Multimodal profiling of oral squamous cell carcinoma identifies genomic alterations and expression programs associated with betel quid chewing.

Betel quid (BQ) chewing is a profound risk for oral squamous cell carcinoma (OSCC) in Southeast Asia. Yet, the detailed mechanisms by which BQ chewing damages the genome and creates a unique tumor niche that ultimately cause OSCC are still not fully understood. To address this, we conducted a multi-omics survey, including exome sequencing of tumor-normal pairs from 261 male patients with OSCC (129 habitual BQ chewers and 132 non-BQ users), alone with integrated single-cell and spatial transcriptomics of a set of tumors. Comparative analyses of the mutational catalog identified enrichment of significantly altered genes (e.g. mutations of TP53 and CHUK, copy gains of MAP3K13 and FADD, copy losses of CDKN2A) associated with BQ chewing. Assessment of oncogenic and co-occurring actionable alterations demonstrated frequently altered oncogenic pathways (Hippo and p53 signaling) and potential combination therapy opportunities linked to BQ use. In addition, evaluation of epithelial, immune, stromal expression programs in the corresponding tissue compartments revealed a shift of tumor microenvironment in BQ-related OSCC, characterized by induced hypoxia of tumor epithelium, altered immunosuppression of dendritic cells, and raised sprouting angiogenesis of tumor endothelium. Quantitative predictions of intercellular communications inferred a more heterogeneous cell-cell crosstalk among BQ-related OSCC, highlighted by extensive interactions of fibroblasts and dendritic cells with other non-epithelial cell types via mostly extracellular matrix-receptor signaling pathways. Collectively, these differences in genomic landscape and tumor niche suggest that OSCC caused by BQ chewing could be an etiological subtype different from their BQ-negative counterparts.