KLF4 and digestive system cancer: However, given that several literatures reported that KLF4 expression was a harmful prognostic indicator in some malignancies, it is very necessary to clarify the precise relation between KLF4 expression and prognostic value in patients diagnosed with digestive system cancers through a systematic review and meta-analysis, which may provide useful information for the application of targeted therapy on cellular KLF4 in the future.