Optogenetic Control of the Integrated Stress Response Limits Glioblastoma Invasion

The integrated stress response (ISR) is a highly conserved cellular signaling network, allowing cells to adapt and respond to various stressors. In one of the toughest cancers to date, glioblastoma multiforme (GBM) with aggressive spread and high recurrence rates, the role of the ISR is yet to be well understood - whether activation may suppress or promote this disease - and drug-treatment of GBM has thus far shown inconclusive results. In this work we use an optogenetic tool, opto- PKR, to specifically trigger ISR-activation with light with high spatiotemporal control via the PKR-kinase, avoiding potential upstream damage or side effects from drugs. Using immunofluorescence and RNA-sequencing we show that targeted ISR-activation reaches levels where both adaptive (ATF4) and terminal response (CHOP) of the ISR are activated, which show downregulation of genes associated with extracellular environment and glial cell migration, further supported by ECM-stain and scratch assays. Further, we show inhibition of aggressive spread for ISR-activated GBM spheroids in collagen 3D culture. Photopatterning of ISR-activation in spheroids demonstrates a cell intrinsic effect at tissue scale, and recovery studies indicate a tunable, non-ablative intervention space. These findings suggest a route to containment and motivate ISR-activating small molecule screening in GBM models.