Effect of glucose deprivation and silencing of transcription factors ATF4 and ATF6 on gene expression in human lung adenocarcinoma cell line A549

Tumours grow faster than the local vasculature, resulting in a shortage of oxygen and nutrients. To explore how lung cancer cells cope with a low-glucose environment, we analysed transcriptional changes in glucose-starved A549 cells using RNA-sequencing. This showed downregulation of multiple pathways related to DNA replication and cell cycle, and regulation of metabolic gene sets. The most upregulated transcriptional response to glucose deprivation was the Unfolded Protein Response (UPR), which has been shown to promote adaptation to proteotoxic and endoplasmic reticulum stress. Glucose shortage robustly induced the three branches of the UPR in several non-small cell lung carcinoma cell lines, as indicated by ATF4 accumulation, XBP1 mRNA splicing and ATF6 cleavage. ATF6 and ATF4 silencing revealed that these factors cooperate to regulate multiple metabolic genes and pathways related to lipid synthesis and to amino acid synthesis and transport. ATF4 additionally regulated the transcriptional induction of mitochondrial OXPHOS-associated pathways.