PIK3CA and lung adenocarcinoma: We identified several targetable pathways in EGFR/KRAS/ALK-negative lung adenocarcinoma including PI3K/mTOR signaling (TSC1, PIK3CA, AKT2), receptor tyrosine kinase signaling (ERBB4), cell cycle regulation (CHEK2, CDC27), and DNA repair (PARP4).