Date Published: May 15, 2019
Publisher: BioMed Central
Author(s): J. Qi, D. R. Esfahani, T. Huang, P. Ozark, E. Bartom, R. Hashizume, E. R. Bonner, S. An, C. M. Horbinski, C. D. James, A. M. Saratsis.
Diffuse intrinsic pontine glioma (DIPG), an infiltrative, high grade glioma (HGG) affecting young children, has the highest mortality rate of all pediatric cancers. Despite treatment, average survival is less than twelve months, and five-year survival under 5%. We previously detected increased expression of Tenascin-C (TNC) protein in DIPG cerebrospinal fluid and tumor tissue relative to normal specimens. TNC is an extracellular matrix (ECM) glycoprotein that mediates cell-matrix interactions, guides migrating neurons during normal brain development and is thought to maintain the periventricular stem cell niche in the developing brain. Tumor TNC expression is reported in adult glioma and other cancers. However, the pattern and effects of TNC expression in DIPG has not been previously explored. Here, we characterize TNC expression in patient derived pediatric supratentorial HGG (n = 3) and DIPG (n = 6) cell lines, as well as pediatric glioma tumor (n = 50) and normal brain tissue specimens (n = 3). We found tumor specific TNC gene and protein overexpression that directly correlated with higher tumor grade (WHO III and IV, p = 0.05), H3K27 M mutation (p = 0.012), shorter progression free survival (p = 0.034), and poorer overall survival (0.041) in association with these factors. TNC knockdown via lentiviral shRNA transfection of HGG (n = 1) and DIPG (n = 3) cell lines resulted in decreased cell proliferation, migration, and invasion in vitro (p < 0.01), while TNC cDNA transfection resulted in increased cell migration, invasion and proliferation (p < 0.01) as well as altered cell morphology in H3K27 M mutant DIPG lines. Whole transcriptome sequencing analysis (RNA-Seq) on DIPG (n = 3) and HGG (n = 2) cell lines after TNC cDNA, shRNA, and empty vector control transfection revealed the effects of TNC expression level on global gene expression profiles. Together, our findings reveal TNC expression in DIPG in association with H3K27 M mutation and VEGF signaling, and suggest that TNC may contribute to DIPG tumor phenotype, and serve as a clinically detectable biomarker for DIPG.
Brain tumors are the most common solid cancer in children. Approximately 15% of pediatric brain tumors arise in the brainstem, of which up to 80% are a subtype known as diffuse intrinsic pontine glioma (DIPG), an infiltrative, high grade glioma affecting young children . DIPG typically affects children between six to nine years of age, and has the highest mortality rate of all pediatric cancers. Due to its characteristic appearance on MR imaging, DIPG is most often diagnosed radiographically at the time of symptom onset, which may include symptoms due to obstructive hydrocephalus and brainstem compression, including cranial nerve deficits and hyperreflexia . The diffuse nature and location of DIPG precludes surgical resection, while chemotherapeutic agents that are more effective in other pediatric and adult gliomas are not effective in DIPG [4, 14, 17, 25, 39]. Standard treatment is focal radiation, which provides temporary symptom improvement but has no effect on overall survival [25, 31, 52, 59]. Despite treatment, average survival is less than twelve months, and five-year survival under 5% , with no improvement in overall survival despite more than 40 years of clinical trials . Given the rapid clinical progression of DIPG and its poor response to treatment, improving our understanding of tumor biology is necessary to achieve more effective therapies.
Diffuse intrinsic pontine glioma (DIPG) is a devastating pediatric brain tumor and the most common cause of cancer death in children. New, more effective therapeutic approaches are needed to improve clinical outcomes of this challenging disease. Tenascin-C (TNC) is a large extracellular matrix (ECM) glycoprotein that mediates cell-cell and cell-matrix interactions , and functions in early cell fate determination in the central nervous system by guiding migrating neurons during brain development in the perivascular stem cell niche . TNC binding on the cell surface is known to induce PDGFRB translocation and Notch signaling . TNC overexpression is reported in adult high grade glioma (HGG) [22, 56, 70] and has been explored as a biomarker of disease and potential therapeutic target . While pediatric glioma is biologically distinct from the adult disease, our previous work characterizing gene and protein expression profiles of pediatric brainstem (DIPG), cerebellar and supratentorial gliomas revealed increased expression of TNC in tumor specimens, suggesting this protein may play a role in DIPG tumor biology . Further, this work revealed greater TNC gene and protein expression, as well as TNC promoter hypomethylation, in histone H3K27 M mutant tumors compared to wild-type. Since H3K27 M mutation is associated with global changes in DNA methylation, altered chromatin structure, and poorer clinical outcomes in pediatric diffuse midline glioma [12, 13], our findings suggest TNC overexpression in H3K27 M mutant tumors may be clinically and biologically relevant. We also demonstrated increased secreted TNC in the cerebrospinal fluid (CSF) from children with DIPG and high grade glioma (HGG) compared to normal controls , suggesting TNC may serve as a clinically detectable biomarker of disease and response to therapy. Therefore, in the present study we aimed to comprehensively characterize TNC expression patterns, clinicopathological correlates and biological effects in pediatric glioma, including DIPG.