G3BP1/2-Targeting PROTAC Disrupts Stress Granules Dependent ATF4 Migracytosis as Cancer Therapy.

Stress granules (SGs) are membraneless cytoplasmic compartments that form in response to stress stimuli. In these compartments, most translation factors stall, except for activating transcription factor 4 (ATF4), which is preferentially translated to ensure cell survival under stressful conditions. Cancer cells encounter various stress conditions in the tumor microenvironment during tumorigenesis; however, how they exploit the pro-survival effects of ATF4 in SGs remains unclear. G3BP1/2 are central nodes of the SG network, regulating SG dynamics. In this study, we designed two small molecules, #129 and PROTAC (Proteolysis Targeting Chimera) degrader 129 (PT-129), which specifically target the NTF2L domain of G3BP1/2, a crucial hub for protein and RNA interactions. These compounds inhibit the formation of stress granules in stressed cells and disassemble pre-existing stress granules. Furthermore, pharmacological inhibition by PT-129 suppressed fibroblast-mediated cancer cell growth in vitro and reduced tumor growth in vivo. Mechanistically, SG facilitates the delivery of ATF4 from fibroblasts to tumor cells via migracytosis, a primary mediator of fibroblast-associated tumor growth. PT-129-mediated disassembly of stress granules disrupts ATF4 delivery, thereby preventing cancer cell proliferation. These compounds, therefore, represent powerful tools for gaining molecular insights into SGs and hold promise for cancer therapeutic interventions by modulating stress granule dynamics.