Cell Differentiation|Cell Line, Tumor|Cell Proliferation|Cluster Analysis|Data Interpretation, Statistical|Databases, Factual|Down-Regulation|Gene Expression Regulation, Neoplastic|Genes, Regulator|Granulocyte Precursor Cells|Humans|Internet|Leukemia|Oligonucleotide Array Sequence Analysis|Proteins|RNA, Messenger|Time Factors|Transcription Factors|Transcription, Genetic|Tretinoin|U937 Cells|Up-Regulation