promoting immune escape is not well understood. Therefore, we propose to identify cell-intrinsic mechanisms that CD47 regulates in GBM.

Methods

To identify intracellular mechanisms regulated by CD47 in GBM, we created a CD47 CRISPR knock-out (KO) cell line using U87 GBM cells. Using the control and CD47 KO cells, we performed a clonogenic assay and transwell migration assay to assess changes in cellular phenotype. Subsequently, we performed bulk RNA-seq followed by gene set enrichment analysis to identify pathways regulated by CD47. To address changes in cell metabolism, a seahorse assay followed by non-targeted metabolomics and metabolic flux analysis was also conducted.

Results

We have found that loss of CD47 in GBM cells reduces cell migration and proliferation in the absence of myeloid cells, suggesting a cell-autonomous function of CD47. Consistently, gene set enrichment analysis in control and CD47 KO GBM cells indicates that cell polarity, axonal guidance, cell differentiation, and cell proliferation pathways are driven by CD47 signaling. Furthermore, our data shows that CD47 regulates metabolic plasticity. We found that CD47 KO cells exhibit elevated levels of several glycolytic metabolites which correlates with increased mitochondrial spare respiratory capacity and mitochondrial biogenesis.

Conclusions

We have identified a novel immune-independent function of CD47 in linking cellular and metabolic plasticity in GBM.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

University of South Australia.

Funding

Neurosurgical Research Foundation.

Disclosure

The author has declared no conflicts of interest.