MUC5B and lung carcinoma: FOXA3 or SPDEF independently induced the mucin genes MUC5AC and MUC5B, biomarkers for IMA, in human A549 lung carcinoma cells that harbor a KRAS mutation (Fig 6A–C; Chen et al, 2014), suggesting that FOXA3 or SPDEF along with mutant KRAS intrinsically drives a mucinous phenotype in human IMA as well.