RAS signaling in lung adenocarcinoma is defined by lineage context and DUSP4 loss.

Abstract

The molecular landscape of lung adenocarcinoma (LUAD) is often illustrated as a driver-oncogene "pie chart," but identical mutations exhibit heterogeneous signaling shaped by co-mutations, transcriptional programs, and lineage context. We propose a lineage-integrated signaling framework using an EGFR mutation signature (mSig). We defined EGFR mSig using differentially expressed genes in EGFR-mutant (mt) LUADs. Semi-supervised clustering and machine learning models were used to test reproducibility in different combinations of datasets. We analyzed molecular subtypes, lineage markers, co-occurring mutations and EGFR copy number alterations in EGFR mSig-defined subtypes of LUAD. EGFR mSig showed robust classification performance (AUROC = 0.83-0.95; mean NPV = 96.3%). Validated gene expression subtypes and lung lineage markers were closely aligned with EGFR mSig status. Most EGFR mSig(+) tumors, including many without EGFR mutations belonged to Bronchioid subtype. A subset of canonical RAS mutations were mSig(+) and mirrored the EGFR mutation pattern. EGFR wild-type (WT)/mSig(-) tumors were enriched for non-Bronchioid subtypes and had co-mutations in TP53 or RAS/RAF/RTKs. We highlighted a parsimonious collection of coordinated mutations identified including RAS, KEAP1, STK11, TP53, and CDKN2A, supportive of prior reports. A novel EGFR mSig that captures the transcriptional footprint of EGFR activation revealed a subset of EGFR WT LUADs with "mt-like" features. mSig refines LUAD taxonomy beyond mutation-only pie-chart models by incorporating lineage and co-mutation context. Lineage-directed stratification with co-alteration identifies clinically relevant groups across EGFR and RAS states and highlights new treatment opportunities for patients currently considered "oncogene-negative." NCI U01CA272541, R01CA262296, U24CA264021, UG1CA233333, R01CA211939.