CHCHD2 mediates glioblastoma cell proliferation, mitochondrial metabolism, hypoxia-induced invasion, and therapeutic resistance

Abstract

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults and remains incurable. The mitochondrial coiled-coil-helix-coiled-coil-helix domain-containing protein 2 (CHCHD2) is demonstrated to mediate mitochondrial respiration, nuclear gene expression, and cell migration, but evidence of this in GBM is lacking. We hypothesized that CHCHD2 would serve a functional role in U87 GBM cells expressing the constitutively active epidermal growth factor receptor variant III (EGFRvIII). Amplification of the CHCHD2 gene was found to be associated with decreased patient overall survival and progression-free survival. CHCHD2 mRNA levels were increased in high-versus low-grade glioma, IDH-wt GBMs, and in tumor versus non-tumor tissue. Additionally, CHCHD2 protein expression was greatest in invasive, EGFRvIII-expressing patient-derived samples. CRISPR-Cas9-mediated knockout of CHCHD2 in EGFRvIII-expressing U87 cells resulted in altered mitochondrial respiration and glutathione status, decreased cell growth and invasion in both normoxia and hypoxia, and increased sensitivity to cytotoxic agents. CHCHD2 was distributed in both mitochondria and nuclei of U87 and U87vIII cells, and U87vIII displayed greater nuclear CHCHD2 compared to isogenic U87 cells. Incubation in hypoxia, serum starvation, and reductive unfolding of CHCHD2 induced nuclear accumulation of CHCHD2 in both cell lines. Collectively, these data indicate that CHCHD2 mediates a variety of GBM cell hallmark characteristics and highlights mitonuclear retrograde signaling as a pathway of interest in GBM cell biology. ImplicationsThese data demonstrate CHCHD2 as a mediator of a number of GBM cell functions representing disease hallmarks, as well as highlight its subcellular distribution in response to metabolic stressors. These results may inspire therapeutic strategies undermining mitochondrial biology to potentially improve GBM tumor management.