Hypoxia drives a nuclear LOX-H1.5 decrotonylation axis that represses DAG1 and licenses invasive progression in oral squamous cell carcinoma

The poor prognosis of oral squamous cell carcinoma (OSCC) is driven largely by local invasion. Progression toward the worst pattern of invasion (WPOI) 4–5 marks an aggressive clinical phenotype. While hypoxia orchestrates this progression, the epigenetic mechanisms through which it facilitates tumor cell disengagement from the basement membrane remain poorly understood. Here, we identify DAG1 , an invasion-suppressive extracellular matrix (ECM) anchor, whose loss correlates with aggressive WPOI patterns and poor prognosis. DAG1 expression levels in OSCC patient samples and cell lines were assessed using immunohistochemistry (IHC), qRT-PCR, and western blotting. Quantitative global crotonylome analysis was performed to identify differential crotonylation in OSCC cells cultured under hypoxia. Cleavage Under Targets and Tagmentation (CUT & Tag) assays were conducted to examine the role of Histone H1 decrotonylation in DAG1 transcription. Invasion assays were used to evaluate the functional effects of DAG1 in vitro. Pharmacological inhibition of LOX was also evaluated in orthotopic tongue xenograft mouse models. Hypoxia downregulated DAG1 expression at both mRNA and protein levels, leading to impaired cell-matrix adhesion and promoted OSCC invasion. Global crotonylome profiling revealed a prominent loss of crotonylation on linker histone H1 variants under hypoxia. Specifically, histone H1.5 was enriched at DAG1 regulatory regions, where its crotonylation is essential for maintaining DAG1 transcription. Furthermore, lysyl oxidase (LOX) was identified as an upstream nuclear regulator of H1.5 decrotonylation and correlates with DAG1 . Silencing of LOX restored H1.5 crotonylation, promoted DAG1 expression, and impaired hypoxia-induced invasiveness. In orthotopic models, DAG1 depletion enhanced local OSCC invasion, whereas pharmacologically targeting LOX attenuated tumor progression and invasion. These results support a model in which hypoxia drives a nuclear LOX-H1.5 decrotonylation axis that represses DAG1 and licenses invasive progression in OSCC. The LOX-H1.5- DAG1 axis uncovers a clinically relevant vulnerability in OSCC.