Mitochondria-targeted metformin analogs activate the ER stress-unfolded protein response pathway to drive apoptosis in pancreatic cancer

Abstract Accumulating evidence indicates that evasion of apoptosis and metabolic reprogramming are necessary for pancreatic cancer growth, early invasion, and chemotherapeutic resistance. Building on our prior work, we investigated the anti-tumor potential of a rationally designed mitochondria-targeted variant of the anti-diabetic drug metformin, Mito-Met 10 , in cell culture models and orthotopic xenografts. Using MALDI-mass spectrometry imaging, therapeutic concentrations of fluorinated Mito-Met 10 were shown to preferentially localize within pancreatic tumors relative to adjacent tissue and liver. Treatment suppressed tumor growth, reduced tumor weights, and increased apoptosis in vivo. Murine and human pancreatic cancer cells demonstrated potent anti-proliferative activity, with low micromolar IC 50 values, and a concomitant induction of apoptotic programmed cell death in vitro. Seahorse metabolic flux analysis revealed reduced basal and ATP-linked mitochondrial respiration following Mito-Met 10 treatment without a compensatory increase in glycolysis. Unbiased bulk RNA sequencing revealed significant enrichment of endoplasmic reticulum stress and unfolded protein response pathways, validated by qPCR across pancreatic cancer models, with broad upregulation of UPR-associated genes, establishing that Mito-Met 10 activation of this stress response is conserved. Mito-Met 10 caused extensive cytoplasmic vacuolization, mitochondrial swelling, and loss of mitochondrial membrane potential, indicative of severe organelle damage. Mito-Met 10 activated PERK-eIF2α-ATF4-CHOP signaling, including upregulation of ATF4 and downstream pro-apoptotic transcriptional programs. Pharmacologic inhibition of ISR abrogated apoptotic signaling, demonstrating that PERK-eIF2α-ATF4-CHOP-mediated ISR activation functionally contributes to the anti-tumor effects of Mito-Met 10 . Consistent with these findings, orthotopic tumors from Mito-Met 10 -treated mice exhibited increased nuclear ATF4 staining compared with vehicle controls. Collectively, this study links mitochondrial stress to ER stress-associated apoptosis and identifies mitochondrial stress as a tractable vulnerability that can be manipulated to positively engage anti-tumor responses in pancreatic cancer.