Int. J. Environ. Res. Public Health 2012, 9 1943 expected by random chance, as calculated using the right-tailed Fisher’s Exact Test. Pathways with enrichment p values <0.05 were considered significant. In a similar fashion, functional enrichment analysis was performed to identify biological functions and disease signatures significantly associated with the AML-associated gene signature predicted to be regulated by AML-associated miRNAs. Significance was calculated in the same manner as the pathway enrichment analysis, where functions with enrichment p values <0.0001 were considered significant. 3. Results 3.1. Identifying the AML Signalisome In this study, we predicted that miRNAs act together to control genomic signaling of biological pathways associated with AML. To test this hypothesis, we analyzed genomic data from individuals with or without AML, and integrated the genomic data with miRNAs and their transcriptional targets in a six step process (Figure 1). Through this process we uncovered for the first time an AML network, or Signalisome, that is regulated by multiple miRNAs. Figure 1. Steps in identifying the AML Signalisome. (1) AML-Associated Gene Expression Signature Identified signature consisting of 731 genes (2) AML-Associated miRNAs Identified 7 key AML- associated miRNAs (3) miRNA-Regulated Genes Predicted 1589 genes targeted by miRNAs (4) miRNA-Mediated AML Gene Signature Identified 78 miRNA-mRNA target matches (5) AML Signalisome Network analysis of the 78 target matches revealed the AML Signalisome (6) Pathway Enrichment AhR pathway identified as the most significantly enriched pathway within the AML Signalisome 3.1.1. AML-Associated Gene Expression Signature Is Identified To identify a set of genes differentially expressed in AML patients relative to non-leukemic patients, we performed a statistical analysis using publically available data. Data from Mills et al. [22] were used in a new manner to compare the genome-wide expression levels between 202 AML patients and 69 non-leukemic patients. Statistical analysis revealed 731 genes (represented by 1,119 probe sets) that were significantly differentially expressed in bone marrow mononuclear cell samples from AML versus non-leukemic patients (Figure 2; see electronic supplementary information, Table S1). As the samples were collected at the time of diagnosis for patients enrolling in the MILE study, this