Still, the frequent occurrence of a low ratio of S34F:WT U2AF1 mRNA, accompanied by increased copy number of wild-type U2AF1 alleles in lung adenocarcinoma cell lines and possibly LUADs, suggests that there may be selection for a lower ratio of S34F:WT in addition to the likely selection, perhaps at an earlier stage of tumorigenesis, for the S34F mutant. This evidence concerns the gene U2AF1 and lung adenocarcinoma.