Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest human malignancies, with limited therapeutic options and a lack of druggable vulnerabilities beyond a narrow set of oncogenic drivers. To identify cancer dependencies that are both essential in vivo and drug-tractable, we performed an unbiased genome-wide CRISPR loss-of-function screen under in vivo tumor-selective pressure. This approach revealed the mitochondrial co-chaperone HSPE1 (Hsp10) as a previously unrecognized, tumor-promoting dependency in PDAC. Genetic depletion of HSPE1 markedly impaired tumor growth, survival, and tumor-initiating capacity across multiple PDAC models in vitro and in vivo, including patient-derived xenografts. Mechanistically, HSPE1 functioned as a central survival node by engaging two parallel and targetable mitochondrial pathways. First, HSPE1 cooperated with its canonical partner HSPD1 to regulate cell-cycle progression, and apoptosis. Second, HSPE1 was functionally associated with mitochondrial dynamics, correlating with altered regulation of the OPA1/OMA1 axis, revealing an HSPD1-independent mechanism linking mitochondrial stress adaptation to cancer cell fitness. This dual signaling architecture exposes a previously unappreciated mitochondrial vulnerability selectively exploited by PDAC cells. Importantly, both HSPE1-regulated pathways were amenable to therapeutic targeting in vivo. Pharmacological inhibition of the HSPD1/HSPE1 complex or the OPA1/OMA1 pathway significantly suppressed tumor growth, while combined targeting produced robust synergistic antitumor activity in both cell line–derived and patient-derived PDAC models. Moreover, this combination strategy provides a modest yet consistent incremental benefit to standard-of-care chemotherapies, underscoring its translational relevance. Together, these findings establish HSPE1 as a bona fide cancer dependency uncovered through in vivo functional genomics, uncover a dual mitochondrial vulnerability, and provide a rational framework for combination therapy design. More broadly, this work highlights the power of in vivo CRISPR screening to directly inform therapeutic strategies and identifies mitochondrial stress adaptation as a promising and generalizable target in cancer.
Boudreault et al. (Thu,) studied this question.