HNF4A and mucinous adenocarcinoma: Although mucinous adenocarcinomas were detected in lung sections from KL mice (Figure 3D), these KRASG12C/LKB1Null tumor cells retained expression of NKX2.1 (Figure 3D, Figure 3—figure supplement 1E), and some cells also expressed the gastrointestinal transcription factor HNF4α (Figure 3—figure supplement 1E).