Activating transcription factor 4 mediates adaptation of human glioblastoma cells to hypoxia and temozolomide

Abstract

The integrated stress response (ISR) is a central cellular adaptive program that is activated by diverse stressors including ER stress, hypoxia and nutrient deprivation to orchestrate responses via activating transcription factor 4 (ATF4). We hypothesized that ATF4 is essential for the adaptation of human glioblastoma (GB) cells to the conditions of the tumor microenvironment and is contributing to therapy resistance against chemotherapy. ATF4 induction in GB cells was modulated pharmacologically and genetically and investigated in the context of temozolomide treatment as well as glucose and oxygen deprivation. The relevance of the ISR was analyzed by cell death and metabolic measurements under conditions to approximate aspects of the GB microenvironment. ATF4 protein levels were induced by temozolomide treatment. In line, ATF4 gene suppressed GB cells (ATF4sh) displayed increased cell death and decreased survival after temozolomide treatment. Similar results were observed after treatment with the ISR inhibitor ISRIB. ATF4sh and ISRIB treated GB cells were sensitized to hypoxia-induced cell death. Our experimental study provides evidence for an important role of ATF4 for the adaptation of human GB cells to conditions of the tumor microenvironment characterized by low oxygen and nutrient availability and for the development of temozolomide resistance. Inhibiting the ISR in GB cells could therefore be a promising therapeutic approach.

The PERK Branch of the Unfolded Protein Response Safeguards Protein Homeostasis and Mesendoderm Specification of Human Pluripotent Stem Cells

“…We found that efficient cardiac specification requires the tryptophanyl‐tRNA synthetase WARS1, a conserved transcriptional target of ATF4 also identified in mouse fibroblasts [ 55 ] and human glioblastoma cells. [ 56 ] Aminoacyl‐tRNA synthetases (ARSs) are essential enzymes for protein synthesis [ 57 ] and have not been previously implicated in ESC biology and heart development. ARSs ligate amino acids to their corresponding tRNAs to initiate protein synthesis in a high‐fidelity manner, with one for each amino acid.…”

Translational modulation by ISRIB alleviates synaptic and behavioral phenotypes in Fragile X syndrome

“…Behavioral outcomes are a key functional measure of underlying improvements in molecular and cellular function, which often impact central regulatory pathways. Previously, ISRIB has been shown to improve cognitive function in brain injury (Chang et al, 2021; Chou et al, 2017), cancer (Lorenz et al, 2021), neuropsychiatric disorders (Kabir et al, 2017), neurodegenerative disorders (Oliveira et al, 2021; Wong et al, 2018; Xu et al, 2021), and even healthy cognition (Sidrauski et al, 2013). Our study demonstrated the beneficial effects of ISRIB in a mouse model of FXS, which in combination with recent studies showing the impact of ISRIB treatment in models of Down syndrome (Zhu et al, 2019) and MEHMO (Mental retardation, Epileptic seizures, Hypogonadism and Hypogenitalism, Microcephaly, and Obesity), a rare X-linked disorder (Young-Baird et al, 2020), expands its therapeutic potential to neurodevelopmental disorders.…”

AMP-kinase mediates adaptation of glioblastoma cells to conditions of the tumour microenvironment

“…Hypoxia was induced with incubation in GasPak pouches for anaerobic culture (Becton-Dickinson, Heidelberg, Germany) as previously described 23,29,26 . Experiments in hypoxia (0.1% O 2 ) or normoxia (21% O 2 ) were performed in serum-free DMEM adjusted to 2 mM glucose.…”

“…The STR profile of LNT-229 cells matched with the known profile for LN-229, which only differ in their p53 status 25 . A STR profile of G55T2 cells has not been deposited in databases yet 26 .…”