EGFR/TBK1-dependent mitochondrial quality control contributes to acquired resistance to temozolomide

Acquisition of secondary resistance to chemotherapy in cancer cells is an ill-characterized multi-step process. We conducted an unbiased, longitudinal proteomic analysis of U251 glioma cells treated by temozolomide as they transit from drug-sensitive to tolerant and then resistant states. This unprecedented analysis revealed key mitochondrial evolutions throughout the process. Following an early stress substantiated by a transient peak of reactive oxygen species, mitochondrial quality control mechanisms enable emergence of the resistant population. We combined genome editing, targeted protein degradation via PROTAC, and pharmacologic inhibitors to investigate the mechanisms underlying stress resolution both at population and single cell scales (including microscopic evaluation and in-situ proximity ligation assays). These studies unravel a Src-activated EGFR and TBK1 axis that initiates autophagic recycling of mitochondria as a necessary step to the emergence of the resistant population.