NOTCH1 and lung cancer: Further studies are needed to determine if, 1) Sox9 overexpression is required for tumor formation in the Kras and Notch1 lung cancer mouse models, 2) if Sox9 acts downstream of Kras or Notch in the Kras lung cancer mouse model, and 3) if Sox9 alone can drive the development of premalignant or malignant lesions.