U2AF1 S34F enhances tumorigenic potential of lung cells by exhibiting synergy with KRAS mutation and altering response to environmental stress

Although U2AF1^S34F is a recurrent splicing factor mutation in lung adenocarcinoma (ADC), U2AF1^S34F alone is insufficient for producing tumors in previous models. Because lung ADCs with U2AF1^S34F frequently have co-occurring KRAS mutations and smoking histories, we hypothesized that tumor-forming potential arises from U2AF1^S34F interacting with oncogenic KRAS and environmental stress. To elucidate the effect of U2AF1^S34F co-occurring with a second mutation, we generated human bronchial epithelial cells (HBEC3kt) with co-occurring U2AF1^S34F and KRAS^G12V. Transcriptome analysis revealed that co-occurring U2AF1^S34F and KRAS^G12V differentially impacts inflammatory, cell cycle, and KRAS pathways. Subsequent phenotyping found associated suppressed cytokine production, increased proliferation, anchorage-independent growth, and tumors in mouse xenografts. Interestingly, HBEC3kts harboring only U2AF1^S34F display increased splicing in stress granule protein genes and viability in cigarette smoke concentrate. Our results suggest that U2AF1^S34F may potentiate transformation by granting precancerous cells survival advantage in environmental stress, permitting accumulation of additional mutations like KRAS^G12V, which synergize with U2AF1^S34F to transform the cell.