Charting cell-type-specific positive genetic interaction at single-cell resolution for lung adenocarcinoma.

Genetic interactions (GIs) drive carcinogenesis and treatment resistance via non-additive phenotypic effects between genes. Traditional bulk-based methods fail to capture cell-type-specific interactions in heterogeneous tumors like lung adenocarcinoma (LUAD), limiting precision oncology. Resolving cell-type-specific GIs at single-cell resolution persists as a major hurdle, hindered by limited analytical methodologies. Here, we develop scPGI-finder, a computational framework that identifies gene pairs whose coordinated high expression is associated with higher proliferation-related fitness at single-cell resolution, which we refer to operationally as single-cell positive genetic interactions (scPGIs). Using scPGI-finder, we identify 49,808 and 15,896 scPGIs spanning epithelial cells and T cells in LUAD, respectively. The predicted scPGIs display tighter junctions in the protein interaction network compared to non-scPGIs. Furthermore, we demonstrate the predictive power of scPGIs for malignancy and immunotherapy response through multi-omics validation across diverse cohorts. Notably, with a mean area under the ROC curve (AUROC) of 0.974 in bulk tissue validation, the epithelial-derived scPGI classifier enables concordant malignancy identification across scales ranging from epithelial single cells and lung cancer cell lines, through spatial transcriptomic maps, to bulk LUAD tissue profiles. Additionally, a six-scPGI T cell signature reliably forecasts immunotherapy efficacy, with AUROC values exceeding 0.80 across multiple datasets. Together, our research advances the understanding of underlying cancer-positive GIs at the single-cell level. scPGIs of epithelial and T cells serve as robust biomarkers for malignancy evaluation and treatment response, offering a translational framework for precision oncology.