Rm ranged from 482 in sample FF2 to 562 miRNA transcripts in the H1299 cell line. Replicate correlations for this platform ranged from 0.932 for FFPE samples to 0.985 for the FF samples. The miRNA detection count obtained by the NanoString platform ranged from 350 for FF2 to 76 for H1299-1 and replicate correlations ranged from 0.643 to 0.989. MiRNA-Seq detection counts ranged from 650 for FFPE9a to 472 for H1299-1. Replicate correlations ranged from 0.916 for H1299 to 0.935 for FFPE9 samples.MicroRNA Expression Patterns in Tested Lung TissuesNext, we assessed the overall ML240 distribution of miRNA expression by plotting the fractional deviation of the mean scaled signal intensity for the top 100 miRNA transcripts in each sample across each of the miRNA platforms (Figure 3). The distribution of expression values across all platforms was relatively consistent, although the ranked order of specific miRNA transcripts differed among the platforms for the same sample (Table S4 A ). Interestingly, Affymetrix, Agilent, miRNA-Seq, and NanoString demonstrated similar patterns of signal across each sample type. However, the Illumina platform was clearly an outlier in this analysis, exhibiting the highest overall percent maximum signal.Reproducibility of miRNA Profiling between FF and FFPE SamplesWe further assessed the performance of each platform by comparing expression values obtained from matched FF and FFPE samples (Figure 2). The overall tissue 
type did not appear to significantly affect the miRNA profiling and the correlation across sample types ranged from r = 0.826 for the Agilent microarray platform to 0.937 for the Illumina microarray. For miRNA-Seq analysis, the two replicates were analyzed using two different Illumina sequencers (GAII vs. HiSeq2000) and they gave similar correlations, with r = 0.906 and 0.868, respectively. The expresComparison to Quantitative PCR by Fluidigm Dynamic ArrayWe compared the expression fold changes between FF1/ H1299-1 and FFPE9a/H1299-1 with miRNA expression differences obtained by RT-PCR using the Fluidigm dynamic arrayMulti-Platform Analysis of MicroRNA ExpressionFigure 1. Experimental design of the miRNA expression platform comparison. RNA from replicate samples JI 101 derived from normal lung, lung tumor, and a cell line were extracted by methods as indicated. All samples were subsequently analyzed by Illumina, Affymetrix, Agilent, NanoString, Illumina miRNA-Seq, and Fluidigm qPCR. doi:10.1371/journal.pone.0052517.g(South San Francisco, CA) and ABI Taqman miRNA assays (Foster City, CA; Table 2). We used Fluidigm-based qPCR to study 41 miRNAs that were shared in the FF1 sample across all miRNA platforms. The miRNA-Seq platform demonstrated the highest correlation with Fluidigm qPCR for RNA isolated from FF tissues (r = 0.7045, p,0.0001), while its correlation with Affymetrix, NanoString, Illumina, and Agilent were respectively lower but still statistically significant (p,0.001). For FFPE sample, 37 transcripts were shared and assessed by quantitative PCR. NanoString demonstrated the highest correlation 10457188 (r = 0.4808, p = 0.0026). The miRNA-Seq platform demonstrated the second best FFPE sample correlation with the qPCR data (r = 0.4720, p = 0.0032), followed by Affymetrix, Agilent, and Illumina. For the qPCR data derived from the FF1 sample, six miRNA transcripts (miR-16, miR-27a, miR20a, let-7f, mir96, and miR-29b) gave log ratio values that were disparately lower than log ratios derived by the Affymetrix, Agilent,.Rm ranged from 482 in sample FF2 to 562 miRNA transcripts in the H1299 cell line. Replicate correlations for this platform ranged from 0.932 for FFPE samples to 0.985 for the FF samples. The miRNA detection count obtained by the NanoString platform ranged from 350 for FF2 to 76 for H1299-1 and replicate correlations ranged from 0.643 to 0.989. MiRNA-Seq detection counts ranged from 650 for FFPE9a to 472 for H1299-1. Replicate correlations ranged from 0.916 for H1299 to 0.935 for FFPE9 samples.MicroRNA Expression Patterns in Tested Lung TissuesNext, we assessed the overall distribution of miRNA expression by plotting the fractional deviation of the mean scaled signal intensity for the top 100 miRNA transcripts in each sample across each of the miRNA platforms (Figure 3). The distribution of expression values across all platforms was relatively consistent, although the ranked order of specific miRNA transcripts differed among the platforms for the same sample (Table S4 A ). Interestingly, Affymetrix, Agilent, miRNA-Seq, and NanoString demonstrated similar patterns of signal across each sample type. However, the Illumina platform was clearly an outlier in this analysis, exhibiting the highest overall percent maximum signal.Reproducibility of miRNA Profiling between FF and FFPE SamplesWe further assessed the performance of each platform by comparing expression values obtained from matched FF and FFPE samples (Figure 2). The overall tissue type did not appear to significantly affect the miRNA profiling and the correlation across sample types ranged from r = 0.826 for the Agilent microarray platform to 0.937 for the Illumina microarray. For miRNA-Seq analysis, the two replicates were analyzed using two different Illumina sequencers (GAII vs. HiSeq2000) and they gave similar correlations, with r = 0.906 and 0.868, respectively. The expresComparison to Quantitative PCR by Fluidigm Dynamic ArrayWe compared the expression fold changes between FF1/ H1299-1 and FFPE9a/H1299-1 with miRNA expression differences obtained by RT-PCR using the Fluidigm dynamic arrayMulti-Platform Analysis of MicroRNA ExpressionFigure 1. Experimental design of the miRNA expression platform comparison. RNA from replicate samples derived from normal lung, lung tumor, and a cell line were extracted by methods as indicated. All samples were subsequently analyzed by Illumina, Affymetrix, Agilent, NanoString, Illumina miRNA-Seq, and Fluidigm qPCR. doi:10.1371/journal.pone.0052517.g(South San Francisco, CA) and ABI Taqman miRNA assays (Foster City, CA; Table 2). We used Fluidigm-based qPCR to study 41 miRNAs that were shared in the FF1 sample across all miRNA platforms. The miRNA-Seq platform demonstrated 
the highest correlation with Fluidigm qPCR for RNA isolated from FF tissues (r = 0.7045, p,0.0001), while its correlation with Affymetrix, NanoString, Illumina, and Agilent were respectively lower but still statistically significant (p,0.001). For FFPE sample, 37 transcripts were shared and assessed by quantitative PCR. NanoString demonstrated the highest correlation 10457188 (r = 0.4808, p = 0.0026). The miRNA-Seq platform demonstrated the second best FFPE sample correlation with the qPCR data (r = 0.4720, p = 0.0032), followed by Affymetrix, Agilent, and Illumina. For the qPCR data derived from the FF1 sample, six miRNA transcripts (miR-16, miR-27a, miR20a, let-7f, mir96, and miR-29b) gave log ratio values that were disparately lower than log ratios derived by the Affymetrix, Agilent,.