Three-dimensional-bioprinted stiff matrix triggers PDAC radioresistance through histone H3 lysine 18 lactylation (H3K18la) potentiates RAD51 activation.

Radiotherapy improves the survival and life quality of individuals diagnosed with locally advanced or terminal pancreatic ductal adenocarcinoma (PDAC). Nevertheless, the ubiquitous of radioresistance resulted in ineffective outcome, which commonly observed the recurrence and malignant progression within the radiation target area. Our clinical observation has shown that PDAC cells resident in rigid tumor niche, therefore, to illuminate the underlying mechanism from the biomechanical perspective is of significant importance. To this end, PDAC models with tunable mechanical properties were constructed through 3D-bioprinted gelatin methacryloyl (GelMA) hydrogel, which enabled the precise manipulation of cellular behavior under physiological stiffness scopes. The effect of matrix stiffness on radiation tolerance of PDAC cells subjected to distinct X-ray radiation was assessed, and the results validated that stiff matrix promoted radioresistance. To elucidate the in-depth mechanism underlying this phenomenon, enrichment analysis was performed on DEGs between soft and stiff groups treated with 4 Gy X-ray radiation. The results showcased that glycolysis process was prominent enriched, further experiment demonstrated that matrix stiffness promoted the glycolysis level and lactate accumulation. The stiff group reinforced histone H3 lysine 18 lactylation level, and the inhibition of histone lactylation efficiently suppressed PDAC radioresistance. shRAD51 assay corroborated that H3K18 lactylation-driven RAD51 transcriptional activation, which established a causal link to radioresistance. Overall, our research shed light on the matrix stiffness mediated histone lactylation, which exerted essential role in PDAC radioresistance and provided insight into future radiotherapy from the perspective of biomechanics.