U2AF1 and myelodysplastic syndrome: As to the MDS/secondary AML patients, mutations in the myeloid transcription factor (RUNX1 and ETV6), chromatin-modifying gene (ASXL1 and BCOR), spliceosome complex (SRSF2 and U2AF1), cohesion complex gene (STAG2), and tumor suppressor gene (TP53) were demonstrated in high proportions compared with the frequencies in the de novo AML patients; this finding was similar to the results of previous reports.